Solution-processed photovoltaic and thermoelectric hybrid systems with efficiency exceeding 50%

Domain: biology
Published: 2026-04-03
Editorial outcome: major_revision

Abstract
Photovoltaic-thermoelectric (PV-TE) hybrid systems offer a platform for enhancing the energy conversion efficiency of photovoltaic devices. However, they still suffer from energy losses and limited efficiency improvements owing to underutilized parasitic thermal energy and electrical parameters mismatches between PV and TE components. Here, we presented a comprehensive theoretical analysis and simulation based on a PV-TE Thermo-Electrical Coupling Model, predicting that the maximum efficiency of the system could reach 60.34% with state-of-the-art PV and commercial TE technologies. Following this model, we fabricated hybrid systems with organic and perovskite solar cells coupled with thermoelectric cells, achieving record-high efficiencies of 34.85% and 42.03% at 298 K, and 43.16% and 50.28% at 313 K, respectively, under AM 1.5G illumination, with optimal thermal utilization and current matching between series-connected PV and TE modules. This work highlights the potential of PV-TE hybrid systems and could offer guidance for designing higher-efficiency systems, driving future advancements in photovoltaics.

Introduction
Sunlight, as a clean and sustainable energy, has long been harnessed through photovoltaic technology on a global scale to generate electricity. Recently, significant advancements have sparked renewed excitement in the field. Notable progress has been made recently in areas such as organic solar cells (OSCs)1,2 and perovskite solar cells (PSCs)3,4, as well as in thermophotovoltaics (TPV)5,6 and concentrating photovoltaics (CPV)7,8. TPV and CPV technologies have garnered considerable interest due to their relatively high efficiencies5,9. However, they require ultrahigh-temperature heat sources10 and condensers11, which complicates their structural design.

As emerging photovoltaic technologies, solution-processed solar cells such as OSCs and PSCs are catching more interest due to their many unique advantages, such as simple fabrication process, low cost, lightweight, and potential for roll-to-roll large-area production4,12,13. To date, the best power conversion efficiency achieved for single-junction OSCs and PSCs and silicon-based solar cells has risen to 21%2,14,15, 27% 4,16,17, and 28%18, respectively. However, further efficiency improvement remains challenging, as these cells can only utilize a limited portion of sunlight in the visible and near-infrared regions, and also the parasitic heat, mainly generated from the sub-bandgap photons and thermalization loss, has been wasted19,20. For any photovoltaic technology, following the law of conservation of energy, to achieve the maximum electricity output , the sunlight must be used in the maximum manner and the parasitic heat generated in the process should be minimized or used at the maximum21,22.

Meanwhile, as it is well-known, the heat generated during the operation of solar cells, primarily from infrared sunlight21,23 and the parasitic heat19,20, not only reduces the efficiency (Supplementary Fig. 1) but also impacts their operational lifespan. This issue is particularly critical for emerging OSCs and PSCs technologies. Therefore, converting the parasitic heat from solar cells into electricity, while maintaining a low operating temperature, could not only enhance the utilization of solar energy and boost power conversion efficiency but also extend the lifespan of the solar cells22,24.

Thermoelectric (TE) technology, which can directly convert thermal energy into electricity via Seebeck effect25,26, has been long used for parasitic heat recovery and utilization in many scenarios27-29. Thus, it would be a perfect fit to combine PV and TE cells together21,22. Indeed, since the concept of PV-TE hybrid system was first proposed in the 1970s30, many pioneering theoretical simulations and experimental studies have been carried out22,31-33. But surprisingly, a comprehensive investigation of the literatures finds that, up to date, the best reported simulated efficiency is only 33.8% for PV-TE hybrid systems9,34. Regarding the experimental studies, unfortunately, the highest reported efficiency of PV-TE hybrid systems is merely approximately 23% under AM 1.5G solar illumination32,35. These surprisingly low efficiencies in literatures for PV-TE hybrid systems in terms of both theoretical and experimental studies indicate that there must be some fundamental issues, and thus some serious and comprehensive analysis is warranted.

It should be noted that the prevailing efficiency measurement for PV-TE hybrid systems is typically defined as the ratio of electrical energy output to incident solar energy input, which is consistent with the calculation of the power conversion efficiency (PCE) for standalone PV cells21,22,35. Contributions from ambient thermal energy or additional cooling sources are typically not considered. This method enables a direct comparison of the performance improvement of PV-TE hybrid systems relative to standalone PV cells.

Above the obvious requirement that the PV and TE cells themselves should be state-of-the-art in the PV-TE hybrid systems, it is crucial that the parasitic heat generated from the sunlight must be efficiently converted into electricity through the TE module to maximize overall system efficiency36-38. Moreover, the output power (efficiency) of any PV-TE hybrid system must adhere to basic physics principles for multi-cell systems to achieve the maximum or energy lossless coupling output39,40. Clearly, the possible maximum output power of the PV-TE hybrid system is the sum of the two given individual PV and TE cells/modules according to the energy conservation law, and this requires the two modules of PV and TE in the hybrid system to have electrically matchable characteristic parameters (note the PV and TE cells are very different in their electrical parameters)41-43. Therefore, to achieve the best-performed PV-TE hybrid system, it is essential to optimize the overall configuration of the hybrid system to simultaneously maximize parasitic heat utilization and achieve energy lossless coupling output between the PV and TE submodules.

Considering the overwhelming complexity, systematic modeling is first required. Thus, we constructed a PV-TE Thermo-Electrical Coupling Model (PT-TECM) to analyze the conditions of maximizing heat utilization and matching electrical parameters, and then simulated the efficiency of PV-TE hybrid systems through the COMSOL Multiphysics® platform.

Following the proposed model above, we predicted that the maximum efficiency of the optimized PV-TE hybrid system could reach 60.34% by using the best single-junction PSCs4,16,17 and commercialized TE materials26,44,45. Guided by these simulations, our fabricated optimized solution-processed solar cells (OSCs and PSCs) and thermoelectric hybrid systems connected in series achieved record efficiency of 34.85% / 43.16% and 42.03% / 50.28% at environmental temperatures (T ) of 298 K/313 K (with the active area of 0.24/0.28 cm2) under AM 1.5G solar illumination, respectively. To demonstrate scalability, we further fabricated a larger-area 1.0 cm2 OSC-TE hybrid system using the same strategy. This larger system also exhibited a high efficiency of 33.48% at 298 K, with an efficiency similar to that of the small-area OSC-TE hybrid system. Furthermore, we fabricated a large-area, flexible and wearable OSC-TE hybrid system capable of directly powering a sensor for real-time pulse monitoring, while the individual OSC module could not achieve this due to its relatively low output power. We believe the results of both theoretical modeling and experimental results demonstrated in this work would provide valuable design guidelines for high-performance PV-TE hybrid systems, particularly for solution-processed PV cells, and significantly expand their application potential in various fields.

Results
Theoretical analysis and modeling for optimized utilization of thermal energy and electrical parameter matching

As mentioned above, to address the overwhelming complexity and guide the fabrication and optimization of such high-performed hybrid systems, the PT-TECM was established (Supplementary Notes 1 and 2) to achieve both the conditions for optimal parasitic heat utilization and electrical parameter matching and further simulate the efficiency (η) of the PV-TE hybrid systems. The simulation involved the development of heat transfer and equivalent circuit models using the COMSOL Multiphysics® platform (Supplementary Note 2). For efficient harvesting of parasitic thermal energy, TE cells are configured as a stacked module located beneath the PV module in the PV-TE hybrid system (Supplementary Note 1.1). In terms of electrical parameter matching, the maximum output power of the hybrid system can be achieved either by connecting two different types of batteries in parallel or in series (Supplementary Note 1.2). However, as detailed in Supplementary Note 1.3, due to the changing temperature and light intensity of the actual application environment, the voltage and current of both PV and TE cells (modules) vary correspondingly. This would lead to severe charging/discharging between the PV and TE cells if connected in parallel, even leading to overheating or battery damage. But for the system connected in series, the PV and TE cells (modules) can still operate relatively stable. Therefore, the connection of PV and TE modules in series would be the best choice and was thus used in this study. For a series-connected PV-TE hybrid system, current matching must be achieved to maximize output power. This means that the PV and TE modules must produce the same output current at their respective maximum output power points to ensure the highest efficiency of the entire system.

Guided by the theoretical analysis above, a heat transfer model of stacked TE modules was used to optimize thermal energy utilization (Supplementary Note 2.1). Current matching between the PV and TE modules was achieved through the appropriate series and parallel configuration of their respective sub-modules, and then the efficiency of the PV-TE hybrid system was calculated using an equivalent circuit model (Supplementary Note 2.2). Importantly, without maximizing parasitic heat utilization and electrical matching, the series-connected OSC or PSC and TE hybrid systems showed a very limited efficiency improvement of ~ 2-3% (Supplementary Fig. 2), similar to previous reports21,24. Using the PT-TECM, it is possible to simulate and optimize the output power and efficiency of any combination of PV and TE cells with different types, and the simulated results subsequently were used to guide us to carry out relevant experiments. Fig. 1a illustrates the structure of the PV-TE hybrid system used in both simulations and experiments, where the PV (OSC or PSC) module (top) is connected to the TE module (bottom) in series with a thermal conductive layer between them, and the effective area of the PV and TE modules keeps always the same. Fig. 1b shows the detailed structure of the OSC, PSC, and TE cell units used in this study. The TE cells are made of bismuth telluride (Bi2Te3)-based thermoelectric materials, due to their high thermoelectric performance and stability at room temperature46,47. The equivalent electrical circuits for the PV-TE hybrid systems are shown in Fig. 1c. AFM images of the OSC and PSC films reveal smooth surface topography. GIWAXS analysis of the OSC indicates well-defined molecular packing and orientation, while XRD patterns of the PSC confirm the formation of a well-crystallized perovskite phase (Supplementary Figs. 3-4). UV-vis absorption spectra demonstrate the spectral complementarity between the PV and TE components for efficient solar energy harvesting (Supplementary Fig. 5). These characterizations demonstrate the reproducibility of device fabrication and provide a solid physical foundation for the integration of the PV-TE hybrid system.

Simulations and experiments for optimized thermal energy utilization

To optimize the utilization of parasitic thermal energy generated by solar cells, a heat transfer model of the stacked PV-TE hybrid structure was established (Supplementary Note 2.1). Using this model, the thermoelectric temperature difference (ΔT) and voltage (VTE) can be obtained by solving Equations S3-S8 (Supplementary Note 2.1). The established general heat transfer framework was then applied to a specific OSC-TE hybrid configuration, consisting of a single OSC (with a reported efficiency of 18% in our previous work48) and multiple commercial TE cells (see Supplementary Note 2.1 and Supplementary Fig. 6 for details). Both the OSC and each individual TE cell possess an identical active area of 0.04 cm2.

To find the best conditions for heat utilization, the ΔT with different numbers (k) of TE layers in the system was simulated using the model, where k ∈ [1, 10] (Supplementary Fig. 7). The hot-side temperature of the PV-TE hybrid system is determined by the heat generated from the solar cell under AM 1.5G solar illumination, while the cold-side temperature could be controlled by various cooling methods. To achieve a large temperature difference and evaluate the maximum efficiency of the hybrid system, the cold-side temperature of the system was maintained at 0 ℃ (273 K). In the likely practical applications scenarios, without external energy input, the condition (0 ℃) might be achieved when the PV-TE hybrid system is deployed in marine environments with seawater cooling (from the equator to the poles, seawater temperature decreases gradually from ~ 25 °C to ~ 0 °C or even below 0 ℃), as well as in polar regions or space, as detailed in the final applications section.

Detailed simulation results for ΔT and VTE of the 0.04 cm2 OSC-TE hybrid systems with different numbers of TE layers are shown in Fig. 2a (the blue shaded area) and Supplementary Fig. 8. In this case, since the overall performance of the series-connected hybrid system is mainly determined by ΔT and VTE from the TE module22, the relationship between the VTE and the number of TE layers (k) were selected to evaluate the efficiency of hybrid system. The shaded region in Fig. 2a represents the performance fluctuation range of the system due to changes in the temperature of the surrounding air, which exchanges heat convectively with the system (Supplementary Note 3). As the k increases from 1 to 10, the ΔT and VTE gradually increase and reach approximately constant when k exceeds 6. Then, the efficiency of the OSC-TE hybrid system was obtained by inserting the VTE into the equivalent circuit model and solving Equations S9-S13 (Supplementary Note 2.2). As a result, the OSC-TE hybrid system reaches the maximum efficiency improvement (Δη = η – ηOSC) at k = 6 (the red shaded area in Fig. 2a), compared to the individual OSC.

Guided by the simulation results above, we fabricated a series of PV-TE hybrid systems using the OSCs with a reported efficiency of 18% in our previous work 48 and commercial TE cells with measured total Seebeck coefficient of 9.72 mV/K (Supplementary Fig. 6). The bottom temperature of the PV-TE hybrid system was maintained at 273 K. The experiment results of ΔT, VTE, and Δη of the system with different values of k are shown in Fig. 2a and Supplementary Fig. 9a. Note the overall performance enhancement (Δη) of the series-connected hybrid system is mainly determined by ΔT and VTE from the TE module. At k = 6, the ΔT and VTE reach their maximum value (approximately 28 K and 0.28 V, respectively), indicating that the TE module achieves optimal thermal energy utilization. At this condition, the 0.04 cm2 OSC-TE hybrid system achieved its highest efficiency of 23.99% (Supplementary Fig. 9b), corresponding to the Δη of 6.17%. Thus, we can conclude that the PV-TE hybrid system could maximize thermal energy utilization at k = 6. The consistency between the experimental and simulation results demonstrates the accuracy of our model and the reliability of the experimental data, highlighting the potential of our PT-TECM for performance optimization.

Simulations and experiments for current matching

Besides maximizing thermal energy utilization, current matching between the PV and TE modules is also a must for achieving maximum efficiency. Note the current at the maximum output power point of the TE module (k = 6) was approximately 7.0 mA, significantly larger than the current of the 0.04 cm2 OSC (1.0 mA). Therefore, to achieve the current matching, the PV module must be constructed with n solar cells connected in parallel to increase its current (Supplementary Fig. 10). Meanwhile, the areas of the PV and TE modules must be kept the same. Thus, each layer of the TE submodule was built with m TE cells connected in series, and then each layer of the TE submodule is again connected in series to form the final TE module, maintaining a constant current in the TE module. The effective area of the PV and TE modules must be equal to ensure maximum utilization of parasitic heat, therefore n = m. The corresponding heat transfer model and equivalent circuit model for current matching are shown in Supplementary Notes 2.1 and 2.2. We can obtain the J-V curve and efficiency of the PV-TE hybrid system with different areas (corresponding to n = m ∈ [1, 9], k = 6) by solving the Equations S9-S13 in Supplementary Note 2.2. The simulated results of Δη of the entire hybrid systems with different electrical matching are presented in the shaded area of Fig. 2b. Again, the shaded region reflected the performance fluctuation of the system due to changes in the temperature of the surrounding air, which exchanges heat convectively with the system (Supplementary Note 4). Note the Δη first increases and then decreases gradually. The PV and TE modules achieved electrical matching (the same current) and thus the highest simulated system efficiency when n = m = 6, k = 6.

Guided by these simulation results, corresponding experiments were conducted using the OSCs and TE cells mentioned above. To achieve the best and also reliable experimental results, we prepared various OSC parallel modules with effective areas ranging from 0.04 to 0.36 cm2, corresponding to n ∈ [1, 9], to have a complete and systematic experimental evaluation. As indicated by the above results and discussion on heat utilization, the number of TE layers was fixed at 6 (k = 6) to maximize heat utilization. Infrared thermal imaging of the PV-TE hybrid systems illustrates the thermal energy harvesting and the cooling effect provided by the TE modules, highlighting the thermal synergy between the PV and TE components (Supplementary Fig. 11). The experimental current ratio between OSC and TE modules and Δη of the OSC-TE hybrid system with different areas were shown in Fig. 2b. As the system area increases (n= m∈ [1, 9], k = 6), the measured current ratio of the OSC and TE modules increased from 0.13 to 1.49, with Δη initially increasing and then decreasing, peaking when the current ratio reached 1.0 (Fig. 2b and Supplementary Fig. 12a). At the peak point, the 0.24 cm2 OSC-TE hybrid system (n = m = 6, k = 6) achieved the maximum heat utilization and current matching simultaneously, resulting in the highest Δη of approximately 16.0% with energy lossless coupling output (Supplementary Fig. 12b), which is consistent with the simulated results (Fig. 2b and Supplementary Note 4). It is noted that the efficiency calculation method of the PV-TE hybrid system (Equation S13, Supplementary Note 2.2) follows the widely used approach in this field21,22,35, where the efficiency is the ratio of electrical energy output to solar energy input. Thus, Δη represents the ratio of the electricity generated by the TE module to the input solar energy. Fig. 2c shows that the OSC-TE hybrid system (n= m = 6, k = 6) achieved the maximum efficiency of 34.85% at 298 K under AM 1.5G solar illumination (Supplementary Table 1), with statistical distribution confirming reproducibility (Supplementary Fig. 13a). Furthermore, the efficiency of the 0.24 cm2 OSC-TE hybrid system with different TE layers (keep n= m= 6, k ∈ [5, 7]) was also evaluated (Supplementary Fig. 13b), and the experimental results further confirm that k = 6 is indeed the optimal value for maximizing thermal energy utilization.

Following the design guideline for optimal OSC-TE hybrid systems, we further fabricated PSC-TE hybrid systems using high-efficiency PSCs (approximately 26% efficiency) reported in our previous work49. As shown in Fig. 2d, the 0.24 cm2 PSC-TE hybrid system (n= m= 6, k = 6) achieved the maximum efficiency of 42.03% at 298 K (Supplementary Table 2), with statistical distribution confirming reproducibility (Supplementary Fig. 14). Under optimal coupling conditions, Figs. 2e and 2f show that the total output power of the integrated PV-TE hybrid system is nearly equal to the sum of the maximum output powers of the PV and TE modules when operating independently. This demonstrates that the system achieved energy lossless coupling between the PV and TE components.

Note that all the above simulated and experimental results of the system are based on basic PV and TE cells with an area of 0.04 cm2. To investigate the scalability of the system, we fabricated a larger-area 1.0 cm2 OSC-TE hybrid system using a single OSC and a six-layer TE module, with both the OSC and TE units having the same area of 1.0 cm2. As shown in Supplementary Fig. 15 and Table 3, the 1.0 cm2 OSC-TE hybrid system also exhibited similar efficiency improvement from 17.13% to 33.48%. The similar efficiency, independent of the device area, would be important for advancing larger-area PV-TE hybrid systems with high efficiency, as the large-area fabrication would be one of the critical factors for practical applications. So far, both the PV (OSC and PSC) and TE devices have achieved large-area module fabrication. A 204 cm2 OSC module with a certified power conversion efficiency of 14.5% was achieved in 202450. The PSC module, with a size of 2 m2, achieved a certified record efficiency of 20.05% in 202551. Bismuth telluride-based thermoelectric generators have also been widely produced and applied at large scale52. These results indicate that the PV-TE hybrid system could have excellent potential for scalability and would be capable of large-scale fabrication and application as technology progresses.

Stability would be also one of the critical factors for practical applications. The PV (OSC and PSC) and TE units have demonstrated excellent stability under continuous illumination and temperature fluctuations. For the photostability, to date, the OSC could retain about 93% of their initial efficiency after 2000 hours of continuous maximum power point tracking (MPPT) under 1 sun condition53. The PSC could also retain about 82% of their initial efficiency after 2500 hours of continuous MPPT under 1 sun condition54. For the thermal stability, to date, the OSC could retain 94% of their initial efficiency after 1032 hours of 85 °C/85% relative humidity damp heat and 200 thermal cycles (- 40 °C to 85 °C) tests55. The PSC could also keep 92% of the initial efficiency when ageing at 85 °C for 1800 h and 94% after 200 thermal cycles between - 40 °C and + 85 °C56. Furthermore, bismuth telluride-based thermoelectric generators have successfully achieved commercial production and application due to their exceptional stability52,57.

To assess the stability of the PV-TE hybrid system, we compared the stability of the integrated system with that of each standalone unit under the same testing conditions. The photostability of standalone PV (OSC and PSC) and PV-TE (OSC-TE and PSC-TE) hybrid systems was evaluated under the ISOS-L-1 protocol. The experimental results indicated that both the OSC-TE and PSC-TE hybrid systems exhibited enhanced photostability compared to the standalone OSC and PSC due to the ability of TE module to harvest heat and provide cooling (Supplementary Fig. 16). Thermal stability was assessed under the ISOS-T-2 protocol by subjecting standalone PV (OSC and PSC) and PV-TE (OSC-TE and PSC-TE) hybrid systems to thermal cycles between 25 °C and 65 °C. The OSC and PSC integrated within the hybrid system exhibited similar thermal stability compared to the standalone OSC and PSC after 100 thermal cycles (Supplementary Figs. 17a - 17b). The TE module exhibited negligible change in output voltage and current after 100 thermal cycles (Supplementary Fig. 17c). In summary, the enhanced photostability and similar thermal stability of PV-TE hybrid system compared with the standalone PV units indicate that the integrated system could achieve or even exceed the reported stability of the PV units, demonstrating the system's potential for reliable, long-term practical applications.

Parametric analysis and record-high efficiencies of PV-TE hybrid systems

To investigate the key factors influencing the efficiency of PV-TE hybrid system, a parametric study was conducted using the PT-TECM. The simulated results indicated that the efficiency of the PV-TE hybrid system increases with higher TE material figure of merit (zT) and higher PV cell efficiency (Fig. 3a and Supplementary Note 5). Moreover, a larger ΔT across the TE module, achieved by a lower cold-side temperature or a higher environmental temperature, can further improve the system efficiency (Fig. 3b and Supplementary Note 6). Additional parameters that might influence system performance, such as the convective heat transfer coefficient and thermal interface material properties, are presented in Supplementary Fig. 18.

Therefore, to explore the efficiency limit of the PV-TE hybrid system, we further carried out the simulation using the state-of-the-art PV cells (OSC with ~ 21% efficiency2,14,15 and PSC with ~ 27% efficiency4,16,17) and the best commercial Bi2Te3-based TE materials (zT ≈ 1.0 at room temperature 26,44,45) (Fig. 3c and Supplementary Note 7). At 298 K (room temperature), the simulated optimal OSC-TE and PSC-TE hybrid systems (n = m = 6, k = 6) could achieve maximum efficiency of 40.67% and 47.06% under AM 1.5G solar illumination, respectively. At 313 K (the environment temperature in a typical hot summer), the optimal OSC-TE and PSC-TE hybrid systems (n = m = 8, k = 6) could reach maximum efficiency of 53.88% and 60.34%, respectively. The reason that n and m are larger at 313 K compared to 298 K is that the higher environment temperature increases the ΔT and current of the TE module, thereby requiring more PV units connected in parallel for current matching.

To verify the simulated results at 313 K, based on the existing OSC (18% efficiency) 48 and PSC (26% efficiency)49 in our laboratory, we further measured the efficiency of the OSC-TE and PSC-TE hybrid systems at 313K. As shown in Fig. 3d, the OSC-TE and PSC-TE hybrid systems (n= m = 7, k = 6) achieved the maximum efficiency of 43.16% and 50.28% at 313 K under AM 1.5G solar illumination, respectively (Supplementary Tables 4 - 5), with statistical distribution confirming reproducibility (Supplementary Fig. 19 - 20). Under optimal coupling conditions, the total output power of the integrated PV-TE hybrid system is also nearly equal to the sum of the maximum output powers of the PV and TE modules when operating independently at 313 K (Supplementary Fig. 21). Compared to the simulation results (Fig. 3c), the lower efficiencies observed in experiments (Fig. 3d) can be attributed to non-ideal practical factors, primarily a lower zT of the employed TE module (zT ≈ 0.9, compared to zT ≈ 1.0 in simulation) and the neglect of interfacial thermal resistance in the simulation model. Fig. 3e compares the simulated and experimental efficiency of our PV-TE hybrid systems in this work with that of previously reported representative OSC-TE, PSC-TE, and inorganic PV-TE hybrid systems in literatures. Note our optimal OSC-TE and PSC-TE hybrid systems have achieved record-high efficiency of 43.16% and 50.28% at 313 K under AM 1.5G solar illumination, respectively, significantly exceeding the efficiency of previously reported OSC-TE24,31, PSC-TE21,22,32,35,58, and inorganic PV-TE33,40,59,60 hybrid systems in literatures (Supplementary Table 6). Our PV-TE hybrid systems also show great advantages and competitiveness, compared with reported tandem PV devices, PV-TE hybrid systems with radiative cooling, and concentrated PV-TE hybrid systems (Supplementary Table 7). Furthermore, as indicated by the simulation in Fig. 3c, it is expected that with continued advancements in PV and TE technologies, the maximum achievable efficiency of PV-TE hybrid systems should be even better.

Methods
Materials for organic solar cells (OSCs)
Donor polymer PM6 was purchased from Solarmer Materials, Inc. Acceptor molecule L8-BO was provided by Jiaxing Hyper Optoelectronic Technology Co., Ltd. Indium tin oxide (ITO) was purchased from Liaoning Advanced Election Technology. Zinc oxide (ZnO) nanoparticles were synthesized the methods reported in literature67. The organic molecule named 2-(3-(dimethylamino)propyl)-1,3-dioxo-2,3-dihydro-1H-benzo[de]-isoquinoline-6,7-dicarboxylic acid (NMA) were synthesized using the methods reported in literature48.

Materials for perovskite solar cells (PSCs)
Tin(IV) oxide, 15% in H2O colloidal dispersion was provided by Alfa Aesar. PbI2 (99.99%) was purchased from TCI. Cesium iodide (CsI, 99.999%) was purchased from Advanced Election Technology Co., Ltd. 2,2',7,7'-Tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spiro-bifluorene (Spiro-OMeTAD) was provided by Woerjiming (Beijing) technical developmentinstitute. Lithium bis (trifluoromethylsulfonyl)-imide (99.9%) was purchased from Sigma-Aldrich, 4-tertbutylpyridine (96.0%) was purchased from TCI. Poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) were all purchased from Xi’an Polymer Light Technology in China. FAI, MACl, and ThPyI were synthesized using the methods reported in literatures68,69.

Thermoelectric materials
The micro thermoelectric cells (model 1MD02-024-03, N = 24) were purchased from RMT Co., Ltd. Each thermoelectric cell, with dimensions of 2 mm × 2 mm × 0.9 mm, consists of 24 pairs of p-n junctions made from bismuth telluride (Bi2Te3) material with copper electrodes. The dimensions of a single Bi2Te3 thermoelectric leg were 0.2 mm × 0.2 mm × 0.3 mm, and the internal resistance and total Seebeck coefficient of each thermoelectric cell were approximately 3.32 - 3.5 Ω and 10.0 mV/K, respectively. The Bi2Te3 semiconductor grains used for fabricating large-area flexible thermoelectric devices were sourced from Changsha KunYong New Materials Co., Ltd, with dimensions of 1.0 mm × 1.0 mm × 2.0 mm.

Device fabrication of OSCs
The OSCs were fabricated following our previous work with an inverted structure of ITO/ZnO/NMA/PM6:L8-BO/MoOx/Ag48. Firstly, the indium tin oxide (ITO)-coated glass substrates were cleaned by ultrasonic treatment in detergent, deionized water, acetone, and isopropyl alcohol under ultrasonication for 15 min each and subsequently dried by a nitrogen blow. Subsequently, a 15 nm thick layer of ZnO was deposited by spin-coating a ZnO precursor solution (prepared by dissolving 100 mg zinc acetate dihydrate and 28 µL ethanolamine in 4 mL of 2-methoxyethano) on the top of the ITO glass substrates at 3000 rpm for 40 s. After being baked at 200 °C in the air for 1.0 h, the ZnO-coated substrates were transferred into a nitrogen-filled glove box. For the hybrid ETL of ZnO/NMA, the NMA film was deposited upon ZnO film from its solution with a concentration of 0.4 mg/mL in methyl alcohol with ammonium hydroxide of 2% volume (to ensure good solubility) and then baked on a hot plate at 120 ℃ for 10 min in ambient atmosphere. For the active layer of PM6:L8-BO (weight ratio of 1:1.2), the PM6:L8-BO blend film was generated by spin-coating the blend solution at a spin-coating rate of 3,000 rpm upon the corresponding ETLs, and then was thermally annealed at 110 °C for 5 min. Then, MoOx (~ 2 nm) and Ag (~ 150 nm) were successively evaporated onto the active layer through a shadow mask. The effective area for the devices was 0.04 - 0.36 cm2 (step: 0.04 cm2), determined using an optical profilometer.

Device Fabrication of PSCs
The PSCs were fabricated according to our previous work49. The ITO substrate was washed sequentially with distilled water, acetone, and isopropanol. Before use, the ITO was cleaned with ultraviolet ozone for 20 min. The SnO2 electron transport layer (2.5 wt%, diluted by water) was coated on the ITO substrate and annealed in air at 170 °C for 30 minutes. After cooling to room temperature, the substrate was treated with ultraviolet ozone for 10 minutes before spin-coating the perovskite solution. Usually, 1.5 M PbI2 with 2 mol % CsI was dissolved in DMF/DMSO (v/v, 94/6), and then stirred at 70 °C for 4 hours. The PbI2 solution was then deposited by spin coating at 1500 rpm for 30 seconds, dried at 70 °C for 1 minute, and then cooled to room temperature. A solution of 2D spacer (2 mg/mL) in isopropanol (IPA) was spin-coated on the PbI2 film at a spin rate of 2000 rpm for 30 seconds, and annealed at 70 °C for 30 seconds. After cooling to room temperature, a solution of FAI/MACl (90:9 mg mL−1) in IPA was spin-coated on top of the PbI2 layer at a rotation speed of 2000 rpm for 35 seconds, followed by thermal annealing at 160 °C for 12 minutes in the air (relative humidity about 65%). After perovskite formation, the samples were transferred to a nitrogen-filled glove box for further processing. For the passivation layer, the ThPyI solution was dissolved in IPA with 4 mg/mL and spin-coated onto the perovskite surface at a spin rate of 5,000 rpm, without any further processing. Then, spin-coated the Spiro-OMeTAD solution (80 mg of Spiro-OMeTAD, 30 µL of 4-tert-butylpyridine and 35 µL of lithium bis(trifluoromethylsulfonyl)-imide (Li-TFSI, 260 mg/mL in acetonitrile) in 1 mL of chlorobenzene) on the perovskite layer with 6000 rpm for 30 seconds. For the thermal stability of devices, 20 mg PTAA was dissolved in 1 mL toluene, then 10 μL Li-TFSI (260 mg/ml in acetonitrile) and 10 μL 4-tert-butylpyridine were added. The PTAA solution was spin-coated on the surface of the perovskite layer at 2000 rpm for 30 s. Finally, a 12 nm MoO3 layer and 100 nm Ag layer were deposited by thermal evaporation under a pressure of 1.0 × 10−4 Pa. The effective area for the devices was 0.04-0.36 cm2 (step: 0.04 cm2), determined using an optical profilometer.

Fabrication of PV-TE hybrid systems
In the PV-TE hybrid systems, the photovoltaic (PV) solar cells (OCSs and PSCs) parallel module was connected in series with the thermoelectric (TE) module. All TE cell units were connected in series in the TE module. The TE electrodes were soldered with copper wires, while the electrodes of the solar cells were connected to copper wires using conductive silver paste. Subsequently, different electrodes were interconnected via copper wires.

Initially, for optimal thermal energy utilization, a 0.04 cm2 PV-TE hybrid system with a single PV and multiple TE cells was constructed. The PV solar cell and each TE cell have an equal area of 0.04 cm2. In the PV-TE hybrid systems, the TE cells were attached to the bottom of the PV cell using a phase change thermal interface material (PCM). When multiple TE cells were employed, they were added one by one in the stack using the PCM (Supplementary Fig. 7). The PCM (PTM7950 series from Honeywell Co., Ltd.), with a thickness of 0.2 mm and a thermal conductivity of ~ 8.5 W/mK, can effectively fill interfacial gaps and reduces thermal contact resistance. Polished brass plates (5 mm × 5 mm) were welded to both sides of each TE cell (2 mm × 2 mm × 0.9 mm) to homogenize the temperature distribution and limit adverse thermal radiative losses.

To achieve current matching, parallel modules of OSCs and PSCs with areas ranging from 0.04 to 0.36 cm2 were fabricated (Supplementary Fig. 10). Then multiple TE units were employed in the xy-plane to match the effective area of the PV module. For each layer, the total area of the TE cells was equal to the effective area of the PV module. In the z-plane, the TE cells were stacked layer by layer using the PCM.

Fabrication of flexible large-area OSC module
The fabrication of a flexible large-area OSC module was performed following a previously reported procedure70. The flexible large-area OSC module was fabricated by applying an inverted architecture of PET/ITO/ZnO/NMA/active layer/MoOx/Ag. ITO-coated PET substrate was ultrasonically treated in detergent, deionized water, acetone, and isopropyl alcohol in sequence for 15 min, followed by blowing dry using argon gas. Afterward, the ZnO layer was blade-coated on the pre-cleaned ITO-coated glass at 50 °C in air with a coating velocity of 10 mm/s and a blade-substrate gap of 200 μm, followed by annealing at 120 °C for 15 mins in atmospheric air. After that, a thin film of NMA was blade-coated on ZnO in the air with a coating velocity of 10 mm/s and a blade-substrate gap of 150 μm. PM6: BTP-BO-4CI (1:1.2, D: 9 mg/mL) in chlorobenzene with 0.3 vol% 1,8-diiodooctane (DIO) was blade-coated at 60 °C with a coating velocity of 20 mm/s and a blade-substrate gap of 400 μm in air. Finally, MoOx (~ 6 nm) and Ag (~150 nm) were successively evaporated onto the active layer through a shadow mask (2 × 10-4Pa). The schematics of the large-area module consisting of four sub-cells connected in series using the methods reported in literature71. The photograph of the flexible large-area OSC module with a 14.4 cm2 effective area is shown in Supplementary Fig. 22.

Fabrication of flexible thermoelectric module
The dimensions of the p-type and n-type thermoelectric legs based on bismuth telluride materials are 1.0 mm × 1.0 mm × 2.0 mm. An array comprising multiple p-n junction pairs, thermally in parallel and electrically in series, was fabricated with dimensions of 55 mm × 55 mm. Copper wires were used as electrodes to connect different legs. The assembled thermoelectric array was then cast using PDMS, which was prepared by mixing PDMS precursor with curing agent at a mass ratio of 10:1. The embedded array was subsequently cured in an oven at 80 ℃ for 4 hours. Finally, a 1.5 mm-thick PDMS composite layer, containing BN and Al2O3 to enhance thermal conductivity, was cast and cured on both sides of the thermoelectric array (Supplementary Fig. 23).

Fabrication of PDMS/BN/Al2O3/DM fabrics
The PDMS/BN/Al2O3/DM fabrics were prepared using a 3D extrusion process and a woven process (Supplementary Fig. 24a, b). Initially, the PDMS precursor and curing agent were mixed at a mass ratio of 10:1. Subsequently, BN (500 nm), Al2O3 (50 nm), and DM (n-Docosane microcapsule) were incorporated into the PDMS mixture in a container. Then, the mixture was placed in a vacuum mixer for 5 minutes at room temperature to achieve a homogeneous phase. The resulting PDMS/BN/Al2O3/DM mixture was transferred to a syringe, extruded, and subsequently cured at 80 ℃ for 4 hours. The fabricated composite fibers had a diameter of 0.6 mm. Finally, the fibers were woven into a fabric, which was integrated into clothing for cooling and heat dissipation applications in flexible PV-TE hybrid devices.

Measurement of J-V curves
The current density-voltage (J-V) characteristics of PV-TE hybrid systems were obtained using a Keithley 2400 source measure unit, the scan speed and dwell times of the J-V curves were fixed at 0.02 V s-1 and 20 ms, respectively. The photocurrent was measured under AM 1.5G illumination using an SS-X50 solar simulator, calibrated with a standard Si solar cell (Enli Technology CO., Ltd., Taiwan, and calibrated report can be traced to NREL).

Measurement of thermoelectric signals
The thermoelectric signals were obtained using a Keithley 2400 source measure unit. Temperature variation and distribution in this work were recorded through a thermocouple, and the temperature can be read out in real-time.

Measurement of photostability and thermal cycling stability
The photostability testing was conducted following the ISOS-L-1 protocol. The standalone PV (OSC and PSC) and the PV-TE hybrid system (OSC-TE and PSC-TE) were encapsulated and tested under continuous 1-sun LED illumination at the open-circuit state in ambient air (20 - 30 °C, 40 - 60% RH). The LED spectrum is shown in Supplementary Fig. 16c. J-V characteristics were recorded using a solar simulator after each 48-hour light-soaking period.

The thermal cycling stability testing was conducted following the ISOS-T-2 protocol. The standalone PV (OSC and PSC) and the PV-TE hybrid system (OSC-TE and PSC-TE) were encapsulated, then placed in an oven and thermally cycled between 25 °C and 65 °C under dark, open-circuit conditions. J-V characteristics were recorded using a solar simulator after every 20 thermal cycling periods.

Data availability
All data are available in the main text or the Supplementary Materials. Additional information can be obtained from corresponding authors upon request. Source data are provided with this paper.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "This manuscript presents some progress in photovoltaic thermoelectric (PV-TE) hybrid systems, demonstrating over 50% energy conversion efficiency under optimized conditions. The author first developed a comprehensive PV-TE thermoelectric coupling model, which theoretically predicts a maximum efficiency of 60.34% using state-of-the-art photovoltaic and commercial TE materials. This is a remarkable prediction that, if experimentally implemented, could completely change solar energy conversion. The experimental verification is equally impressive, as the organic and perovskite PV-TE hybrid systems treated with solution achieved efficiencies of 42.03% and 50.28%, respectively, at 313 K.Although efficiency has a profound impact, there are still some aspects of the paper worth exploring.\n1.The PT-TECM model assumes a constant cold source temperature (273 K), but the temperature of the cold source may fluctuate dynamically in real environments (e.g., the ocean or space). Has the applicability of the model to non-steady state conditions been assessed?\n2.The efficiency of the hybrid system was tested only under short-term and fixed environmental conditions, how stable is the hybrid system in long-term cycling? Can it maintain stable power generation over a long period of time?\n3.PV-TE modules connected in series need to match the current accurately, does it put higher demands on the manufacturing process? How to solve the problem of uneven current distribution in large area devices?\n4.Is the light absorption range of the OSC/PSC fully compatible with the thermal response characteristics of the TE module? Are there unutilized spectral regions resulting in wasted energy?\n5.Is the unit power cost of the hybrid system competitive compared to a single PV or TE system? Are there cost estimates for commercialization on the ground?\n6.How does the hybrid system achieve dynamic current matching to maintain efficient output under variable light or temperature conditions (e.g., cloudy days or alternating day and night)?\n7.At the end, the author discusses in detail some interesting potential future application scenarios (e.g., oceans, space), how should one go over to these extreme environments from the realities of current applications? Have similar simple studies been done?\n8.Perovskite solar cells, while efficient, are prone to degradation. Did the authors observe any performance decay in the hybrid system under prolonged operation?\n9.Solution processing is attractive for manufacturability, but the TE module’s cost and integration challenges should be discussed.\n10.How do these efficiencies compare to other waste-heat recovery methods (e.g., tandem PV or radiative cooling)? A discussion would contextualize the advancement.\n11.The model assumes ideal conditions—what are the expected efficiency losses in outdoor, variable-illumination environments?", "reviewer_2": "This work designs a photovoltaic-thermoelectric (PV–TE) hybrid strategy with promising simulated and experimental performance, reporting significant system efficiencies improvement exceeding 50% from . The work demonstrates satisfactory theoretical grounding and potential for high-impact contributions.\nHowever, to meet the publication standards of Nature Communications, the study still requires substantial improvement in several aspects:\n1. The manuscript does not include any morphological (e.g., SEM or AFM), structural (e.g., XRD), or optical (e.g., UV-vis absorption or Tauc plot) characterizations for the PSC or OSC layers used. Given that the device performance strongly depends on the active layer's quality and crystallinity, I recommend adding representative characterizations to ensure reproducibility and provide a solid physical basis for the reported performance. Moreover, it might help identify any potential interface reactions, voids, or delamination affecting durability.\n2. Although the manuscript presents a coupled thermal-electrical simulation and efficiency model, it lacks any thermal imaging data (e.g., IR thermography) that could experimentally confirm the heat redistribution or cooling effect of the TE modules. I recommend including infrared thermal images or temperature maps of both PSC/OSC and PSC-TE/OCS-TE systems before and after illumination, under different cooling conditions, to visually support the proposed thermal synergy.\n3. While Supplementary Fig. 12 provides efficiency retention over 120 hours of continuous illumination, the system's robustness under repeated thermal cycling has not been evaluated. TE modules, especially in stacked configurations, suffer from interface fatigue and microcrack formation under such conditions. I recommend a thermal cycling test to evaluate long-term operational stability.\n4. The TE modules used in the study involve multilayer stacking, yet the manuscript does not address the thermal uniformity or potential thermal stress effects. It is suggested to include infrared mapping or simulation results to assess potential thermal hotspots or mechanical instability in the multilayer TE stack.\n5. The flexible OSC-TE system powering a pulse sensor is promising, but it lacks sufficient data showing mechanical durability. Thus, I suggest providing bending cycle tests with performance retention metrics. Besides, visual documentation of the device under mechanical deformation and diverse weather conditions would be beneficial.\n6. The TE module’s output contribution is discussed, but no standalone I-V or P-V characterization is presented. This leaves the hybrid device’s energy distribution unclear. This might further cause the unclear separation of PV and TE contributions. I would recommend to respectively give PV-only, TE-only, and PV-TE combined performance under identical conditions.\n7. The abstract, introduction, and discussion could be better structured to emphasize the scientific problem, core innovation, and key findings. Some repetitive phrases and general expressions could be refined for clarity and impact. A thorough language editing is advised to meet the requirements of the journal.\n8. The claimed >50% efficiency is remarkable but needs enhanced clarification for readers: is it electrical efficiency concerning solar input only? Does it account for cold source energy consumption? The lack of this information might confuse or mislead authors at first sight. please, at least clarify this in the Abstract. Moreover, please define your efficiency metrics precisely and compare with recent hybrid PV-TE systems in terms of materials, architecture, and performance.\n9. The PV modelling uses the traditional single diode model rather than the double or triple diode model. The TE component is modeled as a linear voltage source with series resistance. Please justify these modelling approximations.\n10. Many material properties (e.g., thermal conductivity, Seebeck coefficient) are taken from the literature or datasheets provided by the supplier without assessing their impact on simulation results. A sensitivity analysis on these critical parameters is strongly encouraged to ensure the robustness of efficiency predictions.\n11. The study is conducted on small-scale laboratory devices, with no discussion on system integration challenges for commercially relevant large-module sizes. Issues such as thermal sink design, electrical load coupling, and thermal–electrical management in real-world scenarios are not addressed. I suggest adding a paragraph that considers practical implementation pathways and associated engineering challenges.\n12. The manuscript lacks a dedicated section summarizing potential future directions, challenges, and opportunities. The current conclusion section focuses on summarizing the experimental results, the authors could more systematically discuss the focus of subsequent research, material optimization strategies, or potential application expansion. Also, please briefly conclude the shortcomings of this work.", "reviewer_3": "I co-reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co-review manuscripts."}, "author_response": "Replies to reviewers’ comments for Nature Communications\nNCOMMS-25-25787-T\n(Text in blue and red is our replies)\nReviewer 1\n(Remarks to the Author):\nThis manuscript presents some progress in photovoltaic thermoelectric (PV-TE) hybrid\nsystems, demonstrating over 50% energy conversion efficiency under optimized\nconditions. The author first developed a comprehensive PV-TE thermoelectric\ncoupling model, which theoretically predicts a maximum efficiency of 60.34% using state-of-\nthe-art photovoltaic and commercial TE materials. This is a remarkable prediction that,\nif experimentally implemented, could completely change solar energy conversion. The\nexperimental verification is equally impressive, as the organic and perovskite PV-TE\nhybrid systems treated with solution achieved efficiencies of 42.03% and 50.28%,\nrespectively, at 313 K. Although efficiency has a profound impact, there are still some\naspects of the paper worth exploring.\nReply: Thank you very much for the positive comment.\n1. The PT-TECM model assumes a constant cold source temperature (273 K), but the\ntemperature of the cold source may fluctuate dynamically in real environments (e.g.,\nthe ocean or space). Has the applicability of the model to non-steady state conditions\nbeen assessed?\nReply: We sincerely thank the reviewer for highlighting this important point regarding\nthe dynamic fluctuations of cold-source temperatures in real-world environments.\nIn our PV-TE Thermo-Electrical Coupling Model (PT-TECM), the cold-side\ntemperature is defined as a freely adjustable boundary condition, enabling the\nexploration of system behavior under dynamic, non-steady state environments such as\nthose encountered in marine and space applications (Supplementary Note 2 Fig. 2,\nPages 16-17, lines 353-354). In the original manuscript, we have already investigated\nthe influence of varying cold side temperatures on the performance of PV-TE hybrid\nsystems (Fig. 3b).\nFig. 3b\n273\n32%\n)K\ne\n(\n278\nr\nu\nta\r e283\np\nm\ne\nt\ne\n288\nd\nis\nd293\nlo\nC\n20%\n298\n293 298 303 308 313 318\nEnvironmental temperature (K)\n1\nη\nof\nhybrid\nsystems\nThe PT-TECM model adopts a constant cold source temperature of 273 K, as this\nrepresents a commonly accessible low temperature under standard environmental\nconditions. This choice enables the estimation of the maximum temperature gradient\nand cooling effect of the TE module, allowing the evaluation theoretical efficiency limit\nof the PV-TE hybrid system under typical conditions.\nIn response to the reviewer’s comment, we corrected imprecise descriptions in the\nmanuscript in Supplementary Information, Page 17, lines 364-365:\n“Boundary Condition 1: The cold-side temperature of the TE module was adjustable\nand set between 273 K and 298 K.”\n2. The efficiency of the hybrid system was tested only under short-term and fixed\nenvironmental conditions, how stable is the hybrid system in long-term cycling? Can it\nmaintain stable power generation over a long period of time?\nReply: We sincerely thank the reviewer for this important question regarding the long-\nterm operational stability of the hybrid systems.\nAccording to the reviewer’s suggestion, we further evaluated the long-term cycling\nstability of standalone PV devices (OSC and PSC) and their corresponding PV-TE\nhybrid systems under ambient air conditions (20 - 30 °C, 40% - 60% relative humidity).\nThe experimental results have been added to the revised Main text and\nSupplementary information.\nMain text, Page 13, lines 324-330:\n“Furthermore, the long-term cycling stability of OSC-TE and PSC-TE hybrid\nsystems were evaluated (Supplementary Fig. 16). The experimental results show that\nthe OSC-TE hybrid systems exhibited enhanced stability compared to the standalone\nOSCs due to the ability of TE module to harvest heat and provide passive cooling. In\ncontrast, the PSC-TE hybrid systems exhibited reduced stability relative to the\nstandalone PSC, which is attributed to the bias stress imposed by the TE module50.”\n50. Li, N. et al. Barrier reinforcement for enhanced perovskite solar cell stability under\nreverse bias. Nature Energy 9, 1264-1274 (2024).\nSupplementary Information:\nPage 71, Supplementary Fig. 16\nhybrid systems under continuous LED light illumination (AM1.5G) in ambient air (20\n- 30 °C, 40% - 60% RH). (c) LED spectrum used in the stability tests.\nAll OSCs, PSCs, and their corresponding PV-TE hybrid systems were encapsulated\nand tested under continuous AM1.5G LED illumination in ambient air (20-30 °C, 40%-\n60% RH) under open-circuit conditions. J-V characteristics were recorded using a solar\nsimulator after each 48-hour light-soaking period.\nAs shown in the Supplementary Fig. 16a, all the OSC-TE hybrid systems\ndemonstrated superior operational stability compared to standalone OSCs, which is\nprimarily due to the ability of TE module to harvest heat and provide passive cooling.\nCompared to standalone PSCs, the PSC-TE hybrid system exhibited improved stability\nduring the initial 48 hours. However, with extended operation time, the hybrid system\nshowed faster degradation and a significant drop in efficiency (Supplementary Fig. 16b).\nThe reduced efficiency of the PSC-TE hybrid system arises because perovskite solar\ncells are especially susceptible to the high bias imposed by the TE module; the\nperformance loss is driven primarily by field-induced ion migration, metal diffusion,\nand reverse-bias avalanche breakdownS42.\nS42. Li, N. et al. Barrier reinforcement for enhanced perovskite solar cell stability\nunder reverse bias. Nature Energy 9, 1264-1274 (2024).\n3\na\n).u.a(\nycneiciffe\ndezilamroN\n1\n0\n0\n0\n0\n0\n.0\n.8\n.6\n.4\n.2\n.0\nT\n0\n8 0\nS tan d alo n e O S C s 2 0.08 cm O S C -T E (n =m =2, k=6) V (avg )=0.52 V TE 2 0.16 cm O S C -T E (n =m =4, k=6) V (avg )=0.96 V TE 2 0.24 cm O S C -T E (n =m =6, k=6) V (avg )=1.40 V TE 2 0.32 cm O S C -T E (n =m =8, k=6) V (avg )=1.88 V TE\n5 0 1 0 0 1 5 0 2 0 0 2 5 0 3 0 0\nT im e (h )\nc\n1 .2 ).u\nL E D\n.a(\nyr\n0 .9 isnetni\nla 0 .6\nrtceps\nd 0 .3\nezilamo\n0 .0 N\n4 0 0\ns p e\nW\nb\n) 1 .0 .u.a(\n0 .8 yc\nT 8 0\nnei\n0 .6 ciffe\nd 0 .4\ne S tan d alo n e P S C s z 2 0.08 cm P S C -T E (n =m =2, k=6) V ila 2 0.16 cm P S C -T E (n =m =4, k=6) V 0 .2 m 2 0.24 cm P S C -T E (n =m =6, k=6) V roN\n0 .0\n0 2 4 4 8 7 2 9 6\nT im e (h )\nc tru m fo r s ta b ility te s ts\n6 0 0 8 0 0 1 0 0 0\na v e le n g th (n m )\n(avg )=0.52 V TE (avg )=0.96 V TE (avg )=1.40 V TE\n1 2 0 1 4 4\n3. PV-TE modules connected in series need to match the current accurately, does it put\nhigher demands on the manufacturing process? How to solve the problem of uneven\ncurrent distribution in large area devices?\nReply: We sincerely thank the reviewer for highlighting this important practical\nconsideration. Indeed, accurate current matching imposes stricter demands on the\nfabrication process, particularly when scaling to large-area devices.\nIn response to the reviewer’s comment, we have added some related discussion in\nthe revised Main text and Supplementary Information.\nMain text, Pages 17-18, lines 434-438:\n“It is important to note that there are still some engineering challenges that must be\naddressed to enable practical employment of our PV-TE hybrid systems. These include\nthe stability limitations of OSCs and PSCs, large-area fabrication, practical integration\nof TE modules, and dynamic fluctuations in real-world environments (Supplementary\nNote 9).”\nSupplementary Information, Page 51:\nSupplementary Note 9. How to solve the problem of uneven current distribution in\nlarge area PV-TE devices?\nIndeed, accurate current matching imposes stricter demands on the fabrication\nprocess, particularly when scaling to large-area devices. It is quite an important issue\nto solve the uneven current distribution in large-area devices. There are mainly three\naspects.\n1. For PV sub-modules:\nModular circuit integration: The PV surface is divided into smaller, sub-cells to form\na series of modular units. This segmentation improves current uniformity and localizes\nmismatch effects.\nElectrode optimization: The busbar and grid finger layout were designed to minimize\nlateral resistive losses and ensure uniform current extraction across the active area.\nProcess control: Slot-die coating with real-time monitoring of precursor\nconcentration, coating speed, and post-deposition annealing temperature ensures\nuniform film thickness and composition.\nEncapsulation engineering: A multilayer encapsulation structure with optimized\nbarrier films and thermally stable adhesives is used to maintain electrical and\nenvironmental stability over time.\n2. For TE sub-modules:\nMaterial and process optimization: Consistency in Seebeck coefficient, electrical\nconductivity, and thermal conductivity is ensured through tight control over material\ncomposition and sintering temperature.\nThermal gradient homogenization: High thermal conductivity materials and\nthermally conductive interface layers are employed to distribute heat evenly across the\nTE legs.\ntechniques are used to ensure electrical and thermal integrity at every joint, thereby\navoiding local overheating or current crowding.\n3. For the PV-TE hybrid system:\nElectrical binning and screening are conducted to group modules with closely\nmatched output characteristics, further improving current uniformity in series\nconfigurations.\nModular architecture with independent tracking: Each hybrid unit operates as a\ndiscrete module, enabling large-area systems to be constructed through parallel or series\ncombinations. PV sub-modules are paired with maximum power point tracking (MPPT)\ncircuits, while TE sub-modules are equipped with dynamic load tracking to operate near\ntheir individual optimal points.\nAdaptive electrical matching: An adjustable load resistance is connected in series\nwith the TE sub-module, allowing fine-tuning of its IV characteristics. This dynamic\nadjustment ensures that the TE module’s operating current closely tracks that of the PV\nmodule, enabling efficient and synchronized power delivery to the external load or\nenergy storage component.\n4. Is the light absorption range of the OSC/PSC fully compatible with the thermal\nresponse characteristics of the TE module? Are there unutilized spectral regions\nresulting in wasted energy?\nReply: We sincerely thank the reviewer for this important question regarding spectral\ncompatibility and energy utilization within the PV-TE hybrid system.\nAccording to the absorption spectra (Supplementary Fig. 5), the active layer\nPM6:L8-BO in the OSC exhibits strong absorption across 300-900 nm, with\npronounced peaks between 600 and 850 nm. The perovskite film efficiently absorbs\nlight up to 760 nm, followed by a sharp decline. In contrast, the PCM thermal\nconducting layer shows good absorption capacity from 400 to 2000 nm, well beyond\nthe absorption ranges of both the OSC and PSC. For PV-TE hybrid system, the PV\ndevices mainly absorb the UV-Vis light region (< 800 nm) to achieve photoelectric\nconversion. The photons in the infrared region (800-2000 nm), which is not absorbed\nby PV devices, can be effectively absorbed by the PCM thermal conducting layer on\ntop of the TE device and converted into thermal energy. The thermal energy is\nsubsequently converted into electrical energy via the Seebeck effect, thereby enhancing\nthe utilization of the solar spectrum and improving the efficiency of the PV-TE hybrid\nsystem.\nThese findings demonstrate the spectral complementarity between the PV and TE\ncomponents, demonstrating good spectral compatibility between the OSC/PSC and the\nTE module for efficient solar energy harvesting.\nLaboratory), solar radiation at Earth’s surface consists of approximately 52-55%\ninfrared, 42-43% visible, and 3-5% ultraviolet light. According to Supplementary Fig.\n5, the PV layer and PCM thermal conducting layer exhibit complementary absorption\ncharacteristics across the solar spectrum. Solar cell active layers and PCM thermal\nconducting layer can efficiently absorb the solar light of 400-2000 nm. It is suggested\nthat the vast majority of solar energy is absorbed by the PV-TE hybrid system, and the\nwasted energy constitutes a very small proportion.\nTo address this comment, the following text and figures have been revised in the\nrevised Main text and Supplementary Information.\nMain text, Page 7, lines 157-164:\n“AFM images of the OSC and PSC films reveal smooth surface topography. GIWAXS\nanalysis of the OSC indicates well-defined molecular packing and orientation, while\nXRD patterns of the PSC confirm the formation of a well-crystallized perovskite phase\n(Supplementary Figs. 3-4). UV-vis absorption spectra demonstrate the spectral\ncomplementarity between the PV and TE components for efficient solar energy\nharvesting (Supplementary Fig. 5). These characterizations support the reproducibility\nof device fabrication and provide a solid physical foundation for the PV-TE hybrid\nsystem.”\nSupplementary Information, Page 60:\nSupplementary Fig. 5. UV-vis absorption spectra of (a) PM6:L8-BO, (b) the\nperovskite film, and (c) the phase-change thermal interface material (PCM) used to\nconnect the TE module to the solar cell.\n6\na\n)1-mn\n2-m\nW(\nnoitaidarri\nlartcepS\n1\n1\n1\n0\n0\n0\n0\n.8\n.5\n.2\n.9\n.6\n.3\n.0\n(3-5% )\n4 0\nV isib le\n(42-43% )\n0 8 0\nW\n0\na v e\n1 2 0\nle n\nA M\nIn frared\n(52-55% )\n0 1 6 0\ng th (n m\n1\n0\n.5\n)\nG\n0 0\nlo b\n0\n9 0\n7 5\n6 0 4 5\n3 0 1 5\n04\na l\n2 4\n0 0\n0 0\n8 0 0 1 2 0 0 1 6 0 0 2 0 0 0\n)%\n( e c n a b\nro\ns b A\n1.0\n0.8\n0.6\n0.4\n0.2\n0.0\n400 600 800 1000\nA (% )= 1 - R\nW\n(%\nav\n) - T (%\ne le n g\n)\nth (n m )\n).u\n.a\n( e c n a\nb ro\ns b A\n1.0\n0.8\n0.6\n0.4\n0.2\n0.0\n400 600 800 1000\nA (% )= 1 - R\nW\n(%\nav\n) - T (%\ne le n g\n)\nth (n m )\n).u\n.a\n( e c n a\nb ro\ns b A\nP M 6:L 8B O\nW a v e le n g th (n m )\n4\n3\n2\n1\n0\n600 700 800 900\n).u\n.a\n( e c n a b\nro\ns b A\na b\nW a v e le n g th (n\nP ero\nm )\nvskite\nc\nAccording to the absorption spectra above, the active layer PM6:L8-BO in the OSC\nexhibits strong absorption across 300-900 nm, with pronounced peaks between 600 and\n850 nm (Supplementary Fig. 5a). The perovskite film efficiently absorbs light up to\n760 nm, followed by a sharp decline (Supplementary Fig. 5b). In contrast, the PCM\nthermal conducting layer shows good absorption capacity from 400 to 2000 nm\n(Supplementary Fig. 5c), well beyond the absorption ranges of both the OSC and PSC.\nFor the PV-TE hybrid system, the PV devices mainly absorb the UV-Vis light region\n(< 800 nm) to achieve photoelectric conversion. The photons in the infrared region\n(800-2000 nm), which is not absorbed by PV devices, can be effectively absorbed by\nthe PCM thermal conducting layer on top of the TE device and converted into thermal\nenergy. The thermal energy is subsequently converted into electrical energy via the\nSeebeck effect, thereby enhancing the utilization of the solar spectrum and improving\nthe efficiency of the PV-TE hybrid system.\nThese findings demonstrate the spectral complementarity between the PV and TE\ncomponents. The unabsorbed long-wavelength photons pass through the PV layer and\nare subsequently absorbed by the PCM, where they contribute to thermal energy\nbuildup. This heat drives a temperature gradient across the TE module, enabling\nconversion of otherwise unused spectral energy into electrical output via the Seebeck\neffect.\n5. Is the unit power cost of the hybrid system competitive compared to a single PV or\nTE system? Are there cost estimates for commercialization on the ground?\nReply: We greatly appreciate the reviewer for this comment. There have been relevant\nreports on the cost assessment of the levelized cost of electricity (LCOE) of\nphotovoltaic and thermoelectric power generation.\nWe compared the levelized cost of electricity (LCOE) of photovoltaic and\nthermoelectric devices according to the latest literature reports. For traditional PVs, the\naverage LCOE is about $ 0.03~0.091 per kWh (Nat. Commun. 16, 2127 (2025); Nano-\nMicro Lett. 17, 219 (2025)). The emerging OSCs and PSCs have relatively high LCOE\nof $ 0.06~0.2 per kWh (J. Electron. Mater. 54, 3801 (2025)) and $ 0.03~0.22 per kWh\n(Nano-Micro Lett. 17, 219 (2025); Energy Environ. Sci.16, 421 (2023)), respectively.\nCompared with the PVs above, TE devices have higher average LCOE of about\n$ 0.171~0.251 per kWh (Energy Convers. Manage. 2020, 205, 112376; Sustain. Energy\nTechn. 2025, 78, 104338).\nAbout the cost estimation of the PV-TE hybrid system for commercialization on the\nground, we are currently unable to provide an accurate assessment result due to the\ncomplex and diverse cost composition (Supplementary Note 10). Whereas, for major\nfields such as aerospace and aviation, the performance of the materials, components,\nand devices is of the utmost importance, so their cost can be disregarded to a certain\nextent.\nTo address this comment, we have added a detailed discussion in the revised Main\ntext and Supplementary Information.\n“It is important to note that there are still some engineering challenges that must be\naddressed to enable practical employment of our PV-TE hybrid systems. These include\nthe stability limitations of OSCs and PSCs, large-area fabrication, practical integration\nof TE modules, and dynamic fluctuations in real-world environments (Supplementary\nNote 9). Cost consideration also remains a potential issue (Supplementary Note 10).”\nSupplementary Information, Page 53:\nSupplementary Note 10. Discussion on the cost estimation of the PV-TE hybrid\nsystem.\nHere, we compared the levelized cost of electricity (LCOE) of photovoltaic and\nthermoelectric devices according to the latest literature reports. For traditional PVs, the\naverage LCOE is about $ 0.03~0.091 per kWhS35, S36. The emerging OSCs and PSCs\nhave relatively high LCOE of $ 0.06~0.2 per kWhS37 and $ 0.03~0.22 per kWhS36, S38,\nrespectively. Compared with the PVs above, TE devices have higher average LCOE of\nabout $ 0.171~0.251 per kWh S39, S40.\nDevice types Levelized cost of electricity References\nTraditional PVs $ 0.03~0.091 per kWh S35, S36\nOSCs $ 0.06~0.2 per kWh S37\nPSCs $ 0.03~0.22 per kWh S36, S38\nTE device $ 0.171~0.251 per kWh S39, S40\nFor PV-TE hybrid systems, the increase in the integration and complexity of PV and\nTE systems leads to a rise in overall costs. In addition, the cost of the TE system may\naccount for a relatively high proportion in hybrid systems, while the efficiency of the\nTE system is relatively low, which will significantly increase costs. About the cost\nestimation of the PV-TE hybrid system for commercialization on the ground, we are\ncurrently unable to provide an accurate assessment result due to the complex and\ndiverse cost composition. In addition to the respective costs of PV and TE devices, the\nsystem integration cost is also an important component. This includes the coupling\ndesign of PV and TE systems, control circuits, installation, and commissioning etc. This\ncost increases as the complexity of the PV and TE hybrid system rises. A PV and TE\nhybrid system requires the maintenance of both PV and TE components simultaneously,\nand its operation and maintenance costs may be higher than those of a single system.\nTherefore, it is hard to give an accurate cost estimation of the PV-TE hybrid system for\ncommercialization on the ground. Whereas, for major fields such as aerospace and\naviation, the performance of the materials, components, and devices is of the utmost\nimportance, so their cost can be disregarded to a certain extent.\nS35. Wang, Y., et al. Global spatiotemporal optimization of photovoltaic and wind\npower to achieve the Paris Agreement targets. Nat. Commun. 16, 2127 (2025).\nS36. Liu, Y. et al. Cost effectivities analysis of perovskite solar cells: will it outperform\n8\ncrystalline silicon ones? Nano-Micro Lett. 17, 219 (2025).\nS37. Bjuggren, J. M. et al. Determining the cost of organic photovoltaic material and\nits impact on the levelized cost of electricity. J. Electron. Mater. 54, 3801 (2025).\nS38. Bastiani, M. D. et al. The levelized cost of electricity from perovskite\nphotovoltaics. Energy Environ. Sci.16, 421 (2023).\nS39. Araiz, M., et al. Prospects of waste-heat recovery from a real industry using\nthermoelectric generators: Economic and power output analysis. Energy Convers.\nManage. 205, 112376 (2020).\nS40. Alegría, P., et al. 400 W facility of geothermal thermoelectric generators from hot\ndry rocks on the Canary Islands. Sustain. Energy Techn. 78, 104338 (2025).\n6. How does the hybrid system achieve to maintain efficient output under variable light\nor temperature conditions (e.g., cloudy days or alternating day and night)?\nReply: We greatly appreciate the reviewer’s insightful comment regarding the efficient\nperformance of our PV-TE hybrid system under fluctuating environmental conditions.\nUnder overcast skies or at night, the solar irradiance drops significantly, and the PV\ncell produces negligible electrical or thermal output. As a result, it no longer serves as\na viable heat source for the TE module. If the TE module continues to generate even a\nsmall voltage from residual temperature differences, this voltage may act as a reverse\nbias across the PV cell, increasing the risk of device degradation. Our system design\ndoes not accommodate operation under such conditions, which we acknowledge as a\nlimitation.\nNonetheless, several strategies have been proposed in the literature to extend PV-TE\nhybrid operation into low-irradiance periods:\nIntegration of phase-change energy storage materials with the PV-TE hybrid system,\nallowing thermal energy collected during the day to be released at night, sustaining\nelectric generation across day-night cycles (Energy Convers. Manage. 2024, 321,\n119086).\nNocturnal energy harvesting can be achieved using a thermoelectric generator that\nexploits the temperature gradient established by radiative cooling of the PV cell,\nwherein the cell becomes cooler than the environmental temperature and drives a\nthermoelectric current (Appl. Phys. Lett. 2022, 120, 143901).\nTo address this comment, we have added a related discussion in the revised Main text.\nMain text, Page 18, lines 440-444:\n“Tailored thermal storage and cooling strategies, including the use of phase-change\nmaterials for heat storage59, passive and radiative approaches60, and seawater heat sinks,\ncould be developed to support efficient operation across diverse application scenarios\nand dynamic environments.”\n59. Wei, W., et al. A continuous 24-hour power generated PV-TEG-PCM hybrid system\nenabled by solar diurnal photovoltaic/thermal conversion and nocturnal sky\nradiative cooling. Energy Convers. Manage. 321, 119086 (2024).\n9\n60. Assawaworrarit, S., Omair, Z. & Fan, S. Nighttime electric power generation at a\ndensity of 50 mW/m2 via radiative cooling of a photovoltaic cell. Appl. Phys. Lett.\n120, 143901 (2022).\n7. At the end, the author discusses in detail some interesting potential future application\nscenarios (e.g., oceans, space), how should one go over to these extreme environments\nfrom the realities of current applications? Have similar simple studies been done?\nReply: We greatly appreciate the reviewer for this comment. The PV-TE hybrid\nsystems hold significant application potential in extreme environments such as oceans\nand outer space. To enable their deployment under such conditions, improving the\nstability and durability of the PV-TE hybrid systems is paramount.\nThere is extensive research on the application of photovoltaic/thermoelectric\ntechnology in space and ocean environments, which provides theoretical guidance and\ntechnical support for the application design and optimization strategies of PV-TE\nhybrid systems in space and ocean environments.\nTo address this comment, we have added a detailed discussion in the revised Main\ntext and Supplementary Information.\nMain text, Page 17, lines 429-433:\n“Thus, the greater potential demonstrated in this work indicates that PV-TE hybrid\nsystems might be much more competitive than previously thought for many possible\napplications and even to support human activities in ocean and space environments in\nthe future (Supplementary Note 8)”\nSupplementary Information, Page 50:\nSupplementary Note 8. How to achieve practical applications of PV-TE hybrid system\nin space and ocean?\nIn space applications, it is essential to broaden the operational temperature range of\nboth PV and TE devices to withstand extreme temperature fluctuations from -200 ℃ to\n150 ℃. Moreover, the space environment contains many high-energy ions and radiation,\nnecessitating surface modifications of the PV-TE hybrid system to enhance its\nresistance to electron, proton, and ultraviolet irradiation.\nWhen applied to the ocean surface, such as integrating the hybrid system on a marine\nbuoy, the marine climate factors must be considered. Proper encapsulation techniques\nare needed to prevent high salt mist corrosion, strong wave impacts, and the infiltration\nof humidity and water vapor. Surface treatments for the PV-TE hybrid systems are also\nnecessary to prevent the attachment of marine organisms and maintain good\nphotovoltaic stability. Only by addressing these factors can PV-TE hybrid systems be\nsuccessfully applied in the extreme environments above.\nThere is extensive research on the application of photovoltaic technology in space\nand ocean environmentsS29-31, which provides theoretical guidance and technical\nsupport for the application design and optimization strategies of photovoltaic\n10\ntechnology in space and ocean environments.\nRadioisotope thermoelectric generators (RTGs) generate electrical power for\nspacecraft by converting heat from the natural radioactive decay of plutonium-238,\ntypically in the form of plutonium oxide. The large temperature gradient between the\nhot radioactive fuel and the cold environment of space is applied across the\nthermoelectric module to produce electricity. RTGs are among the most reliable and\nviable power sources for lunar surface operations, deep space exploration, and remote\noff-grid applications.\nAs for PV-TE hybrid systems, there have been some preliminary studies on their\nperformance in extreme environments. For example, the temperature at the bottom of\nthe PV-TE hybrid systems was controlled using an ice-water mixture to simulate the\nlow-temperature environment of the ocean, enabling simultaneous solar and\nthermoelectric energy harvestingS32. Additionally, the hybrid system's performance\nunder ultra-high light intensity was studied through concentration effectsS33-34, which\nprovides valuable guidance for the research and application of the hybrid systems in\nspace.\nS29. Cardinaletti, I., et al. Organic and perovskite solar cells for space applications. Sol.\nEnergy Mat. Sol. C. 182, 121-127 (2018).\nS30. Tu, Y. et al. Perovskite solar cells for space applications: progress and\nchallenges. Adv. Mater. 33, 2006545 (2021).\nS31. Verduci, R., et al. Solar energy in space applications: review and technology\nperspectives. Adv. Energy Mater. 12, 2200125 (2025).\nS32. Liu, Z., et al. Novel integration of carbon counter electrode based perovskite\nsolar cell with thermoelectric generator for efficient solar energy conversion.\nNano Energy 38, 457-466 (2017).\nS33. Zhang, J., Xuan, Y. & Yang, L. Performance estimation of photovoltaic-\nthermoelectric hybrid systems. Energy 78, 895-903 (2014).\nS34. Guo, J., & Huai, X. Maximizing electric power through spectral-splitting\nphotovoltaic-thermoelectric hybrid system integrated with radiative cooling. Adv.\nSci. 10, 2206575 (2023).\n8. Perovskite solar cells, while efficient, are prone to degradation. Did the authors\nobserve any performance decay in the hybrid system under prolonged operation?\nReply: We sincerely thank the reviewer for highlighting the issue of long-term stability\nin perovskite solar cells. During the evaluation of the PSC-TE hybrid systems, we\nindeed observed an abrupt decline in the performance of the perovskite solar cell.\n11\na b\n0\n1.0\ny\n2m )\nc n e 0.8 T80 c /A −10\nic m\niffe\nd\n0.6 y\ntis\n(\n−20\ne n\nz ila\nm\nroN\n0\n0\n.\n.\n4\n0 0 0 . . .\nt\n0 1 2\na\n8 6 4\nn\nc c c\nd\nm m m\nal\n2 2 2\no\nP P P\nn\nS S S\ne\nC C C\nP\n- - -\nS\nT T T\nC\nE E E\ns\n( ( ( n n n = = = m m m = = = 2 4 6 , , , k k k = = = 6 6 6 ) ) ) V V V T T T E E E ( ( ( a a a v v v g g g ) ) ) = = = 0 0 1 .5 . . 9 4 2 6 0 V V V\ne D\ntn\ne r r u C −30 V JV TE ( c a u v r g v ) e = o 1 f V PSC-TE\n0.0 −40\n0 24 48 72 96 120 144 0.0 0.5 1.0 1.5 2.0 2.5 3.0\nTime (h) Voltage (V)\nFigure a. Stability measurements of PSC-TE hybrid systems under continuous LED\nlight illumination (AM1.5G) in ambient air (20 - 30 °C, 40% - 60% RH). Figure b. J-V\ncurve of the PSC-TE hybrid system showing reverse-bias breakdown.\nAs shown in the Figure a, compared to standalone PSCs, the PSC-TE hybrid systems\nexhibited improved stability during the initial 48 hours due to the ability of TE module\nto harvest heat and provide passive cooling. However, with extended operation time,\nthe hybrid system showed faster degradation and a significant drop in efficiency.\nBesides, perovskite solar cells exhibited breakdown when connected to thermoelectric\nmodules providing a voltage of 1 V. A sudden increase in current beyond the\nbreakdown voltage suggests electric-field-driven instability in the perovskite solar cell\nunder hybrid operation (Figure b). The likelihood of such failure increased with higher\nthermoelectric voltages.\nInterpretation of result:\nUnder open-circuit conditions, the electromotive force generated by the\nthermoelectric module is applied across the photovoltaic cell, placing it under a\ncontinuous forward bias.\nIn addition, the J-V scanning setup inherently introduces a reverse bias to the PV cell\nat low scan voltages, due to the voltage contribution from the TE module. During J-V\ncharacterization of the PV-TE hybrid system, the scan range is typically set from 0 to\n𝑉 , where the applied voltage 𝑉 is distributed across both the PV and TE\n𝑠𝑐𝑎𝑛 𝑚𝑎𝑥 𝑠𝑐𝑎𝑛\nmodules according to:\n0 ≤ 𝑉 = 𝑉 +𝑉 ≤ 𝑉\n𝑠𝑐𝑎𝑛 𝑃𝑉 𝑇𝐸 𝑠𝑐𝑎𝑛 𝑚𝑎𝑥\n𝑉 = 𝑉 −𝑉\n𝑃𝑉 𝑠𝑐𝑎𝑛 𝑇𝐸\nSince the TE module maintains a stable output voltage at constant temperature, the\neffective voltage across the PV cell when 𝑉 = 0 becomes:\n𝑠𝑐𝑎𝑛\n𝑉 = 0−𝑉\n𝑃𝑉 𝑇𝐸\nThis means the PV cell is subjected to a high reverse bias equal in magnitude to the\nthermoelectric voltage.\nPerovskite solar cells are especially sensitive to such high bias because it accelerates\nion migration, promotes metal-contact diffusion, and can trigger avalanche breakdown\n12\n(Nature Energy 2024, 9,1264-1274). Consequently, bias-induced failure emerges as the\ndominant degradation pathway in PSC-TE hybrid systems.\n9. Solution processing is attractive for manufacturability, but the TE module’s cost and\nintegration challenges should be discussed.\nReply: We greatly appreciate the reviewer for this comment regarding TE module’s\ncost and integration challenges.\nSolution processing is attractive for solar cell manufacturing due to its low cost,\nprocess simplicity, high material utilization, compatibility with flexible substrates, and\nscalability for large-area production. For TE modules, the manufacturing process is also\nquite mature, although their cost is relatively high. According to the latest literature\nreports, the average levelized cost of electricity (LCOE) for TE module is about\n$0.171~0.251 per kWh, as discussed in Supplementary Note 10.\nAbout the integration of TE modules, it is essential to ensure that the electrical\nresistance of each TE module is the same to avoid uneven current distribution.\nAdditionally, the thermal expansion coefficients of the TE materials and the substrate\nor encapsulation materials must be carefully considered.\nAccording to the suggestion of the reviewer, we have added some related discussion\nin the revised Main text and Supplementary Note 11.\nMain text, Page 18, lines 444-447:\n“The low-cost solution processing of OSCs and PSCs, combined with the mature\nsintering and cutting techniques used in TE module fabrication (Supplementary Note\n11), might offer a promising route toward the large-scale practical deployment of PV-\nTE hybrid systems.”\nSupplementary Information, Pages 54-55:\nSupplementary Note 11. Discussion on integration challenge of TE modules.\nAmong thermoelectric materials, bismuth telluride (Bi Te )-based compounds are\n2 3\nthe most commercially mature and cost-effective, with reasonably good thermoelectric\nperformance near room temperature. The manufacturing process for Bi Te -based TE\n2 3\nmodules is well established, however, the overall module cost remains relatively high\ndue to material processing and packaging requirements (Supplementary Note 10).\nIntegration challenges of the TE module:\nFor TE sub-modules, large-area operation often suffers from inhomogeneous thermal\ngradients, which reduce effective power output. Electrical mismatch may result from\nlocal variations in parameters such as the Seebeck coefficient, electrical conductivity,\nand thermal conductivity.\nIn addition, mismatches in thermal expansion coefficients between TE materials and\nencapsulation or substrate layers must be carefully managed to avoid thermally induced\nmechanical stress. Such stress, especially under thermal cycling, can lead to\nmicrocracks or interfacial delamination, ultimately compromising long-term device\n13\nreliability.\nThe mechanical assembly of TE legs, particularly the uniformity of solder joints and\nquality of interfacial bonding, plays a critical role in ensuring thermal and electrical\nreliability. Poor contact quality can cause localized heating and uneven current\ndistribution.\nFurthermore, in practical applications, it is often challenging to match the thermal\nresistances of the heat source and heat sink with that of the TE module, which can\nsignificantly degrade energy conversion efficiency.\nTo address these challenges, several strategies can be employed:\nMaterial uniformity: Optimizing composition and sintering temperature ensures\nconsistent thermoelectric properties.\nThermal expansion matching: Selecting materials with closely matched thermal\nexpansion coefficients minimizes mechanical stress during temperature fluctuations.\nThermal homogenization: High-conductivity interface materials help distribute heat\nevenly across the module.\nReliable interconnects: Using high-quality solder and precise bonding techniques\nensures robust electrical and thermal contacts.\nThermal impedance matching: Ensuring proper alignment between the thermal\nresistance of the TE module and that of the heat source/cold source is essential for\nmaximizing conversion efficiency and achieving optimal system performance.\n10. How do these efficiencies compare to other waste-heat recovery methods (e.g.,\ntandem PV or radiative cooling)? A discussion would contextualize the advancement.\nReply: We greatly appreciate the reviewer for this comment. Compared to other waste-\nheat recovery methods, these efficiencies (43.16% and 50.28%) of PV-TE hybrid\nsystems in our work all show great advantages and competitiveness, compared with the\ntandem PVs, PV-TE hybrid systems with radiative cooling, and concentrated PV-TE\nhybrid systems.\nAccording to the suggestion of the reviewer, we have added some related discussion\nin the revised Main text and Supplementary Information.\nMain text, Page 16, lines 392-395:\n“Our PV-TE hybrid systems also show great advantages and competitiveness,\ncompared with reported tandem PV devices, PV-TE hybrid systems with radiative\ncooling, and concentrated PV-TE hybrid systems (Supplementary Table 5).”\nSupplementary Information, Pages 87-88:\nSupplementary Table 5. Comparison of our PV-TE hybrid systems and reported\ntandem PVs, PV-TE systems with radiative cooling, and concentrated PV-TE systems.\nPSC-TE hybrid system 50.28% This work\nOSC-TE hybrid system 43.16% This work\nGaInP / (GalnAs/GaAsP) / GaInAs tandem cells\n39.46% S51\nTriple-junction solar cells\nPerovskite/silicon tandem cells 34.58% S52\nPerovskite tandem cells 30.1% S53\nConcentrated PV-TE hybrid system 40% S54\nConcentrated PV-TE hybrid system 50% S55\nPV-TE hybrid system with radiative cooling 34.2% S34\nSolar energy losses primarily arise from the thermalization of high-energy ultraviolet\nphotons and the transmission of long-wavelength infrared photons, which cannot be\neffectively utilized. Supplementary Table 5 provides a comparison of representative\nstudies aimed at mitigating spectral thermal losses through strategies such as tandem\nstructures, concentrated designs, and radiative cooling.\nFor tandem PVs, the multilayer solar cell achieves an optical series connection of\ndifferent bandgap semiconductor materials to form a multi-layer PN junction structure.\nEach layer of material absorbs photons of different wavelengths in the solar spectrum.\nThis layered absorption mechanism enables the multilayer cell to cover a wider range\nof the solar spectrum, reduce the waste of photon energy, and thus break through the\nconversion efficiency limit of single-junction cells. The efficiency of tandem PVs can\ncurrently reach 30%-40% S51-53. For concentrated PV-TE hybrid system, an optical\nconcentrator system was used for concentrating solar light energy in a specific area with\na superhigh light intensity, and the predicted efficiency is expected to exceed 40%S54.\nIf more advanced concentrated PV cells and TE devices are used, the concentrated PV-\nTE hybrid system has a potential to have more than 50% efficiency S55.\nFor PV-TE hybrid system with radiative cooling, the PV device is the hot side and\nthe TE device is the cold side, and a radiative cooling layer was attached on top of TE\ndevice for emitting heat to outer space with a temperature of 3 K through the\n“atmospheric window” (wavelength 𝜆 ranges from 8 to 13 μm), so as to achieve a larger\ntemperature difference across the TE device by reducing the cold side temperature of\naddition, the TE device can also generate electricity at night owing to the radiative\ncooling, the total equivalent efficiency of the PV-TE with radiative cooling is further\nincreased up to 34.2% S34.\nS34. Guo, J., & Huai, X. Maximizing Electric Power through Spectral-Splitting\nPhotovoltaic-Thermoelectric Hybrid System Integrated with Radiative Cooling.\nAdv. Sci. 10, 2206575 (2023).\nS51. France, R. M. et al. Triple-junction solar cells with 39.5% terrestrial and 34.2%\nspace efficiency enabled by thick quantum well superlattices. Joule 6, 1121-1135\n(2022).\nS52. Jia, L. et al. Efficient perovskite/silicon tandem with asymmetric self-assembly\nmolecule. Nature (2025). https://doi.org/10.1038/s41586-025-09333-z\nS53. Wei, J. et al. Present status of and future opportunities for all-perovskite tandem\nphotovoltaics. Nat. Energy 10, 681-696 (2025).\nS54. Rezania, A. & Rosendahl, L.A. Feasibility and parametric evaluation of hybrid\nconcentrated photovoltaic-thermoelectric system. Appl. Energy 187, 380-389\n(2017).\nS55. Beeri, O. et al. Hybrid photovoltaic-thermoelectric system for concentrated solar\nenergy conversion: Experimental realization and modeling. J. Appl. Phys. 118, 11\n(2015).\n11. The model assumes ideal conditions—what are the expected efficiency losses in\noutdoor, variable-illumination environments?\nReply: We greatly appreciate the reviewer for this comment regarding the efficiency\nlosses of the PV-TE hybrid systems in outdoor, variable-illumination environments.\nIn response to the reviewers’ suggestion, we conducted additional outdoor tests under\nadequate sunlight on a typical summer day in June. The OSC-TE hybrid system\ndemonstrated efficiencies ranging from 27.13% to 37.62% (43.16% under ideal\nlaboratory conditions), while the PSC-TE system exhibited efficiencies between 32.78%\nand 44.45% (50.28% in the lab). Compared to these ideal values, the absolute efficiency\nlosses under outdoor conditions ranged from approximately 5% to 17%. The\nexperimental results have been added to the revised Main text and Supplementary\nInformation.\nMain text Page 17, lines 416-424:\n“To estimate the power generation potential of the PV-TE hybrid system in realistic\nmarine environments, we monitored solar irradiance and environmental temperature\nover a representative clear-sky day in June. Based on these measurements and using the\naverage surface seawater temperature near Tianjin in June (22 ℃, Bohai Bay), we\nevaluated the performance of the system (Supplementary Fig. 27). The OSC-TE and\nPSC-TE hybrid systems exhibited efficiencies of 27.13%-37.62% and 32.78%-44.45%,\n16\nrespectively, corresponding to absolute efficiency losses of approximately 5%-17%\nrelative to their ideal maximum values.”\nSupplementary Information, Page 82-83:\nSupplementary Fig. 27\nSupplementary Fig. 27. (a) Solar irradiance and environmental temperature recorded\nover a representative clear-sky day in June. J-V curves of the optimized OSC-TE hybrid\nsystem at 12:00 (b) and 17:00 (c), and the optimized PSC-TE hybrid system at 12:00\n(d) and 17:00 (e).\nAs shown in Supplementary Fig. 27a, the solar irradiance during a typical summer\nday from 08:00 to 17:00 reached its peak at noon (1 sun) and decreased to 0.761 sun by\n17:00 in the late afternoon. The environmental temperature remained around 40 °C\nthroughout the day.\n17\n0\n-5\n-1 0\n-1 5\n-2 0\n-2 5\n-3 0\n-3 50\n.0 0 .5 1 .0 1 .5 2 .0 2 .5 3 .0\n)\n2\nm\nc\n/A\nm\n(\ny\nt is\nn\ne\nD\nt\nne r r u\nC\n0\n-8\n-1 6\n-2 4\n-3 2\n-4 0 -4 8\n0 .0 0 .5 1 .0 1 .5 2 .0 2 .5 3 .0\n1 7 :0 0\nIrra d ia n c e = 0 .7 6 1 s\nT = 3 8 C° environm ent T = 2 2 C° ocean surface\nV o lt\nu\na\nn\ng e\nP S C\nE ffic ie n c y : 1 8 P S C -T E E ffic ie n c y : 3 2\n( V )\n.0 .7 2 8 % %\n)\n2\nm\nc\n/A\nm\n(\ny\nt is\nn\ne\nD\nt\nne r r u\nC\n0\n-8\n-1 6\n-2 4\n-3 2\n-4 0\n-4 8\n0 .0\na\n1\n1 )nu\n1 s(\ne 0 cna\n0\nida\n0 rrI\n0\n0\n1 2 :0 0\nIrra d ia n c e = 1 s u n T = 4 0 C° environm ent T = 2 2 C° ocean surface\n0 .5 1 .0\nV o lt a\n1 2 :0 0\nIrra d ia n c e = 1 s u n\nT = 4 0 C° environm ent T = 2 2 C° ocean surface\nV o lt a\n.4\n.2\n.0\n.8\n.6\n.4\n.2\n.0\n1g\ng\nIrra d ia n c\nT e m p e ra\n8 :0 0 1 0 :0 0 1 2T\nO S C E ffic ie n c y : 1 7 .7 0 % O S C -T E E ffic ie n c y : 3 7 .6 2 %\n.5 2 .0 2 .5\ne ( V )\nP S C\nE ffic ie n c y : 2 4 .3 4 % P S C -T E E ffic ie n c y : 4 4 .4 5 %\ne ( V )\netu\nre\n:0 0\nim e\n1 4 :0\nc\ne\n0\n)2mc/Am(\nytisneD\ntnerruC\n1 6 :0 0\n0\n-5\n-1 0\n-1 5\n-2 0\n-2 5 -3 0\n-3 50\n.0\n5 0\n) 4 0 C°(\ne\n3 0 rutare\n2 0\npme\n1 0 T\n0\n1 8 :0 0\n1 7 :0 0\nIrra d ia n c e = 0 .7 6 1 s T = 3 8 C° environm ent T = 2 2 C° ocean surface\n0 .5 1 .0\nV o lt\nu\na\nn\n1g .5e\nO S C E ffic ie n c y O S C E ffic ie n c y\n2 .0\n( V )\n: 1 3 -T E : 2 7 .0 1 % .1 3 %\n2 .5\nThe PV-TE hybrid system is applicable to marine environments, where seawater\ncooling provides the temperature gradient required for thermoelectric generation. To\nsimulate such conditions, the average surface seawater temperature in June near Tianjin\n(22 °C, Bohai Bay) was used as the cold-side reference.\nUnder these conditions, the OSC-TE hybrid system exhibited efficiencies of 27.13%-37.62%,\nas shown in Supplementary Figs. 27b, c, while the PSC-TE hybrid system showed\nefficiencies of 32.78% - 44.45%, as shown in Supplementary Figs. 27d, e.\nThese correspond to absolute efficiency losses of approximately 5%-17% relative to\nthe ideal maximum values under laboratory conditions. These results highlight the\nstrong application potential of PV-TE hybrid systems in practical marine environments.\n(Remarks to the Author):\nThis work designs a photovoltaic-thermoelectric (PV-TE) hybrid strategy with\npromising simulated and experimental performance, reporting significant system\nefficiencies improvement exceeding 50% from. The work demonstrates satisfactory\ntheoretical grounding and potential for high-impact contributions. However, to meet the\npublication standards of Nature Communications, the study still requires substantial\nimprovement in several aspects.\nReply: Thank you very much for the positive comment.\n1. The manuscript does not include any morphological (e.g., SEM or AFM),\nstructural (e.g., XRD), or optical (e.g., UV-vis absorption or Tauc plot) characterizations for the\nPSC or OSC layers used. Given that the device performance strongly depends on the\nactive layer's quality and crystallinity, I recommend adding representative\ncharacterizations to ensure reproducibility and provide a solid physical basis for the\nreported performance. Moreover, it might help identify any potential interface reactions,\nvoids, or delamination affecting durability.\nReply: We are grateful to the reviewer for highlighting the importance of rigorous\nmaterial characterization. We have added AFM and GIWAXS data for the organic\nphotovoltaic (OSC) device, as well as AFM and XRD data for the perovskite solar cell\n(PSC). In addition, we included UV-vis absorption spectra for the OSC, PSC, and the\nthermal interface layer. The characterization results have been added to the revised\nMain text and Supplementary information.\nMain text Page 7, lines 157-164:\n“AFM images of the OSC and PSC films reveal smooth surface topography. GIWAXS\nanalysis of the OSC indicates well-defined molecular packing and orientation, while\nXRD patterns of the PSC confirm the formation of a well-crystallized perovskite phase\n(Supplementary Figs. 3-4). UV-vis absorption spectra demonstrate the spectral\ncomplementarity between the PV and TE components for efficient solar energy\nharvesting (Supplementary Fig. 5). These characterizations support the reproducibility\nof device fabrication and provide a solid physical foundation for the PV-TE hybrid\nsystem.”\nSupplementary Information:\nPages 58, Supplementary Fig. 3 (AFM and GIWAXS for OSC)\nPages 59, Supplementary Fig. 4 (AFM and XRD for PSC)\nPages 60, Supplementary Fig. 5 (UV-vis absorption spectra)\nimages of PM6:L8-BO. The donor and acceptor domains were marked with blue and\nred colors, respectively. (d) 2D GIWAXS patterns of PM6:L8-BO (e) Out-of-plane\n(OOP) and in-plane (IP) line-cut profiles from GIWAXS data of PM6:L8-BO.\nThe detailed parameters of the corresponding 2D GIWAXS.\nq represents the scattering vector corresponding to the maximum intensity peak. [a]\nCalculated from the equation: d-spacing =2π/q. [b] Obtained from the Scherrer equation:\nCCL= 2πK/FWHM, where FWHM is the full-width at half-maximum and K is a shape\nfactor (K= 0.9 here).\nFor the PM6:L8-BO blend films, Supplementary Fig. 3a shows a relatively smooth\nsurface morphology. In Supplementary Figs. 3b and 3c, distinct donor-acceptor (D/A)\ninterpenetrating fibrillar networks can be clearly observed. GIWAXS analysis\n(Supplementary Figs. 3d and 3e) reveals a pronounced (100) diffraction peak in the in-\nplane (IP) direction and a strong (010) peak in the out-of-plane (OOP) direction,\nindicating a predominant face-on molecular packing orientation. The blend films also\nexhibit a short π-π stacking distance and relatively large crystalline coherence length\n(CCL), indicating favorable molecular packing and improved structural orderS41.\nS41. Cao, X. et al. O, S, and N bridged atoms screening on 2D conjugated central units\n)mμ(\nhtgneL\nM\nM\na\n2 .0\n1 .0\n0\n0\na te\n6 : L\nria ls\n8 -B\nd\nO\n1 .0\nL e n g th\nq\n-1 (Å )\n1 .7 3\n(μ m )\n2 .0\n(0 1 0\n[a] d(Å\n)\n3 .6 3\n3\n)m\n0 n(\n-3\n) D\nb\n2 .0\n)mμ(\nh 1 .0 tgneL\n0\n0\niffra c tio n P\nF W H M\n-1 (Å )\n0 .2 4\ne a k\n1 .0\nL e n g th (μ\ne\n).u.a(\nytisnetnI\n[b] C C L\n(Å )\n2 3 .8 2\nm )\n(1 0 0 )\n0\n5\n).g\n0 ed(\n-5\n2 .0\nIP\nO O P\n.5\nq-1\n(Å )\n0 .3 0\nc\n2 .0\n)mμ(\nh 1 .0 tgneL\n0\n1 .0 1\n-1 q (Å )\n(1 0 0 ) D\n[a] d(Å\n)\n2 0 .9 0\n1 .0\nL e n g th (μ\n(0 1 0 )\n.5 2 .0\niffra c tio n P e a\nF W H M\n-1 (Å )\n0 .0 7 9\nm\nk\n)\n7\n3 2\n)V\n0 m(\n-3 2\n.0\n[b] C L\n(Å )\n1 .8 2\nof high‐performance acceptors. Adv. Mater. 37, 2503131 (2025).\nSupplementary Fig. 4. (a) AFM height images and (b) XRD pattern of perovskite film.\nFor the perovskite film, the AFM image (Supplementary Fig. 4a) shows a compact\ngrain structure with good surface coverage, while the XRD pattern (Supplementary Fig.\n4b) confirms the presence of a well-crystallized perovskite phaseS5.\nS5. Gao, Y. et al. Controlled Nucleation and Oriented Crystallization of\nMethylammonium-Free Perovskites via In Situ Generated 2D Perovskite Phases. Adv\nMater 36, e2405921 (2024).\nSupplementary Fig. 5. UV-vis absorption spectra of (a) PM6:L8-BO, (b) the\nperovskite film, and (c) the phase-change thermal interface material (PCM) used to\nconnect the TE module to the solar cell.\nAccording to the absorption spectra above, the active layer PM6:L8-BO in the OSC\nexhibits strong absorption across 300-900 nm, with pronounced peaks between 600 and\n850 nm (Supplementary Fig. 5a). The perovskite film efficiently absorbs light up to\n760 nm, followed by a sharp decline (Supplementary Fig. 5b). In contrast, the PCM\nthermal conducting layer shows good absorption capacity from 400 to 2000 nm\n(Supplementary Fig. 5c), well beyond the absorption ranges of both the OSC and PSC.\nFor the PV-TE hybrid system, the PV devices mainly absorb the UV-vis light region (<\n800 nm) to achieve photoelectric conversion. The photons in the infrared region (800-\n2000 nm), which is not absorbed by PV devices, can be effectively absorbed by the\nPCM thermal conducting layer on top of the TE device and converted into thermal\nenergy. The thermal energy is subsequently converted into electrical energy via the\n21\na\n5 0 0 n m\nmn\n021\nmn\n021-\nb\n).u.a(\nytisnetnI\n1 0 2 02\nq ( d e\n3g 0r\ne e )\n4 0 5 0\na b c\n4\n).u\n.a\n( e c n a\n1\n0\n0\n.\n.\n.\n0\n8\n.a\n( e c n a b\n3\n)%\n( e c n a b\n9\n7\n6 4\n0\n5\n0 5\nA(%)=1- R(%) - T(%)\nb ro\ns b A\n0\n0\n.\n.\n4\n2\nro\ns b A 1\nro\ns b A 3 1 0 5\n0.0 0 0\n400 600 800 1000 600 700 800 900 400 800 1200 1600 2000\nWavelength (nm) Wavelength (nm) Wavelength (nm)\nSeebeck effect, thereby enhancing the utilization of the solar spectrum and improving\nthe efficiency of the PV-TE hybrid system.\nThese findings demonstrate the spectral complementarity between the PV and TE\ncomponents. The unabsorbed long-wavelength photons pass through the PV layer and\nare subsequently absorbed by the PCM, where they contribute to thermal energy\nbuildup. This heat drives a temperature gradient across the TE module, enabling\nconversion of otherwise unused spectral energy into electrical output via the Seebeck\neffect.\n2. Although the manuscript presents a coupled thermal-electrical simulation and\nefficiency model, it lacks any thermal imaging data (e.g., IR thermography) that could\nexperimentally confirm the heat redistribution or cooling effect of the TE modules.\nI recommend including infrared thermal images or temperature maps of both PSC/OSC\nand PSC-TE/OCS-TE systems before and after illumination, under different cooling\nconditions, to visually support the proposed thermal synergy.\nReply: We greatly appreciate the reviewer’s suggestion to strengthen the experimental\nvalidation of the thermal‑management mechanism with direct infrared (IR) evidence.\nWe employed representative OSC-TE (0.04 cm2) and PSC-TE (0.08 cm2) hybrid\nsystems to investigate thermal distribution using infrared imaging. The following text\nand figures have been added to the revised Main text and Supplementary information.\nMain text Pages 11-12, lines 277-280:\n“Infrared thermal imaging of the PV-TE hybrid systems illustrates the thermal energy\nharvesting and the cooling effect provided by the TE modules, highlighting the thermal\nsynergy between the PV and TE components (Supplementary Fig. 11).”\nSupplementary information, Page 66:\nSupplementary Fig. 11\n22\na b\nn = m = 1 n = m = 2\nk = 6 k = 6\n0.04cm2mask\nOSC 0.04 cm2mask 0.08 cm2mask\nPSC\nTE module\n1 cm\nc\nS\nN\nt\no\na n\nsu\nd\nn\nal\nl\no\nig\nn\nh\ne\nt\nOSC\n0\n℃ S\nU\nt\nn\na\nd\nn\ne\nd\nr\na\ns\nlo\nu\nn\nn\ne\nli g\nO\nh\nS\nt\nC\n6 4\n℃ O\nUn\nS\nd\nC\ne\n-\nr\nT E\nsunlight 6 3\n℃\n3 34.2 ℃\n26.8 ℃\n45.8 ℃\n℃ ℃\n5 2 5 2 1.9 ℃ 0\n℃\nd\nS\nN\nt\no\na n\nsu\nd\nn\nal\nl\no\nig\nn\nh\ne\nt\nPSC\n0 3\n℃ S\nU\nt\nn\na\nd\nn\ne\nd\nr\na\ns\nlo\nu\nn\nn\ne\nli g\nP\nh\nS\nt\nC\n8 4\n℃ 31.4 ℃ P\nU\nS\nnd\nC\ne\n-T\nr\nE\nsunlight 6 3\n℃\n27.1 ℃ 47.1 ℃\n℃ ℃\n5 2 5 2 0.8 ℃ 0\n℃\nSupplementary Fig. 11. Optical images of the OSC-TE hybrid system (a) and the PSC-\nTE hybrid system (b). (c) Surface temperature of the standalone OSC before and after\nAM1.5G sunlight illumination, and the temperature gradient map of the OSC-TE\nhybrid system under illumination. (d) Surface temperature of the standalone PSC before\nand after AM1.5G sunlight illumination, and the temperature gradient map of the PSC-\nTE hybrid system under illumination.\nSupplementary Figs. 11a and 11b show the optical images of the OSC-TE and PSC-\nTE hybrid systems. Under AM1.5G sunlight illumination, the surface temperature of\nthe standalone OSC increased to 45.8 °C (Supplementary Fig. 11c), while that of the\nstandalone PSC reached 47.1 °C (Supplementary Fig. 11d). Upon integration with the\nTE modules, the operating temperatures were reduced to 34.2 °C for the OSC and\n31.4 °C for the PSC. Temperature gradients were observed across the TE modules,\nconfirming effective heat redistribution, the cooling effect of thermoelectric integration,\nand the thermal synergy achieved within the PV-TE hybrid systems.\n3. While Supplementary Fig. 12 provides efficiency retention over 120 hours of\ncontinuous illumination, the system's robustness under repeated thermal cycling has not\nbeen evaluated. TE modules, especially in stacked configurations, suffer from interface\nfatigue and microcrack formation under such conditions. I recommend a thermal\ncycling test to evaluate long-term operational stability.\nstability tests. In response, we conducted thermal cycling stability tests on both the OSC\nand PSC devices, as well as the TE module, to evaluate potential degradation resulting\nfrom repeated temperature fluctuations. The experimental results have been added to\nthe revised Main text and Supplementary Information.\nMain text Page 13, lines 330-334:\n“Subsequently, the OSCs, PSCs, and TE module were subjected to rapid thermal\ncycling between -10 °C and 50 °C. As shown in Supplementary Fig. 17, after 100\nthermal cycles, the performance of the OSCs, PSCs, and TE module remained virtually\nunchanged, demonstrating excellent thermal stability.”\nSupplementary information, Page 72:\nSupplementary Fig. 17\n400\n350\n300\nTE Current\n200\n0 20 40 60 80 100\nThermal cycles from -10 to 50 °C\nSupplementary Fig. 17. Thermal cycling stability of OSCs and PSCs (a) and TE\nmodule (b). The rapid thermal cycle was executed by placing the devices in an\nenvironment at -10 °C, followed by transferring them to a hot plate set at 50 °C. Each\nstage lasted for 3 min to achieve thermal equilibrium.\nBoth the photovoltaic and thermoelectric components demonstrated excellent\nthermal durability. The OSC retained 99.65% of its initial power conversion efficiency,\nwhile the PSC retained 97.46% of its original performance. The output voltage and\ncurrent, tested under a 30 K temperature difference, remained nearly unchanged for 100\nthermal cycles.\n4. The TE modules used in the study involve multilayer stacking, yet the manuscript\ndoes not address the thermal uniformity or potential thermal stress effects. It is\nsuggested to include infrared mapping or simulation results to assess potential thermal\nhotspots or mechanical instability in the multilayer TE stack.\nReply: we sincerely thank the reviewer for raising this important point regarding\nhotspots and thermal stress. To mitigate potential hotspot formation, we implemented\nthe following strategies:\n24\n)Vm(\neludom\nET\nfo\negatloV\n20\n16\n12\n8\n4\n)Am(\neludom\nET\nfo\ntnerruC\n)%(\nycneiciffE\n2\n2\n2\n1\n1\n8\n4\n0\n6\n2\nO\nP\ne\nS C\nS C\n2 0\nr m a l c y\n4c 0le\nfr o m\n6 0\n-1 0\nP S C\nO S C\n8 0\nto 5\n: 9 7 .4 6 %\n: 9 9 .6 5 %\n1 0\n0\na b\n(1) Thermal equalization using copper plates: Both the top and bottom surfaces of\neach thermoelectric (TE) module were soldered to 5 × 5 mm copper plates, which serve\nas thermal spreaders to ensure more uniform heat distribution.\n(2) High-conductivity thermal interface materials: A phase-change thermal interface\nmaterial (Honeywell PCM 7950) was applied between adjacent TE modules, as well as\nbetween the PV device and the TE module. This material has a high thermal\nconductivity (8.5 W m⁻¹ K⁻¹) and provides strong physical adhesion, acting as both a\nthermal connector and a mechanical buffer. The phase-change nature of the material\nalso helps alleviate thermal stress through localized heat absorption and redistribution.\nThermal management in the TE module. (a) Optical image of the thermoelectric\nassembly. (b) Simulated temperature gradient showing uniform heat distribution,\nvalidating the effectiveness of the hotspot mitigation strategy.\nThermal stress and mechanical instability:\nOur thermal cycling test (See response to Comment 3) showed no visible\ndelamination or performance degradation, indicating the absence of mechanical\ninstability in the multilayer TE stack. This also supports the reliability of our hotspot\nmitigation strategy, which involves the use of copper plates and PCM to ensure uniform\nheat distribution.\n5. The flexible OSC-TE system powering a pulse sensor is promising, but it lacks\nsufficient data showing mechanical durability. Thus, I suggest providing bending cycle\ntests with performance retention metrics. Besides, visual documentation of the device\nunder mechanical deformation and diverse weather conditions would be beneficial.\nReply: We sincerely thank the reviewer for this valuable suggestion. In response, we\nhave added bending performance data for the flexible PV-TE module and updated\noptical images of the system under various weather conditions and mechanical\ndeformations. The experimental results have been added to the revised Main text and\nSupplementary Information.\nMain text Pages 16-17, lines 405-407:\n“Furthermore, the flexible PV TE hybrid system retained stable performance after 1,000\nbending cycles, highlighting its promise for integration into wearable power\napplications (Supplementary Fig. 26).”\n25\na\nC\nT\nu\nE\np la te\nP C M\nC\nC\nu\nu\nb\np\nP\np\nla\nC\nla\nte\nM\nte\nT E\n（ ℃ ）\nSupplementary information, Page 81:\nSupplementary Fig. 16\nSupplementary Fig. 26. (a) Optical image of the bending test for the flexible PV-TE\nhybrid system. (b) Efficiency retention rate of the flexible PV-TE hybrid system under\ndifferent bending cycles.\nThe bending radius is limited by the electrode configuration of the flexible\nthermoelectric module (Supplementary Fig. 26a). After 1,000 bending cycles, the\nflexible PV-TE hybrid system retains excellent performance, corresponding to the\nefficiency retention rate of ~ 98% (Supplementary Fig. 26b).\nFor visual documentation under mechanical deformation and varying environmental\nconditions, we have included both the optical images of the flexible PV-TE hybrid\nsystem under bending and the wearable demonstration images captured under sunlight\nand integrated onto clothing in the updated Fig. 4a of the main text.\nRevised Fig. 4a (the right image)\n6. The TE module’s output contribution is discussed, but no standalone I-V or P-V\ncharacterization is presented. This leaves the hybrid device’s energy distribution unclear.\nThis might further cause the unclear separation of PV and TE contributions. I would\nrecommend to respectively give PV-only, TE-only, and PV-TE combined performance\nunder identical conditions.\nReply: We sincerely appreciate the valuable suggestion provided by the reviewer and\nfully agree that the individual power contributions are essential for energy‑balance\n26\na\na\nO S C -T E\nO S C -T E\nR e p la\nb\nc\nb\n)%(metsys\nfo\nycneiciffE\ne\n)%(\nycneiciffe\nfo\netar\nnoitneteR\nd\n1 51 2\n1 41 1\n1 31 0\n1 29\n1 18\n1 07\nb y\n0\n0\n0\n0\n0\n0\nb\n0 0\nF le x\ne n\nib\nd in g p e rfo rm a n c e\n2 0 0 4 0 0 2 0 0 4 0 0\nB e n d in N u m b e r o\nle O S C -T E\no\n6\ngf\nf O S C -T E\n0 0 8 6 0 0\nc y c le b e n d\n9 8 .0\n0 08 0 0\nss\n7\n1\n9\n%\n0\n8\n01\n.0 7\n00 0\n%\n0\nanalysis.\nWe measured the J-V and P-V characteristics of the TE module under the optimal\nperformance conditions of the PV-TE hybrid system at 298 K and 313 K, respectively.\nAdditionally, we plotted the power contribution distribution of the PV and TE\ncomponents under different temperatures. The corresponding data have been added to\nthe revised Main text and Supplementary Information.\nMain text Page 13, lines 320-324:\n“Under optimal coupling conditions, Figs. 2e and 2f show that the total output power\nof the integrated PV-TE hybrid system is nearly equal to the sum of the maximum\noutput powers of the PV and TE modules when operating independently. This\ndemonstrates that the system achieves lossless energy coupling between the PV and TE\ncomponents.”\nFig. 2. c,d, Experimental champion J-V curves of OSC-TE (c) and PSC-TE (d) hybrid\nsystems (n = m = 6, k = 6, corresponding to the system area of 0.24 cm2. e, J-V and P-V\ncharacteristics of the TE module in the optimized OSC-TE and PSC-TE hybrid systems\nat 298 K. f, Power contribution of the PV and TE components in the optimized hybrid\nsystems at 298 K.\nMain text, Pages 15-16, lines 378-381:\n“Under optimal coupling conditions, the total output power of the integrated PV-TE\nhybrid system is also nearly equal to the sum of the maximum output powers of the PV\nand TE modules when operating independently at 313 K (Supplementary Fig. 21).”\n27\nc\n)2mc/Am(\nytisned\ntnerruC\ne\n)Am(\ntnerruC\n0\n− 5\n− 1 0\n− 1 5\n− 2 0\n− 2 5\n− 3 0\n0\n1 2\n9\n6\n3\natm\nO S C\nη : 1 8 .0 4 %\nO S C -T E\nη : 3 4 .8 5 %\nn = m = 6\nk = 6\nV o c J s c F F\nC o n d itio n η (% ) 2 (V ) (m A /c m ) (% )\nO S C 0 .8 8 2 6 .7 4 7 6 .9 0 1 8 .0 4\nO S C -T E 2 .2 8 2 7 .0 0 5 6 .5 9 3 4 .8 5\n.0 0 .5 1 .0 1 .5 2 .0\nV o lta g e (V )\nIV c u rv e o f T E m o d u le T : 2 9 8 K atm\nP V c u rv e o f T E m o d u le\n.0 0 .3 0 .6 0 .9 1 .2 1 V o lta g e (V )\n5\n4\n3\n2\n1\n0\n.5\nPower\n(mW)\nd\n)2mc/Am(\nytisned\ntnerruC\nf\n)Wm(\nxamP\n0\n− 5\n− 1 0\n− 1 5\n− 2 0\n− 2 5\n− 3 0\n0\n1 0\n8\n6\n4\n2\natm\nP S C\nη : 2 5 .2 3 %\nP S C -T E\nη : 4 2 .0 3 %\nV o c J s c\nC o n d itio n 2 (V ) (m A /c m )\nP S C 1 .2 0 2 5 .5 7\nP S C -T E 2 .6 1 2 5 .6 5\n.0 0 .5 1 .0 1 .5\nV o lta g e (V )\nT = 2 9 8 K atm\nO S C -b a s e d s y s te m\nP S C -b a s e d s y s te m\nP V d e v ic e P V -T T E m o d u le (O S C /P S C ) s y s te\nn =\nk =\nF F\n(% )\n8 2 .0 5\n6 3 .2 1\n2 .0\nEm\nm6\nP\n= 6\nη (% )\n2 5 .2 3\n4 2 .0 3\n2 .5\n+ P P V TE\nSupplementary Information, Page 76:\nSupplementary Fig. 21. (a) J-V and P-V characteristics of the TE module in the\noptimized OSC-TE and PSC-TE hybrid systems at 313K. (b) Power contribution of the\nPV and TE components in the optimized hybrid systems at 313 K.\n7. The abstract, introduction, and discussion could be better structured to emphasize the\nscientific problem, core innovation, and key findings. Some repetitive phrases and\ngeneral expressions could be refined for clarity and impact. A thorough language\nediting is advised to meet the requirements of the journal.\nReply: We sincerely thank the reviewer for this suggestion. In response, we have\ncarefully revised the abstract, introduction, and discussion sections to better highlight\nthe scientific motivation, core innovation, and major findings of our work. Redundant\nexpressions have been removed, and the language has been polished throughout the\nmanuscript for improved clarity and precision. We believe these revisions significantly\nenhance the overall structure and readability of the manuscript.\n8. The claimed >50% efficiency is remarkable but needs enhanced clarification for\nreaders: is it electrical efficiency concerning solar input only? Does it account for cold\nsource energy consumption? The lack of this information might confuse or mislead\nauthors at first sight. please, at least clarify this in the Abstract. Moreover, please define\nyour efficiency metrics precisely and compare with recent hybrid PV-TE systems in\nterms of materials, architecture, and performance.\nReply: We greatly appreciate the reviewer for this valuable comment. The efficiency\nof PV-TE hybrid systems is defined as the ratio of output electrical energy to the input\nsolar energy. The efficiency calculation follows a widely adopted method in the field,\nensuring consistency and comparability across studies. In this approach, the portion of\n28\na\n)Am(\ntnerruC\n1 2\n8\n4\n00\n.0 0 .3 0 .6\nV o\n0 .9\nlt a g\nIV c u rve s o f T E m o d u le\nP V c u rve o f T E m o d u le\n1 .2 1 .5 1 .8 2\ne ( V )\n8\n6\n4\n2\n0\n.1\n)Wm(\nrewoP\nb\n)Wm(\nxamP\n1\n1\n6\n2\n8\n4\nO S C -b a s e d s y s te m\nP S C -b a s e d s y s te m\nP V d e v ic e T E m o d u le\n(O S C /P S C )\nP V -T E\nh y b rid\ns y s te m\n(c a\nP\n+ P\nPV TE\nla te d s u m )\nenvironmental thermal energy converted into electricity by the TE module is not\nincluded in the input energy. In addition, the energy input from the cold side is excluded,\nas in many practical scenarios such as seawater cooling, the cold side can be treated as\nan unlimited thermal reservoir. Ultimately, the primary objective remains to maximize\nthe conversion efficiency of solar energy, which is the key performance indicator of the\nsystem.\nAccording to the reviewer’s suggestion, we have clarified this point in Abstract,\nIntroduction and Results and Discussions of the revised manuscript.\nMain text Abstract Page 2, lines 24-25:\n“The efficiency of PV-TE hybrid systems is the ratio of output electrical energy to input\nsolar energy.”\nMain text, Introduction Page 4, lines 80-82:\n“It is noted that the efficiency of PV-TE hybrid systems is the ratio of output electrical\nenergy to input solar energy (without considering the contributions from environmental\nthermal energy and cooling sources).”\nMain text Results and Discussions Page 12, lines 290-293:\n“It is noted that the efficiency calculation (Equation S13, Supplementary Note 2.2 in\nSupplementary Information) follows the widely used method in this field22,24,32,35. In\nthis approach, some environmental thermal energy converted into electricity by the TE\nmodule is not included in the total energy input.”\n22. Xu, L. et al. Efficient perovskite photovoltaic-thermoelectric hybrid device. Adv.\nEnergy Mater. 8, 1702937 (2018).\n24. Liu, W., Sun, S. & Zhu, X. Organic photovoltaics integrated with thermoelectric\ngenerator achieving low critical temperature difference and efficient energy\nconversion. Adv. Funct. Mater. 32, 2109410 (2022).\n32. Zhou, Y. et al. A highly-efficient concentrated perovskite solar cell-thermoelectric\ngenerator tandem system. J. Energy Chem. 59, 730-735 (2021).\n35. Zhou, Y. et al. Perovskite solar cell-thermoelectric tandem system with a high\nefficiency of over 23%. Mater. Today Energy 12, 363-370 (2019).\nIn addition, according to the reviewer’s suggestion, we have added related\ncomparison with recent representative hybrid PV-TE systems in terms of materials,\narchitecture, and performance in Supplementary Table 4 in the revised Supplementary\nInformation, corresponding to the Fig. 3e in the Main text.\nSupplementary Information, Pages 85-86:\nSupplementary Table 4\nrepresentative PV-TE hybrid systems.\nMaterials and devices Architecture and working conditions Efficiency Ref.\n⚫ Perovskite solar cell ➢ Tandem PV-TE structure\n(ITO/SnO /FAPbI /Spiro- ➢ Effective area: 0.28 cm2\n2 3\nThis\nOMeTAD/MoOx/Ag) ➢ Layer number of TE modules: 6 50.28%\nwork\n◼ Thermoelectric device ➢ Under AM 1.5 G solar illumination\n(BiTe-based) ➢ Cold side temperature: 273 K\n⚫ Organic solar cell ➢ Tandem PV-TE structure\n(ITO/ZnO/NMA/PM6:L8- ➢ Effective area: 0.28 cm2\nThis\nBO/MoOx/Ag) ➢ Layer number of TE modules: 6 43.16%\nwork\n◼ Thermoelectric device ➢ Under AM 1.5 G solar illumination\n(BiTe-based) ➢ Cold side temperature: 273 K\n➢ Tandem PV-TE structure with a\nsolar selective absorber\n⚫ Si-based solar cell ➢ Copper plate as thermal\n◼ Thermoelectric device concentrator and conductor 23% S43\n(Commercial) ➢ Under AM 1.5 G solar illumination\n➢ Cold side temperature: cooling\nwater (~ 20 ℃)\n➢ Tandem PV-TE structure with a light\n⚫ Si-based solar cell concentrator\n◼ Thermoelectric device ➢ Indirect PV-TE coupling 16.8% S44\n(Commercial) ➢ Under AM 1.5 G solar illumination\n➢ Cold side: cooling water\n➢ Tandem PV-TE structure\n⚫ Si-based solar cell ➢ Resistance matching for lossless\n◼ Thermoelectric device power coupling 16.3% S45\n(Commercial) ➢ Under AM 1.5 G solar illumination\n➢ Cold side: Al heat sink\n30\n➢ Tandem PV-TE structure with a light\n⚫ Perovskite solar cell\nconcentrator\n(CH NH Pb(I Br ) )\n3 3 0.95 0.05 3\n➢ Layer number of TE modules: 1 23.32% S46\n◼ Thermoelectric device\n➢ Under AM 1.5 G solar illumination\n(Commercial)\n➢ Cold side: cooling water\n➢\n➢\n➢ Tandem PV-TE structure with a light\n⚫ Perovskite solar cell\nconcentrator\n(CH NH PbI )\n3 3 3\n➢ Layer number of TE modules: 1 23.2% S47\n◼ Thermoelectric device\n➢ Under AM 1.5 G solar illumination\n(Commercial)\n➢ Cold side temperature: 273 K\n➢ Tandem PV-TE structure\n⚫ Perovskite solar cell ➢ Carbon electrode as infrared light\n(CH NH PbI )\n3 3 3\nabsorption layer for the TEs\n22.2% S32\n◼ Thermoelectric device ➢ Layer number of TE modules: 1\n(Commercial) ➢ Under AM 1.5 G solar illumination\n➢ Cold side: 273 K (ice bath)\n⚫ Organic solar cell ➢ Tandem PV-TE structure\n(ITO/PEDOT:PSS/PM6:A ➢ Effective area: 0.06 cm2\nQ /PDINN/Al) ➢ Layer number of TE modules: 1 18.2% S48\nx-2\n◼ Thermoelectric device ➢ Under AM 1.5 G solar illumination\n(TGP-651 from Micropelt) ➢ Cold side temperature: 293 K\n➢ Tandem PV-TE structure\n⚫ Organic solar cell\n➢ Layer number of TE modules: 1\n◼ Thermoelectric device 14.2% S49\n➢ Under AM 1.5 G solar illumination\n(Commercial)\n➢ Cold side: room temperature\n➢ Tandem PV-TE structure\n⚫ Organic solar cell\n➢ Effective area: 0.12 cm2\n(P3HT/IV60BA)\n➢ Layer number of TE modules: 1 11.24% S50\n◼ Thermoelectric device\n➢ Under AM 1.5 G solar illumination\n(BiTe-based)\nCold side temperature: 293 K\ncell with thermoelectric generator for efficient solar energy conversion. Nano\nEnergy 38, 457-466 (2017).\nS43. Zhu, W., Deng, Y., Wang, Y., Shen, S. & Gulfam, R. High-performance\nphotovoltaic-thermoelectric hybrid power generation system with optimized\nthermal management. Energy 100, 91-101 (2016).\nS44. Hajji, M. et al. Photovoltaic and thermoelectric indirect coupling for maximum\nsolar energy exploitation. Energy Convers. Manage. 136, 184-191 (2017).\nS45. Park, K.-T. et al. Lossless hybridization between photovoltaic and thermoelectric\ndevices. Sci. Rep. 3, 2123 (2013).\nS46. Zhou, Y. et al. A highly-efficient concentrated perovskite solar cell-thermoelectric\ngenerator tandem system. J. Energy Chem. 59, 730-735 (2021).\nS47. Zhou, Y. et al. Perovskite solar cell-thermoelectric tandem system with a high\nefficiency of over 23%. Mater. Today Energy 12, 363-370 (2019).\nS48. Liu, W., Sun, S. & Zhu, X. Organic photovoltaics integrated with thermoelectric\ngenerator achieving low critical temperature difference and efficient energy\nconversion. Adv. Funct. Mater. 32, 2109410 (2022).\nS49. Liu, C., Cui, Y. J., Wang, K. F. & Wang, B. L. Bending strength evaluation and\npower generation performance optimization of a curved photovoltaic-\nthermoelectric hybrid device. Compos. Struct. 321, 117297 (2023).\nS50. Zhang, Y. et al. Integrated energy-harvesting system by combining the advantages\nof polymer solar cells and thermoelectric devices. J. Phys. Chem. C 117, 24685-\n24691 (2013).\n9. The PV modelling uses the traditional single diode model rather than the double or\ntriple diode model. The TE component is modeled as a linear voltage source with series\nresistance. Please justify these modelling approximations.\nReply: We are grateful to the reviewer for prompting us to clarify the modeling\napproach adopted for both the PV and TE submodules. Below, we summarize the\nphysical rationale, the expected accuracy range, and the experimental validations that\nsupport the adequacy of our modeling framework.\nLiterature support:\nDiode model of solar cells\na b\nV V\nc\nV\nmodel, and (c) triple-diode model.\nComparison of PV Diode Models\nModel Single-Diode Model Double-Diode Model Triple-Diode Model\nPhysical Diffusion current Diffusion + Diffusion + recombination +\nMechanism recombination current leakage current\nTypical 5 7 9\nParameters (IL ID n Rs Rsh) (IL ID1 n1 ID2 n2 Rs Rsh) (IL ID1 n1 ID2 n2 ID3 n3 Rs Rsh)\nTypical AM1.5G, Low light, Defect-rich materials,\nApplications room temperature shaded conditions, extreme conditions\nlow-voltage regime\nModel 1.6% (Ref. S1) 0.3% (Ref. S1) 0.08% (Ref. S1)\nError 2.2% (Ref. S2) ＜0.2% (Ref. S3) ＜0.15%( Ref. S4)\nAdvantages Simple and fast to Improved accuracy in Capable of isolating trap-assisted\ncompute low-voltage regions transport, higher accuracy\nLimitations Inaccurate under Moderate complexity Overparameterization, correlation\nshading or weak and fitting time between parameters, high fitting\nillumination complexity\nS1. Elazab, O. S., Hasanien, H. M., Elgendy, M. A. & Abdeen, A. M. Parameters\nestimation of single‐ and multiple‐diode photovoltaic model using whale\noptimisation algorithm. IET Renewable Power Generation 12, 1755-1761(2018).\nS2. Betti, T., Kristić, A., Marasović, I. & Pekić, V. Accuracy of simscape solar cell\nblock for modeling a partially shaded photovoltaic module. Energies 17, 10 (2024).\nS3. Ćalasan, M., Jovanović, D., Rubežić, V., Mujović, S. & Đukanović, S. Estimation\nof single-diode and two-diode solar cell parameters by using a chaotic optimization\napproach. Energies 12, 21 (2019).\nS4. El Marghichi, M. & Dangoury, S. Electrical parameters identification for three\ndiodes photovoltaic based on the manta ray foraging optimization with dynamic\nfitness distance balance. Optik 296, 171548 (2024).\nWe evaluated our solar cells under AM1.5G and room temperature, operating near\nthe maximum power point (MPP). Given that carrier transport in our devices is\ndominated by diffusion and recombination, the single-diode model is sufficient to\nreproduce the J-V characteristics within experimental error.\nLinear Model of Thermoelectric Devices\nNear room temperature, bismuth telluride-based thermoelectric (TE) modules exhibit\nnearly linear behavior. It is widely accepted that their performance can be modeled as\na linear voltage source with series resistance (Journal of Power Sources 1998, 73, 193-\n198).\nFigure (a) shows excellent agreement between the experimental and fitted J-V curves\nof the solar cell. In Figure (b), the TE module exhibits a linear J-V response at room\ntemperature. In Figure (c), we incorporated the experimentally obtained TE voltage and\nresistance values into our model, and the resulting J-V curve closely matches the\nmeasured J-V curve of the PV-TE hybrid system. This consistency confirms the\naccuracy of our modeling framework.\n10. Many material properties (e.g., thermal conductivity, Seebeck coefficient) are taken\nfrom the literature or datasheets provided by the supplier without assessing their impact\non simulation results. A sensitivity analysis on these critical parameters is strongly\nencouraged to ensure the robustness of efficiency predictions.\nReply: We sincerely thank the reviewer for highlighting the importance of verifying\nthe influence of material parameters on the simulation results.\nGiven the computational cost of our coupled PV-TE finite element model and the\nfact that the number of key input parameters is limited (Seebeck coefficient, thermal\nconductivity, electrical conductivity), we conducted a one-at-a-time (OAT) sensitivity\nanalysis across a ±20% range for each variable (Ref. S1).\nThe figure (a) shows the relative variation in system efficiency Δη (%) as a function\nof ±20% variation in each parameter, with the baseline (0%) corresponding to the\nnominal parameter set. The figure (b) summarizes the maximum efficiency variation\nwithin this range, serving as a proxy for the sensitivity of each parameter.\n34\na\n)2mc/Am(\nytisneD\ntnerruC\n−\n−\n−\n−\n−\n1 0\n1 5\n2 0\n2 5\n3 00\n.0\n1 .5\n1 .0\n0 .5\n0 .0\n-0 .5\n-1 .0\n-1 .5\ntandalone P V S im ulated JV curve\nE xperim ental JV curve\n0 .2 0 .4 0 .6\nV o lta g e (V )\n-1 0\n0 .8\n0\n1 .0\nb\n)Am(\ntnerruC\n1\n1\n1\n0\n2\n0\n8\n6\n4\n2\n00\n.0 0 .3\n2 0\nV\n0 .6\no lta g\nIV curves of TE m\nPV curve of TE m\n0 .9 1 .2\ne (V )\nodule\nodule\n1\n5\n4\n3\n2\n1\n0\n.5\n)Wm(\nrewoP\nc\n)2mc/Am(\nytisneD\ntnerruC\n0\n-5\n-1 0\n-1 5\n-2 0\n-2 5\n-3 00\n.0\nP V -TE hybrid system S im ulated JV curve\nE xperim ental JV curve\n0 .2 0 .4 0 .6 0 .8\nV o lta g e (V )\n1 .0 1 .2\n)\n%\n(\nη\nΔ\ne\nv\nit\na\nle\nR\na\n-2 0\nS\nT E\nP\ne e b e c k c o e ffic ie n t\nh e rm a l c o n d u c tiv ity le c tric a l c o n d u c tiv ity\na r a m e t e r v a r ia t io n ( % )\nb\nS e e b e c k\nc o e ffic ie n t\nT h e rm a l\nc o n d u c tiv ity\nE le c tric a l\nc o n d u c tiv ity\n0 .0\nΔ\n= 0 .6 4 % Δ η\n= 0 .2 1 % Δ η\n0 .5 1 .0\nu n d e r ± 2 0 % η %\nΔ\n1 .5\np a\n= 2 .6 3 % Δ η\n= η η (+ 2 0 % ) - η (-2\n2 .0 2 .5\nra m e te r v a ria tio\n0 %\nn\n)\n3 .0\nThe results indicate that system performance is particularly sensitive to the Seebeck\ncoefficient, whereas the effects of thermal conductivity and electrical conductivity are\ncomparatively moderate. These results demonstrate that predictions of our model are\nrobust to reasonable variation in material properties, and the adopted values from\nliterature fall within an acceptable range of uncertainty.\nRef. S1. Wang, X. et al. Global sensitivity analysis and optimization of multi-stage\nTEG based on random and fuzzy mixed input variables. Applied Thermal Engineering\n248, 123212 (2024).\n11. The study is conducted on small-scale laboratory devices, with no discussion on\nsystem integration challenges for commercially relevant large-module sizes. Issues\nsuch as thermal sink design, electrical load coupling, and thermal-electrical\nmanagement in real-world scenarios are not addressed. I suggest adding a paragraph\nthat considers practical implementation pathways and associated engineering\nchallenges.\nReply: We sincerely thank the reviewer for highlighting this important practical\nconsideration. According to the suggestion from the reviewer, we have added a\nparagraph that considers practical implementation pathways and associated engineering\nchallenges in the revised Main text.\nMain text, Page 17-18, lines 434-447:\n“It is important to note that there are still some engineering challenges that must be\naddressed to enable practical employment of our PV-TE hybrid systems. These include\nthe stability limitations of OSCs and PSCs, large-area fabrication, practical integration\nof TE modules, and dynamic fluctuations in real-world environments (Supplementary\nNote 9). Cost consideration also remains a potential issue (Supplementary Note 10).\nPossible strategies to overcome these issues might include such as material design and\ninterface engineering, for both the solar cell and TE units56-58. Tailored thermal storage\nand cooling strategies, including the use of phase-change materials for heat storage59,\npassive and radiative approaches60, and seawater heat sinks, could be developed to\nsupport efficient operation across diverse application scenarios and dynamic\nenvironments. The low-cost solution processing of OSCs and PSCs, combined with the\nmature sintering and cutting techniques used in TE module fabrication (Supplementary\nNote 11), might offer a promising route toward the large-scale practical deployment of\nPV-TE hybrid systems.”\n56. Li, C. et al. Organic solar cells with 21% efficiency enabled by a hybrid interfacial\nlayer with dual-component synergy. Nat. Mater. (2025)\nhttps://doi.org/10.1038/s41563-025-02305-8\n57. Bi, L. et al. Temperature-controlled vacuum quenching for perovskite solar modules\ntowards scalable production. Nat. Photon. (2025). https://doi.org/10.1038/s41566-\n025-01703-3\n35\n58. Liu, D. et al. Lattice plainification advances highly effective SnSe crystalline\nthermoelectrics. Science 380, 841-846 (2023).\n59. Wei, W. et al. A continuous 24-hour power generated PV-TEG-PCM hybrid system\nenabled by solar diurnal photovoltaic/thermal conversion and nocturnal sky\nradiative cooling. Energy Convers. Manage. 321, 119086 (2024).\n60. Assawaworrarit, S., Omair, Z. & Fan, S. Nighttime electric power generation at a\ndensity of 50 mW/m2 via radiative cooling of a photovoltaic cell. Appl. Phys. Lett.\n120, 143901 (2022).\n12. The manuscript lacks a dedicated section summarizing potential future directions,\nchallenges, and opportunities. The current conclusion section focuses on summarizing\nthe experimental results, the authors could more systematically discuss the focus of\nsubsequent research, material optimization strategies, or potential application\nexpansion. Also, please briefly conclude the shortcomings of this work.\nReply: We appreciate the reviewer’s suggestion to broaden the conclusion beyond a\nrecap of results. It should be noted that Comment 12 encompasses the content of\nComment 11 in a broad sense. Therefore, the response to Comment 11 is also part of\nComment 12.\nAccording to the suggestion from the reviewer, we have added some related\ndiscussion in the revised Main text.\nMain text, Page 17-18, lines 434-447:\n“It is important to note that there are still some engineering challenges that must be\naddressed to enable practical employment of our PV-TE hybrid systems. These include\nthe stability limitations of OSCs and PSCs, large-area fabrication, practical integration\nof TE modules, and dynamic fluctuations in real-world environments (Supplementary\nNote 9). Cost consideration also remains a potential issue (Supplementary Note 10).\nPossible strategies to overcome these issues might include such as material design and\ninterface engineering, for both the solar cell and TE units56-58. Tailored thermal storage\nand cooling strategies, including the use of phase-change materials for heat storage59,\npassive and radiative approaches60, and seawater heat sinks, could be developed to\nsupport efficient operation across diverse application scenarios and dynamic\nenvironments. The low-cost solution processing of OSCs and PSCs, combined with the\nmature sintering and cutting techniques used in TE module fabrication (Supplementary\nNote 11), might offer a promising route toward the large-scale practical deployment of\nPV-TE hybrid systems.”\nMain text Page 19, lines 474-480:\n“Although the results presented in this work demonstrate great potential for the\npractical application of PV-TE hybrid systems, further research remains necessary to\nadvance toward real-world applications. These efforts include the use of more advanced\nsolar cells and TE modules for improved performance, further studies on large-area\n36\ndevices and their integration, evaluations of operational stability at both the component\nand system levels, and exploration of performance under varied environmental and\noperational conditions. These aspects are currently being pursued in our group.”\n56. Li, C. et al. Organic solar cells with 21% efficiency enabled by a hybrid interfacial\nlayer with dual-component synergy. Nat. Mater. (2025)\nhttps://doi.org/10.1038/s41563-025-02305-8\n57. Bi, L. et al. Temperature-controlled vacuum quenching for perovskite solar modules\ntowards scalable production. Nat. Photon. (2025). https://doi.org/10.1038/s41566-\n025-01703-3\n58. Liu, D. et al. Lattice plainification advances highly effective SnSe crystalline\nthermoelectrics. Science 380, 841-846 (2023).\n59. Wei, W. et al. A continuous 24-hour power generated PV-TEG-PCM hybrid system\nenabled by solar diurnal photovoltaic/thermal conversion and nocturnal sky\nradiative cooling. Energy Convers. Manage. 321, 119086 (2024).\n60. Assawaworrarit, S., Omair, Z. & Fan, S. Nighttime electric power generation at a\ndensity of 50 mW/m2 via radiative cooling of a photovoltaic cell. Appl. Phys. Lett.\n120, 143901 (2022).\n37"}, {"round": 2, "reviewer_comments": {"reviewer_1": "The specific comments below are intended to assist the authors in further enhancing the rigor and persuasiveness of the paper.\n1.Regarding the efficiency of PV-TE hybrid systems mentioned as \"the ratio of output electrical energy to input solar energy (without considering the contributions from environmental thermal energy and cooling sources),\" what specific parameter does this ratio represent? Is its usage appropriate and reasonable? Is there a precedent or source for this comparison? Does this efficiency definition correspond to \"light-input-driven efficiency\" or \"system-level total energy efficiency\"? The authors are advised to clarify the theoretical basis and literature sources for this efficiency definition and to indicate whether it is widely adopted in hybrid systems to avoid confusion with terms such as \"photo-thermal hybrid efficiency,\" \"total system efficiency,\" or \"net energy efficiency.\" If this efficiency applies only under specific assumptions, its applicable scope should also be clearly stated in the main text.\n2.Regarding the statement \"a heat transfer model of the stacked PV-TE hybrid structure was first established,\" is the term \"first\" truly accurate? Have previous studies not employed such models? Please verify and clarify this claim by citing relevant literature and ensure the rigor and standardization of terminology.\n3.Although the proposed PT-TECM model is structurally complete, the supplementary materials lack the complete temperature-dependent curves or fitting expressions for key thermoelectric parameters (Seebeck coefficient, electrical conductivity, thermal conductivity). Additionally, the simulation does not account for interfacial thermal resistances from welding, bonding, and encapsulation layers commonly present in practical devices, which may significantly overestimate the achievable temperature difference and thermoelectric output. Similarly, information on the PV-TE contact interface is insufficient, which is crucial for heat transfer efficiency and reliability.\n4.The sensitivity of photo-thermal coupling to the solar incident angle has not been analyzed, which may affect conclusions about daily and seasonal scenarios. All lighting experiments in the article and supplementary materials were conducted at fixed angles. However, in practical applications, significant variations in solar altitude angles affect PV absorption, PV heat distribution, and the available heat for TE. Similarly, the efficiency of PV-TE thermal coupling under morning/evening light conditions may differ markedly from that at noon. It is recommended to supplement the analysis with incident angle sensitivity or provide experimental outputs under different solar altitude angles to enhance the comprehensiveness of system performance predictions.\n5.How does this study align with or deviate from reality? The authors should explicitly state the extent of deviation between model assumptions and real-world conditions in the supplementary materials and evaluate the potential efficiency errors or boundary effects caused by this deviation to clarify the applicability of the study's findings in practical deployment.\n6.The discussion on the thermal reliability and long-term operation of the system is insufficient. There is a lack of analysis regarding long-term thermal stress and interfacial fatigue behavior under actual working conditions (continuous illumination, loaded operation). For PV-TE systems operating over extended periods, factors such as aging of encapsulation materials, changes in electrode contact resistance, thermal fatigue of bonding layers, and microcracks induced by thermal cycling could significantly affect output stability.", "reviewer_2": "The authors have substantially addressed all major concerns raised in my previous review, both through additional experiments/analysis and by clarifying the scope and limitations of their claims. Remaining issues are minor and mainly relate to wording and further contextualization rather than fundamental flaws. I therefore recommend acceptance, possibly after minor polishing as follows:\n1) Please explicitly acknowledge the steady-state nature of PT-TECM analysis. Current wording may lead readers unfamiliar with thermal modelling to assume that transient effects are included. Please add a sentence in the text or Fig. 3 caption explicitly stating that “the PT-TECM analysis is based on steady-state thermal equilibrium and does not incorporate transient variations in irradiance, wind speed, or ambient temperature.”\n2) The revised Supplementary Note provides a realistic discussion of engineering challenges; however, the main-text description near Fig. 4 still reads aspirational. Authors can add one sentence indicating that “These scenarios remain conceptual, and real-world deployment will require corrosion-resistant encapsulation, mechanical durability, and long-term validation.”\n3) To avoid overgeneralization, authors need to clarify that the unfavorable LCOE pertains mainly to large-scale terrestrial installations, while special environments (e.g., in aerospace, offshore, or payload-limited environments) may prioritize power density over cost per watt. A brief sentence to this effect would improve clarity.\nOnce the minor textual refinements listed above are implemented, I believe the manuscript is suitable for publication.", "reviewer_3": "I co-reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co-review manuscripts."}, "author_response": "Replies to reviewers’ comments for Nature Communications\nNCOMMS-25-25787A\n(Text in blue is our replies)\nReviewer 1\n:\nThe author responded well to most of our inquiries; however, several critical issues\nstill need to be addressed before we can recommend publication in Nature\nCommunications.\nReply: Thank you very much for the positive comment. Please find below our detailed\nresponses and the corresponding revisions.\n1. In the supplementary long-term stability tests provided by the author, a decline in\nefficiency was observed. However, it remains uncertain whether their work\ndemonstrates a stability advantage. We recommend that the author include comparative\ncases to further illustrate this aspect.\nReply: Thank you very much for the valuable suggestion regarding stability. We\napologize for the confusion, and this issue has been re-addressed in the revised\nmanuscript as details below. Please also note that, additional experiments have been\nconducted to demonstrate the stability advantage of PV-TE hybrid systems.\nIn the original manuscript, we described that our PV-TE hybrid system exhibited a\nstability advantage compared with standalone PV. However, the efficiency of the PSC-\nTE hybrid system drops more rapidly than that of the standalone PSC, as shown in Fig.\nR1b (original Fig. S16b) below. We apologize for this confusion.\nThis issue arose because, during the previous stability testing, different bias voltages\nwere applied to the standalone PSC and the PSC in the integrated PSC-TE system, and\nthe significant impact of different bias on the PSC stability has been well documented\nR1, R2. Specifically, the previous stability of the standalone PSC was evaluated without\nany bias (0 V), while the PSCs in the PSC-TE systems were evaluated under three\nadditional biases all exceeding 0.5 V generated by the TE module (V = 0.52, 0.96,\nTE\nand 1.40 V, respectively). Note due to the existing temperature difference between the\ncold and hot sides in the integrated system, there is inevitably some bias from TE\nmodule applied on the PSC unit in the PSC-TE hybrid system. This bias voltage from\nTE module would significantly impact the stability of the PSC in the PSC-TE system,\nleading to a more rapid decline in efficiency relative to the standalone PSC. This is\nconsistent with the widely reported stability results for PSC, where higher bias causes\nsignificantly larger and quicker performance decline for PSCR1, R2.\nTo clarify this, we have carried out new stability experiments for both the standalone\nto the inevitable bias applied to the PSC unit in integrated PSC-TE system, to get better\ncomparative results under conditions as close as possible, the PSC unit was exposed to\ntwo lower TE bias (V = 0.10 V and V = 0.26 V) in the PSC-TE hybrid systems (to\nTE TE\nensure stable operation), and the standalone PSC was tested under a bias of 0 V a control.\nThe experimental results, as shown in the following Fig. R2b (as the Fig. S16b in the\nrevised SI), indicate that the PSC-TE hybrid system indeed demonstrates better stability\nunder these similar conditions (with a smaller bias voltage difference).\nThese new experiments and the related discussion have been updated in the revised\nSupplementary Information (Fig. S16). The Manuscript has also been revised\naccordingly.\nFig. R1 (original Fig. S16 in the previous version). Photostability measurements\n(following the ISOS-L-1 protocol) of OSC-TE hybrid systems (a) and PSC-TE hybrid\nsystems (b) with different areas, operated with the cold-side temperature maintained at\nFig. R2 (as the Fig. S16 in this revised SI). Photostability measurements (following\nthe ISOS-L-1 protocol) of OSC-TE (a) and PSC-TE (b) hybrid systems with an active\narea of 0.04 cm2, operated either with a metal heat sink or with the cold-side\ntemperature maintained at 273 K, compared with 0.04 cm2 standalone OSC and PSC\ndevices without cooling.\n2\na\n).u.a(\nycneiciffe\ndezilamroN\n1\n0\n0\n0\n0\n0\n1\n0\n0\n0\n0\n0\n.0\n.8\n.6\n.4\n.2\n.0\n.0\n.9\n.8\n.7\n.6\n.5\nT\n0\n0\n80\n0.08-0.32 cm\n2 0.08 cm O S 2 0.16 cm O S 2 0.24 cm O S 2 0.32 cm O S\n5 0\n4 8\nC -T E (n = m = 2, k = 6) V C -T E (n = m = 4, k = 6) V C -T E (n = m = 6, k = 6) V C -T E (n = m = 8, k = 6) V\n1 0 0 1 5 0 2 0 0\nT im e (h )\n9 6 1 4 4 1 9 2\n= 0.52 V TE = 0.96 V TE = 1.40 V TE = 1.88 V TE\n2 5 0 3 0 0\n2 4 0 2 8 8\nb\n).u.a(\nycneiciffe\ndezilamroN\n1\n0\n0\n0\n0\n0\n.0\n.8\n.6\n.4\n.2\n.0\nT\n0\n80\n2 0.08-0.24 cm S tan d alo n e P S C s 2 0.08 cm P S C -T E (n = m = 2, k = 6) V 2 0.16 cm P S C -T E (n = m = 4, k = 6) V 2 0.24 cm P S C -T E (n = m = 6, k = 6) V\n2 4 4 8 7 2 9 6\nT im e (h )\n= 0.52 V TE = 0.96 V TE = 1.40 V TE\n1 2 0 1 4 4\n).u\n.a\n(\ny c\nn\ne\nic\niffe\nd e z ila\nm r o N\nT 80\n0 .0 4 2 c m O S C a n d O S C -T E (n = m = 1 S ta n d a lo n e O S C\nO S C -T E - H e a ts in k V = 0 .1 0 V TE O S C -T E - 2 7 3 K V = 0 .2 6 V TE\nT im e (h )\n, k = 6 )\n1\n0\n0\n0\n0\n0\n.0\n.9\n.8\n.7\n.6\n.5\n0 2 4 4 8 7 2 9 6 1 2 0 1 4 4\n).u\n.a\n(\ny c\nn\ne\nic\niffe\nd e z ila\nm r o\nN\na b\n2 .0 4 c m P S C a n d P S C -T E (n = m = 1 S ta n d a lo n e P S C\nP S C -T E -H e a ts in k V = 0 .1 0 V TE P S C -T E -2 7 3 K V = 0 .2 6 V TE\nT im e ( h )\nk = 6 )\n2. Regarding key issues closely related to commercial prospects-such as cost,\ndegradation, and scalability-the author has only provided explanations. It is\nrecommended that the author conduct experimental validation to address at least one of\nthese aspects to confirm the potential of their work.\nReply: Thank you very much for your suggestion. Following the reviewer’s advice, an\nanalysis of the cost, degradation, and scalability of PV-TE hybrid system has been\nprovided to substantiate the commercial application potential of our work. The details\nare shown below.\nRegarding the issue of cost.\nThis is clearly one of the major issues if indeed the results of our study would be\napplied commercially. The fairest metric for comparison across energy technologies is\nthe levelized cost of energy (LCOE), which is widely used in the fieldR3, R4. Following\nthis method, we evaluated the LCOE of standalone PV (traditional PV, OSC, and PSC),\nTE module, and PV-TE hybrid systems. The detailed economic assessment has been\nadded to the revised Supplementary Information as Note S10. The Manuscript has also\nbeen revised accordingly. For convenience, the main results are summarized in\nTables R1- R3, as shown below.\nAlthough the cost estimate results (Tables R1 - R3) indicate that the PV-TE hybrid\nsystem currently exhibits a higher LCOE compared to standalone PV and TE modules,\nits higher efficiency provides a greater energy advantage. Additionally, LCOE analysis\nmake it clear that future optimization efforts should focus on reducing TE costs and\nimproving annual equivalent operating hours of the system to achieve economic\nbenefits.\nThe main calculated formula for LCOER3:\n(O&M )\n𝐶 +∑𝑇 𝑡\n0 𝑡=1(1+𝑟)𝑡\nLCOE =\n𝐸\n∑𝑇 𝑡\n𝑡=1(1+𝑟)𝑡\n𝐸 = 𝑃 ×𝑁×(1−𝑑)𝑡\nt rated\nWhere C is the total installed cost, O&M is the annual operation and maintenance\n0 t\ncost, T is the project lifetime, t is the year of operation, r is the discount rate, and E is\nt\nthe annual electricity generation. P is the rated capacity (installed power) of the\nrated\nsystem, and N is the number of full-load operating hours per year (annual equivalent\noperating hours), d is the annual degradation rate.\nThe main results:\n(key results from Note S10 - Table 1in the revised SI)\nC (USD/m2) N (h) LCOE (USD/kWh)\nOSC 163R7 0.079\nPSC 114R8 0.041\nTable R2: LCOE of TE modules\n(key results from Note S10 - Table 2 in the revised SI)\nC (USD/m2) N (h) LCOE (USD/kWh)\nTE (ΔT = 100 K) 0.059\nTable R3: LCOE of PV-TE hybrid systems\n(key results from Note S10 - Table 3 in the revised SI)\nC (USD/m2) N (h) LCOE (USD/kWh)\nOSC-TE 3288 0.783\nPSC-TE 3239 0.661\nThe results (Tables R1 - R3) indicate that the current LCOE of PV-TE hybrid system\nis indeed significantly higher than that of standalone PV or TE modules, with the cost\nof the TE module being the primary contributor. It should be noted that, the standalone\nTE modules benefit from longer annual equivalent operating hours (typically used in\nfactory waste heat recovery, with theoretical full-load operation for 8760 hours per year;\n5000 hours were used here), which help lower the LCOE. In contrast, the PV-TE hybrid\nsystem still relies on annual solar irradiance for power generation, with insufficient\nannual equivalent operating hours (approximately 1200 - 1800 hours per yearR6; 1600\nhours were used here), resulting in a higher LCOE.\nAlthough the PV-TE hybrid system currently exhibits a higher LCOE compared to\nstandalone PV or TE systems, its superior efficiency per unit area results in a\nsignificantly higher power density. This is particularly advantageous for high-demand\nsectors such as aerospace, aviation, and remote applications where space and weight\nare critical factors. Looking ahead, efforts should be directed towards reducing the cost\nof TE modules and extending annual equivalent operating hours of PV-TE hybrid\nsystems. Thus, with ongoing technological advancements, the PV-TE hybrid system\nwould have the potential to become a more cost-effective solution in the future, offering\nsubstantial benefits in various specialized applications.\nRegarding the issue of degradation.\nAgain, the stability of the integrated systems is vital for potential commercialization.\nIt would be best if we could conduct full-scale stability testing on the entire system at\na large (commercial) scale and over a long timescale, such as several years. Clearly, we\nare unable to do that at this moment, and this is not either the focus of this work. Another\napproach would be to evaluate the stability of each unit and compare the stability results\nof the integrated system with those of the individual units.\nefficiency after 2000 hours of continuous maximum power point tracking (MPPT)\nunder 1 sun conditionR9. The PSC could retain about 82 % of their initial efficiency\nafter 2500 hours of continuous MPPT under 1 sun conditionR10. For the thermal stability,\nto date, the OSC could also retain 94 % of their initial efficiency after 1032 hours of\n85 °C/85 % relative humidity damp heat and 200 thermal cycles (- 40 °C to 85 °C)\ntestsR11. The PSC could also keep 92 % of the initial efficiency when ageing at 85 °C\nfor 1800 h and 94% after 200 thermal cycles between - 40 °C and + 85 °CR12.\nFurthermore, bismuth telluride-based thermoelectric generators have successfully\nachieved commercial production and application due to their exceptional stabilityR13,\nR14.\nMore importantly, our new photostability experimental results (Fig. S16) indicate\nthat, compared to standalone PV units, the PV-TE hybrid systems exhibit enhanced\nphotostability. Our new thermal stability experimental results (Fig. S17) reveal that the\nPV integrated within the hybrid system exhibited similar thermal stability compared to\nthe standalone PV units after 100 thermal cycles (cycling between 25 °C and 65 ℃),\nwith no adverse effects observed (Fig. S17a - S17b). Furthermore, the TE units in the\nhybrid system also maintain stable performance after 100 thermal cycles (Fig. S17c).\nIn summary, the enhanced photostability and similar thermal stability of the PV-TE\nhybrid system compared with the standalone PV units indicate that the integrated\nsystem could achieve or even exceed the reported stability of PV units, demonstrating\nthe system's potential for reliable, long-term practical applications.\nThe newly related experimental results and discussion above have been added to the\nrevised Manuscript (Page 14).\nRegarding the issue of scalability.\nFirst, there have been numerous studies on the scalability of standalone solar cells\nand TE devices in literatures. For example, organic and perovskite solar cells have\nalready achieved large-area module fabrication. A 204 cm2 OSC module with a certified\npower conversion efficiency of 14.5 % was achieved in 2024R15. The PSC module, with\na size of 2 m2, achieved a certified record efficiency of 20.05 % in 2025R16. Bismuth\ntelluride-based thermoelectric modules have also been widely produced and applied at\nlarge scaleR13. Furthermore, for our integrated PV-TE systems, we have fabricated a\nseries of systems with increased active areas of 0.04, 0.08, 0.12, …, 0.36 cm2 (Fig. 2b),\n1 cm2 (Fig. S14), and further 14.5 cm2 (flexible OSC-TE, Fig. 4a and Figs. S22 - S23),\nall showing similar performance. These results indicate that the PV-TE hybrid system\ndemonstrates excellent potential for scalable fabrication.\nAlso, one of the likely application scenarios for this system might be to integrate it\ninto other systems such as wearable or embedded devices. Thus, in our study, the\nflexible OSC-TE hybrid system has been integrated into a flexible, wearable energy-\nharvesting device (Figs. 4a - 4b) and have also demonstrated its potential for\napplications requiring higher voltage and energy. Furthermore, the PV-TE hybrid\nsystem could also be integrated into various application scenarios, including marine\nenvironments and space (Figs. 4c - 4d).\nImportantly, new outdoor testing under practical environments about the\n5\nperformance of our systems have been carried out and the results (Figs. S27 - S28)\nindicated that the PV-TE hybrid system exhibited higher power output and efficiency\ncompared with standalone PV units, further demonstrating the system's potential for\nreal-world applications.\nThese results mentioned above (both the scalable size fabrication and potential\napplications in various scenarios) demonstrate the excellent scalability of the PV-TE\nhybrid system.\nThe newly related experimental results and discussion have been added to the revised\nManuscript (Page 13).\n6\n3. The damage issue caused by diurnal temperature fluctuations to photovoltaics\nrequires serious attention. While the authors cite literature proposing phase-change\nmaterials (PCMs) for mitigation, the compatibility of this referenced approach with\ntheir composite system remains unverified. We recommend conducting targeted\nexperimentation to develop appropriate solutions addressing this problem.\nReply: Thank you very much for the valuable advice. Following the reviewer’s advice,\nwe have carried out new thermal cycling stability experiments for our integrated PV-\nTE hybrid systems with PCM. The related experimental results, together with relevant\nliterature studies, have demonstrated the compatibility of the PCM with the PV-TE\nhybrid system, as well as the system's ability to withstand temperature fluctuations. The\ndetails are shown below.\nRegarding the damage issue caused by diurnal temperature fluctuations to photovoltaics.\nFirst, in this regard, there have been lots of studies on the thermal stability of OSC\nand PSC to address diurnal temperature fluctuations. For example, the OSC could retain\n94 % of their initial efficiency after 1032 hours of 85 °C/85 % relative humidity damp\nheat and 200 thermal cycles (- 40 °C to 85 °C) testsR11. The PSC could retain 92 % of\nthe initial efficiency when ageing at 85 °C for 1800 h and 94 % after 200 thermal cycles\nbetween - 40 °C and + 85 °CR12.\nThese studies from the extensive literatures indicate that the OSC and PSC could\nhave excellent tolerance to temperature fluctuations. We would hope the widely\nreported excellent results in the literatures could meet the proposed stability validation\nof photovoltaics during diurnal temperature fluctuation.\nThese related literature results and discussion have been added to the revised\nManuscript (Page 14).\nRegarding the compatibility of PCM with PV-TE hybrid system.\nSimilarly, there have been also many studies for PV-TE hybrid system integrated\nwith PCM to reduced temperature fluctuations compared with standalone PV devices\nduring operation, which can even sustain thermoelectric power generation in the\nabsence of sunlightR17. The related figures from this reference are shown in the\nfollowing Fig. R3.\na b\nFig. R3 (These figures are from Reference R17 directly). Mitigating temperature\nfluctuations in PV-TE hybrid systems using PCM. (a) PV panel temperature over time\nfor various systems. (b) Output power for various devices.\n3.5 h, when the temperature dropped rapidly. The PV-PCM-TEG system has a slower\nrate of temperature drop than the standard PV panel because PCM releases heat during\nsolidification and slows down the temperature drop (Fig. R3a). When the lighting stops,\nthe standard PV panel stops generating electricity, but TEG in the PV-PCM-TEG\nsystem continues to generate power (Fig. R3b).”\nRegarding the targeted experimentation.\nFollowing the reviewer’s advice, we have carried out extra thermal cycling stability\nexperiments (cycling between 25 °C - 65 °C) of the standalone PV (OSC and PSC)\nand the PV-TE hybrid systems with PCM, as shown in Fig. R4 below (added as Fig. S17 in\nthe revised SI). After 100 thermal cycles, the OSC and PSC integrated within the hybrid\nsystem exhibited similar thermal cycling stability compared to the standalone OSC and\nPSC (Figs. R4a - R4b), indicating that PCM is well compatible with the PV-TE hybrid\nsystem and does not have an adverse effect on the PV cells, thereby maintaining their\ninherent thermal stability.\nThe results of our new thermal cycling stability experiments, in agreement with the\nliterature findings mentioned above, indicate that PCM is well compatible with the PV-\nTE hybrid system. Furthermore, both the PV (OSC and PSC) and PV-TE hybrid\nsystems with PCM exhibit excellent tolerance to temperature fluctuations.\nThe new thermal cycling stability experimental results has been added to the revised\nSupplementary Information (Fig. S17). The Manuscript has also been revised\naccordingly.\nFig. R4 (added as Fig. S17 in the revised SI). Thermal cycling stability (following\n8\n).u.a(\nycneiciffe\ndezilamroN\n1\n0\n0\n0\n0\n0\n.0\n.9\n.9\n.8\n.8\n.8\n0\n6\n2\n8\n4\nT h e\nrm a l c y c le te s ts (2\nO S C in O S C -T E\nP S C in P S C -T E\n2 0 4 0\nT h e r m a l c\n5 ℃\ny\nO S C : ~ 9 4 .7 %\nP S C : ~ 9 3 .9 %\n⬌ 6 5 ) ℃\n6 0 8 0 1 0 0\nc le , n\na b\nc\n400 20\n)V 350 18 s I\nm\n( e lu d\no\n3 2 0 5 0 0 1 1 6 4\nc\no f T E\nm\n12o\nE\n200 d\nu\nT\nfo c o 150 V oc of TE module\n1\n8\n0le\n(m A V 100 I of TE module ) sc 6\n50\n0 20 40 60 80 100\nThermal cycle, n\n).u.a(\nycneiciffe\ndezilamroN\n1\n0\n0\n0\n0\n0\n.0\n.9\n.9\n.8\n.8\n.8\n0\n6\n2\n8\n4\nT h e\nrm a l c y c le te s ts (2\nS ta n d a lo n e O S C\nS ta n d a lo n e P S C\n2 0 4 0\nT h e r m a l c\n5 ℃\n6\ny c\n⬌\n0\nle\nO S C : ~ 9 4 .8 %\nP S C : ~ 9 4 .5 %\n6 5 ) ℃\n8 0 1 0 0\n, n\nd\n65\n65 ℃\n)℃\n55 ( e r u\nta45\nr e\np\nm 35\ne T 25 ℃ 25\n0 10 20 30 40\nTime (min)\nthe ISOS-T-2 protocol) of standalone OSC and PSC (a) and OSC and PSC within the\nPV-TE hybrid system (b) and the TE module (c). Temperature profile measured by a\nthermocouple as the solar cells went through the temperature cycling test (d).\n(Remarks to the Author):\nThe authors have made commendable revisions in response to the first-round comments,\nwhich have improved the technical depth of the manuscript. The newly added\ndiscussions in the Manuscript and supplementary information provide a more\ncomprehensive view of the challenges in scaling PV-TE hybrid systems, and the\ninclusion of engineering considerations such as current matching, modular design, and\nadaptive load tracking is appreciated. However, further clarifications and revisions are\nneeded to ensure the robustness and reproducibility of the reported results.\nReply: Thank you very much for the positive comment. Please find below our detailed\nresponses and the corresponding revisions.\n1. The newly added Fig. 3b clarifies steady-state efficiency trends across a range of\ncold-side and environmental temperatures, but no real dynamic, time-dependent\nsimulations (e.g., transient cold-side fluctuation) are included. Concerns about the non-\nsteady-state applicability are not fully addressed.\nReply: Thank you very much for your valuable advice. As the reviewer has correctly\npointed out, the original Fig. 3b (as shown in Fig. R5 below for convenience) indeed\npresents a steady-state operating plot with environment and cold-side temperatures as\nvariables, rather than a transient simulation.\nWe currently lack the capability to address a rigorous transient treatment, which\nwould require additional complexities (e.g., forced-convection effects, and possible\nPCM kinetics). Incorporating time-resolved experimental validation into the models\nremains an ongoing engineering challenge that we would be to actively address in future.\nMore importantly, in most real-word applications, we would think that the boundary\nconditions (e.g., ambient temperature, wind speed, irradiance) for PV and TE modules\nand PV-TE hybrid systems tend to fluctuate at a relatively slower pace compared with\nthe mentioned transient cold-side fluctuation over time. Also, steady-state models have\nbeen widely used in the field to predict the operational efficiency and long-term energy\nyield of PV and TE modules and PV-TE hybrid systemsR18, R19, as they capture the key\ntrends and system performance under typical conditions. Nevertheless, we recognize\nthe importance of transient simulations for certain applications and will aim to develop\nand incorporate such models in future work.\n10\n273\n32 %\n278\nη\no\n283 h\nf\ny\nb\n288\ns\ndir\ny\ns\n293 m\net\ns\n298 20 %\n295 300 305 310 315\nFig. R5 (original Fig. 3b in the previous version). Effect of cold-side and\nenvironmental temperatures on the efficiency of the 0.04 cm2 OSC-TE hybrid system\n(n= m= 1, k = 6) under AM 1.5G solar illumination.\n11\n)K(\nerutarepmet\nedis-dloC\nEnvironment temperature (K)\n2. Regarding the stability discussion of hybrid systems under long-term conditions, the\nauthors added relevant experiments, but the tests were under open-circuit conditions\n(not continuous power delivery). Also, the description of the TE modules as benefiting\nfrom “passive cooling” remains ambiguous. The assumption of a cold-side temperature\nmaintained at 0 °C raises concerns because it is not clear whether this condition can be\nachieved without external energy input. If auxiliary cooling is required, the associated\nenergy cost and its impact on net system efficiency should be explicitly discussed.\nWithout clarification, the assumption risks overstating the practical feasibility of the\napproach.\nReply: Thank you very much for your valuable comments. These issues have been\naddressed and the manuscript has been revised accordingly, as detailed below.\nRegarding the issue of stability tests under open-circuit conditions.\nFirst, there are two widely used methods in the standard photostability testing\nprotocol for solar cells: under open-circuit conditions or maximum power point\ntracking (MPPT) for continuous power deliveryR20.\nIn this study, we chose to conduct photostability testing under open-circuit conditions,\nwhich is in accordance with the ISOS-L-1 protocol and is also widely used in the fieldR1.\nWhile evaluating the photostability under MPPT would be ideal, we were unable to\nperform MPPT due to the following reasons: (1) The series-connected PSC-TE hybrid\nsystem has a higher open-circuit voltage compared to the standalone PSC. Therefore,\nusing MPPT to test the JV curve of the PSC-TE hybrid system would apply a continuous\nhigher scanning voltage (bias) than that used for the standalone PSC, which could\ncomplicate the reliability of the stability results (as discussed in response to Comment\n1 for Reviewer 1, higher bias would cause more rapid performance decline for PSCR1,\nR2. (2) Our PV-TE hybrid system requires an integrated cooling device to control the\ncold-side temperature of the system, and the device size prevents it from being\nincorporated into the MPPT testing system in a glove box in our lab. Therefore, we\nchose to conduct photostability experiments under open-circuit conditions.\nWe have clarified that the photostability test was under ISOS-L-1 protocol\n(continuous 1-sun illumination in air at room temperature under open-circuit conditions)\nin the revised Manuscript and Supplementary Information.\nRegarding the assumption of a cold-side temperature maintained at 0 °C. and it is not\nclear whether this condition can be achieved without external energy input.\nIn our study, the hot-side temperature of PV-TE hybrid system is determined by the\nheat generated from the solar cell under AM 1.5G solar illumination, while the cold-\nside temperature is determined by different cooling methods. In our study, we used a\ncooling device to maintain the cold-side temperature at 0 °C, which indeed introduced\nadditional energy input. However, considering the focus of this study and the likely\npractical application scenarios without external energy input, the condition (0 ℃) might\nbe achieved when the PV-TE hybrid system is deployed in marine environments with\nseawater cooling (from the equator to the poles, seawater temperature decreases\ngradually from ~ 25 °C to ~ 0 °C or even below 0 ℃), as well as in polar regions or\nspace.\nManuscript (Page 8) to clarify the assumption of a cold-side temperature maintained at\n0 °C and external energy input.\nRegarding the description of the TE modules as benefiting from “passive cooling”.\nIn our study, we used a cooling device to maintain the cold side at various\ntemperatures (including 0 °C), which indeed constitutes active cooling (requiring\nexternal energy) rather than passive cooling (not relying on external energy). We\napologize for the confusion.\nHowever, considering some likely real-world application scenarios, the cooling of\nthe PV-TE hybrid system might be achieved without external energy input such as by\nusing seawater for cooling. The cooling device was primarily used here to achieve\ndifferent cold-side temperatures of the PV-TE hybrid system for laboratory experiments,\nrather than being a necessary energy source in practical applications. Therefore, we\nrevised the ambiguous description of “passive cooling” to “cooling” in the revised\nManuscript and Supplementary Information, which is also consistency with the\ndescription of cooling in similar studiesR21, R22.\nRegarding the energy cost and net system efficiency:\nRegarding this issue, there are two possibilities. The first is to include the energy\ninput (for cooling the cold side) when calculating the overall system efficiency. The\nsecond is to exclude this energy input for the calculation.\nIn our study, we have calculated net system efficiency and evaluated the energy cost\nfollowing the widely adopted method of excluding that energy inputR21- R23, which could\nindeed lead to an overestimation of system efficiency and an underestimation of the\ncost. The reason might lie in the fact that it is difficult to quantitatively calculate the\nexact energy input from the cold side for such an accurate system efficiency calculation.\n13\n3. The response to the issue of current mismatch in large-area PV-TE hybrid systems\nare detailed in Supplementary Note 9, where the authors outline modular circuit\nintegration, electrode optimization, process control, and adaptive electrical matching\nstrategies. While these additions are valuable, the discussion remains largely conceptual.\nThere is still no supporting experimental validation or simulation results demonstrating\nthe effectiveness of these strategies. Is it possible for the authors to provide preliminary\nvalidation data?\nReply: Thank you very much for your valuable suggestion. Regarding to the “issue of\ncurrent mismatch” in large-area PV-TE hybrid system: As the parameters (electrical\nand optical, etc.) of the PV and TE sub-modules should have been known before the\nintegration and fabrication for the integrated PV-TE system, it should be fine to have\nthe PV and TE sub modules (electrical) current matched initially, even with different\nand large area size of the sub modules. Then the question arose is that when the\ntemperature or sunlight irradiation changes, the initial match could change and become\nmis-matched dynamically. We believe that this dynamically mis-match issue could be\naddressed using an integrated maximum power point tracking (MPPT) system for on-\nsite current monitoring, along with a dynamically reconfigurable topology circuit (a\nphysical switch matrix), to adjust the series-parallel connections between the PV and\nTE sub-modules based on irradiance and environment temperature levelsR24, thereby\nachieving dynamically electrical match between them.\nIndeed, for large area devices (both PV and TE modules and their integrated\nsystems), additional problem might arise. This might include 1) the less consistence of\nperformance (parameters) of the large PV and TE units and 2) larger fluctuation in the\nparameters of the PV and TE sub-modules under the varying environmental\ntemperature and sunlight irradiance. Regarding the first case, better production process\nwould be desired to ensure the parameters as close as possibleR25-R27, and further work\ncould be carried out by screening those large PV and TE modules into different groups\nbased on their different performance parameters if the difference is too large. For the\nsecond issue, clearly the principle of the same approach could be applied as discussed\nabove using the on-site integrated topology circuit, but with a more powerful control\nsystem with a larger adjustable range of such parameters.\nThus, we have revised the Note S9 to address the reviewer’s comments and\nsuggestion, and also to make it clearer. Importantly, we are sorry that at this stage are\nunable to perform further experimental testing or validation regrading this issue, but\nhopefully it could be addressed in our future studies.\n14\n4. Authors provided a comparative literature review but didn’t quantify hybrid system\ncost or LCOE, citing complexity. It is recommended to provide at least a schematic\ndiagram of the system energy budget and simple cost estimates for the two operating\nconditions: passive cooling and active cooling.\nReply: Thank you very much for your valuable suggestion. This is clearly one of the\nmajor issues if indeed the results of our study would be applied commercially. The\nfairest metric for comparison across energy technologies is the levelized cost of energy\n(LCOE), which is widely used in the fieldR3, R4. Following this method, we evaluated\nthe LCOE of standalone PV (traditional PV, OSC, and PSC), TE module, and PV-TE\nhybrid systems. The detailed economic assessment has been added to the revised\nSupplementary Information as Note S10. The main results have been summarized in\nTables R4 - R6 below for convenience.\nAs outlined in response to your Comment 2, in practical application, the cooling of\nthe PV-TE hybrid system can also be achieved without external energy input such as\nby using seawater for cooling. Therefore, the cost analysis focuses exclusively on\npassive-cooling configurations.\nRegarding the cost estimate results:\nAs shown in Tables R4 - R6, although the cost estimate results indicate that the PV-\nTE hybrid system currently exhibits a higher LCOE compared to standalone PV or TE\nmodules, its higher efficiency provides a greater energy advantage. Additionally,\nLCOE analysis make it clear that future optimization efforts should focus on reducing\nTE costs and improving annual equivalent operating hours of the system to achieve\neconomic benefits.\nThe main calculated formula for LCOER3:\n(O&M )\n𝐶 +∑𝑇 𝑡\n0 𝑡=1(1+𝑟)𝑡\nLCOE =\n𝐸\n∑𝑇 𝑡\n𝑡=1(1+𝑟)𝑡\n𝐸 = 𝑃 ×𝑁×(1−𝑑)𝑡\nt rated\nWhere C is the total installed cost, O&M is the annual operation and maintenance\n0 t\ncost, T is the project lifetime, t is the year of operation, r is the discount rate, and E is\nt\nthe annual electricity generation. P is the rated capacity (installed power) of the\nrated\nsystem, and N is the number of full-load operating hours per year (annual equivalent\noperating hours), d is the annual degradation rate.\nThe main results:\n(key results from Note S10 - Table 1in the revised SI)\nC (USD/m2) N (h) LCOE (USD/kWh)\nOSC 163R7 0.079\nPSC 114R8 0.041\nTable R5: LCOE of TE modules\n(key results from Note S10 - Table 2 in the revised SI)\nC (USD/m2) N (h) LCOE (USD/kWh)\nTE (ΔT = 100 K) 0.059\nTable R6: LCOE of PV-TE hybrid systems\n(key results from Note S10 - Table 3 in the revised SI)\nC (USD/m2) N (h) LCOE (USD/kWh)\nOSC-TE 3288 0.783\nPSC-TE 3239 0.661\nThe results (Tables R4 - R6) indicate that the current LCOE of PV-TE hybrid system\nis significantly higher than that of standalone PV or TE modules, with the cost of the\nTE module being the primary contributor. It should be noted that, the standalone TE\nmodules benefit from longer annual equivalent operational hours (typically used in\nfactory waste heat recovery, with theoretical full-load operation for 8760 hours per year;\n5000 hours were used here), which help lower the LCOE. In contrast, the PV-TE hybrid\nsystem still relies on annual solar irradiance for power generation, with insufficient\nannual equivalent operating hours (approximately 1200 - 1800 hours per year; 1600\nhours were used here), resulting in a higher LCOE.\nAlthough the PV-TE hybrid system currently exhibits a higher LCOE compared to\nstandalone PV or TE systems, its superior efficiency per unit area results in a\nsignificantly higher power density. This is particularly advantageous for high-demand\nsectors such as aerospace, aviation, and remote applications where space and weight\nare critical factors. Looking ahead, efforts should be directed towards reducing the cost\nof TE modules and extending annual equivalent operating hours of PV-TE hybrid\nsystems. Thus, with ongoing technological advancements, the PV-TE hybrid system\nwould have the potential to become a more cost-effective solution in the future, offering\nsubstantial benefits in various specialized applications.\n16\n5. Outdoor marine scenario tests require clarification on whether they are true\nmeasurements or modeled evaluations. The authors state that they monitored solar\nirradiance and environmental temperature over a representative clear-sky day in June.\nPlease provide the precise geographical location and coordinates of the test site, as well\nas the recording equipment and calibration details used for both temperature and\nirradiance measurements. A photograph or schematic of the actual experimental setup\nshould also be included to confirm the measurement conditions. Besides, the authors\ntake Tianjin near-shore seawater 22 °C as the cold-side reference. What is the basis for\nsetting seawater at 22 °C? No supporting data source is cited. If this value was obtained\nfrom on-site seawater measurements, please provide the raw measurement records,\nsampling time, and the measurement device specifications (with a photo if available).\nFinally, it remains unclear whether the cold-side was actually stabilized by direct\nseawater cooling (e.g., via a heat exchanger) or whether 22 °C was only imposed as a\nmodel boundary condition in the thermal simulation. Please clarify this explicitly and,\nif measurements were conducted, provide synchronized records of cold-side\ntemperature, TE voltage, and ΔT evolution to validate the efficiency analysis and the\nreported outdoor efficiency loss.\nReply: Thank you very much for your suggestion and careful correction. These issues\nhave been re-addressed and clarified in the revised manuscript as detailed below. Please\nalso note that additional outdoor experiments (in September) with synchronized time-\nseries data have been conducted to validate the efficiency analysis and the reported\noutdoor efficiency loss.\nRegarding the outdoor testing process and conditions.\nIn our study, the outdoor performance testing of the PV-TE hybrid systems was\nconducted under sufficient sunlight and calm, wind-free conditions, on one day in June\n(22 June 2025) and three days in September (7-9 September 2025) in Tianjin, China\n(39.1076° N, 117.1734° E). The PV-TE hybrid systems were exposed to real outdoor\nsunlight (vertical incident) and environmental temperature, while a cooling device\nmaintained the cold-side temperature equivalent to seawater temperature (22 °C in June\nand 24.5 °C in September, based on data from a relevant sea water temperature\nwebsiteR28) in the Bohai Sea near Tianjin, instead of using actual seawater for cooling.\nOutdoor solar irradiance was measured using a standard silicon solar cell, while outdoor\ntemperature was recorded using a thermocouple.\nA schematic diagram of the actual outdoor experiments has been added to the revised\nSupplementary Information (Fig. S27), as shown in Fig. R6 below for convenience.\nThe experimental process and conditions have been described clearly in the revised\nManuscript and Supplementary Information.\nperformance testing for PV-TE hybrid system.\nRegarding the synchronized records of data.\nFollowing the reviewer’s advice, synchronized time-series data (with error bars) of\noutdoor experiments (irradiance, environment temperature, TE voltage and current,\nefficiency of standalone PV and PV-TE hybrid systems) have been added to the revised\nSupplementary Information, as shown in Fig. R7 below (added as Fig. S28 in the\nrevised SI).\nIt should be noted that, since the measurements in June were taken just one day (22\nJune 2025) earlier this year and cannot be repeated, the irradiance and temperature in\nJune were just recorded as a single curve, as shown in Fig. R7a without error bar.\nTherefore, additional outdoor experiments were conducted over three days in\nSeptember (7 - 9 September 2025) under sufficient sunlight and calm, wind-free\nconditions. The cold-side temperature was controlled at 24.5 °C in September,\nconsistent with the average sea surface temperatures near Tianjin (Bohai Bay) in\nSeptemberR25. These new experiments were carried out several times, thus error bar has\nbeen recorded and displayed in these figures (Fig. S28e - S28h).\nThe new experimental results (Fig. R7) indicate that, the OSC-TE hybrid system\nachieved maximum average efficiencies of 35.03 % in June and 29.16 % in September,\nwhile the PSC-TE hybrid system reached 40.71 % in June and 35.83 % in September\n(Fig. R7d and Fig. R7h). The higher efficiency of the hybrid systems in June compared\nto September was attributed to higher environment temperature in June (Fig. R7a and\nFig. R7e), which is consistent with our laboratory results (Fig. 3b). The outdoor\nmaximum efficiency of the PV-TE hybrid system experienced an efficiency loss of\napproximately 9 % in June and 14 % in September, compared to the maximum\nefficiency achieved under ideal laboratory conditions (Fig. 3d).\nThe new outdoor testing results have been added to the revised Supplementary\nInformation (Fig. S28).\nith o\nir (n o\na l e x c h a\nu td o o r s\nw in d )\nn g e\ntill\na\nO u td o o r v e rtic a l in c id e n t s u n lig\nP V\nT E\nC o n tro lle d a t 2 2 in J u n e ℃\na n d 2 4 .5 in S e p te m b e r ℃\nh t\nΔ T\nE x p\ne n v\nte m\no s\niro\np e\ne d to o u td\nn m e n ta l\nra tu re s\no o r\nFig. R7 (original Fig. S27, now revised as Fig. S28 in the revised SI). Outdoor\nperformance testing for OSC-TE and PSC-TE hybrid systems. Solar irradiance and\nenvironmental temperature in June (a) and September (e). Efficiency of standalone\nOSCs and PSCs in June (b) and September (f). Open-circuit voltage and short-circuit\ncurrent of the TE module in June (c) and September (g). Efficiency of OSC-TE and\nPSC-TE hybrid systems in June (d) and September (h), respectively. The irradiance and\ntemperature in June (Fig. S28a) were just recorded as a single curve without error bar.\nOther experiments were carried out several times, thus error bar has been recorded and\ndisplayed in these figures (Fig. S28b - S28h). The center of the error bar is defined as\nthe average value, and error bar is defined as the standard deviation, which is calculated\nfrom the statistical results of at least three individual devices.\n19\na\necnaidarrI\nc\n)V( eludom\nET\nfo co V\ne\necnaidarrI\ng\n)V(\neludom\nET\nfo\nco V\n1 .4\n1 .2\n1 .0\n0 .8\n0 .6\n0 .4\n0 .2\n0 .0\n2 .0\n1 .6\n1 .2\n0 .8\n0 .4\n1 .4\n1 .2\n1 .0\n0 .8\n0 .6\n0 .4\n0 .2\n0 .0\n1 .6\n1 .2\n0 .8\n0 .4\n0 .0\nJu n e\nIrrad ian ce\nT em p eratu re\n8 :0 0 1 0 :0 0 1 2 :0 0\nT im\nJune\nV of TE m odule oc I of TE m odule sc\n8 :0 0 1 0 :0 0 1 2 :0 0\nT im\nS ep tem b er\nIrrad ian ce\nT em p eratu re\n8 :0 0 1 0 :0 0 1 2 :0 0\nT im\nS eptem ber\nV of TE m odule oc I of TE m odule sc\n8 :0 0 1 0 :0 0 1 2 :0 0\nT im\n1 4 :0 0\ne\n1 4 :0 0\ne\n1 4 :0 0\ne\n1 4 :0 0\ne\n1 6 :0 0\n1 6 :0 0\n1 6 :0 0\n1 6 :0 0\n5 0\n4 0\nTem\n3 0 peratu\n2 0 re\n(℃\n1 0 )\n0\n1 8 :0 0\n1 4\nIsc o 1 2 f TE\n1 0 modu\n8 le (m 6 A)\n4\n1 8 :0 0\n4 0\nTe\n3 0 mperat\n2 0 ure\n(℃\n1 0 )\n0\n1 8 :0 0\n1 2\nI 1 0 sc of\nT 8\nE\nmo\n6 dule\n4 (mA)\n2\n1 8 :0 0\nb\n)%(\nycneiciffE\nd\n)%(\nycneiciffE\nf\n)%(\nycneiciffE\nh\n)%(\nycneiciffE\n2 8\n2 4\n2 0\n1 6\n1 2\n4 8\n4 2\n3 6\n3 0\n2 4\n1 8\n2 8\n2 4\n2 0\n1 6\n1 2\n4 2\n3 6\n3 0\n2 4\n1 8\n1 2\nJune S tandalone P S C s\nS tandalone O S C s\n8 :0 0 1 0 :0 0 1 2 :0 0 1 4 :0 0 1 6 :0 0\nT im e\nJune\nP S C -TE O S C -TE\n★ (P S C -TE ) = 40.71 % ηmax\n★ (O S C -TE ) = 35.03 % ηmax\n8 :0 0 1 0 :0 0 1 2 :0 0 1 4 :0 0 1 6 :0 0\nT im e\nS eptem ber S tandalone P S C s\nS tandalone O S C s\n8 :0 0 1 0 :0 0 1 2 :0 0 1 4 :0 0 1 6 :0 0\nT im e\nS eptem ber\nP S C -TE O S C -TE\n★ (P S C -TE ) = 35.83 % ηmax\n★ (O S C -TE ) = 29.16 % ηmax\n8 :0 0 1 0 :0 0 1 2 :0 0 1 4 :0 0 1 6 :0 0\nT im e\n1 8 :0 0\n1 8 :0 0\n1 8 :0 0\n1 8 :0 0\n6. The treatment of convective and radiative heat exchange in the thermal modeling\nrequires further justification. In the Supplementary Information (Note 2), the authors\nfix the convective heat transfer coefficient at h = 5 W/m²K and explicitly set the\nradiative term to Q = 0. However, in the Manuscript (outdoor scenario section,\nradiation\nFig. 3-4), the reported summer environmental temperature reaches up to about 40 °C,\nand the device surface is described or shown in thermal images at >30-45 °C. Under\nsuch conditions, radiative exchange can contribute non-negligibly to the overall thermal\nbalance, and the assumption of Q = 0 may underestimate heat losses.\nradiation\nReply: Thank you very much for your valuable suggestion. The accuracy of the\nconvective heat transfer coefficient values has been validated through relevant literature\nstudies. In response to the reviewer’s concern, an additional simulation about the impact\nof the convective heat transfer coefficient on system efficiency has been included in the\nrevised Supplementary Information. The reason for neglecting thermal radiation was\nthat low-emissivity materials were used in our PV-TE hybrid system, which has been\nclarified in the revised Supplementary Information. The details are shown below.\nRegarding the value of heat transfer coefficient.\nUnder natural conditions, the convective heat transfer coefficient (h) typically ranges\nfrom 5 to 40 W/m2K, with a typical value of 5 W/m2K in light breeze and 40 W/m2K at\nstrong breezeR19.\nIn our study, we used h = 5 W/m2K to explore the maximum efficiency of the PV-TE\nhybrid system under ambient conditions, which is also widely used in the similar\nsimulationsR18, R19.\nIndeed, a higher convective heat transfer coefficient would result in greater heat\ndissipation and reduced system efficiency, as demonstrated by our new simulation\nresults presented in Fig. R8 (added as Fig. S18a in the revised SI) below. However, in\nthe application of PV-TE hybrid systems, efforts could be made to reduce convective\nheat losses, such as through local insulation or the design of adjustable wind shields.\nTherefore, the convective heat transfer coefficient values of 5 W/m2K is reasonable.\nThe new simulation results and related discussion have been added to the revised\nSupplementary Information (Fig. S18a).\na\n7 0.4\n6\n0.3\n5\n)% 4 )V\n(\nη Δ 3\n0.2 (\nV E T\n2\n0.1\n1\n0 0.0\n5 10 15 20 25\nh (W/m2K)\ncoefficient on the efficiency improvement (Δη) of the PV-TE hybrid system (n = m =\n1, k = 6) relative to standalone PV.\nRegarding the assumption of Q = 0.\nradiation\nLow-emissivity surface materials are widely used in the field to limit adverse thermal\nradiative lossesR29. In our study, following this approach, low-emissivity materials were\nadopted to reduce radiative heat losses in the PV-TE hybrid system.\nSpecifically, polished brass plates (ε = 0.03, ε is the surface emissivity of material)\n1\nwere welded on both sides of the TE module, and a smooth stainless-steel mask (ε =\n2\n0.07) was used over the solar cell.\nAs a result, the heat flux of thermal radiation is much lower than that of thermal\nconvection in the PV-TE hybrid system, as shown in the following Table R7. Therefore,\nin our study, thermal radiation is neglected due to its relatively small contribution to\nheat loss.\nWe have clarified the use of low-emissivity materials to limit thermal radiation in the\nrevised Supplementary Information (detailed in the revised SI, Page 17).\nTable R7. The heat flux of thermal radiation and thermal convection.\nEnvironment Temperature Heat flux of Heat flux of Heat flux of\ntemperature of device thermal radiation thermal radiation thermal convection\n(°C) (°C) (W/m2) (W/m2) (W/m2)\n(ε = 0.03) (ε = 0.07) (h = 5 W/m2K)\n1 2\n25 35 1.89 4.42 50\n40 50 2.19 5.11 50\n21\n7. Supplementary Fig. 17 shows OSC/PSC and TE modules tested over 100 cycles with\n3 min dwell time; OSC retains 99.65%, PSC 97.46%; TE performance is nearly\nunchanged. But such an equilibrium assumption is not justified, i.e., no thermal time\nconstant or transient curves are shown. Please provide time traces proving that 3 min\nsuffices and specify N and error bars. Moreover, authors should clarify whether tests\nwere under illumination and load (closer to real operation).\nReply: Thank you very much for your very important comments and valuable advice.\nAs the reviewer has noted, in our previous thermal stability testing the assumption of\nequilibrium has not been verified.\nTo address this issue, new thermal cycling stability experiments have been conducted\nin accordance with the ISOS-T-2 protocolR29. Following the protocol, the standalone\nPV (OSC and PSC) and the PV-TE hybrid systems (OSC-TE and PSC-TE) were placed\nin an oven and thermally cycled between room temperature (25 °C) and 65 °C under\ndark, open-circuit (no-load) conditions. Note the devices were held at 25 °C and 65 °C\nfor 10 minutes to ensure thermal equilibrium under this protocol. To verify thermal\nequilibrium, the temperature profile of the solar cells was measured by a thermocouple\nas they went through the temperature cycling test (Fig. R9d below).\nThese new thermal cycling stability experimental results (Fig. R9 below) reveal that\nthe OSC and PSC integrated within the hybrid system exhibited similar thermal cycling\nstability compared to the standalone OSC and PSC (Figs. R9a - R9b). After 100 thermal\ncycles, the OSC retained approximately 95 % of its initial efficiency, while the PSC\nmaintained about 94 %. Furthermore, the TE module exhibited negligible changes in\nboth output voltage and current when tested under a temperature difference of 30 K\nafter 100 thermal cycles (Fig. R9c). While the results from these new thermal cycling\nstability experiments have slight difference in values compared to the original test\nresults, in principle the conclusion is the same.\nThe new experimental results with error bars have been updated in the revised\nSupplementary Information (Fig. S17). The experiment conditions have also been\nclarified in the revised Supplementary Information (see Methods section).\nISOS-T-2 protocol) of standalone OSC and PSC (a) and OSC and PSC within the PV-\nTE hybrid system (b) and the TE module (c). (d) Temperature profile measured by a\nthermocouple as the solar cells went through the temperature cycling test. The center\nof the error bar is defined as the average value, and error bar is defined as the standard\ndeviation, which is calculated from the statistical results of at least three individual\ndevices.\n23\na\n).u.a(\nycneiciffe\ndezilamroN\nc\n)Vm(\neludom\nET\nfo\nco V\n1 .0\n0 .9\n0 .9\n0 .8\n0 .8\n0 .8\n4 0\n3 5\n3 0\n2 5\n2 0\n1 5\n1 0\n5\n0\n6\n2\n8\n4\n0\n0\n0\n0\n0\n0\n0\n0\n0\n0\nP S C : ~ 9 4 .5 %\nIS O S -T -2 :\nT h e rm a l c y c le te s ts (2 5 ⬌ 6 5 ) ℃ ℃\nS ta n d a lo n e O S C\nS ta n d a lo n e P S C\n0 2 0 4 0 6 0 8 0 1 0 0\nT h e r m a l c y c le , n\nV o f T E m o d u le o c I o f T E m o d u le sc\n0 2 0 4 0 6 0 8 0 1 0 0\nT h e r m a l c y c le , n\n2\n1\n1\n1\n1\n1\n8 6\n0\n8\n6\n4\n2\nof\nTE\nmodule\n(mA)\n).u.a(\nycneiciffe\ndezilamroN\nb\nd\n1\n0\n0\n0\n0\n0\n)℃(\nerutarepmeT\n.0\n.9\n.9\n.8\n.8\n.8\n0\n6\n2\n8\n4\n0\n6\n5\n4\n3\n2\n5\n5\n5\n5\nP S C : ~ 9 3 .9 %\nIS O S -T -2 :\nT h e rm a l c y c le te s ts (2 5 ⬌ 6 5 ) ℃ ℃\nO S C in O S C -T E\nP S C in P S C -T E\n0 2 0 4 0 6 0 8 0 1 0 0\nT h e r m a l c y c le , n\n6 5 ℃\n2 5 ℃\n0 1 0 2 0 3 0 4 0\nT im e (m in )\n8. Supplementary Fig. 26 shows photos and efficiency retention (~ 98%). The authors\nstate that bending radius is limited by the TE electrodes. But key parameters are missing,\nsuch as radius, frequency, and strain.\nReply: Thank you very much for your valuable advice. The key parameters (radius,\nfrequency, and strain) have been added to the revised Fig. S26.\n9. Data availability and statistical reproducibility remain insufficient. The reported\nchampion efficiencies (42.03%, 50.28%) and outdoor curves are single instances.\nMore outdoor time-series data (irradiance, ambient T, wind speed, cold-side T, TE voltage)\nshould be provided for readers. Summarize in box plots or mean ± SD for\nreproducibility compliance.\nReply: Thank you very much for your valuable advice. Following the reviewer’s advice,\nbox plots summarizing the champion efficiencies and additional outdoor time-series\ndata with error bars (mean ± SD) have been added to the revised manuscript, as detailed\nbelow.\nRegarding the reported champion efficiencies.\nBox plots summarizing the reported champion efficiencies (OSC-TE and PSC-TE at\nInformation, as shown in the following Fig. R10 (added as Figs. S13, S14 and S19 in\nthe revised SI). The Manuscript has also been revised accordingly. Please note that the\ndata points corresponding to the champion efficiencies are marked (red circle) in Fig.\nR10 for easy reading. The statistical distribution in Fig. R10 further confirmed the\nreproducibility of the reported champion efficiencies.\nRegarding more outdoor time-series data.\nFollowing the reviewer’s advice, more outdoor time-series data (with error bars) of\noutdoor experiments (irradiance, environment temperature, TE voltage and current,\nefficiency of standalone PV and PV-TE hybrid systems) have been added to the revised\nSupplementary Information, as shown in the Fig. R7 mentioned above (added as Fig.\nS28 in the revised SI). The statistical distribution in Fig. R7 further confirmed the\nreproducibility of the outdoor testing results.\n24\n43\n42\n41\n)%\n(\nη 40\nPSC-TE hybrid system\nT = 298 K atm\n39 n = m ∈ [5, 7]\nk = 6\n38\n5 6 7\nNumber of n and m\nOSC-TE at 313 K PSC-TE at 313 K\nc η max = 43.16 % d η max = 50.28 %\n44 51\n50\n43\n49\n)%42 )%48\n(\nη\n(\nη PSC-TE hybrid system\nOSC-TE hybrid system 47 T atm = 313 K\nn = m ∈ [6, 8] 46 k = 6\nk = 6\n40 45\n6 7 8 6 7 8\nNumber of n and m Number of n and m\nFig. R10 (added as Figs. S13, S14 and S19 in the revised SI). Statistical efficiencies\nof OSC-TE and PSC-TE hybrid systems at 298 K and 313 K. (a) Statistical efficiencies\nof OSC-TE hybrid systems at 298 K with different active areas (n = m ∈ [1, 9], k =\n6). (b) Statistical efficiencies of PSC-TE hybrid systems at 298 K with different active\nareas (n = m ∈ [5, 7], k = 6). Statistical efficiencies of OSC-TE (c) and PSC-TE (d)\nhybrid systems at 313 K with different active areas (n = m ∈ [6, 8], k = 6). Box plots\nindicate the mean (center line), interquartile range (25th-75th percentiles; box bounds),\nminima to maxima (whiskers), and individual data points (circles). Data were collected\nfrom five independent devices per group.\n25\n)%\n(\nη\n3\n3\n3\n3\n2\n2\n2\n2\n6\n4\n2\n0\n8\n6\n4\n2\n1 2\nN\n3u\nm\n4b\ne\nO S C -T E h y b rid\nT = 2 9 8 K\natm\nn = m ∈ [1 ,9 ]\nk = 6\n5 6 7\nr o f n a n d m\ns y s\n8\nte m\nη = 34.85 % η = 42.03 %\nmax max\na b\n10. Supplementary Table 4 compares PV-TE works, but the boundary conditions are\nnot harmonized. Authors are suggested to standardize table annotations (area, cold-side,\nirradiance type, etc.) for fair comparison.\nReply: Thank you very much for your valuable suggestion. We have re-compared our\nwork with representative PV-TE hybrid systems reported to date using harmonized\nboundary conditions.\nThe results have been updated in the revised Table S4, as shown in the following\nTable R8 for convenience.\nTable R8 (as Table S4 in the revised SI). Comparison of this work with representative\nPV-TE hybrid systems reported to date.\nDevice Active Environment Cold-side condition Efficiency Ref.\ntype area temperature (AM 1.5G)\nPSC-TE 0.28 cm2 40 ℃ Controlled at 0 ℃ 50.28 % This\n0.24 cm2 RT 42.03 % work\nOSC-TE 0.28 cm2 40 ℃ 43.16 %\n0.24 cm2 RT 34.85 %\n1 cm2 RT 33.48 %\nOSC-TE 1 cm2 RT Heat sink 18.20 % R30\nOSC-TE 0.12 cm2 RT Ice water mixture (2 ℃) 11.24 % R31\nPSC-TE 0.06 cm2 RT Water cooling (25 ℃) 23.32 % R23\nPSC-TE 0.6 cm2 RT Heat sink and water 23.2 % R32\ncooling\nPSC-TE 0.07 cm2 RT Ice bath 22.2 % R22\nPSC-TE 0.09 cm2 45 ℃ Ice water mixture (0 ℃) 20.3 % R21\nPSC-TE 8.1 cm2 RT Heat sink 12.7 % R33\nc-Si 1600 cm2 33 ℃ Water cooling 23 % (under 63 R34\nPV-TE (20 - 30 ℃) - 68 mW/cm2)\nc-Si 51.35 cm2 RT Water cooling (25 ℃) 22.5 % R35\nPV-TE\nGaAs 1cm2 RT Water cooling (5 ℃) 20 % R36\nPV-TE\nc-Si 4 cm2 RT Heat sink and 16.3 % R37\nPV-TE temperature controller\nNotes: RT is the room temperature. Reported efficiencies are system-level under AM 1.5G\nillumination (100 mW/cm2) unless otherwise specified.\n26\n11. The academic writing standards and formatting consistency of the manuscript can\nbe further improved. Use italic and bold in the manuscript only where required for\nproper usage or sense. Do not format the manuscript for design style. Only the letters\nof variable symbols must be written in italics. In scientific text, italic symbols represent\nphysical quantities/variables, while roman symbols represent units, labels, elements,\nand mathematical operators. Subscripts and superscripts that are not variables (e.g.,\nabbreviations or descriptive labels) should also appear in roman font, not italic.\nReply: Thank you very much for your valuable advice and careful correction. We have\nthoroughly corrected the manuscript’s formatting as follows.\n(1) Any unnecessary bold or italic emphasis have been removed.\n(2) Variables and symbols have been revised correctly (e.g., n, m, k, zT, ΔT, ∇V).\n(3) Subscripts and superscripts have been revised correctly (e.g., R , V , I ).\nTE oc sc\nR1. Li, N. et al. Barrier reinforcement for enhanced perovskite solar cell stability\nunder reverse bias. Nature Energy 9, 1264-1274 (2024).\nR2. Thiesbrummel, J. et al. Ion-induced field screening as a dominant factor in\nperovskite solar cell operational stability. Nature Energy 9, 664-676 (2024).\nR3. Darling, S. B., You, F., Veselka, T. & Velosa, A. Assumptions and the levelized\ncost of energy for photovoltaics. Energy Environ. Sci. 4, 3133-3139 (2011).\nR4. Branker, K., Pathak, M. J. M. & Pearce, J. M. A review of solar photovoltaic\nlevelized cost of electricity. Renew. Sust. Energ. Rev. 15, 4470-4482 (2011).\nR5. IRENA (2025), Renewable power generation costs in 2024, International\nRenewable Energy Agency, Abu Dhabi.\nR6. Global Solar Atlas. https://globalsolaratlas.info/map (accessed 1 October 2025).\nR7. Heliatek. Technical datasheet: HeliaSol® 436-2000-AFA.\nhttps://www.heliatek.com/en/products/heliasol (accessed 1 October 2025).\nR8. Liu, Y. et al. Cost effectivities analysis of perovskite solar cells: will it\noutperform crystalline silicon ones? Nano-Micro Lett. 17, 219 (2025).\nR9. Liu, B. et al. Inverted organic solar cells with an in situ-derived\nSiO N passivation layer and power conversion efficiency exceeding 18%. Nat.\nx y\nPhoton. 19, 195-203 (2025).\nR10. Lin, Y. et al. A Nd@C -polymer interface for efficient and stable perovskite\n82\nsolar cells. Nature 642, 78-84 (2025).\nR11. Qin, J. et al. Improved damp heat and thermal cycling stability of organic solar\ncells. Nat Energy (2025). https://doi.org/10.1038/s41560-025-01885-8.\nR12. Li, G. et al. Stabilizing high-efficiency perovskite solar cells via strategic\ninterfacial contact engineering. Nat. Photon. (2025).\nhttps://doi.org/10.1038/s41566-025-01791-1.\nR13. He, J. et al. Advances in the applications of thermoelectric generators. Appl.\nTherm. Eng. 236, 121813 (2024).\nR14. Palaporn, D. et al. Thermoelectric materials for space explorations. Mater. Adv.\n5, 5351-5364 (2024).\nR15. Basu, R. et al. Large-area organic photovoltaic modules with 14.5% certified\nworld record efficiency. Joule 8, 970-978 (2024).\nR16. Liang, Y. et al. A matrix-confined molecular layer for perovskite photovoltaic\nmodules. Nature (2025). https://doi.org/10.1038/s41586-025-09785-3.\nR17. Li, W. et al. Experimental and numerical study on photovoltaic thermoelectric\n28\n28\nheat storage system based on phase change temperature control. Sol. Energy 274\n112584 (2024).\nR18. Hu, X. et al. Power generation from nanostructured PbTe-based thermoelectrics:\ncomprehensive development from materials to modules. Energy Environ. Sci. 9,\n517-529 (2016).\nR19. Guo, J. & Huai, X. Maximizing electric power through spectral-splitting\nphotovoltaic-thermoelectric hybrid system integrated with radiative cooling.\nAdv. Sci. 10, 2206575 (2023).\nR20. Khenkin, M. V. et al. Consensus statement for stability assessment and reporting\nfor perovskite photovoltaics based on ISOS procedures. Nat. Energy 5, 35-49\n(2020).\nR21. Xu, L. et al. Efficient perovskite photovoltaic-thermoelectric hybrid device. Adv.\nEnergy Mater. 8, 1702937 (2018).\nR22. Liu, Z. et al. Novel integration of carbon counter electrode based perovskite\nsolar cell with thermoelectric generator for efficient solar energy conversion.\nNano Energy 38, 457-466 (2017).\nR23. Zhou, Y. et al. A highly-efficient concentrated perovskite solar cell-\nthermoelectric generator tandem system. J. Energy Chem. 59, 730-735 (2021).\nR24. Fang, X. & Yang, Q. Dynamic reconfiguration of photovoltaic array for\nminimizing mismatch loss. Renew. Sust. Energy Rev. 191, 114160 (2024).\nR25. Wong, W. P. et al. Bismuth telluride-based thermoelectric generators: Advances\nin synthesis, performance enhancement, and device applications. J. Power.\nSources 653, 237722 (2025).\nR26. Yang, F. et al. Large-area flexible organic solar cells. npj Flex. Electron. 5, 30\n(2021).\nR27. Yang, C. et al. Achievements, challenges, and future prospects for\nindustrialization of perovskite solar cells. Light Sci. Appl. 13, 227 (2024).\nR28. Sea Temperature Info. Water temperature in Tianjin.\nhttps://seatemperature.info/tianjin-water-temperature.html (accessed 22 June\n2025).\nR29. Peng, Y. et al. Coloured low-emissivity films for building envelopes for year-\nround energy savings. Nat. Sustain. 5, 339-347 (2022).\nR30. Liu, W., Sun, S. & Zhu, X. Organic photovoltaics integrated with thermoelectric\ngenerator achieving low critical temperature difference and efficient energy\nconversion. Adv. Funct. Mater. 32, 2109410 (2022).\nR31. Zhang, Y. et al. Integrated energy-harvesting system by combining the\nadvantages of polymer solar cells and thermoelectric devices. J. Phys. Chem. C\n117, 24685-24691 (2013).\nR32. Zhou, Y. et al. Perovskite solar cell-thermoelectric tandem system with a high\nefficiency of over 23%. Mater. Today Energy 12, 363-370 (2019).\nR33. Fu, P. et al. Integrating large-area perovskite solar module with thermoelectric\ngenerator for enhanced and stable power output. Nano Energy 65, 104009\n(2019).\nR34. Zhu, W., Deng, Y., Wang, Y., Shen, S. & Gulfam, R. High-performance\nphotovoltaic-thermoelectric hybrid power generation system with optimized\nthermal management. Energy 100, 91-101 (2016).\nR35. Kim, Y. J. et al. High-performance monolithic photovoltaic-thermoelectric\nhybrid power generator using an exothermic reactive interlayer. ACS Appl.\nEnergy Mater. 2, 2381-2386 (2019).\nR36. He, Z., Yang, M., Wang, L., Bao, E. & Zhang, H. Concentrated photovoltaic\nthermoelectric hybrid system: an experimental and machine learning study.\nEngineered Science 15, 47-56 (2021).\nR37. Park, K.-T. et al. Lossless hybridization between photovoltaic and\nthermoelectric devices. Sci. Rep. 3, 2123 (2013).\nNCOMMS-25-25787B\n(Text in blue is our replies)\nReviewer 1\n:\nThe specific comments below are intended to assist the authors in further enhancing\nthe rigor and persuasiveness of the paper.\nReply: Thank you very much for the positive comment. Please find below our detailed\nresponses and the corresponding revisions.\n1. Regarding the efficiency of PV-TE hybrid systems mentioned as \"the ratio of output\nelectrical energy to input solar energy (without considering the contributions from\nenvironmental thermal energy and cooling sources),\" what specific parameter does this\nratio represent? Is its usage appropriate and reasonable? Is there a precedent or source\nfor this comparison? Does this efficiency definition correspond to \"light-input-driven\nefficiency\" or \"system-level total energy efficiency\"? The authors are advised to clarify\nthe theoretical basis and literature sources for this efficiency definition and to indicate\nwhether it is widely adopted in hybrid systems to avoid confusion with terms such as\n\"photo-thermal hybrid efficiency,\" \"total system efficiency,\" or \"net energy efficiency.\"\nIf this efficiency applies only under specific assumptions, its applicable scope should\nalso be clearly stated in the main text.\nReply: Thank you very much for the valuable suggestion. The efficiency calculation\nmethod of the PV-TE hybrid system adopted in this work follows the widely used\nmethod in the field, which is defined as the ratio of electrical energy output to incident\nsolar energy input1-3. Notably, this definition is identical to that of the “photoelectric\nconversion efficiency (PCE)” of the standalone PV device. Its primary purpose is to\nenable a direct comparison of whether the hybrid system provides enhanced electrical\noutput relative to a standalone PV device under identical illumination.\nAs the reviewers might notice that from the literatures mentioned above, at present,\nthe literatures have not provided a universally accepted or rigorously named\nclassification (e.g., \"light-input-driven efficiency\") for this measurement, and it is\ntypically referred to in a general manner as hybrid or overall system efficiency. This\nmeasurement does not correspond to a strictly defined “system-level total energy\nefficiency”, as it excludes environmental thermal energy and cooling contributions.\nIntroducing new terminology without broad consensus may therefore lead to\nadditional confusion. Therefore, we followed the prevailing convention in the field. We\nhave clarified the definition and scope of applicability of this system efficiency\nmeasurement in the revised Main Text (Page 4).\n2. Regarding the statement \"a heat transfer model of the stacked PV-TE hybrid structure\nwas first established,\" is the term \"first\" truly accurate? Have previous studies not\nemployed such models? Please verify and clarify this claim by citing relevant literature\nand ensure the rigor and standardization of terminology.\nReply: Thank you very much for the valuable suggestion. Building upon existing PV-\nTE models reported in the literatures4-6, this work develops a more comprehensive and\nintegrated coupling model for PV-TE hybrid system, which is not the first of its kind in\nthe field. In our original Main Text, the term “first” denotes the initial procedural step\nin our simulation workflow. This step corresponds to the heat transfer model, which is\nthen coupled with the circuit module. To avoid ambiguity and ensure terminological\nprecision, we have revised the sentence accordingly in the revised Main Text.\n3.Although the proposed PT-TECM model is structurally complete, the supplementary\nmaterials lack the complete temperature-dependent curves or fitting expressions for key\nthermoelectric parameters (Seebeck coefficient, electrical conductivity, thermal\nconductivity). Additionally, the simulation does not account for interfacial thermal\nresistances from welding, bonding, and encapsulation layers commonly present in\npractical devices, which may significantly overestimate the achievable temperature\ndifference and thermoelectric output. Similarly, information on the PV-TE contact\ninterface is insufficient, which is crucial for heat transfer efficiency and reliability.\nReply: Thank you very much for the valuable suggestion. Following the reviewer’s\nadvice, the measured temperature-dependent curves for key thermoelectric parameters\n(Seebeck coefficient, electrical conductivity, and thermal conductivity) of the p-type\nand n-type Bi Te legs have been included in the revised Supplementary Information\n2 3\n(Page 66), as shown in the Fig. R1 (added as Fig. S6 in the revised SI) below for\nconvenience.\nIn this work, the model indeed assumed ideal thermal interfaces and does not\nexplicitly account for interfacial thermal contact resistance. While the thermal contact\nresistance between different devices is mitigated by using a phase-change thermal\ninterface material in this work, the intrinsic interfacial resistance arising from welding,\nbonding, and encapsulation layers within the device cannot be eliminated. Reported\nthermal contact resistance values typically range from 1.0 × 10-6 to 1.0 × 10-4 m2K/W7,8,9,\nwhich could lead to variations in the thermoelectric temperature drop and open-circuit\nvoltage of approximately 5 % - 30 %9. Based on these literature results and our\nestablished PV-TE equivalent circuit model, the calculated results indicated that this\nreduction results in an absolute efficiency deviation of about 2 % - 7 % for the hybrid\nsystem.\nWe have clarified that the interfacial thermal resistances were neglected in the model\nand the potential efficiency deviations it may cause, and have included the relevant\ninterfacial information in the revised Supporting Information (Page 18). The Main Text\nhas been also revised accordingly (Page 17).\na b\n250\n240\n230\n220\n210\n200\n190\n180\n0 20 40 60 80\nFig. R1. (added as Fig. S6 in the revised SI). Measured temperature-dependent curves\nof thermoelectric parameters of Seebeck coefficient (a), electrical conductivity (b), and\nthermal conductivity (c) for the p-type and n-type Bi Te material.\n2 3\n4.The sensitivity of photo-thermal coupling to the solar incident angle has not been\nanalyzed, which may affect conclusions about daily and seasonal scenarios. All lighting\nexperiments in the article and supplementary materials were conducted at fixed angles.\nHowever, in practical applications, significant variations in solar altitude angles affect\nPV absorption, PV heat distribution, and the available heat for TE. Similarly, the\nefficiency of PV-TE thermal coupling under morning/evening light conditions may\ndiffer markedly from that at noon. It is recommended to supplement the analysis with\nincident angle sensitivity or provide experimental outputs under different solar altitude\nangles to enhance the comprehensiveness of system performance predictions.\nReply: Thank you very much for the valuable suggestion. Large light-receiving angle\nreduce photovoltaic conversion efficiency by decreasing light intensity per unit area\nand increasing reflection losses. Several mature strategies have been used to mitigate\nangular losses in practical applications such as solar tracking system and micro-sized\nsurface topology10,11. These solutions are modular and can be directly integrated with\nour core PV-TE coupling design for real-world deployment. We fully agree that\nensuring more stable power output under varying daytime solar incident angles is\ncrucial for practical applications and plan to address this in future work.\n)K/Vμ(\ntneiciffeoc\nkcebeeS\nN-type Bi2Te3\nP-type Bi2Te3\nTemperature (℃)\n)mc/S(\nytivitcudnoc\nlacirtcelE\n1\n1\n1\n1\n6\n4\n2\n0\n8\n6\n4\n0\n0\n0\n0\n0\n0\n0\n0\n0\n0\n0\n0\n0\n0\n0 2\nT\n0\ne m p e\n4 0\nra tu re\nN -typ\nP -typ\n6 0\n( ) ℃\ne B\ne B\ni T e 2 3\ni T e 2 3\n8 0\nc\n2.0\n)K\nm 1.9 N-type Bi2Te3\n/W 1.8 P-type Bi2Te3\n( y 1.7\ntiv\n1.6\nitc\nu 1.5\nd\nn 1.4\no\nc 1.3\nla\nm 1.2\nre 1.1\nh\nT 1.0\n0 20 40 60 80\nTemperature (℃)\n5. How does this study align with or deviate from reality? The authors should explicitly\nstate the extent of deviation between model assumptions and real-world conditions in\nthe supplementary materials and evaluate the potential efficiency errors or boundary\neffects caused by this deviation to clarify the applicability of the study's findings in\npractical deployment.\nReply: Thank you very much for the valuable suggestion. The deviation between model\nassumptions and real-world conditions are summarized as follows:\n(1) The PT-TECM analysis is based on steady-state thermal equilibrium and does not\nincorporate transient variations in irradiance, wind speed, or ambient temperature.\nThe convective heat transfer coefficient was fixed at 5 W/m2K, corresponding to heat\ntransfer in a static environment. Variations in this coefficient, such as ranging from 5 to\nThe outdoor maximum efficiency of the PV-TE hybrid system experienced an\nefficiency loss of approximately 9 % in June and 14 % in September, relative to\nlaboratory measurements under ideal steady-state conditions (Fig. S28), mainly due to\ndifferences between the cold-side (0° C in the model vs. 22-25 °C in reality) and\nenvironmental temperatures (40 °C in the model vs. 35 - 40 °C in practice).\n(2) The interfacial thermal resistances were neglected in the model. In practical\napplications, poor thermal contact can significantly increase the interfacial thermal\nresistance, leading to significant performance losses.\nAs mentioned in the reply to your comment 3, this might cause an absolute system\nefficiency degradation of approximately 2 - 7 %.\n(3) In this study, thermal radiative losses were neglected due to the use of low-\nemissivity materials. However, in practical applications, factors such as oxidation of\nlow-emissivity materials may lead to significant deviations in thermal radiation\ncharacteristics, potentially resulting in thermal radiative losses that cannot be ignored.\nDespite quantitative deviations, the synergistic PV-TE coupling mechanism and\nrelative performance trends predicted by steady-state modeling are consistent with\nexperimental observations. The deviation between model assumptions and real-world\nconditions has been clarified in the revised Supplementary Information (Page 18).\n6.The discussion on the thermal reliability and long-term operation of the system is\ninsufficient. There is a lack of analysis regarding long-term thermal stress and\ninterfacial fatigue behavior under actual working conditions (continuous illumination,\nloaded operation). For PV-TE systems operating over extended periods, factors such as\naging of encapsulation materials, changes in electrode contact resistance, thermal\nfatigue of bonding layers, and microcracks induced by thermal cycling could\nsignificantly affect output stability.\nReply: Thank you very much for the valuable suggestion. Indeed, to achieve truly\npractically usable system, much more work including that for a much comprehensive\nand systematic investigation for the stability vs various conditions/parameters is much\nneeded. Definitely, we fully agree that our discussion on thermal reliability and long-\nterm operation of the system is insufficient. We would like to pursue this in future for\nthis part.\nPlease note, in the original manuscript, we have conducted some stability testing in\nthis regard, such as thermal cycling tests (Fig. S17) under the ISOS-T-2 protocol (dark,\nopen-circuit conditions). The experimental results indicate that, after 100 thermal\ncycles, the PV-TE system retained approximately 94 % of its initial performance,\nindicating good thermal and interfacial stability under thermal cycling.\nSolar-thermal cycling tests under concurrent illumination and electrical load (ISOS-\nLT protocol), which are highly important for evaluating long-term operational stability,\nwere not conducted in this study due to equipment limitations. Investigation of the\nassociated long-term failure mechanisms (such as interfacial fatigue behavior) would\nrequire extensive additional testing and in-depth characterization and will be addressed\nin our future work.\nIn response to the review’s concern, we have clarified in the Main Text (Page 19)\nthat real-world deployment of PV-TE hybrid system will require corrosion-resistant\nencapsulation, mechanical durability, and long-term validation.\nReviewer 2\n:\nThe authors have substantially addressed all major concerns raised in my previous\nreview, both through additional experiments/analysis and by clarifying the scope and\nlimitations of their claims. Remaining issues are minor and mainly relate to wording\nand further contextualization rather than fundamental flaws. I therefore recommend\nacceptance, possibly after minor polishing as follows:\nReply: Thank you very much for the positive comment. Please find below our detailed\nresponses and the corresponding revisions.\n1. Please explicitly acknowledge the steady-state nature of PT-TECM analysis.\nCurrent wording may lead readers unfamiliar with thermal modelling to assume that\ntransient effects are included. Please add a sentence in the text or Fig. 3 caption\nexplicitly stating that “the PT-TECM analysis is based on steady-state thermal\nequilibrium and does not incorporate transient variations in irradiance, wind speed, or\nambient temperature.”\nReply: Thank you very much for the valuable suggestion. Following the reviewer’s\nadvice, we have added the suggested sentence to the caption of Fig. 3 in the revised\nMain Text (Page 16): “The PT-TECM analysis is based on steady-state thermal\nequilibrium and does not incorporate transient variations in irradiance, wind speed, or\nambient temperature.”\n2. The revised Supplementary Note provides a realistic discussion of engineering\nchallenges; however, the main-text description near Fig. 4 still reads aspirational.\nAuthors can add one sentence indicating that “These scenarios remain conceptual, and\nreal-world deployment will require corrosion-resistant encapsulation, mechanical\ndurability, and long-term validation.”\nReply: Thank you very much for the valuable suggestion. Following the reviewer’s\nadvice, we have added the suggested sentence to the Main Text near Fig. 4 (Page 19):\n“It is important to note that these scenarios remain conceptual, and real-world\ndeployment will require corrosion-resistant encapsulation, mechanical durability, and\nlong-term validation.”\n3. To avoid overgeneralization, authors need to clarify that the unfavorable LCOE\npertains mainly to large-scale terrestrial installations, while special environments (e.g.,\nin aerospace, offshore, or payload-limited environments) may prioritize power density\nover cost per watt. A brief sentence to this effect would improve clarity.\nReply: Thank you very much for the valuable suggestion. Following the reviewer’s\nadvice, we have added a sentence in the revised Main Text (Page 19) to clarify the\nunfavorable LCOE: “It is also important to note that the disadvantage of its\nunfavorable LCOE might be tuned down for some special environments (e.g., in\naerospace, offshore, or payload-limited environments), where higher power density is\nprioritized over cost per watt.”\nReferences\n1. Xu, L. et al. Efficient perovskite photovoltaic-thermoelectric hybrid device. Adv.\nEnergy Mater. 8, 1702937 (2018).\n2. Liu, Z. et al. Novel integration of carbon counter electrode based perovskite solar\ncell with thermoelectric generator for efficient solar energy conversion. Nano\nEnergy 38, 457-466 (2017).\n3. Zhou, Y. et al. Perovskite solar cell-thermoelectric tandem system with a high\nefficiency of over 23 %. Mater. Today Energy 12, 363-370 (2019).\n4. Yin, E. & Li, Q. Achieving extensive lossless coupling of photovoltaic and\nthermoelectric devices through parallel connection. Renew. Energy 193, 565-575\n(2022).\n5. Guo, J. & Huai, X. Maximizing electric power through spectral-splitting\nphotovoltaic-thermoelectric hybrid system integrated with radiative cooling. Adv.\nSci. 10, 2206575 (2023).\n6. Hu, X. et al. Power generation from nanostructured PbTe-based thermoelectrics:\ncomprehensive development from materials to modules. Energy Environ. Sci. 9,\n517-529 (2016).\n7. Chen, W.-H., Wang, C.-C. & Hung, C.-I. Geometric effect on cooling power and\nperformance of an integrated thermoelectric generation-cooling system. Energy\nConvers. Manage. 87, 566-575 (2014).\n8. Högblom, O. & Andersson, R. Analysis of thermoelectric generator performance\nby use of simulations and experiments. J. Electron. Mater. 43, 2247-2254 (2014).\n9. Kishore, R. A., Kumar, P. & Priya, S. A comprehensive optimization study on\nBi2Te3-based thermoelectric generators using the Taguchi method. Sustain. Energy\nFuels 2, 175-190 (2018).\n10. Zeng, R. et al. All-polymer organic solar cells with nano-to-micron hierarchical\nmorphology and large light receiving angle. Nat. Commun. 14, 4148 (2023).\n11. Zhu, L. et al. Achieving 20.8 % organic solar cells via additive-assisted layer-by-\nlayer fabrication with bulk p-i-n structure and improved optical management. Joule\n8, 1-16 (2024)."}, {"round": 3, "reviewer_comments": {"reviewer_2": "After careful review of the revised manuscript and Supplementary Information, I find that the study is scientifically sound, the main conclusions are well supported by the presented data, and the previously raised concerns have been adequately addressed. The manuscript is now suitable for publication. Nevertheless, one clear consistency error in the Supplementary Information requires correction, and a few minor clarifications are recommended before acceptance.\n1. In Supplementary Note 7, there is an inconsistency in the reported ambient temperature conditions. Supplementary Note 7-Table 3 is labeled as corresponding to 313 K, whereas the table content lists Tatm = 298 K. This appears to be a typo mistake, but should be corrected to ensure internal consistency. All temperature labels in Supplementary Note 7, including table titles, figure captions, axis labels, and parameter listings, should be carefully checked and made fully consistent.\n2. While the manuscript and Supplementary Information clarify that the reported peak efficiencies (e.g., exceeding 50%) are obtained under steady-state conditions with controlled boundary assumptions, these conditions are highly favorable and not representative of typical outdoor operation. I therefore recommend adding a brief reminder near the main efficiency discussion or relevant figure caption, noting that these values correspond to controlled steady-state boundary conditions (including the regulated cold-side temperature), with a reference to the Supplementary Information where outdoor performance deviations are quantified.\n3. The Supplementary Information assumes a uniform 30-year service lifetime for all technologies to enable consistent LCOE comparisons, while also acknowledging that long-term durability remains a challenge for some components. To avoid potential misinterpretation, it would be helpful to explicitly state that this lifetime represents a scenario assumption for benchmarking and comparative analysis, rather than a claim of current technological feasibility.", "reviewer_3": "I co-reviewed this manuscript with one of the reviewers who provided the listed reports. This is part of the Nature Communications initiative to facilitate training in peer review and to provide appropriate recognition for Early Career Researchers who co-review manuscripts."}, "author_response": "Replies to reviewers’ comments for Nature Communications\nNCOMMS-25-25787C\n(Text in blue is our replies)\nReviewer 2\n:\nAfter careful review of the revised manuscript and Supplementary Information, I find\nthat the study is scientifically sound, the main conclusions are well supported by the\npresented data, and the previously raised concerns have been adequately addressed.\nThe manuscript is now suitable for publication. Nevertheless, one clear consistency\nerror in the Supplementary Information requires correction, and a few minor\nclarifications are recommended before acceptance.\nReply: Thank you very much for the positive comment. Please find below our detailed\nresponses and the corresponding revisions.\n1. In Supplementary Note 7, there is an inconsistency in the reported ambient\ntemperature conditions. Supplementary Note 7-Table 3 is labeled as corresponding to\natm\nbut should be corrected to ensure internal consistency. All temperature labels in\nSupplementary Note 7, including table titles, figure captions, axis labels, and parameter\nlistings, should be carefully checked and made fully consistent.\nReply: Thank you very much for pointing out the inconsistency, we have corrected the\ntypo mistake in Supplementary Note 7 and ensured all labels are consistent.\n2. While the manuscript and Supplementary Information clarify that the reported peak\nefficiencies (e.g., exceeding 50%) are obtained under steady-state conditions with\ncontrolled boundary assumptions, these conditions are highly favorable and not\nrepresentative of typical outdoor operation. I therefore recommend adding a brief\nreminder near the main efficiency discussion or relevant figure caption, noting that\nthese values correspond to controlled steady-state boundary conditions (including the\nregulated cold-side temperature), with a reference to the Supplementary Information\nwhere outdoor performance deviations are quantified.\nReply: Thank you very much for the valuable suggestion. We have added the suggested\nreminder in the figure caption of Fig. 3 (Page 35 in the revised main text), where the\npeak efficiency is reported:\n“Note that these peak efficiencies (e.g., > 50 %) are obtained under controlled steady-\nstate conditions, including AM1.5G solar illumination and a regulated cold-side\ntemperature. For performance deviations under outdoor conditions, see Supplementary\nFigs. 27 and 28.”\n3. The Supplementary Information assumes a uniform 30-year service lifetime for all\ntechnologies to enable consistent LCOE comparisons, while also acknowledging that\nlong-term durability remains a challenge for some components. To avoid potential\nmisinterpretation, it would be helpful to explicitly state that this lifetime represents a\nscenario assumption for benchmarking and comparative analysis, rather than a claim of\ncurrent technological feasibility.\nReply: Thank you very much for the valuable suggestion. We have added the suggested\nclarification to the revised Supplementary Information (Page 50):\n“This lifetime represents a scenario assumption for benchmarking and comparative\nanalysis, rather than a claim of current technological feasibility.”"}]

Decision letter