Allylrhodanine-processed all-small-molecule organic solar cell achieves an 18.43% efficiency breakthrough

Domain: neuroscience
Published: 2026-01-28
Editorial outcome: major_revision

Abstract
Solid additives (SAs) improve organic solar cells (OSCs) morphology and performance, yet, their efficiency in all-small-molecule (ASM) OSCs is limited by strong donor-acceptor crystallinity, and the underlying mechanisms remain unclear. Herein, structurally resembling the MPhS-C2 donor, 3-allylrhodanine (3-AR) as a SA enables precise control over the active layer morphology. Interesting, combined theoretical calculations and thin-film morphology analyses reveal 3-AR preferentially interacts with acceptor N3, thereby directing morphology evolution. Moreover, 3-AR effectively narrows the film formation window, suppressing lateral over-aggregation and crystallization, while promoting vertical donor–acceptor homogeneity. This optimized morphology synergistically facilitates efficient charge dissociation and collection, suppresses both bimolecular and trap-assisted recombination, and extends the lifetimes of excitons and charge carriers. Therefore, the 3-AR-treated MPhS-C2:N3 device achieves a remarkable power conversion efficiency (PCE) of 18.43% (certified 18.16%)—the highest reported for binary ASM-OSCs. This work shows additive efficacy is governed by balanced selective interactions, not by simplistic structural similarity.

Introduction
Printable organic solar cells (OSCs), featuring newspaper-like manufacturability along with ultralight/ultrathin/flexible characteristics, are ideally suited for deployment in distributed photovoltaic systems1–4. Recent breakthroughs in device engineering have propelled polymer-based organic solar cells (P-OSCs) beyond the 21% power conversion efficiency (PCE) milestone; however, all-small-molecule OSCs (ASM-OSCs) still remain, with PCEs currently capped at around 18%5–7. In contrast to the batch-dependent performance of P-OSCs, ASM-OSCs offer superior material homogeneity, defined molecular structures, simplified purification, and excellent batch-to-batch consistency, positioning them as highly competitive candidates for industrial-scale manufacturing8–10. However, the strong crystallization tendency of small-molecule donors and acceptors leads to large phase separation domains (>60 nm) with diminishing donor−acceptor interface11, which impedes exciton diffusion (10–30 nm)1,12, thereby reducing short-circuit current density (Jsc) in ASM-OSCs. Besides, their high molecular-ordering features prevent the formation of a bi-continuous interpenetrating network morphology, instead developing island-like structures that act as traps for excitons and charges, inducing morphology recombination and counterproductively degrading the fill factor (FF) parameter in ASM-OSCs13–17.

As a result, precisely controlling the active layer morphology in ASM-OSCs becomes significantly more challenging. Consequently, the delicate balance between molecular crystallization and phase separation within the ASM-OSCs remains difficult to regulate, hindering the achievement of high PCEs (>20%). To date, various strategies have been developed to tune the active layer morphology in ASM-OSCs, including optimization of the donor/acceptor ratio18, use of processing additives19–21, thermal and/or solvent vapor annealing post-treatments22,23, incorporation of ternary components24,25, etc. Among these strategies, solid additives (SAs) have proven particularly effective in finely tuning the nucleation and growth dynamics within ASM-OSCs (Fig. 1). The dual-additive strategy, combined a SA and a solvent additive through their synergistic effects to achieve optimal ASM-OSC active layer morphology. A representative case is DIB and DIM engineered by Lu’s group, which achieved a solvent annealing-free PCE of 15.2% in BTR-Cl:Y6-based ASM-OSCs via a dual-additive strategy, where volatile solid additive (VSA) DIB induced a Y6-based eutectic phase to enhance intermolecular interactions and modulated acceptor phase separation, while solvent additive DIM volatilized to suppress BTR-Cl over-aggregation during film formation26. Additionally, the large π-ring strategy, demonstrated by Gao’s group through combining graphene oxide methyl ester (GOMe) as a SA with a layer-by-layer deposition technique, enabled precise control vertical phase separation and crystallization kinetics in the active layer, achieving a PCE of 17.18% in ZnP-TSEH:4TIC:6TIC-based ASM-OSCs27. Moreover, the polymer additive strategy, implemented by Li’s group through incorporating the insulating polymer styrene-ethylene-butene-styrene (SEBS) as a morphology stabilizer, achieved enhanced stability in BM-ClEH:BO-4Cl-based ASM-OSCs. By suppressing donor molecules degradation and mitigating crystallization/aggregation in the blend film, SEBS significantly enhanced the operational stability under continuous illumination (T80 > 15,000 h)28. Furthermore, VSA strategy, developed by Sun’s group using 1,1-diaminomethyl-3-indolone (IC-FI), structurally analogous to the terminal group of the N3 acceptor, achieved a PCE of 14.43% in BTR-Cl:N3-based ASM-OSCs. This enhancement resulted from strengthened π-π interactions among N3 molecules and dense molecular self-assembly induced by IC-FI volatilization29. What’s more, ternary strategy, demonstrated by Min’s group, achieving the highest PCE of 18.1% reported for ternary MPhS-C2:L8-BO:L8-S9-based ASM-OSCs though co-utilization with the VSA DIB8. As demonstrated in the examples above, SAs show significant potential in regulating crystallization and phase separation in ASM-OSCs. Nevertheless, most SAs have been optimized from those originally developed for P-OSCs, and the underlying interaction mechanisms between SAs and active layer components in ASM-OSCs remain poorly understood.

In this study, we introduce 3-allylrhodanine (3-AR) as a VSAs. While its structure resembles the terminal group of the MPhS‑C2 donor, its functional groups (carbonyl, -C=S, and -C-H, etc.) can form selective interactions with the donor (e.g., Dithienobenzodithiophene (DTBDT) core units) and acceptor (e.g., 2-(5,6-difluoro-3-oxo-2,3-dihydro-1H-inden-1-ylidene)ma-lononitrile (2FIC) units and 6,7-dihydropyrrolo[3,2-g][1,2,5]thiadiazolo[3,4-e]indole core units)30,31, thereby potentially regulating the morphology and improving photovoltaic performance of ASM-OSCs. Theoretical calculations result clearly indicates that, thermodynamically, 3-AR has a greater tendency to interact with N3 molecules. Combined thin-film structural characterization, we found that the thermodynamic differences in intermolecular interactions, which directly dictate the evolution of the final morphology. Moreover, the 3-AR VSA narrows the film formation window, thereby reducing film formation time. It suppresses excessive crystallization of the blend film, promoting the formation of smaller, well-suited phase separation domains laterally, while simultaneously enhancing vertical donor/acceptor homogeneity within the active layer. Thus, the 3-AR VSA enhances charge dissociation and collection kinetics, mitigates bimolecular and trap-assisted recombination, and prolongs exciton and charge lifetimes. Consequently, the 3-AR-optimized ASM-OSCs attained a superior PCE of 18.43%, with an improved Jsc of 27.32 mA/cm² and an unprecedented FF of 78.19%, representing a 0.97-percentage-point gain in PCE over the VSA-free control one (17.46%). This work not only establishes a new efficiency benchmark for binary ASM-OSCs, achieving a third-party certified PCE of 18.16% among single-junction devices to date, but also advances the development of high-performance ASM-OSCs.

Results
Photovoltaic performances of ASM-OSCs
The chemical structures of small molecule donor MPhS-C210, acceptor N332, and 3-AR VSA used in this study are shown in Fig. 2a. To evaluate the effect of the 3-AR additive on the photovoltaic performance of the devices, ASM-OSCs with a conventional structure of indium tin oxides (ITO)/(2-(9H-Carbazol-9-yl) ethyl) phosphonic acid (2PACz)/active layer/H75/Ag were fabricated, where the recently developed H75 serves as the electron transport layer33. The chemical structures of 2PACz and H75 are shown in Supplementary Fig. 1. The processing parameters, including donor-to-acceptor ratio, solution concentration, spin-coating speed, annealing temperature, and additive concentration, were systematically optimized through iterative screening, as detailed in Supplementary Figs. 2–6 and Supplementary Tables 1–5. The optimal device performance is at 2.5 wt.% 3-AR (weight ratios relative to MPhS-C2:N3), with PCEs progressively declining at higher concentrations. Table 1 summarizes the key performance metrics of the control and optimized devices and Fig. 2b displays their current density−voltage (J–V) characteristics. The control device based on MPhS-C2:N3 displayed a PCE of 17.46%, with an open-circuit voltage (Voc) of 0.863 V, a Jsc of 27.03 mA/cm2, and an FF of 74.85%. With 2.5 wt% 3-AR VSA, the device attained a champion PCE of 18.43%, propelled by a notable enhancement in FF of 78.19%, accompanied by a modest increase in Jsc of 27.32 mA/cm2, while maintaining a Voc of 0.863 V. Furthermore, the 3-AR-processed devices garnered independently certified PCEs of 18.16% from the National Center of Inspection on Solar Photovoltaic Products Quality (CPVT), with comprehensive certification reports provided in Supplementary Fig. 7. Crucially, comprehensive statistical analysis of state-of-the-art ASM-OSCs with PCEs exceeding 15% reveal that our 3-AR-processed device exhibits the high Jsc and exceptional FF, synergistically achieving a remarkable PCE of 18.43%, which is the highest value for binary ASM-OSCs reported to date. The comparative data are presented in Fig. 2c and Supplementary Table 6. Supplementary Fig. 8 compares the PCE distributions of 50 devices with/without 3-AR, revealing improved reproducibility and reduced performance variation upon 3-AR treatment8. These results confirm that trace amounts of the 3-AR enhance the Jsc and FF, thereby boosting overall photovoltaic performance of the device. Additionally, 3-AR not only effectively enhances the storage, photo-, and thermal stability of ASM-OSCs but also demonstrates excellent universality by being applicable to both representative all-small-molecule (e.g., B1:L8-BO and BTR-Cl:N3) and polymer systems (e.g., D18-Cl:N3 and PM6:L8-BO), as shown in Supplementary Figs. 9–11 and Supplementary Tables 7–13.

The external quantum efficiency (EQE) curves of MPhS-C2:N3-based devices processed with and without 3-AR additives are shown in Fig. 2d, illustrating their wavelength-dependent photon-to-electron conversion efficiency across the 300–1000 nm range. The 3-AR-processed device exhibits higher EQE across the 510–830 nm compared to the control device, achieving a peak value of 88% (vs. 86% for the control device). The integrated Jsc values calculated from control and 3-AR-processed devices are 26.01 and 26.28 mA/cm2, respectively, closely matching the Jsc derived from J–V measurements34. The internal quantum efficiency (IQE) spectra were derived from reflection (R) and EQE measurements (Supplementary Fig. 12). Compared to the control device, the 3-AR treated device exhibit significantly improved IQE values across the range of 510–830 nm, which contributes to achieving a higher Jsc. This improvement in photo-electron conversion efficiency can be attributed to enhanced exciton dissociation and more efficient charge transport within the 3-AR-processed active layer35.

Volatilization property of 3-AR
As shown in Supplementary Fig. 13, the thermogravimetric analysis (TGA) curve of 3-AR solid powder, heated from 25 to 300°C at a scanning rate of 5°C/min, shows a weight loss of 5% at 150°C and a complete weight loss of 100% at about 225°C. As seen from Supplementary Fig. 14, 3-AR exhibits limited standalone film formation with a non-uniform coverage on the quartz substrate, and thermal annealing at 100°C induces sequential phase transitions: liquefaction within 1 min, partial evaporation by 6 min, and complete elimination after 10 min, confirming its superior volatility. Fourier transform infrared spectroscopy (FTIR) spectra reveal the 3-AR’s characteristic peak at 1734 cm−1 in the MPhS-C2:N3 blend film, which vanishes after 100°C thermal annealing, further confirming complete volatilization of 3-AR (Supplementary Fig. 15). Given the high volatility of 3-AR, its complete absence was further verified by nuclear magnetic resonance (NMR) spectroscopy (Supplementary Fig. 16). Comparative analysis of the films before and after annealing showed that the characteristic signals of the 3-AR disappeared entirely after the thermal annealing treatment. In short, the residue-free volatilization of 3-AR is critical for achieving stable and additive-free active layers in OSCs36.

Theoretical calculation and intermolecular interactions
We calculated the molecular electrostatic potential (ESP) distribution and dipole moments of MPhS-C2, N3, and 3-AR by using density functional theory (DFT) to investigate the intermolecular interactions between 3-AR and photoactive materials. As illustrated in Supplementary Fig. 17, MPhS-C2 and N3 exhibited distinct ESP characteristics. The MPhS-C2 showed a more negative ESP distribution, with fewer positive charges on the molecular surface. In contrast, the N3 predominantly displayed a positive ESP distribution, with localized negative regions at its carbonyl, cyano, and fluorine substituents. For the 3-AR, the strong electronegativity of the sulfinyl and carbonyl groups results in a weak negative ESP distribution across its main molecular surface, while positive charge regions were localized on the hydrogen and propylene groups of the thiazolidine ring. Based on Coulomb’s law, 3-AR exhibits preferential interactions with the N3. To further elucidate the interaction mechanism, complexes of 3-AR with either the end groups or core units of MPhS-C2 and N3 were constructed, and their respective binding energies (ΔEb) were calculated, as illustrated in Fig. 2e. The ΔEb are calculated to be −18.44 (C–H···S and C=O···H) and −18.99 (C–H···H) kcal/mol for the 3-AR with the end groups of MPhS-C2 and N3, respectively, as determined by the Eq. (1) (see details in Methods). 3-AR is found to have more negative ΔEb values of −19.61 (C=S···H) and −21.07 (C–N···H) kcal/mol when interact with the core units of MPhS-C2 and N3, molecules, respectively. Generally, the more negative ΔEb values indicate that the stronger intermolecular interactions. The results suggest that 3-AR preferentially tends to stack on the core units of MPhS-C2 and N3 molecules rather than on their end groups.

Two-dimensional ¹H-¹H nuclear overhauser effect spectroscopy (NOESY) can determine spatial proximity between protons within 5 Å and was thus used to probe intermolecular interactions between additives and photoactive materials37. Although the NOESY spectrum of 3-AR with MPhS-C2 (Supplementary Fig. 18a) showed no crossover resonance peaks, the possibility of other types of interactions could not be ruled out. Therefore, NMR titration was performed (Supplementary Fig. 19a), which showed chemical shift changes (δ = 7.8) in the ¹H NMR spectra with increasing proportion of 3-AR, confirming an interaction between MPhS-C2 and 3-AR. On the other hand, the NOESY spectrum of 3-AR with N3 solution (Supplementary Fig. 18b) displayed weak but discernible cross resonance peaks (marked by the green box) between the terminal proton of N3 (Ha, δ = 8.40) and a proton of 3-AR (Hb, δ = 4.0), indicating the spatial proximity and interaction between N3 and 3-AR38. This result was further supported by NMR titration experiments (Supplementary Fig. 19b). Collectively, these NMR analyses and DFT calculations demonstrate that 3-AR participates in distinct intermolecular interactions with MPhS-C2 and N3 through different functional groups, thereby effectively modulating the morphology of the active layer.

The kinetics of film formation
In-situ ultraviolet-visible (UV–Vis) absorption spectroscopy was used to track morphology evolution kinetics during film formation, revealing how 3-AR modulates crystallization via solvent evaporation control. The time-resolved color mapping of UV–Vis spectra for MPhS-C2, N3 and MPhS-C2:N3 films prepared without and with 3-AR are displayed in Fig. 3a and Supplementary Fig. 20a, b, while the corresponding spectra are shown in Supplementary Fig. 21. The film formation process evolves through three distinct stages: (I) solvent evaporation, (II) nucleation and crystallization (phase transition process), and (III) film solidification39. The duration of stage II (Δt) plays a critical role in molecular self-assembly kinetics. Typically, prolonged Δt facilitates molecular rearrangement for ordered packing, whereas shortened Δt restricts intermolecular interactions, thereby suppressing molecular crystallization40,41. For neat films, Supplementary Fig. 20c reveals that 3-AR modulates the film formation kinetics of MPhS-C2 and N3 divergently during stage II: the MPhS-C2’s processing window shortens from 0.20 to 0.10 s, likely suppressing excessive crystallization of MPhS-C2, while the N3’s duration extends from 0.097 to 0.191 s, facilitating ordered N3 molecular packing, as confirmed by grazing-incidence wide-angle X-ray scattering (GIWAXS) analysis. Analysis of MPhS-C2:N3 blend film formation kinetic reveals three key insights (Fig. 3b): (1) MPhS-C2 preferentially nucleation and crystallization from solution (t = 0.39 s), then N3 starts to crystallization, indicating that the crystallization of MPhS-C2 is the driving force for the phase separation; (2) 3-AR additives extend the temporal gap between MPhS-C2 finishing crystallization and N3 starting nucleation (Δt from 0.38 to 0.48 s). This extended temporal gap may improve donor–acceptor miscibility and suppress the early nucleation of N342; (3) 3-AR additives shorten stage II processing time (MPhS-C2: Δτ from 0.097 to 0.095 s; N3: Δτ from 0.190 to 0.097 s), effectively inhibiting excessive MPhS-C2:N3 blend crystallization, which is helpful to promote an optimal nanoscale phase morphology (as evidenced by GIWAXS). 3-AR additives moderately reduce the active layer film formation time, effectively suppressing excessive donor/acceptor crystallization through kinetic modulation, which facilitates an optimal and small nanoscale phase separation morphology.

Thin film morphology analysis
The surface free energy (γ) of the active layer components treated without and with 3-AR additives was investigated by measuring the contact angle of the films with deionized water and formamide. The contact angle diagram and calculation results are shown in Supplementary Fig. 22 and Supplementary Tables 14–15. The γ values of MPhS-C2, MPhS-C2:3-AR, N3, and N3:3-AR films are estimated to be 18.57, 30.45, 18.04, and 27.78 mJ/m2, respectively. According to literature reports, the γ of 2PACz is approximately 48 mJ/m²43. The increased surface free energies after 3-AR treatment indicate improved wettability and reduced interfacial energy mismatch with the 2PACz hole transport layer, facilitating formation of intimate Ohmic contact during spin coating and lowering interfacial resistance. This enhanced interfacial compatibility also contributes to multidimensional morphology optimization. The synergistic effects arising from enhancements the lateral nanostructure and vertical phase uniformity will be analyzed in the following section44,45.

GIWAXS was employed to probe the impact of 3-AR on film morphology and crystallinity. For neat MPhS-C2 films, the in-plane (IP) (010) peak at q = 1.799 Å⁻¹ and out-of-plane (OOP) (100/200/300) peaks at q = 0.249/0.526/0.793 Å⁻¹ indicate edge-on molecular packing46. The 3-AR treatment preserves this orientation but reduces crystalline coherence length (CCL), calculated from the full width at half-maximum (FWHM) of these peaks, indicating suppressed MPhS-C2 crystallization, as detailed in Supplementary Fig. 23 and Supplementary Table 16. Neat N3 films exhibit face-on orientation with IP (100) lamellar peak at q = 0.278 Å⁻¹ and OOP (010) π−π stacking at q = 1.763 Å⁻¹. The 3-AR treatment reduces the lamellar CCL from 9.32 to 9.14 nm but increases the π−π stacking CCL from 3.37 to 3.46 nm, suggesting enhanced molecular packing orderliness of N3, as detailed in Supplementary Fig. 24 and Supplementary Table 17. The MPhS-C2 transitions from edge-on to face-on molecular orientation when blended with N3, as indicated by the overlapping (010) OOP peak (d-spacing ≈ 3.45–3.60 Å), which arises from co-planar π–π stacking of MPhS-C2 and N3 components, as detailed in Fig. 3c and d and Supplementary Table 1847. In the MPhS-C2:N3 blend film, 3-AR treatment reduces the CCL values in both orientations. Specifically, the CCLs for the (010) OOP and (100) IP peaks decrease from 4.30 to 4.06 nm and from 15.43 to 15.10 nm, respectively. Although 3-AR treatment suppresses crystallization of the donor MPhS-C2 while promoting that of the N3 acceptor, in-situ absorption measurements reveal that the MPhS-C2 donor precipitates first from the solution. This suggests that the early-precipitating MPhS-C2, with inhibited crystallization, drives phase separation while simultaneously constraining the crystallization of the acceptor N3. This effect ultimately results in overall weakened crystallization within the blend film. The 3-AR additive concurrently suppresses the crystallization of both MPhS-C2 and N3 components, acting as a dual crystallization inhibitor—a rare characteristic among OSC additives. This unconventional mechanism facilitates optimized nanoscale phase separation.

Atomic force microscopy (AFM) and transmission electron microscopy (TEM) were employed to characterize the surface morphology and nanoscale phase separation of the active layer with and without 3-AR. The AFM height image of neat MPhS-C2 film shows a root-mean-square (RMS) surface roughness of 3.61 nm (Supplementary Fig. 25a), whereas the 3-AR-processed MPhS-C2 film exhibits slightly reduced roughness (RMS = 3.37 nm), suggesting effective suppression of excessive donor crystallization. This observation well-aligns with the reduced crystallinity evidenced by GIWAXS. However, the 3-AR-processed N3 film exhibits a slight increase in surface roughness (RMS = 1.93 nm vs. 1.63 nm), likely due to increased CCL observed in GIWAXS analysis, as depicted in Supplementary Fig. 25b. The 3-AR-processed MPhS-C2:N3 blend film exhibited a reduced RMS value of 1.80 nm compared to 1.90 nm for the untreated film, indicating suppressed crystallinity and improved surface homogeneity through additive-mediated crystallization control, as shown in Fig. 3e. In addition, AFM phase images exhibit that 3-AR mitigates MPhS-C2 over-aggregation, resulting in optimally phase-separation domains with ordered and uniform nanoscale protrusions in the blend film, as shown in Supplementary Fig. 26. Further TEM observations of the MPhS-C2:N3 blend film, shown in Fig. 3f, reveal that the 3-AR-treated film exhibits significantly reduced nanoscale phase separation, featuring a distinct whisker-like network uniformly interpenetrating smaller domains compared to the untreated counterpart. The incorporation of the 3-AR effectively modulates the film’s nano-structure morphology by suppressing excessive phase separation, thereby facilitating efficient exciton dissociation and enabling superior charge transport properties.

Film-depth-dependent light absorption spectroscopy (FLAS) was employed to probe 3-AR’s modulation effects on vertical phase separation, with mapping of component distribution gradients, exciton population profiles, and spatially exciton generation rates. The absorption spectra of MPhS-C2:N3 blend films at varying film depths are shown in Fig. 4a, revealing three critical observations: (1) The donor and acceptor exhibit characteristic absorption peaks at 570/623 nm for MPhS-C2 and 830 nm for N3, consistent with their respective single-component spectra (Supplementary Fig. 27). (2) The absorption peaks are sharper near the film surface, which is attributed to rapid surface crystallization as the chloroform solvent evaporates first at the interface. In contrast, slower solvent evaporation in the bulk promotes intermixing of MPhS-C2 and N3, suppressing crystallization in the bottom layers. (3) The reduced 0-0/0-1 vibronic peak intensity ratio correlates with decreased MPhS-C2 molecular crystallization under 3-AR-processed blend film compared to control film, which is consistent with GIWAXS results.

The component distribution gradients across the film depths exhibited a flattened characteristic in the 3-AR-processed blend film, indicating improved vertical homogeneity of component distribution within the active layer, as shown in Fig. 4b. Furthermore, the exciton population profiles and spatially exciton generation rates, derived from FLAS data simulations, as shown in Fig. 4c, d. In the control blend film, the maximum exciton generation rate (Gmax) is localized within the 40−60 nm region. This localization increases the charge transport distance and raises the risk of recombination. In contrast, 3-AR-processed blend film shows a uniform exciton generation distribution, concentrated within the top 20 nm and bottom 40 nm regions. This optimized spatial distribution enables dissociated charges to quickly migrate to the electrodes, thereby enhancing charge transport and collection efficiency, along with a notable improvement in Jsc and FF23.

Exciton and charge carrier dynamics
To elucidate the 3-AR’s modulation effects on charge transport characteristics in MPhS-C2:N3-based devices, the dark J–V characteristics of unipolar devices (electron-transport: ITO/ZnO/Active layer/H75/Ag; hole-transport: ITO/2PACz/Active layer/MoO₃/Ag) were analyzed via space-charge-limited current (SCLC) method. As shown in Supplementary Fig. 28 and Supplementary Table 19, the electron mobility (μe = 1.28 × 10⁻⁴ cm2V⁻¹s⁻¹) and hole mobility (μh = 0.93 × 10⁻⁴ cm⁻²V⁻¹s⁻¹) are improved in 3-AR-processed devices compared to the control devices (μe = 1.03 × 10⁻⁴, μh = 0.69 × 10⁻⁴ cm⁻²V⁻¹s⁻¹), due to synergistic morphology optimization. Besides, the more balanced μe/μh ratio of 1.37 (vs. 1.50 in control devices) indicates effective suppression of space-charge accumulation, which in turn can enhance FF value2,7.

We further analyze the photocurrent density (Jph) and effective voltage (Veff) to reveal enhanced exciton dissociation (Pdiss: 97.48 to 98.06%) and charge collection efficiency (Pcoll: 86.94 to 88.48%) in 3-AR additives-treated devices, demonstrating optimized carrier dynamics for improved Jsc, as illustrated in Supplementary Fig. 294,15. Charge recombination analysis reveals suppressed bimolecular (α value from 0.975 to 0.996) and trap-assisted recombination (n value from 1.07 to 1.04) in 3-AR additives-treated devices via light-intensity-dependent Jsc/Voc measurements, as shown in Supplementary Fig. 30, demonstrating enhanced charge transport19,48. Furthermore, we quantified the trap density by deep-level transient spectroscopy (DLTS). As shown in Supplementary Fig. 31, comparing with control device, the trap density of the 3-AR treated device decreased from 3.14 × 10¹⁷ to 3.07 × 10¹⁷ cm⁻³. The reduced trap density indicates suppressed trap-assisted recombination, which is beneficial for improving FF and PCE of the device49. In addition, steady-state photoluminescence (PL) spectroscopy (Supplementary Fig. 32) reveals that the 3-AR-treated MPhS-C2:N3 blend film achieves enhanced PL quenching efficiencies of 95.01%/97.86%, respectively (94.37%/97.17% for control film). This improvement promotes exciton dissociation and facilitates highly efficient bidirectional charge separation50,51.

Transient photocurrent (TPC) and transient photovoltage (TPV) characterization techniques were employed to probe the 3-AR’s modulation effects on the charge extraction kinetics and recombination dynamics in the devices52. As shown in Supplementary Fig. 33a, TPC decay curves reveal accelerated charge extraction in 3-AR-processed device (τ = 0.24 μs) compared with control counterparts (τ = 0.32 μs), correlating with enhanced carrier collection efficiency. Besides, as shown in Supplementary Fig. 33b, TPV decay curves show prolonged charge carrier lifetimes (τ = 5.80 μs) in the 3-AR-processed device, compared with the control counterparts (τ = 3.47 μs). This enhanced carrier longevity significantly suppresses recombination losses. The results validate the 3-AR-processed device possesses multiscale morphology, ranging from nanoscale phase separation to microscale spatial distribution, which synergistically enhance charge transport characteristics, ultimately leading to higher Jsc and FF values.

The charge transfer dynamics within MPhS-C2:N3 blend films were systematically investigated using femtosecond transient absorption (fs-TA) spectroscopy. The 2D fs-TA spectra of the control and 3-AR-processed blend films are shown in Fig. 5a, while Fig. 5b displays representative transient absorption spectra at selected delay times. Upon selective excitation of the N3 acceptor at 825 nm, characteristic excited-state signatures of the acceptor were observed at early time delays (Supplementary Fig. 34), featuring ground state bleaching (GSB) signals at 710 nm and 850 nm, along with an excited state absorption (ESA) at 920 nm. As charge transfer progressed, the signals associated with the excited state of the acceptor decayed rapidly, while GSB signals attributed to the donor MPhS-C2 appear around 580 nm and 635 nm, indicating the occurrence of a hole transfer process from N3 to MPhS-C2. Concurrently, a new ESA signal emerged at 1010 nm, which can be attributed to the charge transfer state of N3. Comparative analysis of the fs-TA kinetics at 1010 nm revealed distinct trends between control and 3-AR-treated films. As illustrated in Fig. 5c, the kinetics at 1010 nm exhibited significantly slower decay in 3-AR-treated films, demonstrating effective suppression of charge recombination and extended charge carrier lifetime. To quantitatively deconvolute the temporal evolution of distinct species involved in the photoelectric conversion process, we performed global analysis based on a consecutive kinetic model, obtaining evolution-associated difference spectra (Fig. 5d, Supplementary Fig. 35 and Supplementary Table 20)53. This analysis resolved three key time constants: τ₁ (ultrafast interfacial charge transfer), τ₂ (exciton diffusion-mediated charge transfer), and τ₃ (charge recombination). Relative to the control film, the 3-AR-treated blend exhibited a reduction in τ₁ from 1.8 to 1.5 ps and in τ₂ from 51.9 to 40.7 ps, alongside an increase in τ₃ from 4595 to 5335 ps. The shortened τ₁ and τ₂ constants indicate enhanced exciton diffusion to the donor-acceptor interface and more efficient dissociation into free charges, consistent with an optimized phase-separated morphology and improved interfacial mixing induced by 3-AR treatment. The prolonged τ signifies an extended charge-separated state lifetime, reflecting reduced trap-assisted non-radiative recombination. Further investigation into the photoexcitation transfer kinetics54 (Supplementary Fig. 36 and Supplementary Table 21) revealed that 3-AR treatment increased the exciton lifetime (τe) from 17.22 to 17.44 ps and the charge lifetime (τc) from 569.85 to 595.61 ps. The concurrent extension of both exciton and charge lifetimes contributes to reduced charge recombination losses, improved exciton dissociation efficiency, and enhanced charge carrier mobility55. Collectively, these results underscore that 3-AR treatment effectively optimizes the blend film morphology, facilitating exciton dissociation and charge transport, which ultimately leads to the observed enhancements in Jsc and FF.

Methods
Materials and device fabrication
The small molecule donor MPhS-C2 was purchased from Solarmer Materials (Beijing) Inc. The acceptor N3 and hole interface layer (2-(9H-Carbazol-9-yl)ethyl)phosphonic acid (2PACz) were purchased from Derthon Materials, Inc. Solid additive 3-allylrhodanine (3-AR) was bought from Aladdin Scientific Corp. H75 was synthesized as previously reported (Adv. Funct. Mater. 33, 2303386 (2023)). Chloroform (CF) was bought from Sigma-Aldrich. All the materials were used as received without further and purification.

All devices were fabricated with a conventional structure (ITO/2PACz/Active layer/H75/Ag). Pre-patterned ITO-glass substrates were cleaned by sequential sonication in detergent, deionized water, acetone, and isopropanol for 15 min, then dried by Nitrogen gun, and subsequent ultraviolet-ozone treatment for 20 min. Then the ethyl alcohol solution of 2PACz (0.27 mg/mL) was spin-coated at 3000 rpm on top of the cleaned ITO substrates and annealed at 100°C for 10 min. For the active layer, the weight ratio of donor and acceptor was kept at 1.4:1.0 (w/w), and the blend solution had a total concentration of 20 mg/mL in CF. After stirred at 50°C for 1 h, different weight ratio of 3-AR was added to the blend solution, and the blend solution was spin-coated at around 2000 rpm for 30 s. The as-cast films were solvent (CF) annealed for 30 s and then thermally annealed at 100°C for 10 min. The electron transporting layer of H75 was deposited on the top of the active layer from a 1.0 mg/ml methanol solution via spin-coating at 3000 rpm for 20 s. Finally, the Ag cathode (~100 nm) was thermally evaporated on top of the substrates under high vacuum (<2×10–4 Pa).

Device characterization
Optical characterization. The J–V curves of all devices were measured under AM 1.5G solar illumination at 100 mW/cm2 using a Keysight B2901BL Precision Source/Measure Unit and an SS-X50 solar simulator (Enli Technology Co., Ltd., Taiwan) with a standard Si solar cell as a calibration standard. The EQE curves were measured by QE-R solar cell spectral response measurement system (Enli Technology Co., Ltd., Taiwan) in ambient air.

Density functional theory (DFT) calculation. All quantum chemical calculations are performed using Gaussian 16. The optimized geometries, ESP distribution, and dipole moment of molecules are calculated using the B3LYP density functional with the 6-311G(d,p) basis set. For the active layer system, under the same density functional and basis set, and the solvent effect was additionally considered. The binding energies between 3-AR additives and MPhS-C2 donor (or N3 acceptor) the components were calculated by the following Eq. (1):

Ebinding = Ecomplex − (E MPhS-C2(or N3) + E 3-AR) (1)

In-situ UV–vis absorption spectrum. In-situ UV–vis absorption spectra were acquired by a spectrometer (DU-300, Shaanxi Puguang Weishi Co. Ltd.). The spectrometer consists of a tungsten halogen light source, detector and spin coating instrument. The detector collects the transmission spectra ranged from 200 to 1050 nm during coating. The light source and detector were turned on before spin-coating the film, so time zero is the point at which the detector collected the first solution absorption spectrum. Before time zero, there is only noise in the absorption spectrum (Adv. Mater. 36, 2313105 (2024), Adv. Mater. 36, 2313532 (2024)).

FTIR characterizations. The FT-IR absorption spectra were measured on Nicolet iS5 (Thermo Fisher Scientific) with wavenumber ranging from 400 to 4000 cm−1.

Hole and electron mobility measurements. The electron and hole mobility were measured by using the method of space-charge limited current (SCLC) for electron-only devices with the structure of ITO/ZnO/active layers/H75/Ag and hole-only devices with the structure of ITO/2PACz/active layers/MoO₃/Ag. The charge carrier mobility was determined by fitting the dark current to the model of a single carrier SCLC according to the Eq. (2) (Adv. Funct. Mater. 33, 2305450 (2023)):

J = 9ε0εrμV2 / 8L3 (2)

where J is the current density, L is the film thickness of the active layer, μ is the charge carrier mobility, εr is the relative dielectric constant of the transport medium, and ε0 is the permittivity of free space. V is the internal voltage in the device and V = Vappl − Vbr − Vbi, where Vappl is the applied voltage to the device, Vbr is the voltage drop due to contact resistance and series resistance across the electrodes, and Vbi is the built-in voltage due to the relative work function difference of the two electrodes. The carrier mobilities can be calculated from the slope of the J1/2 − V curves.

Grazing incidence wide-angle X-ray scattering (GIWAXS) characterization. The GIWAXS measurement was carried out at the PLS-II 6DU-SAXS and 9A beamline of the Pohang Accelerator Laboratory in Korea. The scattering signal was recorded using a 2-D CCD detector (Rayonix SX165). The X-ray light had an energy of 11.24 KeV. The incidence angle of X-rays was adjusted to 0.09–0.12° to maximize the signal-to-background ratio.

Atomic force microscope (AFM). AFM measurements were performed by using a Scanning Probe Microscope Dimension iCon in tapping mode under atmosphere conditions at room temperature. All film samples were spin-cast on glass/ITO substrates.

Transmission electron microscopy (TEM). TEM images were performed using a JEOL USA JEM-1400 transmission electron microscope. The specific image system for EM (CCD camera).

Film-depth-dependent absorption spectroscopy (FLAS). The FLAS was performed by a PDU-400 spectrometer from Shaanxi Puguangweishi Technology Co. Ltd. The FLAS is in-situ measured by a setup which is composed of a halogen light source, a quasivacuum chamber generating soft plasma (pressure below 30 Pa, the flow rate of oxygen is 4 L/S), and a CCD spectrometer, which are connected by optical fibers. The film surface was incrementally etched by the soft ion source, without damage to the materials underneath the surface, which was in situ monitored by a spectrometer. From the evolution of the spectra and the Beer–Lambert’s Law, film-depth-dependent absorption spectra were extracted. The composition distribution along the film-depth direction was obtained from the film-depth-dependent spectra by fitting the sub-layer absorption using the absorption of the pure components. The exciton generation contour is numerically simulated upon inputting sub-layer absorption spectra into a modified optical transfer-matrix approach (Adv. Funct. Mater. 35, 2415499 (2024). Rev. Sci. Instrum. 94, 023907 (2023)).

Surface energy characterization. Contact angle measurements were carried out by an OCA20 Contact-angle System (Dataphysics, Germany), using water and formamide by sessile drop analysis. The interfacial surface energy values of materials can be obtained to Young’s equation.

Femtosecond transient absorption spectroscopy (fs-TA). The fs-TA measurements were performed on an ultrafast fs-TA spectrometer (HARPIA, Light Conversion). The output of a femtosecond laser (repetition rate of 40 kHz, 1030 nm central wavelength, and pulse duration of ~120 fs, PHAROS, Light Conversion) was split into two parts. One went through optical parametric amplification (ORPHEUS twins, Light Conversion) and then became a pump to excite thin films. The other went through the delay stage and produced white light via sapphire acting as the probe light. The pump and probe were focused on the sample. The optical path difference between the pump light and the probe light, which was controlled by the motorized optical delay-line, was used to get the relative time delay between the probe light and the pump light. The collimated and concentrated probe beams are collected by a fiber-coupled multi-channel spectrometer with a CCD sensor. As the delay between the pump light and the detector light varies continuously, the signal strength of the detector light received through the sample to be measured changes (Chem 8, 3051 (2022). Adv. Mater. 36, 2406690 (2024)).

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "In this article, Lu et al. designed 3-allyl-rhodanine (3-AR) as an additive, leveraging its structural similarity to the terminal groups of small-molecule donors. The additive's structure is novel, distinguishing itself from many benzene- and thiophene- based compounds. Moreover, this represents the first case of an additive explicitly designed to be based on the structure of a small molecule donor. As a result, 3-AR demonstrates effective enhancement of the performance of all-small-molecule organic solar cells (ASM-OSCs), enabling a breakthrough efficiency of 18.43%. From the reviewer opinion, this manuscript should be recommended for publishing in Nature Communications after addressing the questions below:\nQ1. On line 15 of page 5 and line 9 of page 6, etc, the J-V format in the manuscript, the standard formats of Voc and Jsc. It is suggested that the authors make careful revisions.\nQ2. For clearer identification of the 3-AR characteristic peak in the FTIR, I recommend annotating the 1734 cm⁻¹ position in Supplementary Fig. 10.\nQ3. Please explain “3-AR-processed blend film showed a uniform exciton generation distribution, concentrated within the top 20 nm and bottom 40 nm regions.” to avoid any confusion.\nQ4. On line 14 of page 9, the authors wrote “The 3-AR-processed MPhS-C2:N3 blend film exhibited a reduced RMS value of 1.80 nm compared to 1.90 nm for the untreated control film, ……as shown in Fig. 4c.” Please pay attention to concise sentences and avoid repetitive words.\nQ5. On line 2 of page 12, the ratio values of μe and μh shown in Supplementary Table 12 and the main manuscript are quite different. The authors should explain this data clearly.\nQ6. Please provide the surface energy of 2PACz in the surface energy section or refer to the literature to show the compatibility match of the active layer.\nQ7. In Figure 5a, please mark the positions of the 0-0/0-1 peaks to avoid confusion.", "reviewer_2": "The authors reported a new solid additive (SA), namely 3-allylrhodanine (3-AR) to precisely regulate the ASM-OSC active layer morphology. They found that 3-AR can effectively narrow the film formation window, suppressing lateral over- aggregation and crystallization, while promoting vertical donor-acceptor homogeneity within the active layer. Consequently, the 3-AR-processed MPhS-C2:N3-based ASM-OSCs achieved a high efficiency of 18.43%, certified as 18.16%. Although the authors have achieved credible device performance metrics, several technical issues require resolution prior to publish in Nat. Commun. after major revisions.\n1. The purportedly commercially sourced solid additives appear critical to device performance and blend morphology. The authors should provide certified purity validation through supporting analytical characterizations (e.g., NMR spectroscopy, mass spectrometry).\n2. The chemical structure of 2PACz and H75 should be provided.\n3. A recent publication reports 18.51% device efficiency (https://doi.org/10.1039/D5EE01162K), rendering the current work (18.4%) no longer the highest values. Relevant performance claims require immediate revision per community-established benchmarking standards.\n4. The control and SA-modified devices show comparable EQE spectral ranges, they display different JSC and EQE amplitude responses. To clarify the underlying charge transport kinetics, the authors should provide internal quantum efficiency (IQE) and PL quenching measurements for these devices.\n5. The carbonyl stretching region (1660-1760 cm⁻¹) exhibits characteristic vibrations in both pristine additives and blend films. The 1734 cm⁻¹ peak in solid additives and corresponding features slightly below this position in three blend samples (Figure S10) all align with C=O vibrations. Crucially, the putative 1734 cm⁻¹ signal in blends may belongs to spectral noise, precluding definitive assignment of additive elimination. We therefore suggest quantitative NMR validation to unambiguously determine additive removal efficacy from the complex matrix.\n6. Binding energies of 3-AR with MPhS-C2 and N3 register as -33.21 and -35.35 kcal/mol, respectively. These results remain mechanistically inconclusive regarding solid-additive working mechanism. We suggest two-dimensional NMR spectroscopy (specifically NOESY or ROESY) to resolve spatial configurations and quantitatively delineate the operative mechanisms at molecular resolution.\n7. Given the prospects for large-scale application, although ASM OSCs based on this system have achieved notable device efficiency, an observed efficiency gap persists when compared to state-of-the-art polymer-based OSCs exceeding 21% PCE. Therefore, it is critical to investigate: (1) whether this additive enhances operational stability; and (2) how is the performance regarding maximum power point tracking (MPP-T80) and thermal stability under heating for corresponding devices?\n8. What is the application universality of this SA? Does its efficacy exclusively pertain to all-small-molecule systems, or alternatively, is it functionally limited only to the present MPhS-C2:N3 blend framework? Cross-system validation across diversified active layers is warranted to ascertain its adaptability spectrum.\n9. For the photovoltaic parameters presented in the Supporting Information tables that are not derived from a single-device measurement, the corresponding standard deviations must be rigorously provided to ensure statistical significance.", "reviewer_3": "In this manuscript, Cao et al. regulated active layer morphology of all-small-molecule organic solar cells (ASM-OSCs) by using a solid additive 3-allylrhodanine (3-AR). 3-AR narrows the film formation window, suppressing over-aggregation and crystallization, while promoting vertical donor-acceptor homogeneity within the active layer. As a result, the 3-AR-processed MPHs-C2:N3-based ASM-OSCs showed a power conversion efficiency (PCE) of 18.43%. The major issues of this research are lack of innovation and insufficiency of data and analysis, and this reviewer can't recommend publication in Nature Communications. Below are some detailed comments:\n1. First, the strategy of employing solid additives (structurally analogous to certain groups in the donor or acceptor) to regulate active-layer morphology for enhanced photovoltaic performance has been extensively documented in the literature. Second, the authors only proved that 3-AR (a structure similar to the donor terminal group) can improve performance. While numerous similar donor terminal groups exist, can all enhance performance? If not, what specifically distinguishes 3-AR? Third, the PCE of 18.43% does not represent the state-of-the-art value for ASM-OSCs (18.51%, Energy Environ. Sci., 2025, 10.1039/D5EE01162K).\n2. The transient absorption characterization and analysis require further refinement. The generation of photoexcited species occurring around 1 ps appears unexpectedly slow. Experimental validation is needed to determine whether a GSB signal emerges when exciting the acceptor material at 400 nm. Additionally, the rising kinetics of the N3 GSB signal requires detailed analysis to determine the timescales for both exciton dissociation and exciton diffusion. More critically, hole transfer dynamics is typically the rate-limiting step in OSCs compared to electron transfer/energy transfer. A comprehensive study of hole transfer kinetics is essential to conclusively understand exciton and carrier dynamics within the active layer because focusing solely on electron transfer/energy transfer lacks persuasiveness.\n3. The mechanistic explanation states that 3-AR’s interaction with MPhS-C2 shortens the Stage II duration of MPhS-C2. Why does its stronger interaction with N3 prolong the Stage II duration of N3? Moreover, 3-AR enhances crystallization in single-component systems but suppresses crystallization in bulk-heterojunction blends, necessitating mechanistic clarification.\n4. Sun's group developed an IC-FI solid additive, structurally analogous to the end group of N3, enhancing the molecule self-assembly of N3 (J. Mater. Chem. A 2021, 9, 2857–2863), while 3-AR (structurally analogous to end group of MPhS-C2) enhances acceptor N3 crystallization rather than MPhS-C2, why?\n5. The authors mention trap-assisted recombination. Further data on the trap density should be provided.\n6. The photo, thermal and operational stability of the device needs to be provided.", "reviewer_4": "Comments:\nThis manuscript reports a volatility solid additive—3-allyl-rhodanine (3-AR)—that structurally resembles the terminal group of the high-performance small-molecule donor MPhS-C2 to explore its role in regulating morphological structures and enhancing photovoltaic performance in all-small-molecule organic solar cells (ASM-OSCs). Owing to 3-AR narrows the film formation window and suppresses excessive crystallization of the blend film, it promotes the formation of smaller, well-suited lateral phase-separation domains while simultaneously enhancing vertical donor/acceptor homogeneity in the active layer, thereby affording a record PCE of 18.43% (certified 18.16%) in MPhS-C2:N3-based OSCs. This manuscript is comprehensive in characterization and clear in expression. For the following considerations some minor points should be addressed prior to publication.\n1. In the sentence: \"Crucially, comprehensive statistical analysis of state-of-the-art ASM-OSCs with PCEs exceeding 15%......, synergistically achieving a record PCE of 18.4%, which is the highest value reported to date.\". The author should accurately fill in the efficiency values.\n2. The authors think that the complete volatilization of 3-AR after the heat treatment at 100°C for 10 minutes (Figure S9), contradicting the result of TGA diagram (Figure S8). The author should give reasonably explanation.\n3. The author mentioned the full width at half-maximum (FWHM) in the manuscript, but no corresponding values were found in the main manuscript or supporting information. The author should provide the FWHM values.\n4. The author should clearly explain the significant difference between the μe/μh ratios reported in Supplementary Table 12 and those in the main manuscript.\n5. In the characterization of SCLC, the corresponding values of electron and hole mobility date inconsistency expressed by scientific counting methods. The author should carefully unify the format of these values."}, "author_response": "COMMENTS TO AUTHOR:\nReviewer #1: In this article, Lu et al. designed 3-allyl-rhodanine (3-AR) as an additive, leveraging its structural similarity to the terminal groups of small-molecule donors. The additive's structure is novel, distinguishing itself from many benzene- and thiophene- based compounds. Moreover, this represents the first case of an additive explicitly designed to be based on the structure of a small molecule donor. As a result, 3-AR demonstrates effective enhancement of the performance of all-small-molecule organic solar cells (ASM-OSCs), enabling a breakthrough efficiency of 18.43%. From the reviewer opinion, this manuscript should be recommended for publishing in Nature Communications after addressing the questions below:\nQ1. On line 15 of page 5 and line 9 of page 6, etc, the J-V format in the manuscript, the standard formats of V and J . It is suggested that the authors make careful revisions.\noc sc\nResponse: Thank you for your helpful comments. We revised the standard format of the abbreviations for open-circuit voltage and short-circuit current density in the manuscript. The main revisions are highlighted with red words:\n“……, thereby reducing short-circuit current density (J ) in ASM-OSCs.”\nsc\n“……, with an improved J of 27.32 mA/cm² and an unprecedented FF of 78.19%.”\nsc\n“……, with an open-circuit voltage (V ) of 0.863V, a J of 27.03 mA/cm2.”\noc sc\n“……, accompanied by a modest increase in J of 27.32 mA/cm2.”\nsc\n“……, that our 3-AR-processed device exhibits the high J and exceptional FF……”\nsc\n“These results confirm that trace amounts of the 3-AR enhance the J and FF, ……”\nsc\n“The integrated J values calculated from control and 3-AR-processed devices are\nsc\n26.01 and 26.28 mA/cm2, respectively, closely matching the J s derived from J-V.”\nsc\n“……, demonstrating optimized carrier dynamics for improved J , ……”\nsc\n“……. via light-intensity-dependent J /V measurements, ……”\nsc oc\n“……., ultimately leading to higher J and FF values.”\nsc\nQ2. For clearer identification of the 3-AR characteristic peak in the FTIR, I recommend annotating the 1734 cm⁻¹ position in Supplementary Fig. 10.\nResponse: We appreciate the reviewer for this suggestion. We clearly mark the position of 1734cm-1 in Supplementary Fig. 15. The main revisions are highlighted with red words:\nSupplementary Fig. 15 FTIR spectra of the 3-AR, and MPhS-C2:N3 (1.4:1.0, w/w), MPhS-C2:N3 (2.5 wt.% 3-AR) without/with TA treatment under 100 °C for 10 min.\nQ3. Please explain “3-AR-processed blend film showed a uniform exciton generation distribution, concentrated within the top 20 nm and bottom 40 nm regions.” to avoid any confusion.\nResponse: We thank the reviewer for the comments. To better illustrate this issue, we plotted the exciton generation rate curves of the films with and without 3-AR treatment on a graph (with a depth of 0 nm as the top and 100 nm as the bottom). It can be clearly seen from the graph that in the regions within the top 20 nm and the bottom 40 nm, the difference in the exciton generation rate curves between the 3-AR-treated films and the untreated ones is the smallest, indicating a more uniform exciton generation rate.\nQ4. On line 14 of page 9, the authors wrote “The 3-AR-processed MPhS-C2:N3 blend film exhibited a reduced RMS value of 1.80 nm compared to 1.90 nm for the untreated control film, ……as shown in Fig. 4c.” Please pay attention to concise sentences and avoid repetitive words.\nResponse: We appreciate the reviewer for this suggestion. In this sentence, the meanings of “untreated” and “control” are repetitive. We have deleted “control” in the manuscript. The main revisions are highlighted with red words on page 11:\n“The 3-AR-processed MPhS-C2:N3 blend film exhibited a reduced RMS value of 1.80 nm compared to 1.90 nm for the untreated film, ……as shown in Fig. 3e.”\nQ5. On line 2 of page 12, the ratio values of μ and μ shown in Supplementary Table\ne h\n12 and the main manuscript are quite different. The authors should explain this data clearly.\nResponse: We thank the reviewer for the comments. We carefully checked the ratio between μ and μ and made revisions in the manuscript. The main revisions are\ne h\nhighlighted with red words on page 13:\n“Besides, the more balanced μ /μ ratio of 1.37 (vs. 1.50 in control devices) indicates\ne h\neffective suppression of space-charge accumulation, which in turn can enhance FF\nvalue.”\nQ6. Please provide the surface energy of 2PACz in the surface energy section or refer to the literature to show the compatibility match of the active layer.\nResponse: We appreciate the reviewer for the comments. By referring to relevant literature, the surface free energy (𝛾) of 2PACz is approximately 48 mJ/m² (J. Am. Chem. Soc. 2025, 147, 24, 21241–21251, ACS Energy Lett. 2025, 10, 4, 1865–1873, Adv. Funct. Mater. 2025, 35, 2414844, J. Mater. Chem. A 2025, 13, 15574-15584). The 𝛾 values of the MPhS-C2, MPhS-C2:3-AR, N3, and N3:3-AR films obtained from our experiments were 18.57, 30.45, 18.04, and 27.28 mJ/m², respectively. Compared with the untreated films, the 𝛾 values of the 3-AR-treated films increase, which reduces the difference in 𝛾 from the transport layer. Generally, the smaller the difference in 𝛾 between the active layer and the transport layer, the better their interfacial compatibility. This result is conducive to improving wettability, reducing the interfacial energy mismatch with the 2PACz hole transport layer, forming intimate ohmic contact, reducing physical defects at the interface, and thereby promoting efficient charge transportation and extraction. The main revisions are highlighted with red words on page 10:\n“According to literature reports, the γ of 2PACz is approximately 48 mJ/m².41”\nQ7. In Figure 5a, please mark the positions of the 0-0/0-1 peaks to avoid confusion.\nResponse: Thank you for your helpful comments. We clearly labeled the 0-1 and 0-0 characteristic peaks in Fig. 4a to facilitate a clearer analysis of the data. The main revisions are highlighted with red words:\nFig. 4 The film-depth-dependent light absorption spectra. a The film-depth- dependent light absorption spectra of the devices.\nReviewer #2: The authors reported a new solid additive (SA), namely 3-allylrhodanine (3-AR) to precisely regulate the ASM-OSC active layer morphology. They found that 3-AR can effectively narrow the film formation window, suppressing lateral over- aggregation and crystallization, while promoting vertical donor-acceptor homogeneity within the active layer. Consequently, the 3-AR-processed MPhS-C2:N3-based ASM-OSCs achieved a high efficiency of 18.43%, certified as 18.16%. Although the authors have achieved credible device performance metrics, several technical issues require resolution prior to publish in Nat. Commun. after major revisions.\n1. The purportedly commercially sourced solid additives appear critical to device performance and blend morphology. The authors should provide certified purity validation through supporting analytical characterizations (e.g., NMR spectroscopy, mass spectrometry).\nResponse: We thank the reviewer for the comments. Determining the purity of 3-AR through nuclear magnetic resonance spectroscopy is crucial for device performance. The following is a detailed 1H NMR data analysis of 3-AR, which strongly verifies the purity of solid additives.\n1H NMR (400 MHz, Chloroform-d) δ 5.80 (ddt, J = 17.2, 10.2, 6.0 Hz, 1H), 5.32 – 5.20 (m, 2H), 4.60 (dt, J = 5.9, 1.4 Hz, 2H), 3.99 (s, 2H).\n1H NMR spectra of 3-AR in Chloroform-d.\n2. The chemical structure of 2PACz and H75 should be provided.\nResponse: We appreciate the reviewer for this suggestion. We have included the chemical structure of 2PACz and H75 in the Supplementary Information and added the corresponding descriptive text in the revised manuscript. The main revisions are highlighted with red words on page 5:\n“The chemical structures of 2PACz and H75 are shown in Supplementary Fig. 1.”\nSupplementary Fig. 1 The chemical structures of 2PACz and H75.\n3. A recent publication reports 18.51% device efficiency (https://doi.org/10.1039/D5EE01162K), rendering the current work (18.43%) no longer the highest values. Relevant performance claims require immediate revision per community-established benchmarking standards.\nResponse: Thank you for your helpful comments. At the time of submission, the 18.43% efficiency reported in our manuscript was the highest value for all-small-molecule organic solar cells (ASM-OSCs), as the 18.51% result had not yet been published. We have taken note of the recent report by Min et al. on an 18.51%-efficient ASM-OSC (Energy Environ. Sci., 2025,18, 7302-7312 https://doi.org/10.1039/D5EE01162K). It is important to highlight that their work employs a ternary strategy, whereas our study focuses on a binary system. Thus, the 18.43% efficiency in our work still represents the highest value for binary ASM-OSCs. Based on this, we have incorporated the efficiency of 18.51% into the corresponding Fig. 2c and Supplementary Table 6, with related text also revised in the manuscript. The main revisions are highlighted with red words:\n“Therefore, the 3-AR-treated MPhS-C2:N3 device achieves a remarkable PCE of 18.43% (certified 18.16%)—the highest reported for binary ASM-OSCs.” (Page 2)\n“Consequently, the 3-AR-optimized ASM-OSCs attained a superior PCE of 18.43%, with an improved J of 27.32 mA/cm² and an unprecedented FF of 78.19%, …...”(Page\nsc\n4)\n“With 2.5 wt.% 3-AR VSA, the device attained a champion PCE of 18.43%, …....”\n(Page 5)\n“……, synergistically achieving a remarkable PCE of 18.43%, which is the highest value for binary systems reported to date.” (Page 6)\n“As a result, the 3-AR-processed device yielded an outstanding PCE of 18.43%, with a certified value of 18.16%, which marks the highest reported PCE for binary ASM- OSCs.” (Page 17)\nFig. 2 Chemical structures, photovoltaic performance, and theoretical calculation.\nc Plots of the PCE versus J for the efficient ASM-OSCs reported in the literature.\nsc\nSupplementary Table 6 Summary of photovoltaic performance parameters with PCE>15% in ASM OSCs.\nV\nActive layer OC J [mA/cm2] FF [%] PCE [%] Ref.\nsc\n[V]\nBTR-Cl:Y6 0.843 24.78 74.2 15.5 1\n15.3\nB1:BO-4Cl 0.83 25.27 73 2\n(15.1) a\nB1:BTP-eC9 0.832 24.98 75.44 15.68 3\nBT-2F:N3 0.845 24.28 75.02 15.39 4\n… … … … …\n…\n… … … … … …\nMPhS-C2:BTP-eC9:SSe-NIC 0.880 26.85 76.27 18.02 21\nMPhS-C2:L8-BO:L8-S9 0.884 26.43 77.46 18.10 22\nMPhS-C2:BTP-eC9:Se-Giant 0.903 26.34 76.33 18.16 23\n18.51\nMPhS-C2:SD86 :BTP-eC9 0.885 26.85 77.89 29\n(18.40) a\nMPhS-C2:N3 0.863 27.03 74.85 17.46 This work\n18.43\nMPhS-C2:N3 (Additive 3-AR) 0.863 27.32 78.19 This work\n(18.16) a\na the corresponding certified PCE.\n4. The control and SA-modified devices show comparable EQE spectral ranges, they display different J and EQE amplitude responses. To clarify the underlying charge\nsc\ntransport kinetics, the authors should provide internal quantum efficiency (IQE) and PL quenching measurements for these devices.\nResponse: We thank the reviewer for the comments. As recommended, we have conducted comprehensive internal quantum efficiency (IQE) and photoluminescence (PL) quenching measurements on both the control and 3-AR-modified devices. The results have been incorporated into the revised manuscript and discussed in detail on page 6 (IQE analysis) and page 13 (PL analysis). The main revisions are highlighted with red words:\n“The internal quantum efficiency (IQE) spectra were derived from reflection (R) and EQE measurements (Supplementary Fig. 12). Compared to the control device, the 3- AR treated device exhibits significantly improved IQE values across the range of 510– 830 nm, which contributes to achieving a higher J . This improvement in photo-\nsc\nelectron conversion efficiency can be attributed to enhanced exciton dissociation and more efficient charge transport within the 3-AR-processed active layer.33 ”\nSupplementary Fig. 12 The reflection spectrum and IQE curves of the devices without and with 3-AR.\n“In addition, steady-state photoluminescence (PL) spectroscopy (Supplementary Fig. 32) reveals that the 3-AR-treated MPhS-C2:N3 blend film achieves enhanced PL quenching efficiencies of 95.01%/97.86%, respectively (94.37%/97.17% for control film). This improvement promotes exciton dissociation and facilitates highly efficient bidirectional charge separation.48,49 ”\nSupplementary Fig. 32 (a) Photoluminescence (PL) spectra of MPhS-C2 pure film and related MPhS-C2:N3 blend films excited at 550 nm. (b) PL spectra of N3 pure film and related MPhS-C2:N3 blend films excited at 730 nm.\nIn summary, the newly added IQE and PL data unequivocally confirm that the superior J and EQE amplitude of the 3-AR-modified devices originate from enhanced charge\nsc\ntransport and extraction kinetics, which minimizes recombination losses. We are grateful to the reviewer for suggesting these supplementary experiments, which have significantly strengthened the mechanistic discussion in our manuscript.\n5. The carbonyl stretching region (1660-1760 cm⁻¹) exhibits characteristic vibrations in both pristine additives and blend films. The 1734 cm⁻¹ peak in solid additives and corresponding features slightly below this position in three blend samples (Figure S10) all align with C=O vibrations. Crucially, the putative 1734 cm⁻¹ signal in blends may belongs to spectral noise, precluding definitive assignment of additive elimination. We therefore suggest quantitative NMR validation to unambiguously determine additive removal efficacy from the complex matrix.\nResponse: We appreciate the reviewer for this suggestion. we performed NMR experiments to obtain conclusive evidence. The NMR results (Supplementary Fig. 16) clearly show the absence of characteristic signals from the additive in the annealed blend film. Therefore, we can definitively conclude that the additive has been completely removed. This NMR evidence resolves the ambiguity associated with the FTIR characterization, placing our conclusion on a more robust foundation. We have added this conclusion to the revised manuscript and included the corresponding NMR data in the Supplementary Information. The main revisions are highlighted with red words on page 7:\n“Given the high volatility of 3-AR, its complete absence was further verified by nuclear magnetic resonance (NMR) spectroscopy (Supplementary Fig. 16). Comparative analysis of the films before and after annealing showed that the characteristic signals of the 3-AR disappeared entirely after the thermal annealing treatment.”\nSupplementary Fig. 16 1H NMR spectra of the (a) 3-AR, MPhS-C2:N3 (1.4:1.0, w/w), MPhS-C2:N3 (2.5 wt.% 3-AR) and (b) MPhS-C2:N3 (5 wt.% 3-AR), MPhS-C2:N3 (10 wt.% 3-AR) without/with TA treatment under 100 °C for 10 min.\n6. Binding energies of 3-AR with MPhS-C2 and N3 register as -33.21 and -35.35 kcal/mol, respectively. These results remain mechanistically inconclusive regarding solid-additive working mechanism. We suggest two-dimensional NMR spectroscopy (specifically NOESY or ROESY) to resolve spatial configurations and quantitatively delineate the operative mechanisms at molecular resolution.\nResponse: We thank the reviewer for this insightful comment. Following the suggestion, we have performed 2D NMR spectroscopy, specifically NOESY, to directly probe the spatial configuration and intermolecular interactions between 3-AR and the MPhS-C2 or N3 molecules in solution. Furthermore, NMR titration analyses were conducted, which confirmed that the interactions between 3-AR and MPhS-C2 or N3 involve distinct functional groups. To ensure accuracy, we also re-calculated the interaction energies using DFT for the complete donor-acceptor molecular structures. By integrating these computational simulations with high-resolution 2D NMR experiments, we have now elucidated the specific interactions between 3-AR and MPhS-C2 or N3, thereby clarifying the underlying mechanism. The corresponding experimental results and discussion have been added to the revised manuscript. The main revisions are highlighted with red words on page 7-8:\n“The ΔE are calculated to be -18.44 (C–H···S and C=O···H) and -18.99 (C–H···H)\nb\nkcal/mol for the 3-AR with the end groups of MPhS-C2 and N3, respectively, as determined by the Equation 1 (see details in Methods). The 3-AR is found to have more negative ΔE values of -19.61 (C=S···H) and -21.07 (C–N···H) kcal/mol when interact\nb\nwith the core units of MPhS-C2 and N3 molecules, respectively.”\n“Two-dimensional ¹H-¹H nuclear overhauser effect spectroscopy (NOESY) can determine spatial proximity between protons within 5 Å and was thus used to probe intermolecular interactions between additives and host materials.35 Although the NOESY spectrum of 3-AR with MPhS-C2 (Supplementary Fig. 18a) showed no crossover resonance peaks, the possibility of other types of interactions could not be ruled out. Therefore, NMR titration was performed (Supplementary Fig. 19a), which showed chemical shift changes (δ = 7.8) in the ¹H NMR spectra with increasing proportion of 3-AR, confirming an interaction between MPhS-C2 and 3-AR. On the other hand, the NOESY spectrum of 3-AR with N3 solution (Supplementary Fig. 18b) displayed weak but discernible cross resonance peaks (marked by the green box) between the terminal proton of N3 (Ha, δ = 8.40) and a proton of 3-AR (Hb, δ = 4.0), indicating the spatial proximity and interaction between N3 and 3-AR.36 This result was further supported by NMR titration experiments (Supplementary Fig. 19b).\nCollectively, these NMR analyses and DFT calculations demonstrate that 3-AR participates in distinct intermolecular interactions with MPhS-C2 and N3 through different functional groups, thereby effectively modulating the morphology of the active layer.”\nSupplementary Fig. 18 2D 1H−1H NMR spectra of (a) MPhS-C2:3-AR and (b) N3:3- AR in Chloroform-d.\nSupplementary Fig. 19 1H NMR spectra of (a) MPhS-C2 and (b) N3 with different proportions of 3-AR in Chloroform-d.\n7. Given the prospects for large-scale application, although ASM OSCs based on this system have achieved notable device efficiency, an observed efficiency gap persists when compared to state-of-the-art polymer-based OSCs exceeding 21% PCE. Therefore, it is critical to investigate: (1) whether this additive enhances operational stability; and (2) how is the performance regarding maximum power point tracking (MPP-T80) and thermal stability under heating for corresponding devices?\nResponse: Thank you for your helpful comments. We fully agree that beyond high PCE, outstanding stability of ASM OSC is a prerequisite for future commercialization. Following the reviewer's suggestion, we have conducted a series of stability tests, including storage stability, photostability , and thermal stability, and the results are very encouraging. We have dedicated a section in the Supplementary Information (page 14) to discuss these findings in detail and incorporated corresponding descriptions in the revised manuscript (page 6).The main revisions are highlighted with red words:\n“Additionally, 3-AR as an SA not only effectively enhances the storage, photo-, and thermal stability of ASM-OSCs but also demonstrates excellent universality by being applicable to both representative all-small-molecule and polymer systems (Supplementary Fig. 9-11 and Supplementary Table 7).” (on page 6)\n“The N₂-storage stability, photostability, and thermal stability of MPhS-C2:N3-based ASM-OSCs were systematically evaluated. As illustrated in Supplementary Fig. 9a, the tracking of normalized PCE over time demonstrates a remarkable enhancement in the storage stability of the 3-AR-treated devices. These devices retained 81.66% of their initial efficiency after 1968 hours of N₂-storage, outperforming the untreated devices, which maintained only 73.63%. A similar trend was observed under illumination and thermal stress: after 106 hours of 1-sun irradiation, the 3-AR-based ASM-OSCs preserved 80.20% of their initial PCE, compared to 74.95% for the control group (Supplementary Fig. 9b). Moreover, the 3-AR-treated devices exhibited superior thermal stability, maintaining 80.05% of initial performance after annealing at 50 °C for 70 hours, versus 74.80% for the untreated devices (Supplementary Fig. 9c). These results demonstrate that 3-AR effectively improves the N₂ storage, photostability, and thermal resistance of devices, highlighting its potential for advancing the commercialization of ASM-OSCs.” (on page Supplementary 14)\nSupplementary Fig. 9 Normalized PCE of (a) storage stability, (b) photostability stability and (c) thermal stability of the unencapsulated devices in a N -filled glove box.\n2\n8. What is the application universality of this SA? Does its efficacy exclusively pertain to all-small-molecule systems, or alternatively, is it functionally limited only to the present MPhS-C2:N3 blend framework? Cross-system validation across diversified active layers is warranted to ascertain its adaptability spectrum.\nResponse: We thank the reviewer for the comments. To directly validate the universality of 3-AR solid additive, we applied it to four representative active layer systems, including all-small-molecule systems (B1:L8-BO, BTR-Cl:N3) and polymer systems (D18-Cl:N3, PM6:L8-BO). Encouragingly, 3-AR delivers superior photovoltaic performance, as consistently demonstrated in experiments involving diverse active layer systems, indicating good general applicability. The relevant experimental data and discussion have been added to page 6 of the revised manuscript and Supplementary page 15. The main revisions are highlighted with red words:\n“Additionally, 3-AR not only effectively enhances the storage, photo-, and thermal stability of ASM-OSCs but also demonstrates excellent universality by being applicable to both representative all-small-molecule (e.g., B1:L8-BO and BTR-Cl:N3) and polymer systems (e.g., D18-Cl:N3 and PM6:L8-BO), as shown in Supplementary Fig. 9-11 and Supplementary Table 7.” (on page 6)\n“Meanwhile, the broad applicability of 3-AR was further evaluated using four representative and high-performing photoactive systems, including B1:L8-BO, BTR- Cl:N3, D18-Cl:N3 and PM6:L8-BO. The chemical structures of B1, BTR-Cl, PM6 and L8-BO are depicted in Supplementary Fig. 10. The corresponding J–V characteristics and EQE spectra are shown in Supplementary Fig. 11, respectively. The key photovoltaic parameters are summarized in Supplementary Table 7. Notably, the 3-AR- treated devices exhibited enhanced PCEs in these four systems: 16.61% for B1:L8-BO- based ASM-OSCs, 16.70% for BTR-Cl:N3-based ASM-OSCs, 18.40% for D18- Cl:N3-based OSCs, and 18.25% for PM6:L8-BO-based OSCs, all outperforming their counterpart devices fabricated without the additive. These consistent results demonstrate that 3-AR effectively improves the photovoltaic performance of diverse photoactive systems, highlighting its broad applicability in optimizing both ASM- and polymer-based OSCs.” (on page Supplementary 15)\nSupplementary Fig. 10 The chemical structures of B1, BTR-Cl, D18-Cl, PM6 and L8-BO.\nSupplementary Fig. 11 The J–V and EQE curves of (a) B1:L8-BO, (b) BTR-Cl:N3, (c) D18-Cl:N3, and (d) PM6: L8-BO-based OSCs without and with 3-AR.\nSupplementary Table 7 Device performance parameters of B1:L8-BO, BTR-Cl:N3, D18-Cl:N3, and PM6: L8-BO-based OSCs treated without and with 3-AR.\nV J / J a FF PCE [%]\noc sc sc\nActive layer Additive\n[V] [mA/cm2] [%] (ave.) b\n0.898 24.05 / 22.88 72.90 15.75\nW/O\n(0.890 ± 0.005) (23.55 ± 0.27) (73.65 ± 1.02) (15.44 ± 0.17)\nB1:L8-BO\n0.884 24.51 / 23.73 76.65 16.61\n3-AR\n(0.884 ± 0.004) (24.07 ± 0.30) (76.22 ± 0.71) (16.22 ± 0.19)\n0.844 26.31 / 25.38 71.34 15.84\nW/O\n(0.841 ± 0.006) (25.38 ± 0.74) (72.77 ± 2.13) (15.52 ± 0.24)\nBTR-Cl:N3\n0.841 26.57 / 25.65 74.77 16.70\n3-AR\n(0.843 ± 0.008) (26.23 ± 0.34) (73.71 ± 1.71) (16.29 ± 0.28)\n0.871 27.93 / 26.65 73.89 17.97\nW/O\n(0.872 ± 0.002) (27.80 ± 0.11) (73.94 ± 0.46) (17.93 ± 0.10)\nD18-Cl:N3\n0.866 28.10 / 26.81 75.61 18.40\n3-AR\n(0.869± 0.003) (28.07 ± 0.19) (75.17 ± 0.51) (18.33 ± 0.12)\n0.898 26.73 / 25.44 73.54 17.61\nW/O\n(0.896 ± 0.004) (26.55 ± 0.25) (73.86 ± 0.73) (17.56 ± 0.15)\nPM6: L8-BO\n0.896 26.94 / 25.61 75.74 18.25\n3-AR\n(0.887 ± 0.005) (26.87 ± 0.16) (76.03 ± 0.54) (18.11 ± 0.11)\na Integrated J from EQE.\nsc\nb The statistical values in brackets were calculated from 10 devices.\n9. For the photovoltaic parameters presented in the Supporting Information tables that are not derived from a single-device measurement, the corresponding standard deviations must be rigorously provided to ensure statistical significance.\nResponse: We appreciate the reviewer for the comments. Following your suggestion, we have thoroughly reanalyzed the original data from all relevant devices. The key photovoltaic parameters are now presented as \"average value ± standard deviation\" in the revised Supplementary Tables 1-5. We believe this modification significantly enhances the completeness and statistical robustness of our data. The main revisions are highlighted with red words.\nSupplementary Table 1 The photovoltaic parameters of MPhS-C2:N3-based AMS- OSCs with different weight ratios of D: A.\nConcentr spin-\nV J / J a) PCE [%]\noc sc sc\nD:A -ation coating TA FF [%]\n[V] [mA/cm2] (ave.) b)\n[mg/mL] speeds\n115°C 0.849 27.90/26.47 71.17 16.85\n1.6:1 20 2000\n/10min (0.852 ± 0.002) (27.54 ± 0.28) (71.36 ± 0.80) (16.75 ± 0.19)\n115°C 0.852 27.77/26.69 72.61 17.10\n1.4:1 20 2000\n/10min (0.850 ± 0.004) (27.94 ± 0.17) (71.70 ± 0.69) (17.03 ± 0.10)\n115°C 0.858 27.62/26.69 69.95 16.57\n1.2:1 20 2000\n/10min (0.847 ± 0.006) (27.75 ± 0.23) (69.62 ± 0.58) (16.38 ± 0.21)\na) Integrated J from EQE.\nsc\nb) The statistical values in brackets are calculated from 5 devices.\nSupplementary Table 2 The photovoltaic parameters of MPhS-C2:N3-based AMS- OSCs (1.4:1.0, w/w) with different solution concentration of active layer.\nConcentr spin-\nV J / J a) PCE [%]\noc sc sc\nD:A -ation coating TA FF [%]\n[V] [mA/cm2] (ave.) b)\n[mg/mL] speeds\n115°C 0.853 27.48/26.25 71.48 16.75\n1.4:1 18 2000\n/10min (0.851 ± 0.005) (27.25 ± 0.59) (71.20 ± 0.98) (16.50 ± 0.16)\n115°C 0.852 27.90/26.59 72.18 17.15\n1.4:1 20 2000\n/10min (0.854 ± 0.005) (27.63 ± 0.24) (72.29 ± 0.73) (17.05 ± 0.15)\n115°C 0.846 27.90/26.40 71.62 16.90\n1.4:1 22 2000\n/10min (0.849 ± 0.008) (27.57 ± 0.23) (71.37 ± 0.56) (16.71 ± 0.19)\n115°C 0.846 27.96/26.72 69.51 16.44\n1.4:1 24 2000\n/10min (0.849 ± 0.007) (27.74 ± 0.36) (69.20 ± 0.35) (16.31 ± 0.13)\na) Integrated J from EQE.\nsc\nb) The statistical values in brackets are calculated from 5 devices.\nSupplementary Table 3 The photovoltaic parameters of MPhS-C2:N3-based AMS- OSCs (1.4:1.0, w/w) with different spin-coating rates of active layer.\nConcentr spin-\nV J / J a) PCE [%]\noc sc sc\nD:A -ation coating TA FF [%]\n[V] [mA/cm2] (ave.) b)\n[mg/mL] speeds\n1.4:1 20 1600 115°C 0.850 27.81/26.69 69.72 16.49\n/10min (0.843 ± 0.007) (27.53 ± 0.17) (69.22 ± 0.50) (16.07 ± 0.26)\n115°C 0.858 27.66/26.55 71.15 16.89\n1.4:1 20 1800\n/10min (0.860 ± 0.012) (27.44 ± 0.44) (70.81 ± 0.98) (16.71 ± 0.12)\n115°C 0.853 27.52/26.29 73.44 17.24\n1.4:1 20 2000\n/10min (0.856 ± 0.003) (27.59 ± 0.24) (72.82 ± 0.47) (17.20 ± 0.05)\n115°C 0.851 27.44/26.39 71.89 16.78\n1.4:1 20 2200\n/10min (0.852 ± 0.002) (27.75 ± 0.23) (69.96 ± 1.45) (16.54 ± 0.26)\n115°C 0.852 27.26/26.20 71.70 16.64\n1.4:1 20 2400\n/10min (0.853 ± 0.011) (27.44 ± 0.17) (69.39 ± 1.44) (16.24 ± 0.24)\na) Integrated J from EQE.\nsc\nb) The statistical values in brackets are calculated from 5 devices.\nSupplementary Table 4 The photovoltaic parameters of MPhS-C2:N3-based AMS- OSCs (1.4:1.0, w/w) under different TA temperatures.\nConcentr spin-\nV J / J a) PCE [%]\noc sc sc\nD:A -ation coating TA FF [%]\n[V] [mA/cm2] (ave.) b)\n[mg/mL] speeds\n70°C/ 0.869 27.31/26.28 70.09 16.63\n1.4:1 20 2000\n10min (0.855 ± 0.010) (27.37 ± 0.27) (70.52 ± 1.14) (16.49 ± 0.23)\n85°C/ 0.867 27.54/26.41 71.07 16.97\n1.4:1 20 2000\n10min (0.860 ± 0.005) (27.30 ± 0.22) (71.46 ± 1.17) (16.77 ± 0.22)\n100°C/ 0.863 27.03/26.01 74.85 17.46\n1.4:1 20 2000\n10min (0.855 ± 0.005) (27.08 ± 0.09) (74.81 ± 0.46) (17.32 ± 0.11)\n115°C/ 0.852 27.82/26.76 72.15 17.09\n1.4:1 20 2000\n10min (0.857 ± 0.003) (27.31 ± 0.30) (72.10 ± 0.57) (16.81 ± 0.21)\n130°C/ 0.810 27.88/26.56 69.38 15.67\n1.4:1 20 2000\n10min (0.824 ± 0.017) (27.88 ± 0.10) (67.19 ± 1.37) (15.42 ± 0.23)\na) Integrated J from EQE.\nsc\nb) The statistical values in brackets are calculated from 5 devices.\nSupplementary Table 5 The photovoltaic parameters of the optimized AMS-OSCs based on MPhS-C2:N3 (1.4:1.0, w/w) with different weight ratios of 3-AR additive under TA at 100°C/10min.\nJ J a) FF PCE [%]\nsc sc\nAdditive V [V]\noc [mA/cm2] [mA/cm2] [%] (ave.) b)\n0.862 27.17 75.60 17.71\n1.0 wt% 25.87\n(0.860 ± 0.005) (27.22 ± 0.25) (74.96 ± 0.74) (17.56 ± 0.16)\n0.863 27.32 78.19 18.43\n2.5 wt% 26.28\n(0.861 ± 0.003) (27.34 ± 0.26) (77.62 ± 0.74) (18.24 ± 0.12)\n0.858 26.88 77.91 17.97\n5 wt% 26.13\n(0.861 ± 0.006) (27.13 ± 0.17) (75.90 ± 1.42) (17.74 ± 0.15)\n0.853 26.22 76.33 17.08\n10 wt% 25.16\n(0.854 ± 0.004) (26.52 ± 0.35) (74.79 ± 0.88) (16.93 ± 0.18)\na) Integrated J from EQE.\nsc\nb) The statistical values in brackets are calculated from 5 devices.\nReviewer #3: In this manuscript, Cao et al. regulated active layer morphology of all- small-molecule organic solar cells (ASM-OSCs) by using a solid additive 3- allylrhodanine (3-AR). 3-AR narrows the film formation window, suppressing over- aggregation and crystallization, while promoting vertical donor-acceptor homogeneity within the active layer. As a result, the 3-AR-processed MPHs-C2:N3-based ASM- OSCs showed a power conversion efficiency (PCE) of 18.43%. The major issues of this research are lack of innovation and insufficiency of data and analysis, and this reviewer can't recommend publication in Nature Communications. Below are some detailed comments:\n1. First, the strategy of employing solid additives (structurally analogous to certain groups in the donor or acceptor) to regulate active-layer morphology for enhanced photovoltaic performance has been extensively documented in the literature. Second, the authors only proved that 3-AR (a structure similar to the donor terminal group) can improve performance. While numerous similar donor terminal groups exist, can all enhance performance? If not, what specifically distinguishes 3-AR? Third, the PCE of 18.43% does not represent the state-of-the-art value for ASM-OSCs (18.51%, Energy Environ. Sci., 2025, 10.1039/D5EE01162K).\nResponse: We thank the reviewer for the comments. First, the strategy of using solid additives (structurally similar to certain groups in donors or acceptors) to regulate the morphology of the active layer and enhance photovoltaic performance has been reported in the literature. It is worth noting that the additive structures reported in these cases (Figure R1) are typically structurally similar to those of non-fullerene acceptors (e.g., Y6, N3) and polymer donors (e.g., PM6, D18), which are mainly used in polymer organic solar cells (P-OSCs). However, research on additives specifically designed for small-molecule donors remains very limited. Furthermore, due to the well-defined structures and similar physicochemical properties of donor and acceptor materials in ASM-OSCs, traditional additives often fail to regulate their morphology. Additionally, current understanding of the working mechanism of additives is still primarily empirical, lacking systematic design principles for ASM-OSCs. Therefore, our work is innovative to a certain extent, featuring a simple process and achieving the highest efficiency reported to date for binary all-small-molecule organic solar cells.\nFigure R1. The chemical structure of representative additive molecules designed based on the donor and acceptor.\nSecond, We initially selected a variety of rhodanine derivatives—including rhodanine, 3-methylrhodanine, 3-aminorhodanine, 3-allylrhodanine and 3-phenylrhodanine—as solid additives for MPhS-C2:N3-based ASM-OSCs (Figure R2). A preliminary efficiency screening was conducted using devices with the structure ITO/PEDOT:PSS/BHJ/Phen-NaDPO/Ag. The results (Table R1) indicated that 3- allylrhodanine, 3-aminorhodanine, and 3-methylrhodanine all contributed to improved device performance. Among them, 3-allylrhodanine demonstrated the most significant enhancement, effectively optimizing the active layer morphology. Given the lack of a clear structural logic among the substituents of these three derivatives, we focused subsequent efforts on elucidating the mechanism by which 3-allylrhodanine modulates morphology and enhances performance. In contrast, the introduction of 3- phenylrhodanine resulted in decreased device performance. Based on its physical properties, we speculate that its high molecular weight (boiling point 353 °C at atmospheric pressure) hindered its complete evaporation from the active layer during the 100 °C thermal annealing process. This residual additive likely disrupted the ordered stacking of the donor and acceptor materials, leading to an unfavorable active layer morphology for charge transport and consequently impairing device performance. Additionally, rhodanine itself was excluded from further study due to its poor solubility in chloroform, which caused visible particle formation in the solution and prevented uniform dispersion within the active layer.\nFigure R2. The chemical structure of rhodanine derivatives.\nTable R1. Device performance parameters of MPhS-C2:N3-based OSCs treated without and with a variety of rhodanine derivatives.\nAdditive V [V] J [mA/cm2] FF [%] PCE [%]\noc sc\nW/O 0.845 26.22 74.08 16.42\nrhodanine --- --- --- ---\n3-methylrhodanine 0.846 26.28 76.12 16.92\n3-aminorhodanine 0.847 25.82 76.65 16.75\n3-allylrhodanine 0.850 26.43 76.04 17.08\n3-phenylrhodanine 0.844 25.74 73.24 15.92\nThird, at the time of submission, the 18.43% efficiency reported in our manuscript was the highest value for all-small-molecule organic solar cells (ASM-OSCs), as the 18.51% result had not yet been published. We have taken note of the recent report by Min et al. on an 18.51%-efficient ASM-OSC (Energy Environ. Sci., 2025,18, 7302-7312 https://doi.org/10.1039/D5EE01162K). It is important to highlight that their work employs a ternary strategy, whereas our study focuses on a binary system. Thus, the 18.43% efficiency in our work still represents the highest value for binary ASM-OSCs. Based on this, we have incorporated the efficiency of 18.51% into the corresponding Fig. 2c and Supplementary Table 6, with related text also revised in the manuscript. The main revisions are highlighted with red words:\n“Therefore, the 3-AR-treated MPhS-C2:N3 device achieves a remarkable PCE of 18.43% (certified 18.16%)—the highest reported for binary ASM-OSCs.” (Page 2)\n“Consequently, the 3-AR-optimized ASM-OSCs attained a superior PCE of 18.43%, with an improved J of 27.32 mA/cm² and an unprecedented FF of 78.19%, …...”(Page\nsc\n4)\n“With 2.5 wt.% 3-AR VSA, the device attained a champion PCE of 18.43%, …....”\n(Page 5)\n“……, synergistically achieving a remarkable PCE of 18.43%, which is the highest value for binary systems reported to date.” (Page 6)\n“As a result, the 3-AR-processed device yielded an outstanding PCE of 18.43%, with a certified value of 18.16%, which marks the highest reported PCE for binary ASM- OSCs.” (Page 17)\nFig. 2 Chemical structures, photovoltaic performance, and theoretical calculation.\nc Plots of the PCE versus J for the efficient ASM-OSCs reported in the literature.\nsc\nSupplementary Table 6 Summary of photovoltaic performance parameters with PCE>15% in ASM OSCs.\nV\nActive layer oc J [mA/cm2] FF [%] PCE [%] Ref.\nsc\n[V]\nBTR-Cl:Y6 0.843 24.78 74.2 15.5 1\n15.3\nB1:BO-4Cl 0.83 25.27 73 2\n(15.1) a\n… … … … …\n…\n… … … … … …\nMPhS-C2:BTP-eC9:SSe-NIC 0.880 26.85 76.27 18.02 21\nMPhS-C2:L8-BO:L8-S9 0.884 26.43 77.46 18.10 22\nMPhS-C2:BTP-eC9:Se-Giant 0.903 26.34 76.33 18.16 23\n18.51\nMPhS-C2:SD86 :BTP-eC9 0.885 26.85 77.89 29\n(18.40) a\nMPhS-C2:N3 0.863 27.03 74.85 17.46 This work\n18.43\nMPhS-C2:N3 (Additive 3-AR) 0.863 27.32 78.19 This work\n(18.16) a\na the corresponding certified PCE.\n2. The transient absorption characterization and analysis require further refinement. The generation of photoexcited species occurring around 1 ps appears unexpectedly slow. Experimental validation is needed to determine whether a GSB signal emerges when exciting the acceptor material at 400 nm. Additionally, the rising kinetics of the N3 GSB signal requires detailed analysis to determine the timescales for both exciton dissociation and exciton diffusion. More critically, hole transfer dynamics is typically the rate-limiting step in OSCs compared to electron transfer/energy transfer. A comprehensive study of hole transfer kinetics is essential to conclusively understand exciton and carrier dynamics within the active layer because focusing solely on electron transfer/energy transfer lacks persuasiveness.\nResponse: Thank you for your helpful comments. We measured the transient absorption spectrum of the neat acceptor film under 400 nm pump excitation. In the neat acceptor film (Figure R3), we clearly observed a GSB signal at 850 nm. This observation indicates that under 400 nm pump excitation, both MPhS-C2 and N3 are directly excited in the blend film, suggesting the existence of dual-channel charge generation pathways. This implies that both electron and energy transfer from photoexcited MPhS-C2 to N3 can occur, as reflected in the GSB kinetics. However, related studies have demonstrated that energy transfer is followed by a subsequent hole transfer step from N3 to MPhS-C2, resulting in a similar charge separation effect as direct electron transfer. Therefore, we did not specifically distinguish between these two pathways, but instead, we represented them as the photoexcited transfer kinetics from MPhS-C2 to N3 (Angew. Chem. Int. Ed. 2024, e202318595 https://doi.org/10.1002/anie.202318595; Energy Environ. Sci. 2023, 16, 3373, https://doi.org/10.1039/D3EE00602F).\nFigure R3. fs-TA spectra of the neat N3 film (pump at 400 nm).\nGiven the complexity of dual-channel charge transfer, electron transfer and energy transfer alone are insufficient to fully comprehend the charge transfer dynamics within the active layer. Consequently, we further employed 825 nm pump light to selectively excite N3. The corresponding experimental data and conclusions are provided in the revised manuscript and supplementary information, offering a more comprehensive elucidation of the hole transfer dynamics within the active layer. The main revisions are highlighted with red words on page 14-15:\n“The charge transfer dynamics within MPhS-C2:N3 blend films were systematically investigated using femtosecond transient absorption (fs-TA) spectroscopy. Fig. 5a presents the 2D fs-TA spectra of the control and 3-AR-processed blend films, while Fig. 5b displays representative transient absorption spectra at selected delay times. Upon selective excitation of the N3 acceptor at 825 nm, characteristic excited-state signatures of the acceptor were observed at early time delays (Supplementary Fig. 34), featuring ground state bleaching (GSB) signals at 710 nm and 850 nm, along with an excited state absorption (ESA) at 920 nm. As charge transfer progressed, the signals associated with the excited state of the acceptor decayed rapidly, while GSB signals attributed to the donor MPhS-C2 appear around 580 nm and 635 nm, indicating the occurrence of a hole transfer process from N3 to MPhS-C2. Concurrently, a new ESA signal emerged at 1010 nm, which can be attributed to the charge transfer (CT) state of N3. Comparative analysis of the fs-TA kinetics at 1010 nm revealed distinct trends between control and 3-AR-treated films. As illustrated in Fig. 5c, the kinetics at 1010 nm exhibited significantly slower decay in 3-AR-treated films, demonstrating effective suppression of charge recombination and extended charge carrier lifetime. To quantitatively deconvolute the temporal evolution of distinct species involved in the photoelectric conversion process, we performed global analysis based on a consecutive kinetic model, obtaining evolution-associated difference spectra (Fig. 5d, Supplementary Fig. 35 and Supplementary Table 14).51 This analysis resolved three key time constants: τ₁ (ultrafast interfacial charge transfer), τ₂ (exciton diffusion-mediated charge transfer), and τ₃ (charge recombination). Relative to the control film, the 3-AR-treated blend exhibited a reduction in τ₁ from 1.8 ps to 1.5 ps and in τ₂ from 51.9 ps to 40.7 ps, alongside an increase in τ₃ from 4595 ps to 5335 ps. The shortened τ₁ and τ₂ constants indicate enhanced exciton diffusion to the donor-acceptor interface and more efficient dissociation into free charges, consistent with an optimized phase-separated morphology and improved interfacial mixing induced by 3-AR treatment. The prolonged τ signifies an extended charge-separated state lifetime, reflecting reduced\n3\ntrap-assisted non-radiative recombination. Further investigation into the photoexcitation transfer kinetics 52 (Supplementary Fig. 36 and Supplementary Table 15) revealed that 3-AR treatment increased the exciton lifetime (τ ) from 17.22 ps to\ne\n17.44 ps and the charge lifetime (τ ) from 569.85 ps to 595.61 ps. The concurrent\nc\nextension of both exciton and charge lifetimes contributes to reduced charge recombination losses, improved exciton dissociation efficiency, and enhanced charge carrier mobility.53 Collectively, these results underscore that 3-AR treatment effectively optimizes the blend film morphology, facilitating exciton dissociation and charge transport, which ultimately leads to the observed enhancements in J and FF.”\nsc\nSupplementary Fig. 34 (a) 2D transient absorption spectra of the neat N3 film. (b) fs- TA spectra of the neat N3 film at selected time delays.\nFig. 5 a 2D transient absorption spectra of the blend films. b fs-TA spectra of the blend films at selected time delays. c Kinetic traces of CT state ESA probing at 1010 nm for the blend films. d The line graph of the global fitting results.\nSupplementary Fig. 35 Global fitting of kinetic traces of the blend films.\nSupplementary Fig. 36 a) 2D color plots of fs-TA spectra of the blend films. b) The representative spectra at selected time delays of the blend films. c) Exciton and charge lifetimes times estimated from fitting the fs-TA kinetics of the blend films. d) The column plots of τ and τ .\ne c\nSupplementary Table 14 The global fitting result of kinetic traces of the blend films without and with 3-AR.\nAdditive τ₁ (ps) τ (ps) τ (ps)\n2 3\nW/O 1.8 ±0.08 51.9 ±3.45 4595 ± 171\nWith 3-AR 1.5 ±0.06 40.7 ± 2.70 5335 ± 240\n3. The mechanistic explanation states that 3-AR’s interaction with MPhS-C2 shortens the Stage II duration of MPhS-C2. Why does its stronger interaction with N3 prolong the Stage II duration of N3? Moreover, 3-AR enhances crystallization in single-component systems but suppresses crystallization in bulk-heterojunction blends, necessitating mechanistic clarification.\nResponse: We thank the reviewer for the comments. The two seemingly contradictory phenomena you pointed out are precisely the most interesting and important findings in our work.\nFirst, the prolonged duration of Stage II for N3 due to its stronger interaction with 3-AR is a matter of nucleation kinetics. For MPhS-C2, 3-AR likely functions as a nucleating agent: its relatively weak interaction with MPhS-C2 is sufficient to provide effective nucleation sites, significantly reducing the nucleation energy barrier. This enables MPhS-C2 molecules to rapidly attach and arrange in an orderly manner, resulting in a \"shortened phase transition duration\" (Adv. Funct. Mater. 2025, e14342 https://doi.org/10.1002/adfm.202514342). However, when 3-AR interacts with the acceptor N3, the stronger interaction between them effectively enhances their compatibility. This improved compatibility suppresses the premature aggregation behavior of N3 during the early nucleation stage (Adv. Funct. Mater. 2025, 2503009 https://doi.org/10.1002/adfm.202503009). As a result, we observe a \"prolonged phase transition duration\" for N3 (Supplementary Fig. 20). This retardation of the kinetic process facilitates the formation of finer, thermodynamically more stable crystal structures in N3, which aligns with the GIWAXS characterization results indicating improved crystallinity in the 3-AR-treated N3 film.\nSecond, the phenomenon where 3-AR promotes crystallization in single- component systems but suppresses it in blend systems underscores the complexity of the bulk heterojunction (BHJ) system. The core of this behavior lies in the mutual constraints between the donor MPhS-C2 and acceptor N3 molecules, and how the introduction of 3-AR alters this dynamic balance. In the single-component N3 system, the molecular environment is homogeneous, with no competitive interactions. The strong interaction between 3-AR and N3 directly promotes the orderly arrangement of N3 molecules, thereby unequivocally enhancing crystallization. However, in the BHJ blend system, the interpenetration and mutual dilution of MPhS-C2 and N3 molecules significantly restrict their free movement and orderly packing. Our in-situ UV-Vis results (Fig. 3a, b) reveal that MPhS-C2 tends to nucleate and crystallize preferentially and rapidly, driving initial phase separation in the blend solution. At the same time, the strong interaction between 3-AR and N3, along with the resulting improved compatibility, suppresses the early nucleation of N3. This extends the time interval (Δt) between the final crystallization of the donor and the onset of nucleation for the acceptor from 0.38 s to 0.48 s (Angew. Chem. Int. Ed. 2025, e202515280 https://doi.org/10.1002/anie.202515280). As this Stage I time window lengthens, the solvent evaporates more thoroughly, subsequently enabling N3 to undergo a faster phase transition in the following stage (Δτ shortened from 0.190 s to 0.097 s). This effectively prevents N3 from forming excessively large phase domains due to over- crystallization, which are detrimental to device performance. Thus, while 3-AR moderately suppresses the overall crystallinity of the blend film on a macroscopic scale (as supported by GIWAXS data), it promotes the formation of more numerous, smaller-sized crystallites through precise kinetic regulation and guides the construction of a more ideal nanoscale phase-separated morphology (consistent with AFM and TEM results). This optimized microstructure features a larger donor/acceptor interface area and more continuous charge transport channels, ultimately leading to significant improvements in device performance (as confirmed by SCLC, TPC, PL, and J-V characterizations).\nIn summary, 3-AR directly promotes crystallization in single-component systems, whereas in the complex environment of the donor/acceptor blend, it moderately prolongs the nucleation process and regulates phase transition kinetics. While macroscopically suppressing excessive crystallization, it enhances micro-level orderliness, ultimately achieving an ideal active layer morphology (Angew. Chem. Int. Ed. 2025, 64, e202501816 https://doi.org/10.1002/anie.202501816).\n4. Sun's group developed an IC-FI solid additive, structurally analogous to the end group of N3, enhancing the molecule self-assembly of N3 (J. Mater. Chem. A 2021, 9, 2857–2863), while 3-AR (structurally analogous to end group of MPhS-C2) enhances acceptor N3 crystallization rather than MPhS-C2, why?\nResponse: We thank the reviewer for the comments. Although the 3-AR is structurally similar to the terminal group of the donor MPhS-C2, it ultimately promotes the crystallization of the acceptor N3. This seemingly paradoxical phenomenon profoundly reveals that the mechanism of solid additives in multi-component blend systems is far more complex than the simple principle of \"structural similarity\". Through in-depth theoretical calculations and thin-film structural characterization, we found that the core driving force for this phenomenon stems from the thermodynamic differences in intermolecular interactions, which directly dictate the evolution of the final crystalline morphology. The specific analysis is as follows:\nFirst, density functional theory (DFT) calculations provided key evidence at the molecular level (Fig. 2e). Although 3-AR is structurally similar to MPhS-C2, its binding energy with the acceptor N3 (-21.07 kcal/mol) is slightly higher than that with MPhS-C2 (-19.61 kcal/mol). This result clearly indicates that, thermodynamically, 3- AR has a greater tendency to interact with N3 molecules. This challenges the conventional notion that \"structural similarity implies affinity\", demonstrating that subtle differences in the overall molecular electron cloud distribution and steric effects collectively determine the final binding preference. Therefore, the difference in binding energy is the initial thermodynamic origin driving the selective regulation of N3 by 3- AR.\nSecond, GIWAXS results (Fig. 3c-d and and Supplementary Figs. 23-24) further validated the above theoretical inference at the thin-film morphological level, achieving a perfect correlation between the \"thermodynamic mechanism and the microstructure\": the crystallinity and molecular ordering of N3 were significantly improved after the addition of 3-AR. In contrast, the CCL of MPhS-C2 decreased upon the addition of 3- AR, suggesting a slight suppression of its crystallization process.\nIn summary, the strong agreement between theoretical and experimental data forms a complete evidence chain. The selective intermolecular interactions of 3-AR at the molecular level manifest as the differential crystallinity of the donor and acceptor at the macroscopic scale. This work emphasizes that the effectiveness of an additive molecule depends on the selective balance of its interactions with various components within the complex blend system, rather than mere structural similarity.\nWe have systematically reorganized and elaborated on the working mechanism of 3-AR in the revised manuscript. We believe these modifications have substantially improved the clarity, completeness, and persuasiveness of the mechanistic description in our work. The main revisions are highlighted with red words on page 16:\n“It should be noted that structurally, 3-AR resembles MPhS-C2 donor, yet its binding energy with the acceptor N3 (–21.07 kcal/mol) is slightly higher than that with MPhS- C2 (–19.61 kcal/mol), indicating a thermodynamic preference for interaction with N3 molecules. This finding challenges the conventional notion that \"structural similarity implies affinity.\" Furthermore, GIWAXS results reveal that the addition of 3-AR significantly enhances the crystallinity and molecular ordering of N3, while the CCL of MPhS-C2 decreases, suggesting a moderate suppression of its crystallization. These observations corroborate, at the film morphology level, a coherent alignment between thermodynamic mechanisms and microstructural evolution. This finding profoundly reveals that the effectiveness of an additive molecule depends on its selective balance of interactions with various components within the complex blend system, rather than being solely governed by the simplistic principle of \"structural similarity.\" ”\n5. The authors mention trap-assisted recombination. Further data on the trap density should be provided.\nResponse: We thank the reviewer for the comments. We further quantified the trap density by using deep-level transient spectroscopy (DLTS). The corresponding results and discussions are added to page 13 of the revised manuscript. The main revisions are highlighted with red words:\n“Furthermore, we quantified the trap density by deep-level transient spectroscopy (DLTS). As shown in Supplementary Fig. 31, comparing with control device, the trap density of the 3-AR treated device decreased from 3.14 × 1017 to 3.07 × 1017 cm-3. The reduced trap density indicates suppressed trap-assisted recombination, which is beneficial for improving FF and PCE of the device.47”\nSupplementary Fig. 31 DLTS of the MPhS-C2:N3-based AMS-OSCs without and with 3-AR.\n6. The photo, thermal and operational stability of the device needs to be provided.\nResponse: Thank you for your helpful comments. We fully agree that beyond high PCE, outstanding stability of ASM OSC is a prerequisite for future commercialization. Following the reviewer's suggestion, we have conducted a series of stability tests, including storage stability, photostability , and thermal stability, and the results are very encouraging. We have dedicated a section in the Supplementary Information (page 14) to discuss these findings in detail and incorporated corresponding descriptions in the revised manuscript (page 6).The main revisions are highlighted with red words:\n“Additionally, 3-AR not only effectively enhances the storage, photo-, and thermal stability of ASM-OSCs but also demonstrates excellent universality by being applicable to both representative all-small-molecule (e.g., B1:L8-BO and BTR-Cl:N3) and polymer systems (e.g., D18-Cl:N3 and PM6:L8-BO), as shown in Supplementary Fig. 9-11 and Supplementary Table 7.” (on page 6)\n“The N₂-storage stability, photostability, and thermal stability of MPhS-C2:N3-based ASM-OSCs were systematically evaluated. As illustrated in Supplementary Fig. 9a, the tracking of normalized PCE over time demonstrates a remarkable enhancement in the storage stability of the 3-AR-treated devices. These devices retained 81.66% of their initial efficiency after 1968 hours of N₂-storage, outperforming the untreated devices, which maintained only 73.63%. A similar trend was observed under illumination and thermal stress: after 106 hours of 1-sun irradiation, the 3-AR-based ASM-OSCs preserved 80.20% of their initial PCE, compared to 74.95% for the control group (Supplementary Fig. 9b). Moreover, the 3-AR-treated devices exhibited superior thermal stability, maintaining 80.05% of initial performance after annealing at 50 °C for 70 hours, versus 74.80% for the untreated devices (Supplementary Fig. 9c). These results demonstrate that 3-AR effectively improves the N₂ storage, photostability, and thermal resistance of devices, highlighting its potential for advancing the commercialization of ASM-OSCs.” (on page Supplementary 14)\nSupplementary Fig. 9 Normalized PCE of (a) storage stability, (b) photostability stability and (c) thermal stability of the unencapsulated devices in a N -filled glove box.\n1. In the sentence: “Crucially, comprehensive statistical analysis of state-of-the-art ASM-OSCs with PCEs exceeding 15%......, synergistically achieving a record PCE of 18.4%, which is the highest value reported to date.”. The author should accurately fill in the efficiency values.\nResponse: Thank you for your helpful comments. We have checked and revised the efficiency values in the manuscript. The main revisions are highlighted with red words:\n“Crucially, comprehensive statistical analysis of state-of-the-art ASM-OSCs with PCEs exceeding 15% reveals that our 3-AR-processed device exhibits the high J and\nsc\nexceptional FF, synergistically achieving a remarkable PCE of 18.43%, which is the highest value for binary systems reported to date.”\n2. The authors think that the complete volatilization of 3-AR after the heat treatment at 100°C for 10 minutes (Figure S9), contradicting the result of TGA diagram (Figure S8). The author should give reasonably explanation.\nResponse: We thank the reviewer for the comment. The evaporation kinetics of the materials differ due to their distinct physical states. In the solid particulate form, as analyzed by TGA, mass transfer is inherently restricted by limited interfacial exposure. In contrast, the film state drastically enhances the surface-to-volume ratio, facilitating evaporation.The bulk powder 3-AR with its limited specific surface area exhibits slow volatilization. Therefore, 3-AR exhibites 5% weight loss at approximately 150 °C (Supplementary Fig. 13). However, Supplementary Fig. 14 shows a film formed by spin-coating a 20 mg/mL 3-AR chloroform solution, exhibiting a high specific surface area, so it can be completely volatilized even after annealing at 100 °C for 10 minutes. Therefore, the above results are not contradictory.\n3. The author mentioned the full width at half-maximum (FWHM) in the manuscript, but no corresponding values were found in the main manuscript or supporting information. The author should provide the FWHM values.\nResponse: Thank you for your helpful comments. We added the FWHM data to the supplementary information, as detailed in Supplementary Table 10-12. The main revisions are highlighted with red words:\nSupplementary Table 10 Detailed GIWAXS data of the MPhS-C2 films without and with 3-AR additive.\nW/O With 3-AR\nMPhS-C2\nq q\nFilms\nd-spacing FWHM CCL d-spacing FWHM CCL\n[Å -1 ] [Å] [Å-1] [Å] [Å -1 ] [Å] [Å-1] [Å]\nIP (010) 1.799 3.492 0.099 57.212 1.799 3.492 0.101 55.735\n(100) 0.249 25.249 0.034 167.601 0.249 25.210 0.038 147.840\nOOP (200) 0.526 11.950 0.037 150.957 0.527 11.923 0.041 139.557\n(300) 0.793 7.925 0.047 120.934 0.795 7.908 0.051 111.536\nSupplementary Table 11 Detailed GIWAXS data of the N3 films without and with 3-AR additive.\n(100) Peak in IP (010) Peak in OOP\nN3 Films\nq q\nd-spacing FWHM CCL d-spacing FWHM CCL\n[Å -1 ] [Å] [Å-1] [Å] [Å -1 ] [Å] [Å-1] [Å]\nW/O 0.278 22.593 0.061 93.238 1.763 3.563 0.168 33.700\nWith 3-AR 0.277 22.698 0.062 91.384 1.764 3.563 0.164 34.584\nSupplementary Table 12 Detailed GIWAXS data of the MPhS-C2:N3 films without and with 3-AR additive.\n(100) Peak in IP (010) Peak in OOP\nBHJ Films\nq q\nd-spacing FWHM CCL d-spacing FWHM CCL\n[Å -1 ] [Å] [Å-1] [Å] [Å -1 ] [Å] [Å-1] [Å]\nW/O 0.270 23.303 0.037 154.336 1.766 3.557 0.131 43.032\nWith 3-AR 0.269 23.342 0.037 151.038 1.763 3.563 0.139 40.551\n4. The author should clearly explain the significant difference between the μ /μ ratios\ne h\nreported in Supplementary Table 12 and those in the main manuscript.\nResponse: We thank the reviewer for the comment. We carefully checked the ratio between μ and μ and made revisions in the manuscript. The main revisions are\ne h\nhighlighted with red words:\n“Besides, the more balanced μ /μ ratio of 1.37 (vs. 1.50 in control devices) indicates\ne h\neffective suppression of space-charge accumulation, which in turn can enhance FF\nvalue.”\n5. In the characterization of SCLC, the corresponding values of electron and hole mobility date inconsistency expressed by scientific counting methods. The author should carefully unify the format of these values.\nResponse: We thank the reviewer for the comment. We carefully checked the values of μ and μ , corrected the corresponding errors, and unified the format of scientific\ne h\nnotation. The main revisions are highlighted with red words:\n“As shown in Supplementary Fig. 28 and Supplementary Table 13, the electron mobility (μ = 1.28 × 10⁻⁴ cm² V⁻¹ s⁻¹) and hole mobility (μ = 0.93 × 10⁻4 cm² V⁻¹ s⁻¹)\ne h\nare improved in 3-AR-processed devices compared to the control devices (μ = 1.03 ×\ne\n10⁻⁴, μ = 0.69 × 10⁻4 cm² V⁻¹ s⁻¹), due to synergistic morphology optimization. Besides,\nh\nthe more balanced μ /μ ratio of 1.37 (vs. 1.50 in control devices) indicates effective\ne h\nsuppression of space-charge accumulation, which in turn can enhance FF value.”\nSupplementary Table 13 The hole (μ )/electron mobilities (μ ) values of the MPhS-\nh e\nC2:N3-based AMS-OSCs without and with 3-AR.\nThickness μ μ\ne h\nBlend films μ μ\n(nm) 10-4 cm 2V-1s-1 10-4 cm 2V-1s-1 e/ h\nMPhS-C2:N3 100 1.03 0.69 1.50\nMPhS-C2:N3:3-AR 100 1.28 0.93 1.37\nCOMMENTS TO AUTHOR:\nReviewer #4 (Remarks to the Author): In this work, Cao et al. designed 3- allylrhodanine (3-AR) as a solid addition, structurally analogous to the MPhS-C2 donor terminal group, control active layer morphology. As a result, the 3-AR-treated MPhS- C2:N3 device achieves a remarkable power conversion efficiency (PCE) of 18.43% (certified18.16%), which is the highest reported for binary ASM-OSCs. Regarding the reviewer #3's response, I consider some of the replies to be reasonable, and the manuscript has been further improved. However, certain responses still present significant issues requiring further revision.\n1. It is recommended that authors retain only the highest value for third-party certified data.\nResponse: We appreciate the reviewer for this suggestion. Accordingly, we have revised the manuscript to retain only the highest third-party certified efficiency of 18.16%.The main revisions are highlighted with red words on line 1 of page 6:\n“Furthermore, the 3-AR-processed devices garnered independently certified PCEs of 18.16% from the National Center of Inspection on Solar Photovoltaic Products Quality (CPVT), with comprehensive certification reports provided in Supplementary Fig. 7.”\nTable 1 The photovoltaic parameters of the ASM-OSCs based on MPhS-C2:N3 processed without and with 3-AR additives.\nJ J a) PCE [%]\nsc sc\nAdditive V [V] FF [%]\noc [mA/cm2] [mA/cm2] (ave.) b)\n0.863 27.03 74.85 17.46\nW/O 26.01\n(0.857 ± 0.005) (26.96 ± 0.19) (74.91 ± 0.56) (17.31 ± 0.12)\n0.863 27.32 78.19 18.43\nWith 3-AR 26.28\n(0.86 ± 0.003) (27.31 ± 0.22) (77.34 ± 0.64) (18.15 ± 0.12)\nWith 3-ARc) 0.844 27.89 / 77.17 18.16\na) Integrated J from EQE.\nsc\nb) The statistical values in brackets are calculated from 10 devices.\nc) certified by CPVT, Wuxi, China.\n2. The author claims that current understanding of the working mechanism of additives is still primarily empirical and lacks systematic design principles for ASM-OSCs. And then, the author designs the new solid addition to control active layer morphology. The manuscript does not establish a rational design principle or validation for the solid additive. The approach of using additives with functional groups similar to the donor or acceptor appears to be an empirical optimization strategy rather than a principled one. The authors must provide a convincing explanation of the design principle and its verification to establish the scientific significance of their work.\nResponse: We sincerely thank you for the careful review of this work and your valuable comments. The point you raised regarding “the need to establish a reasonable design principle and verify it, rather than merely relying on empirical strategies” is crucial for enhancing the scientific depth and general guiding significance of this work. The statement “using additives similar to the donor functional groups” in our manuscript was oversimplified and may easily lead readers to misunderstand it as a purely empirical strategy. In fact, the core logic of our design is not simply structural similarity, but rather based on the understanding and selective modulation of intermolecular interactions within the active layer.\nWe designed and selected 3-AR, which shares functional groups similar to the donor end groups. Its functional groups (such as carbonyl, -C=S and -C-H, etc.) can form selective interactions with both donor and acceptor molecules (J. Am. Chem. Soc. 2022, 144, 14731−14739 https://doi.org/10.1021/jacs.2c05303. Adv. Energy Mater. 2023, 13, 2302063 https://doi.org/10.1002/aenm.202302063. Nat. Commun. 2023, 14:1760 https://doi.org/10.1038/s41467-023-37526-5. Joule, 2025, 9, 101996 https://doi.org/10.1016/j.joule.2025.101996 ). Additionally, the additive exhibits an appropriate volatilization temperature, allowing it to be completely removed during thermal annealing. This enables the modulation of molecular assembly kinetics and thermodynamics, thereby inducing the formation of an optimized and thermodynamically stable bulk heterojunction morphology. Based on this design principle, we have validated its effectiveness and scientific rigor from multiple perspectives in the manuscript: NOESY and NMR titration data directly demonstrate the explicit hydrogen-bonding interactions between the designed solid additive and the acceptor, while the interaction signals between the donor molecules and the additive are very weak, confirming the selectivity of the interactions. Subsequently, DFT calculations quantified the binding energies between the additive and the donor or acceptor molecules. The calculation results clearly show that the binding energy of the additive with the acceptor is significantly higher than that with the donor, providing theoretical support for the selective interactions. Furthermore, TGA, FTIR, and ¹H NMR collectively prove the good volatility of 3-AR, avoiding adverse effects on the active layer morphology due to its residue. In-situ absorption spectroscopy, GIWAXS, TEM, and FLAS demonstrate that 3-AR treatment not only optimizes the phase- separated morphology—slightly reducing the crystalline coherence length and decreasing the domain size—but also enhances the vertical uniformity of the active layer through multi-level morphological modulation. The optimized morphology synergistically improves charge mobility, exciton dissociation efficiency, and extends exciton and charge lifetimes (as confirmed by SCLC, TPC, TPV, and fs-TA measurements). Ultimately, devices processed with 3-AR achieved excellent efficiency. Additionally, device stability test data indicate that the morphology formed after additive removal exhibits good thermodynamic stability.\nThrough the above explanation, the scientific significance of our work is clearly established: we have deepened and validated what may appear as an empirical optimization strategy into a design principle based on selective intermolecular interactions, with clear physicochemical implications. Simultaneously, we reveal that the effectiveness of additive molecules depends on the selective balance of their interactions with various components in a complex mixed system, rather than being determined solely by simple “structural similarity.” We believe that the manuscript provides a convincing principled explanation and thorough validation for the design of solid additives. The main revisions are highlighted with red words:\n“Herein, structurally resembling the MPhS-C2 donor, 3-allylrhodanine (3-AR) as a SA enables precise control over the active layer morphology……This work shows additive efficacy is governed by balanced selective interactions, not by simplistic structural similarity.” (On page 2 of the revise manuscript)\n“In this study, we introduce 3-allyl-rhodanine (3-AR). While its structure resembles the terminal group of the MPhS‑C2 donor, its functional groups (carbonyl, -C=S, and -C- H, etc.) can form selective interactions with the donor (e.g., Dithienobenzodithiophene (DTBDT) core units) and acceptor (e.g., 2-(5,6-Difluoro-3-oxo-2,3-dihydro-1H-inden- 1-ylidene)ma-lononitrile (2FIC) units and 6,7-Dihydropyrrolo[3,2- g][1,2,5]thiadiazolo[3,4-e]indole core units)30,31, thereby potentially regulating the morphology and improving photovoltaic performance of ASM-OSCs.” (On page 4 of the revise manuscript)\n“It should be noted that while 3-AR is structurally similar to the MPhS-C2 donor, its binding energy with the acceptor N3 is more negative (–21.07 kcal/mol) than that with MPhS- C2 (–19.61 kcal/mol). This indicates a thermodynamic preference for interacting with N3. The result differs from the commonly reported trend that structurally similar additives tend to interact with like components29,56.” (On page 16 of the revise manuscript)\n3. The normalized stability decay curves in Supplementary Fig. 9 do not accurately reflect the absolute degradation of device performance. These should be replotted using the absolute values of key parameters (such as PCE, FF, J ) versus time to clearly show the actual degradation.\nsc\nResponse: Thank you for your helpful comments. The normalized PCE stability decay curve in Supplementary Fig. 9 was plotted from the mean and standard deviation of five devices each with and without 3-AR treatment, ensuring statistical significance. Since normalized data cannot reflect the absolute degradation of device performance, we have provided the key parameters of these devices in Supplementary Tables 6-12 to clearly illustrate the actual performance degradation. The main revisions are highlighted with red words:\n“Additionally, 3-AR not only effectively enhances the storage, photo-, and thermal stability of ASM-OSCs but also demonstrates excellent universality by being applicable to both representative all-small-molecule (e.g., B1:L8-BO and BTR-Cl:N3) and polymer systems (e.g., D18-Cl:N3 and PM6:L8-BO), as shown in Supplementary Fig. 9-11 and Supplementary Table 7-13.” (On page 6 of the revise manuscript)\nSupplementary Table 7 Key performance parameters of the control devices over time under N storage.\nsc\nGroup Time [h] V [V] FF [%] PCE [%]\noc\n[mA/cm2] PCE\n0 0.866 27.16 72.63 17.09 1\n24 0.860 27.18 70.81 16.55 0.9684\n48 0.846 27.30 69.11 15.95 0.9333\n96 0.853 27.18 67.19 15.57 0.9111\n144 0.843 27.22 65.65 15.07 0.8818\n(1)\n192 0.808 27.73 65.21 14.61 0.8549\n288 0.809 27.97 62.37 14.11 0.8256\n744 0.822 27.40 59.28 13.35 0.7812\n1368 0.805 27.62 58.96 13.11 0.7671\n1968 0.797 27.66 57.98 12.79 0.7484\n0 0.864 26.90 73.98 17.19 1\n(2) 24 0.856 27.32 71.61 16.75 0.9744\n48 0.850 26.96 70.93 16.24 0.9447\n96 0.843 27.09 68.80 15.72 0.9145\n144 0.817 27.37 68.39 15.29 0.8895\n192 0.817 27.67 65.64 14.83 0.8627\n288 0.821 27.74 62.29 14.19 0.8255\n744 0.804 27.40 62.00 13.66 0.7946\n1368 0.803 26.94 59.48 12.87 0.7487\n1968 0.781 27.36 57.98 12.39 0.7208\n0 0.865 27.06 75.24 17.61 1\n24 0.855 26.81 74.27 17.04 0.9676\n48 0.851 27.06 71.69 16.52 0.9381\n96 0.855 27.17 69.65 16.17 0.9182\n144 0.844 27.08 68.27 15.61 0.8864\n(3)\n192 0.824 27.54 67.93 15.41 0.8751\n288 0.815 27.49 66.86 14.99 0.8512\n744 0.813 27.30 64.59 14.33 0.8137\n1368 0.793 27.40 63.04 13.70 0.7780\n1968 0.798 27.70 60.33 13.33 0.7570\n0 0.853 26.95 75.01 17.24 1\n24 0.844 26.95 73.86 16.79 0.9739\n48 0.833 26.77 72.71 16.21 0.9403\n96 0.834 26.49 72.08 15.92 0.9234\n144 0.819 26.89 68.91 15.18 0.8805\n(4)\n192 0.813 26.79 67.12 14.62 0.8480\n288 0.801 27.09 64.75 14.06 0.8155\n744 0.807 27.55 61.98 13.78 0.7993\n1368 0.782 27.32 62.57 13.36 0.7749\n1968 0.783 27.06 59.23 12.55 0.7280\n(5) 0 0.848 27.13 75.06 17.27 1\n24 0.845 27.13 74.62 17.10 0.9902\n48 0.832 27.29 72.09 16.37 0.9479\n96 0.825 27.10 71.88 16.06 0.9299\n144 0.815 27.46 68.60 15.35 0.8888\n192 0.809 27.45 66.83 14.84 0.8593\n288 0.799 27.62 64.56 14.25 0.8251\n744 0.822 27.25 60.32 13.52 0.7829\n1368 0.781 27.48 59.11 12.69 0.7348\n1968 0.796 27.28 55.43 12.04 0.6972\nSupplementary Table 8 Key performance parameters of the 3-AR treated devices over time under N storage.\nsc\nGroup Time [h] V [V] FF [%] PCE [%]\noc\n[mA/cm2] PCE\n0 0.860 27.26 76.71 17.98 1\n24 0.860 26.94 75.54 17.49 0.9727\n48 0.847 26.90 75.27 17.15 0.9538\n96 0.851 26.62 74.87 16.96 0.9433\n144 0.845 27.09 73.39 16.80 0.9344\n(1)\n192 0.841 27.17 72.15 16.48 0.9166\n288 0.826 27.06 73.16 16.35 0.9093\n744 0.812 27.55 69.03 15.45 0.8593\n1368 0.817 27.36 66.30 14.82 0.8242\n1968 0.807 26.09 67.37 14.19 0.7892\n0 0.860 26.86 77.39 17.88 1\n24 0.859 26.59 76.75 17.54 0.9810\n(2)\n48 0.844 26.71 75.59 17.04 0.9530\n96 0.845 26.72 74.81 16.89 0.9446\n144 0.831 27.10 74.44 16.77 0.9379\n192 0.849 27.04 71.62 16.45 0.9200\n288 0.845 26.34 73.54 16.37 0.9155\n744 0.839 26.79 69.57 15.63 0.8742\n1368 0.826 26.92 68.60 15.24 0.8523\n1968 0.805 27.08 67.49 14.71 0.8227\n0 0.859 26.65 77.14 17.65 1\n24 0.859 26.52 76.68 17.46 0.9892\n48 0.852 26.73 75.60 17.21 0.9751\n96 0.846 26.61 75.58 17.02 0.9643\n144 0.849 26.47 75.09 16.87 0.9558\n(3)\n192 0.847 26.97 71.72 16.39 0.9286\n288 0.837 26.69 71.47 15.97 0.9048\n744 0.828 26.89 68.49 15.26 0.8646\n1368 0.822 26.89 68.04 15.04 0.8521\n1968 0.817 27.23 65.27 14.53 0.8232\n0 0.856 26.94 75.96 17.52 1\n24 0.848 27.03 75.66 17.34 0.9897\n48 0.845 26.84 74.92 16.98 0.9692\n96 0.844 26.58 74.59 16.73 0.9549\n144 0.834 26.65 73.59 16.35 0.9332\n(4)\n192 0.828 27.05 71.16 15.94 0.9098\n288 0.828 26.84 69.20 15.38 0.8779\n744 0.824 27.49 66.30 15.02 0.8573\n1368 0.824 26.79 67.05 14.80 0.8447\n1968 0.815 27.22 65.48 14.53 0.8293\n0 0.861 27.21 76.55 17.93 1\n(5)\n24 0.852 27.24 76.70 17.81 0.9933\n48 0.852 27.03 75.71 17.45 0.9732\n96 0.843 27.19 75.05 17.20 0.9593\n144 0.854 26.75 73.47 16.79 0.9364\n192 0.837 27.08 73.72 16.71 0.9320\n288 0.825 27.42 72.23 16.33 0.9108\n744 0.819 27.65 69.50 15.74 0.8779\n1368 0.818 27.46 68.62 15.41 0.8595\n1968 0.797 27.74 65.18 14.40 0.8031\nSupplementary Table 9 Key performance parameters of the control devices over time under 1-sun illumination.\nJ Normalized\nsc\nGroup Time [h] V [V] FF [%] PCE [%]\noc\n[mA/cm2] PCE\n0 0.856 27.94 72.45 17.34 1\n24 0.841 27.50 64.80 14.98 0.8639\n72 0.818 27.23 62.28 13.87 0.7999\n(1)\n120 0.786 26.64 60.69 12.71 0.7330\n168 0.757 26.74 58.54 11.85 0.6834\n216 0.717 26.79 55.77 10.71 0.6176\n0 0.858 26.95 76.23 17.64 1\n24 0.836 26.47 69.62 15.40 0.8730\n72 0.808 26.30 66.68 14.17 0.8033\n(2)\n120 0.789 26.13 65.74 13.56 0.7687\n168 0.747 25.99 63.16 12.26 0.6950\n216 0.730 25.81 61.62 11.62 0.6587\n0 0.859 27.27 75.14 17.61 1\n(3) 24 0.827 26.88 68.34 15.19 0.8626\n72 0.758 26.54 67.66 13.61 0.7729\n120 0.738 26.82 64.38 12.75 0.7240\n168 0.731 26.60 63.77 12.40 0.7041\n216 0.707 26.61 60.59 11.40 0.6474\n0 0.859 26.93 73.14 16.92 1\n24 0.826 26.94 66.15 14.72 0.8700\n72 0.784 26.74 63.38 13.28 0.7849\n(4)\n120 0.754 26.51 62.59 12.50 0.7388\n168 0.717 26.08 65.05 12.17 0.7193\n216 0.691 26.56 59.39 10.89 0.6436\n0 0.854 27.66 72.14 17.05 1\n24 0.831 27.28 66.70 15.13 0.8874\n72 0.802 26.64 63.30 13.52 0.7930\n(5)\n120 0.771 26.57 62.22 12.74 0.7472\n168 0.731 26.43 60.15 11.62 0.6815\n216 0.721 26.29 57.44 10.89 0.6387\nSupplementary Table 10 Key performance parameters of the 3-AR treated devices over time under 1-sun illumination.\nJ Normalized\nsc\nGroup Time [h] V [V] FF [%] PCE [%]\noc\n[mA/cm2] PCE\n0 0.856 27.31 75.04 17.54 1\n24 0.847 26.84 71.46 16.25 0.9265\n72 0.817 26.54 68.23 14.80 0.8438\n(1)\n120 0.799 26.55 66.91 14.20 0.8096\n168 0.777 26.43 62.47 12.84 0.7320\n216 0.751 26.23 64.68 12.75 0.7269\n0 0.864 27.06 75.66 17.69 1\n(2)\n24 0.849 26.49 73.29 16.48 0.9316\n72 0.821 26.36 68.13 14.74 0.8332\n120 0.805 26.12 66.71 14.02 0.7925\n168 0.774 26.12 66.18 13.38 0.7564\n216 0.760 26.03 63.87 12.64 0.7145\n0 0.855 27.72 75.60 17.92 1\n24 0.853 27.65 70.80 16.69 0.9314\n72 0.825 27.46 66.04 14.97 0.8354\n(3)\n120 0.755 27.16 68.28 14.01 0.7818\n168 0.758 27.08 67.41 13.84 0.7723\n216 0.708 26.89 65.35 12.44 0.6942\n0 0.857 27.80 75.39 17.97 1\n24 0.851 27.08 75.50 17.40 0.9683\n72 0.838 26.65 69.75 15.58 0.8670\n(4)\n120 0.787 26.16 68.92 14.20 0.7902\n168 0.767 25.98 66.83 13.32 0.7412\n216 0.755 26.06 64.59 12.70 0.7067\n0 0.860 27.53 73.82 17.47 1\n24 0.841 27.46 71.62 16.54 0.9468\n72 0.820 26.50 67.60 14.69 0.8409\n(5)\n120 0.791 26.84 65.44 13.89 0.7951\n168 0.789 26.63 64.22 13.50 0.7728\n216 0.753 26.95 61.08 12.40 0.7098\nSupplementary Table 11 Key performance parameters of the control devices over time under continuous thermal aging at 50°C.\nJ Normalized\nsc\nGroup Time [h] V [V] FF [%] PCE [%]\noc\n[mA/cm2] PCE\n(1) 0 0.859 27.12 73.30 17.07 1\n24 0.852 26.87 69.41 15.88 0.9303\n72 0.743 26.52 62.54 12.32 0.7217\n120 0.684 26.13 63.20 11.29 0.6614\n168 0.617 26.15 65.00 10.48 0.6139\n216 0.625 26.15 57.70 9.43 0.5524\n0 0.859 27.37 73.65 17.31 1\n24 0.858 26.94 73.25 16.92 0.9775\n72 0.731 26.82 67.14 13.15 0.7597\n(2)\n120 0.727 26.52 61.44 11.84 0.6840\n168 0.672 26.23 58.88 10.38 0.5997\n216 0.624 26.09 58.29 9.49 0.5482\n0 0.861 27.13 73.63 17.19 1\n24 0.846 26.79 72.68 16.48 0.9587\n72 0.740 26.42 63.95 12.51 0.7277\n(3)\n120 0.665 26.14 62.19 10.80 0.6283\n168 0.635 25.98 63.95 10.56 0.6143\n216 0.601 25.90 57.65 8.97 0.5218\n0 0.854 27.13 76.33 17.69 1\n24 0.846 26.50 72.22 16.20 0.9158\n72 0.746 26.45 65.67 12.97 0.7332\n(4)\n120 0.678 26.01 62.89 11.10 0.6275\n168 0.640 26.23 61.36 10.30 0.5822\n216 0.610 26.12 59.06 9.41 0.5319\n0 0.850 27.34 74.78 17.37 1\n24 0.840 27.03 70.26 15.96 0.9188\n(5) 72 0.741 26.89 64.70 12.90 0.7427\n120 0.670 26.27 59.71 10.50 0.6045\n168 0.635 26.20 60.49 10.06 0.5792\n216 0.596 26.26 57.28 8.96 0.5158\nSupplementary Table 12 Key performance parameters of the 3-AR treated devices over time under continuous thermal aging at 50°C.\nJ Normalized\nsc\nGroup Time [h] V [V] FF [%] PCE [%]\noc\n[mA/cm2] PCE\n0 0.859 27.21 76.66 17.91 1\n24 0.845 26.68 73.40 16.56 0.9246\n72 0.837 26.63 64.07 14.28 0.7973\n(1)\n120 0.816 25.98 59.74 12.66 0.7069\n168 0.804 26.14 58.19 12.23 0.6829\n216 0.780 25.49 53.51 10.63 0.5935\n0 0.864 27.10 76.72 17.97 1\n24 0.856 27.13 72.47 16.84 0.9371\n72 0.847 26.83 64.08 14.56 0.8102\n(2)\n120 0.823 26.17 61.95 13.34 0.7423\n168 0.791 26.20 55.94 11.59 0.6450\n216 0.786 25.74 55.03 11.13 0.6194\n0 0.853 27.31 75.77 17.65 1\n24 0.853 26.30 73.38 16.46 0.9326\n72 0.825 25.73 69.18 14.68 0.8316\n(3)\n120 0.826 25.31 63.37 13.26 0.7510\n168 0.821 25.41 59.33 12.38 0.7014\n216 0.786 25.18 56.12 11.10 0.6291\n0 0.861 27.21 76.55 17.93 1\n24 0.857 26.99 71.19 16.47 0.9186\n(4)\n72 0.845 26.72 62.96 14.21 0.7925\n120 0.810 26.04 61.41 12.96 0.7228\n168 0.804 26.20 58.49 12.33 0.6877\n216 0.791 25.52 55.30 11.16 0.6224\n0 0.857 27.39 74.92 17.58 1\n24 0.849 26.96 72.76 16.65 0.9471\n72 0.828 26.40 62.58 13.68 0.7782\n(5)\n120 0.818 26.17 59.02 12.63 0.7184\n168 0.802 26.19 57.27 12.02 0.6837\n216 0.766 25.35 53.46 10.38 0.5904\n4. In Supplementary Fig. 20c, the time interval for adding or not adding 3-AR in N3 is imprecise during the solution-to-film conversion stage. I propose that 3-AR has a negligible effect on the film formation time of N3, which remains constant at approximately 0.1 seconds. Its primary influence is on shortening the film formation time of the donor, MPhS-C2. This observation suggests a processing sequence in which the acceptor (N3) aggregates first, followed by the donor. Consequently, the authors are requested to re-analyze the relevant data, provide a reasonable explanation for this observed mechanism, and furnish detailed parameters for each stage of the process, including the precise film formation times and aggregation order.\nResponse: We sincerely thank the reviewer for their careful review and valuable comments. The issue raised regarding the imprecise representation of the time intervals for the solution-to-film transition stage of N3 with and without 3-AR in Supplementary Fig. 20c is of great importance for improving our paper. Upon re-examining the data, we found that the initial presentation of the chart was indeed not clear enough, and we apologize for any confusion caused.\nBased on your suggestion, we have conducted additional measurements and analysis of the relevant process. The experimental results confirm that the phase transition time of N3 is indeed prolonged upon the addition of 3-AR (from 0.097 s to 0.191 s, see the revised Supplementary Fig. 20c). This extension facilitates more orderly stacking of N3 molecules, thereby improving their crystallinity, which is consistent with the results obtained from GIWAXS measurements.To further validate this observation, we optimized the time interval settings for data acquisition during the in-situ absorption measurements and performed multiple sets of repeat experiments. The results obtained under different temporal resolutions (as shown in Figures 1 and 2) consistently demonstrate that the introduction of 3-AR prolongs the phase transition time of N3 (Figure 1: from 0.130 s to 0.191 s; Figure 2: from 0.097 s to 0.191 s). The data from multiple experiments show good consistency, indicating the generalizability of this phenomenon. Moreover, similar observations have been reported in recent literature, where solid additives were shown to modulate the phase transition kinetics of acceptors (Adv. Mater. 2023, 35, 2301583 https://doi.org/10.1002/adma.202301583.), further supporting our findings.\nBased on the above results, we have comprehensively revised the relevant charts (Supplementary Figs 20–21) and textual descriptions in the manuscript to more accurately and clearly present the differences in phase transition times and their impact on film morphology and performance. We once again thank the reviewer for your constructive feedback, which has significantly enhanced the scientific rigor of this paper. The main revisions are highlighted with red words:\n“while the N3's duration extends from 0.097 to 0.191 s, facilitating ordered N3 molecular packing, as confirmed by grazing-incidence wide-angle X-ray scattering (GIWAXS) analysis.” (On page 9 of the revise manuscript)\nSupplementary Fig. 20 2D time-resolved in-situ absorption spectra of (a) MPhS-C2 and (b) N3 during spin coating. (c) The maximum peak variations of MPhS-C2 and N3 during the solution-to-film transformation stage.\nSupplementary Fig. 21 In situ UV-vis absorption spectroscopy of the (a) MPhS-C2, (b) N3 and (c) MPhS-C2:N3 films without and with 3-AR additive, respectively.\nFigure 1 (a) 2D time-resolved in-situ absorption spectra, (b) in situ UV-vis absorption spectroscopy and (c) the maximum peak variations of N3 during the solution-to-film transformation stage.(Within 2 seconds, 31 points were taken, with a time interval of approximately 0.0645 seconds)\nFigure 2 (a) 2D time-resolved in-situ absorption spectra, (b) in situ UV-vis absorption spectroscopy and (c) the maximum peak variations of N3 during the solution-to-film transformation stage. (Within 2 s, 42 points were taken, with a time interval of approximately 0.0476 s)"}, {"round": 2, "reviewer_comments": {"reviewer_1": "The authors have satisfactorily addressed all the concerns. I recommend acceptance of this work in its present form.", "reviewer_2": "Accepted without revised", "reviewer_4": "The authors have addressed all the concerns raised by the reviewers and the manuscript can be accepted.\n----\nIn this work, Cao et al. designed 3-allylrhodanine (3-AR) as a solid addition, structurally analogous to the MPhS-C2 donor terminal group, control active layer morphology. As a result, the 3-AR-treated MPhS-C2:N3 device achieves a remarkable power conversion efficiency (PCE) of 18.43% (certified18.16%), which is the highest reported for binary ASM-OSCs.\nRegarding the reviewer #3's response, I consider some of the replies to be reasonable, and the manuscript has been further improved. However, certain responses still present significant issues requiring further revision.\n1. It is recommended that authors retain only the highest value for third-party certified data.\n2. The author claims that current understanding of the working mechanism of additives is still primarily empirical and lacks systematic design principles for ASM-OSCs. And then, the author designs the new solid addition to control active layer morphology. The manuscript does not establish a rational design principle or validation for the solid additive. The approach of using additives with functional groups similar to the donor or acceptor appears to be an empirical optimization strategy rather than a principled one. The authors must provide a convincing explanation of the design principle and its verification to establish the scientific significance of their work.\n3. The normalized stability decay curves in Supplementary Fig. 9 do not accurately reflect the absolute degradation of device performance. These should be replotted using the absolute values of key parameters (such as PCE, FF, JSC) versus time to clearly show the actual degradation.\n4. In Supplementary Fig. 20c, the time interval for adding or not adding 3-AR in N3 is imprecise during the solution-to-film conversion stage. I propose that 3-AR has a negligible effect on the film formation time of N3, which remains constant at approximately 0.1 seconds. Its primary influence is on shortening the film formation time of the donor, MPhS-C2. This observation suggests a processing sequence in which the acceptor (N3) aggregates first, followed by the donor. Consequently, the authors are requested to re-analyze the relevant data, provide a reasonable explanation for this observed mechanism, and furnish detailed parameters for each stage of the process, including the precise film formation times and aggregation order."}, "author_response": ""}, {"round": 3, "reviewer_comments": {"reviewer_4": "The reviewer satisfied with the revision and recommended the acceptance of the manuscript"}, "author_response": ""}]

Decision letter