Moisture-responsive crystallization strategy for efficient CsPbI_3 solar cells fabricated under high-humidity conditions

Domain: physics
Published: 2026-03-03
Editorial outcome: major_revision

Abstract
The intrinsic phase instability of CsPbI3 perovskites necessitates stringent fabrication conditions, significantly hindering the practical deployment. In the DMA-mediated CsPbI3 nucleation system, the Cs+/DMA+ ion exchange critically governs the resulting film quality. Here, we employ a moisture-responsive crystallization strategy utilizing propyltriethoxysilane (PTES) to deposit CsPbI3 under ambient air with high humidity (55%). We demonstrate that the siloxane groups can capture DMA+ in the intermediate DMAPbI3, facilitating DMA+ extraction and Cs+ incorporation, thereby accelerating crystallization kinetics. This approach enables CsPbI3 PSCs to achieve a power conversion efficiency (PCE) of 21.00% with an impressive fill factor (FF) of 86.1% while processing perovskite under relative humidity (RH) of 55%. Higher PCEs of 21.85% and 22.60% (certified 22.02%) were achieved for devices fabricated at a lower RH of 25% and for films spin-coated under an N2 atmosphere followed by annealing in ambient air, respectively. Furthermore, PTES-treated devices exhibit excellent operational stability under ambient conditions.

Introduction
CsPbI3 has garnered significant attention owing to its exceptional chemical stability and remarkable photoelectric performance1–7. Recent advancements in CsPbI3-based perovskite solar cells (PSCs) have demonstrated significant progress, achieving efficiencies over 22%8. Unfortunately, the small ionic radius of Cs+ ion leads to great lattice distortion9, rendering CsPbI3 prone to a phase transition into the optically inactive δ phase in ambient air10,11. This phase transition is significantly accelerated under the erosive effect of moisture12. During film formation, the high solvation enthalpy of halide ions lowers the formation energy of vacancies, enabling water molecules to increase halide vacancy density. The vacancies weaken the ionic bonding between adjacent [PbI6]4− octahedra, catalyzing phase transitions2,13,14. Additionally, moisture molecules can extract Cs+ ions from the surface lattice, further reducing the energy barrier for phase transitions driven by octahedral distortions12,15. Consequently, most high-efficiency CsPbI3 devices are fabricated within inert gases or low humidity (RH < 40%) environments to suppress degradation16–20. This stringent environmental control presents a significant barrier to scalable, cost-effective production. Therefore, the fabrication of high-efficiency CsPbI3 PSCs in ambient air without restrictions of relative humidity (RH) remains a significant challenge.

In recent years, organic molecule additive engineering has emerged as a widely adopted strategy to regulate the growth of CsPbI3 thin films in air and maintain their phase stability21,22. Reported additives generally function by interacting with atmospheric moisture to mitigate water-induced lattice degradation23 or by introducing hydrophobic components that protect the perovskite during film formation24. Organosilane and siloxane compounds such as 3-Aminopropyltrimethoxysilane (APTMS) have been used in hybrid perovskites to passivate grain boundaries and improve hydrophobicity25–27. However, these treatments are applied mainly at the surface of MA/FA-based perovskites and rely on moisture-sensitive groups, which limit their effectiveness under the high-humidity conditions required for CsPbI3 processing. And these approaches remain limited in the ability to regulate the crystallization dynamics of CsPbI3 under ambient conditions.

To date, the crystallization of high-quality CsPbI3 primarily relies on spontaneous, additive-free nucleation driven by DMA+/Cs+ ion exchange5,28–30. Accelerating DMA+ removal while maintaining sufficient time for crystal growth is essential for forming well-defined γ-CsPbI3 films31–33. Previous studies further show that moderate humidity facilitates DMA+ extraction, whereas excessive moisture disrupts nucleation and leads to poor crystallinity21,34,35. Thus, effectively harnessing atmospheric moisture to regulate CsPbI3 crystallization is key to fabricating high-performance devices under high-humidity conditions. However, most reported crystallization-control strategies rely on hygroscopic functional groups (e.g., –NH2, –COOH, or –SO3H), whose inherent moisture sensitivity limit the applicability at elevated humidity16,36. This gap underscores the urgent need for new crystallization-regulation mechanisms that remain robust under elevated humidity levels.

Here, we propose a moisture-driven crystallization regulation strategy for the preparation of high-quality CsPbI3 films under high-humidity conditions. As a multifunctional additive, propyltriethoxysilane (PTES) promotes the formation of dense CsPbI3 films with enlarged grain sizes. We further reveal a direct interaction between siloxane species and DMA+, which plays a decisive role in guiding CsPbI3 crystallization in humid environments. Namely, PTES accelerates the detachment of DMA+ ions from the DMAPbI3 structure, facilitating Cs+ insertion into the [PbI6]4− framework. Moreover, PTES reacts with ambient moisture to form Si−O−Si and Si−O−Pb cross-linked networks that reinforce the lattice and stabilize the γ-phase even under elevated humidity. Notably, this crystallization-regulation mechanism arises intrinsically from the siloxane chemistry of PTES itself without assistance from additional functional groups. The resulting Si−O−Pb bonding minimizes internal defects, reduces iodine vacancies, and improves band alignment, enabling ultrafast charge transfer. Hence, PTES-treated CsPbI3 PSCs achieved a record efficiency of 21.00% with an impressive fill factor (FF) of 86.1%. The strategy enables CsPbI3 solar cells to be fabricated entirely in ambient air, with performance comparable to glovebox-processed devices, effectively overcoming environmental constraints in fabrication process.

Results
Organosiloxanes possess distinctive hydrolysis properties, allowing them to react with moisture and self-assemble into hydrophobic Si−O−Si networks37,38. We employ propyltriethoxysilane (PTES) as an additive to regulate the growth of CsPbI3 under a humid environment. Under moisture exposure, PTES undergoes hydrolysis to generate Si−OH groups, which spontaneously condense into a self-assembled Si−O−Si network (Supplementary Fig. 1)39–41. Intriguingly, hydrolyzed intermediate Si−OH can coordinate with Pb2+ via Lewis acid–base interactions, forming Si−O−Pb bonds40–42. This strong coordination anchors the [PbI6]4− octahedra and cross-links the CsPbI3 lattice, thereby regulating the film quality and stabilizing the γ-phase21,24,37. Furthermore, the trace water generated from PTES hydrolysis and condensation might even promote the crystallization of CsPbI332,43. Although Trimethoxypropylsilane (PTMS) and 3-Aminopropyltriethoxysilane (APTES) were also evaluated, our comparison of their electrostatic potentials and their influence on CsPbI3 film morphology (Supplementary Fig. 2 and Supplementary Note 1) highlights the clear advantage of PTES. PTES exhibits a milder hydrolysis process, which supports uniform crystallization of CsPbI3 under humid conditions. In contrast, the faster hydrolysis of PTMS and the strong moisture-induced cross-linking of APTES lead to premature siloxane aggregation and severe film disruption. These differences indicate that PTES is the most suitable silane additive for stabilizing CsPbI3 growth in high-humidity environments. Leveraging this chemical reactivity, PTES is introduced into the CsPbI3 precursor solution to modulate crystallization dynamics and improve film formation under high-humidity conditions.

All CsPbI3 films were fabricated via a one-step spin-coating method using ethyl acetate as the anti-solvent, followed by thermal annealing at 180°C. All processes of perovskite films were conducted under ambient conditions with a relative humidity (RH) of ~55%. The untreated and PTES-treated CsPbI3 films are labeled as the control and target samples, respectively.

To elucidate the PTES-assisted crystallization mechanism of CsPbI3 under high-humidity conditions, we investigated the evolution of film crystallinity during annealing. As shown in Fig. 1a, the target films darken more rapidly than the control, indicating accelerated crystallization dynamics. XRD measurements of films annealed for different times (Fig. 1b, c and Supplementary Fig. 3) show the DMAPbI3 peak (~11.8°) steadily decreases and disappears in target samples. In contrast, the control samples first show an increase, then a slow decline (Supplementary Fig. 4). This suggests that in control samples, DMA+ ions remain bound to the [PbI6]4− framework due to their higher binding energy, promoting intermediate DMAPbI3 formation before eventual conversion to γ-CsPbI3 via Cs+/DMA+ ion exchange during extended annealing32. However, PTES facilitates the early release of DMA+ through adsorption between siloxane groups and DMA+ in DMAPbI340,44,45, suppressing intermediate phase crystallization and accelerating Cs+ incorporation. Furthermore, PTES further suppresses the crystallization of the DMAPbI3 intermediate, facilitating additional lattice compression and enhancing the structural stability of CsPbI3 (Supplementary Figs. 5 and 6 and Supplementary Notes 2 and 3).

To further elucidate the regulatory mechanism of PTES on the crystallization dynamics and lattice evolution of CsPbI3, in situ Raman spectroscopy was systematically conducted during the annealing process (Fig. 1d). The characteristic peaks observed at 108 cm−1 and 90 cm−1 are attributed to the symmetric stretching vibration of Pb−I−Pb bridging bonds and the asymmetric breathing mode of [PbI6]4− octahedra, respectively. Upon thermal annealing, the thermally activated atomic rearrangement drives lattice relaxation and suppresses octahedral distortions, manifesting as a progressive redshift of the 108 cm−1 mode. Concurrently, enhanced crystallinity suppresses defect-mediated localized lattice distortions, leading to the complete disappearance of the 90 cm−1 feature. Notably, target samples showed a faster decrease of the 90 cm−1 mode, indicating an accelerated transition to symmetric Pb–I vibrations. The Raman band at ~160 cm−1 is attributed to I–I stretching vibrations of molecular iodine (I2) or localized iodine aggregation near vacancy sites, originating from oxidation of I⁻ under ambient O2/H2O exposure. This process leads to the formation of iodine vacancies and lattice instability in the control film. In contrast, PTES incorporation suppresses this reaction by forming a hydrophobic and crosslinked Si–O–Si/Si–O–Pb network that inhibits moisture adsorption and stabilizes the Pb–I framework. Moreover, the regulation of CsPbI3 crystallization by PTES is further supported by confocal Raman mapping of the 108 cm⁻¹ vibrational mode (Fig. 1e and f). Unlike the spatially heterogeneous signal in the control, target films display a more uniform and intense distribution, consistent with improved morphology in Fig. 1a. This enhancement results from homogeneous nucleation driven by Si–OH groups from PTES. These groups likely attach to precursor colloids, creating evenly distributed nucleophilic sites that lower the nucleation barrier and speed up CsPbI3 crystallization.

We calculated adsorption energies of siloxane species on various atomic sites within the DMAPbI3 intermediate (Fig. 1g). PTES shows the strongest adsorption at the DMA+ site (Ead = –1.06 eV), followed by the I (–0.65 eV) and Pb (–0.54 eV) sites, indicating a preferential interaction that destabilizes DMA+. Building on these adsorption insights, we next evaluated the escape energy barriers of DMA+ on three representative facets of DMAPbI3 (Fig. 1h and Supplementary Fig. 7). In the absence of PTES, DMA+ removal is hindered by positive activation barriers. By contrast, PTES significantly lowers the escape barriers across all facets, with the most pronounced reduction observed on the (001) plane, where the barrier drops from +0.32 eV to –0.58 eV. This facet-dependent modulation demonstrates that PTES reshapes the thermodynamic landscape of DMA+ volatilization, rendering its extraction energetically favorable and thereby accelerating the phase transition from DMAPbI3 to CsPbI3.

The accelerated crystallization dynamics may stem from adsorption between PTES and DMA+, which facilitates DMA+ extraction and Cs+ incorporation. These reactions were confirmed by 1H nuclear magnetic resonance (NMR) and Fourier-transform infrared (FTIR) spectroscopy (Fig. 2a, b). In the NMR spectra, the disappearance of Si−O−C2H5 peaks at 3.73 and 1.14 ppm in PTES upon mixing with DMAPbI3 indicate siloxane group reactivity. Concurrently, the −CH3 peak of DMAPbI3 shifts from 2.55 ppm, confirming changes in the chemical environment of DMA+. Detailed 1H spectra are provided in Supplementary Figs. 8 and 9. FTIR analysis further corroborates the reaction. The −NH3+− stretching vibration in DMAPbI3 shifts from 1562 cm−1 to 1570 cm−1 after PTES treatment, while the Pb−N stretching at 805 cm−1 disappears, replaced by the appearance of Si−N band at 936 cm−1. These spectral transitions indicate the breaking of Pb−N bonds and the formation of Si−N bonds under thermal and humid conditions, accelerating the detachment of DMA+ and the insertion of Cs+ into [PbI6]4−. Simultaneously, on the PTES-treated DMAPbI3 samples, the disappearance of Si−O−C signals at 950 cm−1 and 775 cm−1, along with the appearance of Si−OH (842 cm−1) and Si−O−Si (1017 cm−1), further confirms the hydrolysis of PTES and the subsequent formation of cross-linked networks. To demonstrate that these reactions during film formation, FTIR was conducted on control and target samples annealed at 70°C and 180°C (Fig. 2c). At 70°C pre-annealing of the target films, the appearance of Si−N (935 cm−1) and Si−OH (842 cm−1) peaks indicates early-stage adsorption and hydrolysis. Upon further annealing, Si−N bonds decompose while Si−OH species condense into Si−O−Si or react with Pb to form Si−O−Pb networks. These cross-linked networks not only stabilize the perovskite lattice but also inhibit moisture penetration, thereby preserving the γ-CsPbI3 phase during film formation21,24,37.

X-ray photoelectron spectroscopy (XPS) was employed to investigate the surface composition of CsPbI3 films and further elucidate the role of PTES under high-humidity conditions. Figure 2d depicts that the Si 2p signal at ~102 eV appear exclusively in target film, confirming the retention of PTES within the CsPbI3 matrix. Moreover, time-of-flight secondary ion mass spectrometry (ToF–SIMS) depth further confirms that hydrolyzed PTES is uniformly incorporated into the CsPbI3 bulk in the form of Si–O–based species, rather than being confined to the interface (Supplementary Fig. 10). Meanwhile, the N 1s signal (Supplementary Fig. 11a) is nearly absent in the target sample but persists in the control, indicating efficient DMA+ removal facilitated by PTES, consistent with the XRD results. The Pb 4f core-level spectra (Fig. 2e) reveal peak positions at 142.4 and 137.6 eV for the target film, corresponding to a 0.3 and 0.2 eV shift, respectively, compared to the control. The peak shift suggests an interaction between PTES and Pb, attributed to the formation of Si−O−Pb cross-linking networks. In addition, a slight shift of the I 3d peak toward lower binding energy in the target film (Supplementary Fig. 11b) suggests a reduced density of iodine vacancies. These findings demonstrate that PTES effectively suppresses halide vacancy formation and enhances film quality by stabilizing the CsPbI3 surface chemistry under humid ambient conditions.

Mechanistically, hydrolyzed PTES produces Si–OH and Si–O– species that interact with DMA+ and regulate its release from the DMAPbI3 intermediate, enabling a gradual transition toward CsPbI3. As annealing proceeds, PTES condenses to form Si–O–Si and Si–O–Pb linkages, thereby strengthening local lattice connectivity and mitigating structural fluctuations during phase conversion. This coordinated process accelerates Cs+ incorporation into the [PbI6]4− framework, promotes uniform crystallization, and suppresses defect formation. At the same time, the in situ-formed hydrophobic siloxane network further reduces moisture ingress, thereby supporting the stabilization of γ-CsPbI3 under humid conditions. Together, these effects enable PTES to harness ambient moisture constructively and yield high-quality CsPbI3 films even in high-humidity environments.

X-ray diffraction (XRD) analysis (Supplementary Fig. 12 and Supplementary Note 4) reveals characteristic peaks at 14.4° and 28.9°, corresponding to the (110) and (220) planes of γ-phase CsPbI346,47. A minor peak at 11.8° attributed to DMAPbI3 is present in control sample, indicating incomplete evaporation of DMA+32. The absence of DMAPbI3 peak in the target sample suggests that PTES enhances DMA evaporation, promoting complete ions conversion. Particularly, the (110) peak in the target sample exhibits a rightward shift and reduced shoulder intensity, implying improved preferential orientation, lattice compression, and reduced interplanar spacing—factors associated with enhanced structural stability48. In addition, the markedly smaller slope in the W–H plot further confirms the release of internal microstrain within the perovskite lattice. To further investigate the lattice stress-strain behavior, grazing incidence X-ray diffraction (GIXRD) was performed at varying incident angles (ω) (Fig. 3a and b). In control samples, peak shifts toward higher angles with increasing ω indicate surface tensile strain. In contrast, the target samples show negligible peak movement, confirming strain relaxation and improved lattice uniformity49. The specific mechanism of stress-strain release and the microstrain values are depicted in Fig. 3c.

The morphology of the control and different concentration target samples was examined utilizing top-view scanning electron microscopy (SEM) (Supplementary Fig. 13). The control films exhibit a non-compact morphology with visible pinholes and cracks, primarily resulting from moisture-induced degradation, in agreement with previous studies21,22,24,35. Following PTES treatment, the CsPbI3 films exhibit significantly improved compactness, highlighting the effectiveness of PTES in modulating film quality under high-humidity conditions. Cross-sectional SEM images (Supplementary Fig. 14) further reveal enhanced crystallinity and a more ordered structure in the target samples. Atomic force microscopy (AFM) analysis (Supplementary Fig. 15) shows a marked reduction in surface roughness from 17.10 nm (control) to 7.83 nm (target), indicating a smoother film surface and improved crystallinity, which are favorable for enhanced interfacial contact.

As shown in the UV-Vis spectra (Supplementary Fig. 16 and Supplementary note 5), both perovskite films display comparable absorption profiles, with the target film exhibiting enhanced absorption near 550 nm, attributed to improved crystallinity and film quality. Ultraviolet photoelectron spectroscopy (UPS) (Supplementary Fig. 17a) reveals valence band maxima of −5.47 eV (control) and −5.27 eV (target), yielding conduction band minima of −3.76 and −3.56 eV, respectively. The corresponding energy level diagram (Supplementary Fig. 17b) illustrates that PTES induces an upward shift in energy levels, improving alignment with the hole transport layer and facilitating hole extraction. Notably, the Fermi level of the target film shifts upward by ~0.1 eV, enhancing the driving force for carrier separation and reducing open-circuit voltage (Voc) losses. KPFM analysis (Fig. 3d–f) further confirms this shift, showing a higher and more uniform contact potential difference (CPD) in the target film. The influence of PTES on carrier dynamics was examined via steady-state and time-resolved photoluminescence (PL and TRPL) measurements. As shown in Fig. 3g, the target CsPbI3 film exhibits markedly enhanced PL intensity with a blue-shifted emission peak, indicative of reduced defect density. TRPL analysis (Fig. 3h and Supplementary Table 1) reveals a substantially prolonged average carrier lifetime from 7.90 ns (control) to 44.25 ns (target), confirming suppressed nonradiative recombination. Furthermore, confocal PL mapping (Fig. 3i and Supplementary Fig. 18) shows a more intense and spatially uniform emission from the target film, highlighting improved film homogeneity and compositional uniformity.

The J-V characteristics with FTO/TiO2/SA/CsPbI3/PTABr/Spiro-OMeTAD/Au, photovoltaic parameters and cross-sectional SEM image of target device are shown in Fig. 4a and Supplementary Table 2. The control devices achieve a PCE of 18.19%, whereas the target device achieved the PCE of 21.00% with an outstanding FF of 86.1%. It is the highest reported FF among CsPbI3 PSCs to date. The reduced hysteresis in the target device can be attributed to the PTES-induced reduction of interfacial and bulk defect densities, which suppresses ion migration and interfacial charge accumulation. The target device also demonstrated excellent repeatability, with the tighter PCE distribution, as supported by the statistical data from 40 devices (Fig. 4b and Supplementary Fig. 19). Optimization of PTES concentration identified 4 mol% (relative to DMAPbI3) as optimal (Supplementary Figs. 20, 21 and Table 3). The high efficiency and strong reproducibility also benefit from the commonly used additives DMACl and PbAc2. XRD, PL, and UV–vis measurements (Supplementary Fig. 22 and Supplementary Note 6) confirm their respective roles in both control and PTES-treated samples, and demonstrate that the additional DMA and Pb sources do not interfere with PTES-mediated crystallization or introduce extra DMA⁺ or Pb2+ into the final CsPbI3 films. Figure 4c displays the external quantum efficiency (EQE) curves and corresponding integrated current densities of the control and target devices, yielding 18.97 mA/cm2 and 19.79 mA/cm2, respectively. The steady-state power output (SPO), tracked under maximum power point (MPP) conditions (Fig. 4d), further confirms device stability. The target device maintains a current density of 19.48 mA/cm2 and PCE of 20.65%, compared to 18.47 mA/cm2 and 17.64% for the control.

To further verify the scalability of the PTES approach, we fabricated 1 cm2 devices (Supplementary Fig. 23), which exhibited a PCE of 18.81%, confirming the applicability of this method for larger-area perovskite solar cells. Moreover, to validate the general applicability of PTES, devices were fabricated under varying humidity levels (Fig. 4e, f and Supplementary Fig. 24). The target device achieved an impressive PCE of 22.60% (prepared in an N2 atmosphere and annealed in air), with a certified efficiency of 22.02% (Supplementary Fig. 25), as well as 21.85% under RH ~25%. The statistical chart of target devices is shown in Supplementary Fig. 26. PCE evolution under different humidity conditions demonstrate the excellent reproducibility and highlights the universal efficacy of PTES across environments (Supplementary Fig. 27). Notably, the target devices consistently outperform prior CsPbI3 PSCs fabricated under similar conditions, with substantial enhancements in FF as illustrated in Fig. 4g, h and Supplementary Table 5. Furthermore, we performed XPS measurements on target CsPbI3 films prepared under different humidity conditions (RH = 25%, 50%, 75%) to evaluate the effect of moisture on siloxane crosslinking (Supplementary Fig. 28, Supplementary Note 7 and Table 6). The quantitative XPS results show that humidity strongly regulates PTES hydrolysis and crosslinking. As RH increases from 25% to 50%, the Si and O signals rise markedly, indicating enhanced formation of the Si–O–Si network. At RH=75%, the crosslinking level approaches saturation. Device performance follows this trend, indicating that siloxane crosslinking is intrinsically beneficial and enhances moisture tolerance. Nevertheless, excessive humidity still induces structural degradation even at higher crosslinking levels. The markedly faster efficiency loss observed in control devices under high humidity further highlight the protective role of siloxane crosslinking. Moreover, even for films processed in a N2 atmosphere, PTES-mediated crystallization still occurs because annealing is conducted in ambient air with RH of 20–30%, allowing sufficient hydrolysis and crosslinking to influence CsPbI3 nucleation and growth.

Space charge limited current (SCLC) measurements were conducted to quantify trap densities in the perovskite films (Supplementary Fig. 29 and Supplementary Note 8), highlighting the effectiveness of PTES in suppressing defect formation. Additionally, SCLC fitting reveals that the target device exhibits a significantly improved electron mobility (Supplementary Fig. 30 and Supplementary Note 9). Dark J–V characteristics (Supplementary Fig. 31) revealed reduced leakage current in the target device, indicating suppressed carrier recombination due to fewer trap states. Mott–Schottky analysis further showed an increased built-in potential (Vbi) of 1.04 V in the target device, reflecting improved charge separation efficiency, consistent with the observed Fermi level shift (Supplementary Fig. 32 and Supplementary Note 10). Electrochemical impedance spectroscopy (EIS) analysis (Supplementary Fig. 33 and Table 7) demonstrated lower series resistance (Rs) and charge-transfer resistance (Rct) in target devices, corroborating the enhanced charge transport and extraction properties imparted by the additive.

To assess the impact of PTES on the long-term stability of PSCs, various storage stability tests were conducted on both control and target devices. Evidently, the presence of PTES significantly enhances the long-term stability of the target devices (Supplementary Figs. 34, 35, Supplementary Notes 11, 12 and Table 8). MPP tracking under varying conditions further corroborated the improved stability (Fig. 4i, j). Under N2 atmosphere, the encapsulated target device retained 90% of its initial PCE after 800 h of continuous illumination. In ambient air at 50% RH, the unencapsulated target device maintained ~80% of its efficiency after nearly 100 h, significantly outperforming the control. These results highlight the efficacy of the PTES additive strategy in enhancing both intrinsic and extrinsic stability of CsPbI3 perovskite solar cells, even under challenging environmental conditions.

Methods
Materials
Titanium tetrachloride (TiCl4, 99.9%), lead acetate (PbAc2, 99%), Dimethylamine hydrochloride (DMACl, 99%), Triethoxypropylsilane (PTES, 98%), 3-Amino-1-propanesulfonic acid (SA, 97%), and Ethyl acetate (EA, 99.7%) were purchased from Aladdin. Lead(II) iodide (PbI2, 99.99%), cesium iodide (CsI, 99.999%), Phenylethylamine Hydroiodide (PEAI, 99%), 4-tert-butylpyridine (TBP, 96%), 2,2’,7,7’-Tetrakis(N, N-di-p-methoxyphenylamine)−9,9-spirobifluorene (Spiro-OMeTAD, 99.86%) and tris (2-(1H-pyrazol-1-yl)−4-tert-butyl-pyridine) cobalt(III) tri[bis(trifluoromethane)sulfonimide] (FK209) were purchased from Advanced Election Technology Co., Ltd. N, N-Dimethylformamide (DMF, 99.8%), Dimethyl sulfoxide (DMSO, 99.9%), Chlorobenzene (CB, 99.8%), Li-bis-(trifluoromethanesulfonyl) imide (Li-TFSI, 99.5%) and Hydriodic acid (HI, 57 wt%), Phenyltrimethylammonium bromide (PTABr, 98%) were purchased from Sigma-Aldrich. And hypophosphorus acid (H3PO2, 50 wt% aqueous solution) was purchased from Macklin. Poly(3-hexylthiophene-2,5-diyl) (P3HT) were purchased from Xi’an Yuri Solar Co., Ltd. We did no further purification to all the experimental materials before we used.

Synthesis of DMAPbI3
DMAPbI3 [DMA=(CH3)2NH2+] was synthesized using PbI2 (2.305g) dissolved in 5 mL DMF at 80°C under active stirring for 30 min in air atmosphere. Immediately after, 5 mL HI were added to the solution, and a small amount of H3PO2 was subsequently added into the mixture to form a transparent solution. Stop stirring and allow it to cool to room temperature. After standing for two hours, collect the precipitate, wash it with ethanol 4-5 times, and then vacuum dry it overnight at 60°C29.

Preparation of precursor solution
For the preparation of control devices under air conditions, the perovskite precursor solution (1M) was prepared by dissolving 0.634g DMAPbI3, 0.2676g CsI, 7.5mg PEAI, 2.5mg DMACl, and 10mg PbAc2 in DMF/DMSO mixed solvent (volume ratio = 4:1), which was stirred for 16 h. For the target devices, PTES was added at 3–6% of the DMAPbI3 molar amount, and all other conditions matched those of the control CsPbI3 precursor. For the preparation of champion devices under N2 atmosphere, the perovskite precursor solution (0.8M) was prepared by dissolving 0.5072g DMAPbI3, 0.2141g CsI, 7.5mg PEAI, 2.5mg DMACl, 10mg PbAc2 and 9.6 μL PTES in 1 mL DMF/DMSO mixed solvent (volume ratio = 4:1). Spiro-OMeTAD precursor solution was prepared by dissolving 90mg of spiro-OMeTAD, 40 μL of 4-tBP, 23 μL of Li-TFSI solution (520mg Li-TFSI in 1 mL acetonitrile) and 20 μL FK209 solution (300mg FK209 in 1 mL acetonitrile) in 1 mL of chlorobenzene.

Device fabrication
Fluorine-doped tin oxide glass (FTO, 2*2 cm2) is cleaned for 30 min with detergent, deionized water, acetone, ethanol, and deionized water. Then, FTO is treated with oxygen plasma for 5 min. The TiO2 layer was deposited by immersing FTO glass substrates in 200 mL aqueous solution containing 4.5 mL titanium tetrachloride at 70°C for 60 min, then rinsed with distilled water and annealed at 200°C for 30 min. Before spin-coating the perovskite precursor solution, spin-coat 0.5 mg/mL of SA aqueous solution at a speed of 4000 rpm for 20 s, and then anneal at 100°C for 10 min. The perovskite precursor solution was spin-coated on the top of preheated compact TiO2 substrate at 600 rpm for 6 s, 3000 rpm for the 30 s. At 15 seconds to the end of the spin coating, 300 μL of antisolvent ethyl acetate (EA) were dropped within 1 s. After that, the precursor film was annealed at 180°C for 10 min in the air (RH 25-75%). 1 mg/ml of PTABr was applied to the upper surface of CsPbI3 at 4000 rpm 20 s and annealed at 100°C for 10 min. Subsequently, the Spiro-OMeTAD hole transport layer (HTL) was prepared by dynamic spin coating at 1500 rpm for 30 s. The resulting films are then oxidized for 16–24 h. For stability test devices, 1 mg/ml PMMA CB solution is coated onto the perovskite film at 6000 rpm for 20 s, and then annealed at 100°C for 10 min. And HTL is replaced with 10 mg/ml P3HT, spin-coated at 3000 rpm for 30 s, and annealed at 100°C for 30 min. Finally, a 75 nm thick Au layer was deposited by thermal evaporation.

Device fabrication in N2 atmosphere
The perovskite precursor solution was coated onto the TiO2 substrate modified with SA at 600 rpm 6 s and 3000 rpm 30 s. The substrate was then annealed in N2 atmosphere at 70°C until the film became transparent and a little foggy. Transfer to an environment with 25-35% RH and heat at 180°C for 10 min. After completion, cool to room temperature and then transfer to N2 atmosphere. The remaining steps are the same as those for air preparation.

Peer review rounds
[{"round": 1, "reviewer_comments": {"reviewer_1": "his manuscript presents a potentially valuable strategy for ambient-condition fabrication of CsPbI₃ perovskite solar cells using PTES as a moisture-responsive additive. While the reported efficiencies are competitive and the experimental design is generally sound, the mechanistic claims lack sufficient theoretical and quantitative support, key data such as mobility and large-area device performance are missing, and several interpretations (e.g., intermediate phase suppression) are inconsistent with the provided data. Moreover, the novelty relative to existing siloxane-based strategies is not clearly established (e.g., the underlying mechanism—particularly the role of siloxane groups in DMA⁺ extraction and lattice stabilization—bears notable similarity to previously reported siloxane-assisted strategies). Therefore, substantial revision is required to strengthen the mechanistic justification, clarify data inconsistencies, and convincingly demonstrate innovation and reproducibility. Decision: Major Revision.\n1、Siloxane materials have been widely studied and applied in perovskite solar cells (e.g., https://doi.org/10.1002/eem2.12554; DOI: 10.1039/c9ee02028d; https://doi.org/10.1002/adom.202201672). What are the structural advantages of PTES used in this paper? Compared with the published ones, what are the innovations? The author needs to conduct a more rigorous comparative argumentation.\n2、In terms of research mechanism, the author proposes that PTES accelerates the volatilization process of DMA through Si-O groups, but this lacks support from relevant theoretical calculations. It is suggested to supplement relevant theoretical calculations to further verify this conclusion, such as the interaction between PTES and various ions in the perovskite precursor, as well as the escape energy barrier of DMA.\n3、The authors mentioned that “PTES reacts with ambient moisture to form a hydrophobic network through Si−O−Pb and Si−O−Si bonding, leading to in situ crosslinking of the perovskite lattice that strengthens lattice interactions and effectively prevents further moisture intrusion”. However, what is the distribution of PTES in the perovskite? There are doubts as to whether this reaction process can occur in the bulk of the perovskite. Does it exist in the bulk of the perovskite as independent PTES molecules or as a Si−O−Si network?\n4、In line 88, “PTES undergoes hydrolysis to generate Si-OH groups, which spontaneously condense into a self-assembled Si−O−Si network”. It is noted that during the condensation reaction of Si-OH groups, water molecules are generated, which may serve as an internal water vapor source. This conflicts with the core claim of humidity stability and may induce local phase transitions or defects. The authors did not demonstrate the potential impact of the water generated from condensation on the perovskite, so further research and convincing evidence are required. Additionally, could the higher PCE shown in Figure 5d under N2 environment be related to this factor?\n5、The humidity-responsive characteristics of PTES are only demonstrated by the film-forming effect at 55% RH, without quantifying the correlation between the crosslinking density of the siloxane and performance under different humidity conditions.\n6、In line 128, “In contrast, PTES facilitates the early release of DMA+ through adsorption between siloxane groups and DMA+ in DMAPbI3, suppressing intermediate phase crystallization and accelerating Cs+ incorporation. Furthermore, PTES further suppresses the crystallization of the DMAPbI3 intermediate, facilitating additional lattice compression and enhancing the structural stability of CsPbI3”. The authors mention that the interaction between PTES and DMA inhibits the crystallization of the intermediate phase DMAPbI3. However, the relevant XRD data show the opposite result. For example, in Figure 2b,c and Supplementary Figure 7, the PTES-treated target film at the initial stage (0 min) exhibits a stronger intermediate phase signal. The authors are requested to provide an explanation for this.\n7、Siloxane networks are typically insulators, which may introduce interfacial barriers or carrier traps, affecting carrier transport. It is recommended to supplement the carrier mobility data of both PTES-treated and untreated films.\n8、In line 222, “confocal PL mapping demonstrates a more intense and spatially uniform emission for the PTES-treated film”. However, the quantitative analysis in this part is insufficient, and it is recommended to provide more intuitive data for illustration.\n9、In line 331, “The effective area of the gold electrode is 4 mm2”. It is suggested that the authors supplement the performance data of devices with a larger area to further verify the scalability feasibility of the PTES strategy.\n10、The CsPbI3 PSCs reported in this paper achieve a PCE of 21.00% (with an FF as high as 86.1%) under 55% RH, which ranks among the leading levels for similar devices. It is recommended that the authors provide third-party certification results.", "reviewer_2": "Dai et al. address a critical challenge in the field of perovskite photovoltaics: the intrinsic phase instability of all-inorganic CsPbI₃, particularly when fabricated under ambient humidity. By developing a moisture-responsive crystallisation strategy using propyltriethoxysilane, the work has high relevance for scalable solutions. Achieving a PCE of over 21% with an exceptional fill factor of 86.1% under high humidity is a significant and timely contribution. The work is of high interest to researchers in inorganic perovskite solar cells. However, the manuscript requires substantial revision to improve its clarity, provide deeper mechanistic context, and include some critical experimental details to meet the highest standards of Nature Communications. Therefore, a thorough revision is recommended for the manuscript to be accepted for publication.\n1. Presentation and Language: The manuscript requires thorough editorial work to enhance its readability. It contains numerous examples of passive voice, misspelt words, and incorrect word usage.\n1. For example, there are instances of run-on sentences and minor typos (e.g., \"crystallizationtheir\") and redundancies in the same sentence (\"limited in the ability to regulate their ability\").\n2. The manuscript throughout alternates between \"CsPbI3\" (without subscript) and \"CsPbI₃\" (with subscript).\n3. Some sentences are overly complex. For example, \"The vacancies weaken the ionic bonding between adjacent [PbI6]4− octahedra, catalysing phase transitions\" is clear and effective. In contrast, sentences like \"Notably, the PTES-treated CsPbI₃ samples exhibited a faster attenuation of the 90 cm−1 mode, reflecting an accelerated transition to symmetric Pb–I vibrations mediated by PTES-assisted crystallization\" could be simplified for better readability.\n4. Use terminology consistently. For example, choose consistent use of terminology (e.g., \"target\" vs. \"PTES-treated\" samples; \"control\" vs. \"untreated\") and stick with it.\n5. Choose one term and abbreviation (e.g., EQE or IPCE) and use it consistently in both the main text and the experimental section.\n6. Ensure all figures, especially those in the SI, are high-resolution. Figure captions should be more descriptive and self-contained, enabling readers to understand the figure without needing to refer back to the main text. Some figures are referenced in the text but not shown (e.g., Supplementary Figs.). Ensure all key data is included in the main manuscript or as high-quality supplementary figures. Figure captions should be more descriptive.\n7. The \"Results and Discussion\" section is extensive and encompasses a wide range of topics. It would be significantly clearer if broken down with subheadings, such as: Crystallographic and Morphological Improvements, Mechanism of PTES-Assisted Crystallisation, Optoelectronic Properties, Photovoltaic Performance, and Stability. This is just a suggestion.\n8. It would be helpful to have an overview of the TOC image in the main text.\n2. Overview:\n1. The manuscript introduces propyltriethoxysilane (PTES) as a multifunctional additive to regulate the crystallization of CsPbI₃ under high-humidity conditions. PTES and related organosilane compounds have been explored in the context of hybrid perovskites, primarily for surface passivation, hydrophobicity enhancement, and interface engineering. For example, (3-Aminopropyl)triethoxysilane (APTES) and other silanes have been used to passivate grain boundaries and improve moisture resistance in MAPbI₃ and FAPbI₃ systems (Adv. Mater. 2018, 30, 1802764; J. Mater. Chem. A 2019, 7, 23427). Siloxane-based crosslinking has been reported to enhance the mechanical and environmental stability of perovskite films (ACS Appl. Mater. Interfaces 2019, 11, 21536). However, the use of PTES specifically in all-inorganic CsPbI₃ perovskites is novel, and the manuscript would benefit from a brief review of these prior works to highlight the novelty.\n2. The rationale for selecting PTES over other silane-based or organosiloxane additives is not fully elaborated in the current version. It would strengthen the manuscript to clarify the design logic:\ni. Was PTES chosen for its specific hydrolysis rate, chain length, or compatibility with the perovskite precursor chemistry?\nii. Did the authors screen other silane derivatives, or is there a particular chemical interaction (e.g., the ability to form Si–O–Pb bonds) that makes PTES uniquely effective?\n3. Most importantly, the experiment details do not provide details of the addition of PTES and preparation conditions.\n4. According to the experimental details, the perovskite precursor solution contains DMACl, PEAI, PbAc₂, DMAPbI₃, and CsI, although their specific roles are not discussed in detail within the manuscript. DMACl is commonly utilised as a volatile cation source to produce DMAPbI₃, and the presence of DMA⁺ can aid in controlling nucleation and grain growth. However, since DMAPbI₃ is already pre-synthesised and included as one of the precursor components, this aspect warrants further consideration. The manuscript suggests that PTES facilitates the extraction of DMA⁺; however, it would be beneficial to discuss the necessity of adding additional DMA⁺ (through DMACl, which would necessitate further extraction) and whether its presence is crucial for achieving the observed film quality.\ni. Additionally, PbAc₂ is recognised as a lead source modulator that controls film morphology and defect density. Acetate ions can influence crystallisation kinetics and passivate defects, as reported in several previous studies. The manuscript should clarify the need for using PbAc₂ as an additional lead source (in addition to DMAPbI₃) or whether it also plays a role in defect passivation or film formation. Does it have any effect on the coordination with DMA+?\nii. A brief discussion on the roles of DMACl and PbAc₂, referencing relevant literature. If possible, providing control experiments or citing previous studies that demonstrate their effects on film quality and device performance would be beneficial.\niii. Also, there is no mention of PEAI in any part of the manuscript.\n3. Crystallographic Analysis\n1. The XRD and GIXRD analyses are well presented, showing phase purity and strain relaxation. However, quantitative analysis (e.g., Rietveld refinement, d-spacing, microstrain) would strengthen the claims of lattice compression.\n2. The suppression of the DMAPbI₃ intermediate is a key point. Consider including in situ XRD or temperature-dependent XRD to more directly track phase evolution. Additionally, DMA+ extraction is of high relevance; it is crucial to quantify and demonstrate DMA+ concentration in final films, if present, and particularly if multiple beta or gamma phases are present.\n3. The link between lattice compression, reduced microstrain, and device performance should be discussed in more detail.\n4. Photovoltaic Properties:\n1. An explicit mention of the final device architecture (FTO/TiO₂/CsPbI₃/PTABr/Spiro-OMeTAD/Au) should be included in the main text (as in Figure 5a cross-section) and captions.\n2. Address whether J-V hysteresis was observed and, if so, how it was mitigated or quantified.\n3. Key data, such as the statistical distribution of PCEs (Supp. Fig. 14), are essential for the main argument and can be moved from the SI to the main manuscript.\n4. The number of devices tested and the statistical spread of key parameters (PCE, FF, Voc, Jsc) should be more prominently reported in the main text, not just in the Supplementary Information. All physical properties or device parameters obtained should have error bars to emphasise reproducibility. Include error bars and statistical analysis in all plots showing device performance. For stability, display both absolute and normalised PCE values over time.\n5. While the manuscript claims record performance in ambient conditions and compares the performances in Figure 5e-f and Table 4, it misses some of the recent publications. For example: References such as Adv. Mater. 2020, 32, 2001243; Adv. Funct. Mater. 2025, e10544; Energy Environ. Sci., 2025,18, 4130-4141; Adv. Sci. 2025, 12, 241266 etc.\n6. While stability is addressed, the testing protocols (e.g., ISOS standards) and environmental conditions should be described in more detail to facilitate comparison with other works. The reporting needs to be more specific. For MPP tracking, specify the temperature, light source (including whether a UV filter was used), and encapsulation method (e.g., glass/epoxy). For ambient stability, specify the temperature and light/dark cycling conditions.\n5. Characterisation\n1. The suite of characterisations (XRD, SEM, AFM, PL, TRPL, XPS, FTIR, NMR, UPS, KPFM, SCLC, EIS) is impressive and supports the claims. However, most of these analyses are only briefly mentioned, without providing details on sample preparation, data acquisition conditions, and data analysis methods. Every characterisation should adhere to a detailed scientific standard.\n2. XPS, UPS, KPFM, SCLC, photovoltaic device and stability characterisation details are entirely missing.\n3. Clearly state the stability testing protocols (e.g., ISOS-L1, ISOS-D1), including illumination intensity, temperature, encapsulation, and humidity.\n6. References:\n1. Please check the consistency and formatting of all references, as a glance shows errors in formatting. For example, Refs 35, 41, and 43 are missing issue numbers.\n2. In the Experimental Section, under Device fabrication section: “The process of preparing under inert atmosphere was demonstrated in previous work.\" However, no reference is provided.\n3. Also, for the synthesis route adopted for DMAPbI3, previous references should be provided.\n4. Also, for SCLC and Mott-Schottky equations, or any established equations used in the SI, should be referred to appropriately.\n5. Supplementary Table 4 and Figs. 5e and f miss some of the recent publications under high humidity. For example: References such as Adv. Mater. 2020, 32, 2001243; Adv. Funct. Mater. 2025, e10544; Energy Environ. Sci., 2025,18, 4130-4141; Adv. Sci. 2025, 12, 2412666", "reviewer_3": "This manuscript presents a practically relevant strategy for stabilizing γ-phase CsPbI3 perovskite films through additive engineering, enabling the fabrication under ambient air conditions. The additive of PTES facilitates DMA⁺ extraction and promotes the formation of cross-linked Si–O–Si and Si–O–Pb networks. These interactions effectively modulate crystallization kinetics, enhance lattice integrity, and suppress phase degradation under humid conditions. The achieved fill factor and PCE under ambient conditions are among the best reported for CsPbI3 solar cells. This work is important for the preparation of stable CsPbI3 solar cells in air. The manuscript is also organized. Even so, key mechanistic claims require further clarification and validation to strengthen the work’s impact. Detailed comments are as below.\n1. The manuscript shows that PTES promotes DMA⁺ extraction and accelerates crystallization. However, rapid DMA⁺ removal may temporarily increase defect density and affect film quality. The authors should clarify how PTES mitigates this issue.\n2. The slight blue shift observed in the Pb 4f XPS spectra may not be sufficient to conclusively confirm the formation of covalent Si–O–Pb networks, as such shifts could also originate from surface adsorption effects rather than genuine lattice-level crosslinking. Please provide more evidences to confirm the formation of covalent Si–O–Pb networks.\n3. The manuscript emphasizes the role of PTES in facilitating the release of DMA+ from the DMAPbI3 lattice. DMA+ may also react with ambient moisture to form byproducts, which could potentially affect film uniformity or long-term stability. It remains unclear whether any intermediate species or organic byproducts were formed.\n4. In lines 144–145, the authors attribute the Raman peak at 160 cm−1 to molecular iodine or iodine vacancy, suggesting degradation of the control film upon environmental exposure. However, the formation pathway of I2 under ambient conditions remains unclear and requires further clarification.\n5. In Supplementary Fig. 23b, the XRD intensities at different time points appear inconsistent. It is recommended that the data be normalized to the (110) peak to more clearly highlight the evolution of the δ-phase signal.\n6. Please proofread the manuscript for typos and redundancy, such as the repeated “PTES” in line 80.\n7. The color scheme of the figures in the Supplementary Information is inconsistent with that of the main text. Please consider unifying the style for better visual coherence."}, "author_response": "Response to reviewers\nReviewer #1 (Remarks to the Author): his manuscript presents a potentially valuable\nstrategy for ambient-condition fabrication of CsPbI perovskite solar cells using PTES\n3\nas a moisture-responsive additive. While the reported efficiencies are competitive and\nthe experimental design is generally sound, the mechanistic claims lack sufficient\ntheoretical and quantitative support, key data such as mobility and large-area device\nperformance are missing, and several interpretations (e.g., intermediate phase\nsuppression) are inconsistent with the provided data. Moreover, the novelty relative to\nexisting siloxane-based strategies is not clearly established (e.g., the underlying\nmechanism—particularly the role of siloxane groups in DMA+ extraction and lattice\nstabilization—bears notable similarity to previously reported siloxane-assisted\nstrategies). Therefore, substantial revision is required to strengthen the mechanistic\njustification, clarify data inconsistencies, and convincingly demonstrate innovation and\nreproducibility. Decision: Major Revision.\nResponse: We extend our sincere gratitude to the reviewer for the insightful comments\non our work. In response to your kind suggestions, we have revised the manuscript and\nconducted additional experiments to further substantiate the points raised. Below are\nour detailed responses :\n1. Siloxane materials have been widely studied and applied in perovskite solar cells\n(e.g., https://doi.org/10.1002/eem2.12554; DOI: 10.1039/c9ee02028d;\nhttps://doi.org/10.1002/adom.202201672). What are the structural advantages of\nPTES used in this paper? Compared with the published ones, what are the\ninnovations? The author needs to conduct a more rigorous comparative\nargumentation.\nResponse: We sincerely appreciate the reviewer’s insightful comment and the relevant\nreferences provided on siloxane-based materials in perovskite solar cells. Indeed, the\ncited studies mainly focus on polymeric siloxanes or polysilazanes applied as surface\npassivation layers for stabilizing inorganic perovskites. These studies highlight the\nadvantages of polymer-based siloxane frameworks in improving interfacial quality and\nmoisture resistance, but they do not actively engage in or regulate the process of\nperovskite crystallization. In contrast, the core innovation of our work lies in employing\na small-molecule alkoxysilane (PTES) as a precursor additive rather than a post-\ndeposition coating, thus enabling active modulation of the perovskite lattice formation.\nThis distinction endows PTES with structural and mechanistic functions that differ\nfundamentally from previously reported polymeric siloxane systems.\nSpecifically, the siloxane group in PTES accelerates the extraction of DMA⁺ from\nthe intermediate phase DMAPbI and steers the nucleation pathway toward the photo-\n3\nactive γ-phase CsPbI . This behavior arises from a specific chemical interaction\n3\nbetween the siloxane moiety and DMA, an unique effect that has not been reported\nin previous studies employing siloxane-based additives in perovskite solar cells\n(10.1021/acs.jpclett.5c02129; 10.1021/acsenergylett.4c01323; 10.1002/sus2.70032).\nHere, we identify this interaction for the first time and demonstrate that it plays a key\nrole in guiding CsPbI crystallization, particularly under high-humidity conditions.\nfunctional groups, and the siloxane unit alone is found to be sufficient to modulate\nlattice formation. This behavior contrasts sharply with conventional crystallization-\ncontrol strategies that rely on functional groups such as –NH , –COOH, –SH, or –SO −\n2 3\n(10.1002/sus2.70032; 10.1002/adfm.202309894; 10.1016/j.cej.2022.139495;\n10.1002/aenm.202502006). Reports in which siloxane chemistry directly governs\nperovskite crystallization are extremely limited, underscoring the distinctiveness of the\nmechanism revealed in this study.\nFurthermore, the in-situ formation of Si–O–Si and Si–O–Pb networks during\ncrystallization process enables the construction of a three-dimensional hydrophobic and\nmechanically reinforcing scaffold throughout the bulk, rather than solely at the surface.\nThis bulk network effectively strengthens water–oxygen barrier capability and\nmitigates crystallization-induced stress, which are essential for achieving stable γ-\nphase CsPbI under high humidity condition (55% RH). In contrast, previously\n3\nreported surface siloxane strategies are ineffective under such circumstance. To address\nthe reviewer’s request for clearer comparative discussion, we have revised the\nIntroduction and Discussion sections to explicitly articulate the structural advantages\nand mechanistic innovations introduced by PTES (Lines 51-68), as follows:\n“However, these treatments are applied mainly at the surface of MA/FA-based\nperovskites and rely on moisture-sensitive groups, which limits their effectiveness\nunder the high-humidity conditions required for CsPbI processing. And these\n3\napproaches remain limited in the ability to regulate the crystallization dynamics of\nCsPbI under ambient conditions.”\n3\n“However, most reported crystallization-control strategies rely on hygroscopic\nfunctional groups (e.g., –NH , –COOH, or –SO −), whose inherent moisture sensitivity\n2 3\nlimits the applicability at elevated humidity. This gap underscores the urgent need for\nnew crystallization-regulation mechanisms that remain robust under elevated humidity\nlevels.”\n“We further reveal, for the first time, a direct interaction between siloxane species\nand DMA+, which plays a decisive role in guiding CsPbI crystallization in humid\n3\nenvironments. Namely, PTES accelerates the detachment of DMA+ ions from the\nDMAPbI structure, facilitating Cs+ insertion into the [PbI ]4− framework. Moreover,\n3 6\nPTES reacts with ambient moisture to form Si−O−Si and Si−O−Pb cross-linked\nnetworks that reinforce the lattice and stabilize the γ-phase even under elevated\nhumidity. Notably, this crystallization-regulation mechanism arises intrinsically from\nthe siloxane chemistry of PTES itself without assistance from additional functional\ngroups”\nWe thank the reviewer again for helping us strengthen the clarity and positioning\nof our work.\n2. In terms of research mechanism, the author proposes that PTES accelerates the\nvolatilization process of DMA through Si−O groups, but this lacks support from\nrelevant theoretical calculations. It is suggested to supplement relevant theoretical\ncalculations to further verify this conclusion, such as the interaction between PTES\nand various ions in the perovskite precursor, as well as the escape energy barrier of\nDMA.\nResponse: We thank the reviewer for this valuable suggestion regarding the need for\ntheoretical support to validate the proposed mechanism by which PTES accelerates the\nvolatilization of DMA+. In response, we have now included a comprehensive set of\nDFT calculations that examine (i) the adsorption behavior of PTES-derived siloxane\nspecies on different atomic sites of the DMAPbI intermediate and (ii) the escape\n3\nenergy barriers associated with DMA+ removal from representative crystallographic\nfacets.\nAs shown in Figures R1, PTES exhibits the strongest adsorption at the DMA+ site\n(E = –1.06 eV), followed by the I (–0.65 eV) and Pb (–0.54 eV) sites, which clearly\nad\nindicates that PTES preferentially interacts with the organic cation in the DMAPbI\n3\nintermediate and perturbs its local chemical environment, thereby weakening the\nintrinsic DMA+–[PbI ] interaction, making DMA+ more susceptible to be displaced\n6\nduring the subsequent Cs+- DMA+ exchange process. Such strong competitive\ninteractions provide a compelling energetic rationale for the accelerated removal of\nDMA+ observed experimentally and support the conclusion that PTES plays a central\nmechanistic role in facilitating the DMAPbI -to-CsPbI phase transition.\n3 3\nFig. R1 (a) Adsorption configurations and energies of PTES with DMA+, Pb2+, I− and\nCs+, (b) Corresponding adsorption energies for PTES on the four evaluated sites.\nWe have incorporated these results and the corresponding discussion into the\nrevised manuscript (Figures 1g, h), the detailed description are as follows:\n“To elucidate how PTES regulates the early-stage crystallization of CsPbI , we\n3\ncalculated adsorption energies of siloxane species on various atomic sites within the\nDMAPbI intermediate (Fig. 1g, h and Supplementary Fig. 4 ). PTES shows the\n3\nstrongest adsorption at the DMA+ site (E = –1.06 eV), followed by the I (–0.65 eV)\nad\nand Pb (–0.54 eV) sites, indicating a preferential interaction that destabilizes DMA+.\nThese calculation results provide clear evidence that PTES lowers the local\nstability of DMA+ in the precursor lattice, which creates a thermodynamically favorable\npathway for DMA⁺ release. The calculated escape energy barriers of DMA+ on typical\ncrystallographic facets further support this conclusion. As shown clearly in Fig R3,\nPTES consistently reduces these barriers and even makes the escape process exergonic\non the (001) facet. Together, these findings confirm that PTES accelerates DMA+\nvolatilization and facilitates the phase transition from DMAPbI to CsPbI .\n3 3\nFig R3. Calculations of DMA+ escape energy barriers on typical DMAPbI facets with\n3\nand without PTES.\nWe have incorporated these results and the corresponding discussion into the\nrevised manuscript (Figures 1i and k), the detailed description are as follows:\n“Building on these adsorption insights, we next evaluated the escape energy\nbarriers of DMA+ on three representative facets of DMAPbI (Fig. 1g and h). In the\n3\nabsence of PTES, DMA+ removal is hindered by positive activation barriers. By\ncontrast, PTES significantly lowers the escape barriers across all facets, with the most\npronounced reduction observed on the (001) plane, where the barrier drops from +0.32\neV to –0.58 eV. This facet-dependent modulation demonstrates that PTES reshapes the\nthermodynamic landscape of DMA+ volatilization, rendering its extraction\nenergetically favorable and thereby accelerating the phase transition from DMAPbI to\n3\n3. The authors mentioned that “PTES reacts with ambient moisture to form a\nhydrophobic network through Si−O−Pb and Si−O−Si bonding, leading to in situ\ncrosslinking of the perovskite lattice that strengthens lattice interactions and\neffectively prevents further moisture intrusion”. However, what is the distribution\nof PTES in the perovskite? There are doubts as to whether this reaction process can\noccur in the bulk of the perovskite. Does it exist in the bulk of the perovskite as\nindependent PTES molecules or as a Si−O−Si network?\nResponse: We thank the reviewer for raising this important question regarding the\nspatial distribution and chemical state of PTES within the CsPbI film. To directly\n3\naddress this concern, we conducted ToF-SIMS depth profiling, which provides high-\nsensitivity elemental mapping across the entire film thickness (Fig R4). The obtained\nresults clearly show that the Si O fragment signals remain strong and continuous\nx y\nthroughout the bulk region rather than being confined to the surface. In particular, the\nSiO-related secondary ion intensity reaches its maximum within the middle of the film\nand remains detectable until approaching the substrate interface, demonstrating that Si–\nO band containing species are predominantly incorporated into the perovskite bulk.\nThe depth-dependent behavior indicates that PTES undergoes hydrolysis and\ncondensation during crystallization and becomes embedded within the forming lattice\ninstead of remaining at the film surface. The presence of Si–O signals deep inside the\nfilm confirms that the siloxane species form within the bulk and are not restricted to\ninterfacial or top-layer reactions. Such distribution is consistent with a distributed Si–\nO–Si / Si–O–Pb cross-linking structure, rather than isolated PTES molecules\nlocalized at grain boundaries.\nWe have now included the ToF-SIMS data and corresponding discussion in the\nrevised manuscript (Supplementary Fig. 10), which provides direct experimental\nevidence supporting bulk incorporation of PTES-derived Si–O species. The additional\ncontent in Supplementary are as follows:\n“ToF-SIMS depth profiling reveals that PTES-derived Si O species are\nx y\ndistributed throughout the entire CsPbI film rather than confined to the surface. This\n3\nindicates that hydrolyzed siloxane groups diffuse into the bulk during crystallization. It\ncontributes directly to bulk lattice formation through in situ Si–O–Pb and Si–O–Si\nbonding. Such incorporation supports the proposed mechanism that PTES strengthens\nlattice connectivity and improves structural stability under humid processing\nconditions.”\nFig R4. TOF-SIMS measurements of PTES-treated CsPbI film.\n3\n4. In line 88, “PTES undergoes hydrolysis to generate Si-OH groups, which\nspontaneously condense into a self-assembled Si−O−Si network”. It is noted that\nduring the condensation reaction of Si−OH groups, water molecules are generated,\nwhich may serve as an internal water vapor source. This conflicts with the core\nclaim of humidity stability and may induce local phase transitions or defects. The\nauthors did not demonstrate the potential impact of the water generated from\ncondensation on the perovskite, so further research and convincing evidence are\nrequired. Additionally, could the higher PCE shown in Figure 5d under N\n2\nenvironment be related to this factor?\nResponse: We appreciate the reviewer’s insightful comment concerning whether the\nwater released during PTES hydrolysis and condensation might compromise the\nstructural stability of CsPbI . To address this issue, we conducted additional analyses\n3\nto assess its potential impact on the perovskite framework.\nIn the early stages of precursor nucleation, when the film is still in an amorphous\nor DMAPbI -rich transition state, PTES reacts with moisture in the air, leading to\n3\nhydrolysis and subsequent condensation. During this stage, the generated moisture\nevaporates along with the solvents during spin coating and initial annealing. Previous\nstudies have indicated that trace amounts of water within the film can facilitate the\nnucleation and crystallization of perovskites (J. Am. Chem. Soc. 2024, 146, 7, 4642–\n4651; Joule 2023, 7, 11, 2595-2608). Therefore, we propose that the trace water\nproduced from the hydrolysis and condensation of PTES might not negatively affect\nthe initial crystallization of the film. In fact, compared to this trace moisture, high\nhumidity levels in the surrounding air are likely to exert a greater influence on the film's\nearly nucleation. Furthermore, both the FTIR spectra of the DMAPbI -PTES mixture\n3\nand the CsPbI films under 70 °C pre-annealing show no additional water-related\n3\nsignals (Fig. R5), suggesting that the moisture generated from PTES condensation\nlikely evaporates or participates in the crystallization process during the initial\nnucleation phase.\nFig R5. FTIR spectra of the DMAPbI -PTES mixture and the CsPbI films under 70°\n3 3\nC pre-annealing.\nToF-SIMS depth profiling reveals that upon the completion of film crystallization,\nthere is no accumulation of ion fragments associated with water (H O) or hydroxyl\n2\ngroups (OH) within the film, as shown in Fig. R4. Additionally, XRD and UV-Vis\nspectroscopy do not indicate any signs of δ-phase formation at any tested concentration\nof PTES, as illustrated in Fig. R6. These results suggest that the water generated\nthrough condensation does not remain trapped within the perovskite lattice and does\nnot induce phase instability of the material.\nFig R6. (a) XRD patterns and (b) UV-Vis spectra of control and target films.\nThe humidity stability of CsPbI films treated with PTES is significantly improved\n3\ncompared to the control sample, indicating that any transient moisture produced does\nnot adversely affect their long-term humidity resilience. In contrast, the enhanced\nstability is primarily attributed to the formation of Si–O–Pb and Si–O–Si networks as\nconfirmed by the ToF-SIMS, FTIR, and XPS analyses discussed above.\nRegarding the reviewer’s concern about the slight increase in PCE observed under\nN condition in Figure 5d, we first clarify that although the CsPbI films were prepared\n2 3\nunder a nitrogen atmosphere, the high-temperature annealing was still performed in\nambient air with 20–30% relative humidity. Consequently, PTES hydrolysis and\ncondensation reactions occurred during annealing.\nWe attribute the observed performance difference primarily to the reduced ambient\nmoisture-induced degradation during the initial crystallization stage under inert\natmosphere, which creates a more favorable environment for film growth. There is no\nevidence linking transient water formation to either performance enhancement or\ndecline. Furthermore, device statistics collected under both N and air environments\n2\nshow consistent trends, which further supports the conclusion that water produced\nduring condensation does not affect device operation.\nTo avoid further misunderstanding, we have added a statement on lines 93–94 of\nthe manuscript noting that trace water may promote CsPbI crystallization, as follows:\n3\n“Furthermore, the trace water generated from PTES hydrolysis and condensation\ndoes not necessarily means harmful and might even promote the crystallization of\nCsPbI .”\n3\n5. The humidity-responsive characteristics of PTES are only demonstrated by the\nfilm-forming effect at 55% RH, without quantifying the correlation between the\ncrosslinking density of the siloxane and performance under different humidity\nconditions.\nResponse: We appreciate the reviewer’s insightful comment regarding the need to\nquantitatively correlate the crosslinking density of the siloxane network formed by\nPTES with device performance under varying humidity conditions. To address this, we\nconducted X-ray photoelectron spectroscopy (XPS) measurements on CsPbI films\n3\nprepared and stored under controlled relative humidity (RH) environments of 25%,\n50%, and 75%, as shown in Fig. R7. Following established approaches that use XPS\npeak area ratios to evaluate SAM coverage factors (Nature, 2025, 644, 912–919,\nhttps://doi.org/10.1038/s41586-025-09333-z; Science, 2024, 383, 6688, 1236-1240,\nhttps://doi.org/10.1126/science.adj9602), we quantify the crosslinking density using\nthe ratio of the combined silicon (Si) and oxygen (O) peak areas to that of lead (Pb),\ndefined as crosslinking density = (A + A ) / A . This normalization reflects the\nSi O Pb\nrelative extent of the siloxane network within the perovskite lattice.\nOur analysis indicates that siloxane crosslinking itself is not detrimental to device\nperformance. As the relative humidity increases from 25% to 50%, the crosslinking\ndensity rises markedly, yet the device efficiency remains relatively high, suggesting that\ncrosslinking plays a beneficial role in stabilizing the perovskite lattice. Even at 75%\nRH, where the crosslinking density approaches saturation, the observed efficiency loss\ncannot be attributed solely to increased crosslinking. Instead, it reflects the\noverwhelming impact of persistent moisture ingress under high-humidity conditions.\nNotably, control devices without PTES exhibit a much more severe efficiency\ndegradation at elevated humidity, underscoring that siloxane crosslinking mitigates,\nrather than exacerbates, moisture-induced degradation, although it cannot fully\ncounteract the adverse effects of excessive environmental humidity.\nThis quantitative evaluation complements the previously reported film-forming\neffects observed at 55% RH and provides a comprehensive understanding of the\nhumidity-responsive characteristics of PTES. We have incorporated these findings and\ntheir discussion into the revised manuscript to fully address the reviewer’s concerns\n(Supplementary Fig. 27).\n“X-ray photoelectron spectroscopy (XPS) analysis was conducted on CsPbI₃ films\nprepared under different relative humidity (RH) conditions of 25%, 50%, and 75% to\ninvestigate the distribution and chemical environment of silicon, oxygen, and lead\nspecies. The Si 2p, O 1s, and Pb 4f core-level spectra were recorded for each sample.\nAt 25% RH, the Si and O signals were relatively low, with peak areas of 4309.11 and\n26944.25, respectively, while the Pb peak area was 434622.19, indicating a lower\ndegree of siloxane crosslinking within the perovskite lattice. The calculated\ncrosslinking density is approximately 0.072 under these conditions. When the RH\nincreased to 50%, the Si peak area rose markedly to 33716.73, while the O peak area\ndecreased slightly to 18137.31, and the Pb signal reduced to 203903.33, reflecting\nenhanced formation of the Si–O–Si network and possible changes in the perovskite\nstructure. The corresponding crosslinking density significantly increased to about 0.255.\nAt 75% RH, the Si and O peak areas further increased to 74748.68 and 37746.18,\nrespectively, with the Pb peak area at 425780.82, suggesting further development of the\nsiloxane network, and the crosslinking density slightly rose to approximately 0.264.\nThese spectral variations and the calculated crosslinking densities align well with the\ndevice performance trends under different humidity conditions, indicating that siloxane\ncrosslinking contributes positively to photovoltaic efficiency, although excessive\nhumidity ultimately dominates the degradation behavior.”\n“Furthermore, We performed XPS measurements on PTES-treated CsPbI films\n3\nprepared under different humidity conditions (RH = 25%, 50%, 75%) to evaluate the\neffect of moisture on siloxane crosslinking (Supplementary Fig. 27, Supplementary\nNote 7 and Table 6 ). The quantitative XPS results show that humidity strongly regulates\nPTES hydrolysis and crosslinking. As RH increases from 25% to 50%, the Si and O\nsignals rise markedly, indicating enhanced formation of the Si–O–Si network. At\nRH=75%, the crosslinking level approaches saturation. Device performance follows\nthis trend, indicating that siloxane crosslinking is intrinsically beneficial and enhances\nmoisture tolerance. Nevertheless, excessive humidity still induces structural\ndegradation even at higher crosslinking levels. The markedly faster efficiency loss\nobserved in control devices under high humidity further highlights the protective role\nof siloxane crosslinking. Moreover, even for films processed in a N atmosphere, PTES-\n2\nmediated crystallization still occurs because annealing is conducted in ambient air with\nRH of 20–30%, allowing sufficient hydrolysis and crosslinking to influence CsPbI\n3\nnucleation and growth.”\nFig R7. XPS spectra of Si, O, and Pb in the films after PTES treatment under RH (a)\n25%, (b) 50%, and (c) 75% conditions.\nTable R1 The crosslinking density of PTES under different environmental humidity\nconditions.\ncrosslinking\nA A A density\nSi O Pb\n(A +A )/A\nsi O Pb\nRH 25±5%% 4309.11 26944.25 434622.19 7.19%\nRH 50±5%% 33716.73 18137.31 203903.33 25.45%\nRH 75±5%% 74748.68 37746.18 425780.82 26.42%\n6. In line 128, “In contrast, PTES facilitates the early release of DMA+ through\nadsorption between siloxane groups and DMA+ in DMAPbI , suppressing\n3\nintermediate phase crystallization and accelerating Cs+ incorporation. Furthermore,\nPTES further suppresses the crystallization of the DMAPbI intermediate,\n3\nfacilitating additional lattice compression and enhancing the structural stability of\nCsPbI ”. The authors mention that the interaction between PTES and DMA inhibits\n3\nthe crystallization of the intermediate phase DMAPbI . However, the relevant XRD\n3\ndata show the opposite result. For example, in Figure 2b,c and Supplementary\nFigure 7, the PTES-treated target film at the initial stage (0 min) exhibits a stronger\nintermediate phase signal. The authors are requested to provide an explanation for\nthis.\nResponse: We thank the reviewer for your insightful questions and constructive\nfeedback. Regarding the apparent inconsistency between our mechanistic interpretation\nand the XRD evolution presented in Figure 2b,c and Supplementary Figure 7, we\nprovide a detailed clarification below.\nThe PTES-treated film shows a stronger DMAPbI intermediate peak at the initial\n3\nstage (0 min), but this should not be interpreted as enhanced intermediate crystallization.\nTime-resolved XRD reveals that in the presence of PTES, the DMAPbI peak is highest\n3\nonly at the onset and then steadily decreases during annealing. In contrast, the control\nfilm exhibits a different trend: the DMAPbI peak initially increases, reflecting\n3\ncontinued crystallization of the intermediate, and begins to decline only after about 3\nminutes when the conversion to CsPbI starts. These observations indicate that PTES\n3\nsuppresses further crystallization of DMAPbI and promotes its rapid decomposition,\n3\nwhereas the intermediate in the control film undergoes an additional crystallization step\nbefore transitioning to CsPbI .\n3\ntime point appeared much higher in the PTES-treated sample than in the control. This\nwas caused by our previous normalization method, where all XRD curves were scaled\nto the maximum peak intensity within each dataset. This approach unintentionally\ncreated the false impression that the PTES-treated film exhibited a stronger initial\nDMAPbI peak. We apologize for this confusion.\ndata using the initial peak intensity (0 min) as the normalization reference for each\nsample independently. This more appropriate normalization clearly demonstrates that\nthe PTES-treated DMAPbI intermediate does not exhibit enhanced crystallization;\n3\ninstead, it decays monotonically during annealing. The revised data have been updated\nin the manuscript, and the corrected evolution plot is included as Fig. R8.\nFig R7. XPS spectra of Si, O, and Pb in the films after PTES treatment under RH (a)\n25%, (b) 50%, and (c) 75% conditions.\n7. Siloxane networks are typically insulators, which may introduce interfacial barriers\nor carrier traps, affecting carrier transport. It is recommended to supplement the\ncarrier mobility data of both PTES-treated and untreated films.\nResponse: We thank the reviewer for the valuable comment and the concern regarding\nthe potential insulating nature of siloxane networks. To directly address this point, we\nmeasured the electron mobility of both control and target CsPbI devices using space-\n3\ncharge–limited current (SCLC) devices, as shown in Fig. R9.\nThe electron mobility (μ) was extracted from the Mott–Gurney law in the trap-free\nSCLC region:\n9 𝑉2\n𝐽 = 𝜀 𝜀 𝜇\n8 0 𝑟 𝐿3\nWhere:\nJ is the current density,\nε is the relative dielectric constant of CsPbI (taken as 6.3),\nr 3\nε is the vacuum permittivity,\n0\nμ is the electron mobility,\nV is the applied voltage,\nL is the film thickness (control: 346 nm; PTES-treated: 385 nm).\nThe calculated electron mobilities are as follows:\nControl device: 4.3 × 10−3 cm2 V−1 s−1\nTarget device: 7.1 × 10−3 cm2 V−1 s−1\nThese results clearly demonstrate that the PTES treatment enhances the electron\nmobility by approximately 65% compared to the control film. Although the Si–O–Si\nnetwork formed within the lattice is intrinsically insulating, its ultrathin, spatially\ndispersed nature allows electrons to tunnel across these domains, thereby avoiding any\ndetrimental impact on the overall conductivity of the film. This improvement strongly\nsuggests that the siloxane framework does not act as an interfacial barrier or source of\ncarrier traps; instead, it likely passivates surface defects and grain boundaries, reduces\ntrap-assisted recombination, and facilitates a more efficient carrier-transport pathway.\nTherefore, the presence of the siloxane network does not introduce insulating\nbarriers; instead, PTES contributes to a more uniform and defect-suppressed crystal\nframework, ultimately enhancing carrier transport within the CsPbI film.\n3\n8. In line 222, “confocal PL mapping demonstrates a more intense and spatially\nuniform emission for the PTES-treated film”. However, the quantitative analysis in\nthis part is insufficient, and it is recommended to provide more intuitive data for\nillustration.\nResponse: We thank the reviewer for highlighting the need for more quantitative and\nintuitive analysis of the photoluminescence (PL) mapping data. In response, we have\nfurther processed the PL intensity distribution of both control and PTES-treated (target)\nfilms and represented the data in the form of histograms, as shown in Fig. R10. The\nhistograms clearly demonstrate that the target film exhibits a more concentrated\ndistribution of higher PL intensities compared to the control, confirming not only an\noverall increase in emission intensity but also improved spatial uniformity. This\nquantitative representation provides a clearer and more compelling illustration of the\nenhanced optoelectronic quality of the PTES-treated films. We have included this\nadditional analysis and figure in the revised manuscript to address the reviewer’s\ncomment comprehensively.\nFig. R10 The intensity distribution map of PL mapping results.\n9. In line 331, “The effective area of the gold electrode is 4 mm2”. It is suggested that\nthe authors supplement the performance data of devices with a larger area to further\nverify the scalability feasibility of the PTES strategy.\nResponse: We appreciate the reviewer’s suggestion to evaluate the scalability of the\nPTES treatment by testing larger-area devices. To this end, we fabricated devices with\nan active area of 1 cm2, which achieved a power conversion efficiency of 18.81%,\nas illustrated in Fig. R11. This result demonstrates that the PTES strategy is effective and\nscalable beyond small-area devices, maintaining high performance in larger formats.\nAccordingly, we have added the following statement to the revised manuscript:\n“To further verify the scalability of the PTES approach, we fabricated 1 cm²\ndevices (Supplementary Fig. 23), which exhibited a forward-scan PCE of 18.81%,\nconfirming the applicability of this method to larger-area perovskite solar cells.”\nFig. R11 The J-V curve of a device with an effective area of 1 cm2.\n10. The CsPbI PSCs reported in this paper achieve a PCE of 21.00% (with an FF as\n3\nhigh as 86.1%) under 55% RH, which ranks among the leading levels for similar\ndevices. It is recommended that the authors provide third-party certification results.\nResponse: We appreciate the reviewer’s helpful suggestion. Due to practical\nconstraints associated with environmental fluctuations and measurement logistics, we\nwere unable to obtain independent certification for devices fabricated entirely under 55%\nRH conditions. However, leveraging the PTES additive, we successfully certified high-\nefficiency CsPbI devices fabricated in an N atmosphere with subsequent annealing\n3 2\ncarried out in ambient air, achieving a certified PCE of 22.02% (Fig. R12), which\nrepresents the highest certified efficiency reported to date for CsPbI -based devices.\nambient air, we consider this certification to be valid and representative. These results\nrobustly confirm that the PTES-enabled moisture-responsive crystallization strategy is\neffective in regulating CsPbI crystallization and enabling record device performance.\nPhotovoltaic Products Quality (CPVT).\nReviewer #2 (Remarks to the Author): Dai et al. have made significant revisions to the manuscript, satisfactorily addressing my key concerns. As the authors have\npositioned PTES as a strategy for ambient processability, I am disappointed that they were unable to provide third-party\ncertification for the ambient-processed devices requested by Reviewer 1, and instead chose to provide certification for inert-\nprocessed devices. While the latter represents a record in itself, the explanation provided for the absence of equivalent\ncertification for ambient-processed devices—which are the core focus of the study—is not convincing.\nI also note significant discrepancies between the text quoted in the rebuttal letter and the corresponding text in the revised\nmanuscript. In addition, I identified substantial changes in the manuscript that were not highlighted. For example, in the\ndevice fabrication section, the authors have added a detail indicating that SA was spin-coated prior to the perovskite layer;\nthis was neither discussed previously nor highlighted in the revised version.\nOverall, the achievement reported in the manuscript sets a benchmark for the inorganic perovskite field and should be\nconsidered for publication in Nature Communications. For future publications, I would strongly advise the authors to ensure\ngreater consistency and transparency in their studies, experimental reporting, and throughout the peer review processes.\nReviewer #3 (Remarks to the Author): The manuscript has been well revised and it could be accepted as is"}, {"round": 2, "reviewer_comments": {"reviewer_1": "The authors have addressed my previous concerns. The revised manuscript can be published without revision.", "reviewer_2": "DAi et al. have made significant revisions to the manuscript, satisfactorily addressing my key concerns. As the authors have positioned PTES as a strategy for ambient processability, I am disappointed that they were unable to provide third-party certification for the ambient-processed devices requested by Reviewer 1, and instead chose to provide certification for inert-processed devices. While the latter represents a record in itself, the explanation provided for the absence of equivalent certification for ambient-processed devices—which are the core focus of the study—is not convincing.\nI also note significant discrepancies between the text quoted in the rebuttal letter and the corresponding text in the revised manuscript. In addition, I identified substantial changes in the manuscript that were not highlighted. For example, in the device fabrication section, the authors have added a detail indicating that SA was spin-coated prior to the perovskite layer; this was neither discussed previously nor highlighted in the revised version.\nOverall, the achievement reported in the manuscript sets a benchmark for the inorganic perovskite field and should be considered for publication in Nature Communications. For future publications, I would strongly advise the authors to ensure greater consistency and transparency in their studies, experimental reporting, and throughout the peer review processes.", "reviewer_3": "The manuscript has been well revised and it could be accepted as is"}, "author_response": ""}]

Decision letter