In-Situ Investigation of Perovskite Solar Cells Under Coupled Vacuum-Thermal Cycling in Extreme Space Environments

Perovskite solar cells (PSCs), due to low-cost and lightweight nature, hold promise for aerospace use. Understanding the behavior of various components of perovskite solar cells under the harsh space conditions remains a critical priority. To date, conventional investigation methods do not allow for complete exclusion of moisture and oxygen from the environment and cannot adequately simulate conditions, which are close to the space environment. In this study, we present an in-situ characterization system that enables investigation of samples under extreme vacuum conditions (10 -8 Pa) and a wide temperature range, with elimination of atmospheric influence. Under ultrahigh vacuum and repeated thermal cycling(150 K-430 K), the perovskite absorber undergoes irreversible decomposition, producing degradation products such as metallic lead, lead iodide, and volatile organic compounds. Elevated temperatures induce phase transitions within the material, while thermally driven ion migration across interfaces intensifies non-radiative recombination processes. These structural and compositional changes result in a notable decline in device performance, with the power conversion efficiency decreasing from 24.39% to 20.15% after five thermal cycles, primarily due to reduced short-circuit current. The observed degradation is attributed to material decomposition, thermal instability, and interfacial diffusion, highlighting key challenges for PSC stability in space environments. Article category: Research Artical Subcategory: Solar Cell In-Situ Investigation of Perovskite Solar Cells Under Coupled Vacuum-Thermal Cycling in Extreme Space Environments Xianchao Lu, Zhiyong Wang, Qianru Lin, Jie Sheng*, Azat F. Akbulatov, Sergey M. Aldoshin, Pavel A. Troshin, Yantao Shi*, Liyi Li* X. C. Lu, Prof. J. Sheng State Key Laboratory of Space Environment Interaction with Matters，Harbin Institute of Technology, Harbin 150001, PR China. School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, PR China. Email:[email protected] Z.Y. Wang, Prof. Y.T. Shi State Key Laboratory of Fine Chemicals, School of Chemistry, Frontier Science Center for Smart Materials, Dalian University of Technology, Dalian 116024, PR China. Dr. Q.R. Lin, Prof. L.Y. Li State Key Laboratory of Space Environment Interaction with Matters，Harbin Institute of Technology, Harbin 150001, PR China. Email: [email protected] Prof. A. F. Akbulatov, Prof. S. M. Aldoshin Federal Research Center for Problems of Chemical Physics and Medicinal Chemistry, Russian Academy of Sciences (FRC PCP MC RAS), Academician Semenov Ave. 1, Chernogolovka, Moscow Region, 142432, Russia. Prof. P. A. Troshin Federal Research Center for Problems of Chemical Physics and Medicinal Chemistry, Russian Academy of Sciences (FRC PCP MC RAS), Academician Semenov Ave. 1, Chernogolovka, Moscow Region, 142432, Russia. Zhengzhou Research Institute of HIT, 26 Longyuan East 7th, Jinshui District, Zhengzhou, Henan Province, 450000, PR China.

perovskite solar cells, in-situ investigation, extreme space environment

Perovskite solar cells (PSCs), due to low-cost and lightweight nature, hold promise for aerospace use. Understanding the behavior of various components of perovskite solar cells under the harsh space conditions remains a critical priority. To date, conventional investigation methods do not allow for complete exclusion of moisture and oxygen from the environment and cannot adequately simulate conditions, which are close to the space environment. In this study, an in-situ characterization system is presented that enables investigation of samples under extreme vacuum conditions (10 -8 Pa) and a wide temperature range, with elimination of atmospheric influence. Under ultrahigh vacuum and repeated thermal cycling(150 K-430 K), the perovskite absorber undergoes irreversible decomposition, producing degradation products such as metallic lead, lead iodide, and volatile organic compounds. Elevated temperatures induce phase transitions within the material, while thermally driven ion migration across interfaces intensifies non-radiative recombination processes. These structural and compositional changes result in a notable decline in device performance, with the power conversion efficiency decreasing from 24.39% to 20.15% after five thermal cycles, primarily due to reduced short-circuit current. The observed degradation is attributed to material decomposition, thermal instability, and interfacial diffusion, highlighting key challenges for PSC stability in space environments. 1. Introduction The rapid advancement of deep-space exploration and near-Earth orbit satellite technologies demands solar cells with exceptional extreme-environment endurance. [1–3] Perovskite solar cells (PSCs), owing to their high power conversion efficiency (PCE, >27%) and lightweight nature, have emerged as promising candidates for space-based energy supply systems. [4-6] However, the harsh space conditions-including thermal cycling (-185℃ to 150℃), [7] high vacuum (<10 -6 Pa) and cosmic radiation can induce phase transitions, [8-10] chemical degradation, [11-12] and interfacial ion migration, [13-15] leading to rapid device performance degradation. [16-17] Conventional methylammonium lead iodide (MAPbI 3 ) perovskites decompose significantly below 100℃, which limits their suitability for space applications. [18–20] In contrast, PSCs employing formamidinium lead iodide (FAPbI 3 ) as the photoabsorber exhibit high PCE and exceptional thermal stability, [21-23] attributed to the extended π-conjugation, efficient charge delocalization, and high defect formation energy of FA⁺ cations. [24,25] These properties stabilize the photoactive α -phase even after annealing at 150℃, [26-28] positioning FAPbI 3 -based PSCs as promising candidates for next-generation space photovoltaics. Ground-based simulation of space environments is essential for evaluating the suitability of emerging solar cell technologies for aerospace applications. However, a key challenge remains for PSCs: their high sensitivity to atmospheric moisture and oxygen makes it difficult to decouple the effects of simulated environmental factors from those caused by ambient air. This has become a major limitation in the accurate assessment of PSCs under space-relevant conditions. Moreover, conventional ground-based tests typically focus on a limited temperature range (−40°C to 85 °C), failing to capture the complex degradation mechanisms triggered by the extreme thermal cycling conditions encountered in space (150 K-430 K). Therefore, there is a pressing need to develop testing approaches that can isolate the influence of atmospheric conditions while covering a wider temperature range consistent with space environments. Unfortunately, no such comprehensive methodology has been reported, leaving a critical gap in the evaluation framework for aerospace-grade PSCs. In response to this challenge, the present study establishes a closed-loop research platform that integrates material synthesis, environmental simulation, and performance characterization, providing a solid theoretical foundation for advancing space-qualified perovskite photovoltaic technologies. Using this platform, we systematically investigate environmental effects on FAPbI 3 thin films and solar cells under fully controlled vacuum conditions (10 -8 Pa), effectively eliminating moisture and oxygen interference. This approach reveals a fundamental understanding of how vacuum and extreme thermal cycling drive the structural evolution of FAPbI 3 and contribute to device performance degradation. Our results provide mechanistic insights into stability of FAPbI 3 -based PSCs under space-relevant conditions, but also establish a novel methodological framework for evaluating of moisture- and oxygen-sensitive materials. 2. Results and Discussion 2.1. In-situ Methodology for Microstructural Characterization of Space Environmental Effects on Perovskite Solar Cells Figure 1 illustrates the methodology for investigating the intrinsic thermal stability of perovskite materials under simulated space environments using an ultrahigh vacuum interconnected system (Equipment Photo Figure S1 ). The experimental workflow initiates by connecting a nitrogen-purged glovebox to the ultra-high vacuum (UHV) system, enabling direct transfer of freshly synthesized perovskite films into the contamination-free vacuum environment. The perovskite thin films were transferred via robotic arm to: (1) the high/low-temperature stage of the X-ray photoelectron spectroscopy (XPS) system (Process G1-X2), and (2) the environmental simulation chamber (ESC) equipped with quadrupole mass spectrometry (QMS) (Process G1-E3) under a fully enclosed UHV environment. Both systems performed synchronized thermal cycling across the 150 K-430 K range using a precisely controlled temperature program with heating/cooling rates of 3 K min -1, effectively simulating the thermal shock conditions characteristic of space photovoltaic operation. The integrated system enables in-situ monitoring of chemical bond cleavage dynamics and gaseous product evolution through simultaneous XPS and QMS measurements, establishing a multiscale correlation between material degradation kinetics and space environmental effects. Figure 1. Schematic of the perovskite absorber fabrication and in-situ decomposition analysis system (topview) under coupled vacuum-thermal cycling conditions. (UHV~10 -8 Pa; Thermal cycling: 150 K–430 K) 2.2. Mechanistic Insights into FAPbI 3 Degradation under Space Environments Figure 2 a-d presents the evolution of Pb 4 f, N 1 s, and C 1 s photoelectron spectra for FAPbI 3 thin films during thermal cycling. In Figure 2a, the pristine film exhibits characteristic Pb 4 f doublets at 143.3 eV (Pb 4 f 5/2 ) and 138.4 eV (Pb 4 f 7/2 ), corresponding to the Pb 2+ oxidation state. The thermal cycling induces notable changes in the Pb 4 f 5/2 and Pb 4 f 7/2 bands. Specifically, upon heating to 430 K during the first thermal cycle, new peaks emerge at 141.35 eV and 136.64 eV, attributed to metallic Pb 0 formation，which is one of the most detrimental defects within perovskite film. Since the decomposition temperature of PbI 2 exceeds 400℃（>673K），it is concluded that the formation of metallic Pb 0 is induced by light or X-ray radiation. [29-31] The content of metallic Pb 0 nearly reaches the saturation by the end of this thermal cycle. Aside from peak broadening caused by thermal excitation at elevated temperatures, the Pb 4 f spectra remain largely stable during the subsequent two thermal cycles (Figure S2). Figure 2 . XPS spectra of (a) Pb 4 f, (b) N 1 s, and (c) C1 s bands during the thermal cycling. (d) Evolution of atomic ratios of I/Pb, N/Pb, and C/Pb under thermal cycling conditions. Figure 2b presents the evolution of N 1 s photoelectron spectra during thermal cycling. The N 1 s peak intensity decreases significantly with thermal cycling. Additionally, the diffraction peak shifts noticeably toward higher binding energies, indicating substantial impacts of thermal cycling on the stability and chemical environment of the FA⁺ cation. At the initial state of 150 K, the N 1 s peak appears sharp, reflecting a stable chemical environment for FA⁺ within the lattice, where molecular vibrations are suppressed by the low temperature. As temperature increases, the peak intensity gradually diminishes with noticeable broadening (Figure S3a). During subsequent thermal cycles (Figure S3b-c), the peak intensity decay rate decreases, while the N 1 s characteristic peaks essentially disappear. This suggests significant and irreversible depletion of organic cations from the film surface accompanied by the formation of volatile gaseous products during thermal cycling. Such volatilization leads to degradation of the perovskite absorber layer, adversely affecting its optoelectronic properties. Figure 2c shows that the original C 1 s photoelectron spectrum of the pristine FAPbI 3 film can be deconvoluted into three distinct peaks located at 286.2 eV (C-N), 288.35 eV (C=N), and 284.8 eV (C-C/C-H). The C-C/C-H peak is attributed to hydrocarbons absorbed during the solution-processing fabrication. During the first thermal cycle (150 K-430 K-150 K), the C-N and C=N peak intensities decrease dramatically, indicating substantial decomposition of the FA⁺ structure. Subsequent thermal cycles show less pronounced changes, with the characteristic C-N and C=N peaks almost disappearing after the third cycle. Furthermore, within each thermal cycle (Figure S4), spectral changes at low temperatures (< 290 K) are minimal, while significant alterations occur at elevated temperatures (290 K-430 K), demonstrating that the degradation of the absorber layer primarily takes place at high temperatures. This decomposition is irreversible, as no spectral recovery was observed during the cooling. Figure 2d presents the atomic ratio evolution of the perovskite absorber layer during thermal cycling, where the I/Pb, C/Pb, and N/Pb ratios were calculated from the fitted XPS peak areas. The relative elemental concentrations exhibit significant changes during the first thermal cycle, while subsequent cycles show smaller evolution, thus indicating that the samples are approaching a stabilized state. After the initial cycle, the I/Pb ratio decreases markedly from 3.67 to 2.11, deviating from the theoretical stoichiometric ratio and suggesting the FAPbI 3 degradation with the elimination of organic cations and the formation of PbI 2 as a product. This conclusion is supported by the C/Pb ratio drop from 2.91 to 0.945, and the N/Pb ratio decline from 2.31 to 0.477. The most significant compositional changes occur during the heating segment from 360 K to 430 K in the first thermal cycle, indicating that the elevated temperatures exacerbate the thermal decomposition of the absorber layer. Based on these findings, significant losses of C, N, and I elements occur during the thermal cycling. To identify the gaseous products formed from the depletion of these elements, in-situ QMS analysis was conducted during the thermal cycling process. Figure 3 a shows the in-situ QMS two-dimensional spectrum of the absorber layer during three thermal cycles, including a magnified view of the first cycle. The results demonstrate that gas release was the most significant during the initial thermal cycle, with subsequent cycles exhibiting enhanced emission signals primarily during high-temperature phases. This trend correlates well with the XPS spectral evolution. Throughout the thermal cycling process, nine distinct mass-to-charge ratio (m/z) signals were identified: m/z = 15, 16, 17 corresponding to NH 3 or CH 3 evolution peaks; m/z = 18 corresponding to H 2 O signals; m/z =26, 27 corresponding to HCN signals; m/z = 28 corresponding to N 2 or CO signals; m/z = 42, 43, 44 corresponding to FA-related signals; m/z = 58, 59 corresponding to (CH 3 ) 3 N signals; m/z = 81, 54, 28, 27 corresponding to C 3 H 3 N 3 (most probably, triazine) and its fragment ions; and m/z = 127, 128 corresponding to HI evolution signals. These findings are consistent with the previous reports on the heat-induced degradation of the FAPbI 3 perovskite films. [11,12,32] Figure 3. (a) QMS spectra during thermal cycling. (b) Magnified view of m/z 1-150 range for the first cycle. (c) The evolution of the XRD patterns of the FAPbI3 films after several thermal cycles. Figure 3b reveals temperature-dependent evolution patterns of gaseous products through detailed analysis of the magnified spectrum. NH 3 and HCN emissions start at approximately 175 K, reaching their first intensity maxima near 290 K. During the isothermal period, the release gradually subsides, but increases again as the temperature rises, with emission tapering off during the cooling phase. Similarly, FA (CN 2 H 4 ) evolution begins around 175 K, with a first peak at 290 K, followed by a decline in intensity until a second peak emerges around 430 K. HI generation starts at 220 K, shows maximum intensity at 290 K, decreases with temperature elevation, and demonstrates renewed release peak at 430 K. In addition, trace amounts of (CH 3 ) 3 N and C 3 H 3 N 3 are detected near both 290 K and 430 K. These results suggest that gas release from the perovskite absorber layer occurs across both sub-ambient and elevated temperatures, with different gaseous products evolving at distinct thermal stages. Such unusual “double wave” decomposition behavior suggests that the original FAPbI 3 films were enriched with the formamidinium iodide (FAI) from the surface, which is consistent with the element ratios revealed by XPS (Figure 2d). Upon thermal cycling, the excessive FAI decomposes first at sub-ambient temperatures since it is not integrated in the perovskite crystal lattice. The real FAPbI 3 degradation starts at elevated temperatures, which explains the appearance of the second “decomposition wave”. The staged decomposition characteristics provide critical insights for determining optimal operational temperature ranges and identifying suitable orbital deployment parameters for space applications. To further investigate the evolution of the crystal structure of the perovskite absorber layer during thermal cycling, the thermally cycled films were transferred under high vacuum through an interconnected system into a glovebox, enabling rapid characterization after sealed transfer to prevent ambient exposure. Figure 3c presents the XRD patterns of FAPbI 3 films subjected to different thermal cycles. The pristine sample (FA-T-0) exhibits the characteristic photoactive α-phase structure with a diffraction peak at 2θ=14.2°. After the first thermal cycle (FA-T-1), a new diffraction peak appears at 2θ=11.8° corresponding to PbI 2 formation, indicating partial decomposition of FAPbI 3 into PbI 2 under thermal cycling conditions. At the subsequent thermal cycles (FA-T-2 and FA-T-3), the intensity of the PbI 2 diffraction peak gradually increases. This trend is fully consistent with the XPS spectral evolution and, in particular, the observed decay of N 1s and C 1s peaks evidencing the depletion of organic cations. Complementary SEM characterization (Figure S5) reveals progressive microstructural degradation, including grain boundary blurring and near-complete loss of the original film morphology with increasing the number of the thermal cycles. AFM analysis (Figure S6) confirms substantial surface roughening, further evidencing phase decomposition under thermal cycling. These results suggest that the alternating thermal stress induced by extreme temperature fluctuations during thermal cycling leads to the decomposition of the FAPbI 3 phase and significant changes in the crystal structure of the perovskite absorber layer. 2.3. Device Performance Degradation Mechanisms To evaluate the stability of perovskite solar cells under extreme vacuum-thermal cycling conditions, a structurally robust p-i-n configuration - ITO/NiOx/SAMs/Perovskite/C 60 -PCBM/BCP/Ag was employed, as illustrated in Figure 4a. Devices were subjected to photovoltaic performance tests after different numbers of thermal cycles under the simulated AM0 solar spectrum illumination (irradiance of 1366 W/m 2 ). Figure 4b presents the current density-voltage ( J-V ) characteristics before and after thermal cycling. The devices demonstrated excellent initial performance with a champion power conversion efficiency (PCE) of 24.39%. Following five thermal cycles, the maximum PCE decreased to 20.15%, while maintaining reasonable photovoltaic performance. Figure 4. Structural evolution and photovoltaic performance degradation of formamidinium-based perovskite solar devices under AM0 illumination and thermal cycling: (a) Schematic of the device architecture (b) The evolution of the J-V characteristics upon thermal cycling measured under simulated AM0 spectrum illumination (1366 W m -2 ). The evolution of the device parameters: (c) short-circuit current density. (d) fill factor (FF). (e) open-circuit voltage. (f) power conversion efficiency. Figures 4c-d summarize the evolution of photovoltaic parameters ( J SC, FF, V OC, and PCE) of perovskite solar cells upon vacuum-thermal cycling. The short-circuit current density ( J SC ) shows a significant decrease upon thermal cycling, while the FF retains approximately 94% of its initial value. The open-circuit voltage ( V OC ) fluctuates without substantial decay. After 5 thermal cycles, the average PCE decreases from 23.1% to 19.4%. As discussed above, the decline in device efficiency is primarily attributed to the reduction in short-circuit current density ( J SC ). According to in-situ XPS and QMS data, the perovskite absorber layer undergoes continuous gas release during the thermal cycling process, with the most pronounced outgassing observed during the first cycle. This indicates severe material decomposition at this stage, which introduces additional defects in the perovskite film and enhances non-radiative trap-assisted recombination of photogenerated carriers. However, despite a significant reduction in gas evolution during the second thermal cycle , J SC still exhibits notable degradation. This suggests that material decomposition alone does not fully account for the observed performance loss at this stage. To unravel the possible origin of this later-stage degradation, we performed XPS depth profiling analysis of the devices after different number of the thermal cycles as shown in Figure 5 . Compared to the pristine sample (Figure 5a), the elemental distribution profiles show no significant changes after the first thermal cycle (Figure 5b). However, after the second and third thermal cycles (Figure 5c-d), obvious broadening of elemental distribution ranges are observed, with noticeable diffusion of Ag + from the top electrode into the device interior, as well as migration of Pb 2+ and I - toward the electron transport layer (ETL). Similarly, Ni 2+ from the hole-transport layer penetrates into the perovskite absorber layer. These observations evidence significant ion migration across functional layers during thermal cycling. Very similar behavior was reported for p-i-n perovskite solar cells exposed to light, when time-of-flight secondary ion mass spectrometry (ToF SIMS) analysis also revealed Ag, Pb, I and Ni interdiffusion. [33,34] The revealed degradation pathways associated with the material interdiffusion at the interfaces could significantly affect the device performance. First, the migration of Ag⁺ and I⁻ ions induces interfacial chemical reactions at the ETL interface leading to the formation of secondary byproducts such as silver iodide (AgI). These byproducts impede charge carrier transport, increase interfacial resistance, and consequently degrade the device performance. Second, the formation of charge traps due to ion migration can enhance non-radiative recombination, reduce the lifetime of photogenerated carriers, and lead to a drop in fill factor. Third, ion-electron coupling effects induced by ionic migration between functional layers may increase leakage currents, thereby reducing the short-circuit current density. Figure 5. In-situ Ar⁺ etching surface elemental analysis of formamidinium-based perovskite devices during vacuum-thermal cycling: (a) Pristine device. (b) After 1 thermal cycle. (c) After 2 thermal cycles. (d) After 3 thermal cycles To visualize the interfacial degradation effects, cross-sectional SEM characterization was performed on devices before and after thermal cycling (Figure S7). Comparative analysis reveals delamination and the emergence of cracks at the interface between the perovskite absorber layer and the underlying hole transport layer after thermal cycling. This interfacial failure is attributed to the thermal stress. Additionally, noticeable voids appear in the perovskite layer, likely resulting from thermal decomposition of the perovskite absorber and volatilization of the organic species. These morphological changes impact charge transport within the bulk of the active layer and at the interfaces, thus aggravating non-radiative recombination and thereby deteriorating the photovoltaic performance of the devices. 3. Conclusion This study introduces an ultrahigh-vacuum in-situ research platform combined with ex situ rapid encapsulation-transfer characterization, enabling systematic investigation of FAPbI 3 -based perovskite solar cells under coupled vacuum–thermal cycling conditions. The structural evolution and decomposition pathways of the perovskite absorber were comprehensively analyzed, alongside compositional dynamics and photovoltaic performance degradation of the devices. After five thermal cycles, a 16% reduction in power conversion efficiency was observed, accompanied by significant morphological changes and PbI 2 formation in the absorber layer. In-situ XPS confirmed the generation of metallic PbI 2 and depletion of organic cations, with the most pronounced decomposition occurring during the first cycle. In-situ QMS analysis identified the major gaseous products as NH 3, HCN, CN 2 H 4, C 3 H 3 N 3, and HI, all exhibiting temperature-dependent evolution. The completed perovskite solar cells showed a decay in the photovoltaic performance from 23.1% to 19.4% after thermal cycling, thus demonstrating considerable resilience to extreme temperature variations. Depth profiling revealed ionic migration (Ag +, Pb 2+, I -, Ni 2+ ) and material intermixing across the interfaces, which appears to be the major device degradation pathway. These findings provide critical mechanistic insights into the environmental stability of FAPbI 3 films under space-relevant conditions and establish a robust methodological framework for evaluating and improving the durability of perovskite and other air-sensitive materials in aerospace applications. Supporting Information Supporting Information is available from the Wiley Online Library or from the author.

X.L. and Z.W. contributed equally to this work. The financial support on the National Natural Science Foundation of China (52272193) and the Fundamental Research Funds for the Central Universities (DUT22LAB602), the Russian side was provided by the Ministry of Science and Higher Education of the Russian Federation (agreement № 075-15-2024-532). Conflict of Interest Statement The authors declare that there are no conflicts of interest regarding this manuscript. Received: (will be filled in by the editorial staff) Revised: (will be filled in by the editorial staff) Published online: (will be filled in by the editorial staff)

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This study introduces a fully vacuum-integrated platform to simulate space-relevant stressors and monitor in-situ the thermal-vacuum-induced degradation of perovskite solar cells. Real-time XPS and QMS analyses uncover compositional and chemical instabilities, while ex situ XRD, cross-sectional SEM，AFM and performance measurements correlate structural evolution with photovoltaic degradation under ultrahigh vacuum and thermal cycling. In-Situ Investigation of Perovskite Solar Cells Under Coupled Vacuum-Thermal Cycling in Extreme Space Environments Supporting Information In-Situ Investigation of Perovskite Solar Cells Under Coupled Vacuum-Thermal Cycling in Extreme Space Environments Xianchao Lu, Zhiyong Wang, Qianru Lin, Jie Sheng*, Azat F. Akbulatov, Sergey M. Aldoshin, Pavel A. Troshin, Yantao Shi*, Liyi Li* Experimental Section Fabrication of materials and devices The glass substrates were sequentially cleaned with deionized water, ethanol, and isopropanol, followed by drying under a nitrogen stream. A solution containing 0.25 g of Ni(OCOOCH 3 ) 2 ·4H 2 O was prepared by dissolving in a mixture of 10 mL ethanol and 60 μL ethanolamine. This aqueous solution was spin-coated onto ITO substrates at 4000 rpm for 30 s and subsequently annealed at 300 ℃ for 40 min. Self-assembled monolayers (SAMs) of MeO-2PACz and 6PACz were dissolved in ethanol at a concentration of 0.5 mg mL -1, sequentially spin-coated (4000 rpm, 30 s), and annealed at 100 ℃ for 10 min. An Al 2 O 3 dispersion (0.4 wt.% in isopropanol) was spin-coated at 5000 rpm for 30 s onto the Co-SAMs layer, followed by annealing at 100 ℃ for 10 min. A precursor solution was prepared by mixing FAI and PbI 2 in a 1:1 molar ratio within a solvent system of DMF:DMSO (7:1 v/v). After thorough stirring, 50 μL of the solution was deposited on the substrate via a two-step spin-coating process: 1000 rpm for 10 s followed by 5000 rpm for 30 s. During the second step, 150 μL of toluene was drop-casted onto the substrate 15 s prior to spin-coating completion. The resulting film was annealed at 120 ℃ for 40 min. A PCBM solution (6 mg mL -1 in chlorobenzene, 100 μL) was spin-coated at 2000 rpm for 30 s onto the FAPbI 3 absorber layer and annealed at 100 ℃ for 5 min. A BCP solution (0.5 mg mL -1 in ethanol) was spin-coated at 4000 rpm for 30 s. Finally, the substrate with the electron transport layer was mounted in a custom shadow mask and transferred to a metal thermal evaporation chamber. After achieving a base pressure below 10 -4 Pa, an ~85 nm-thick Ag electrode was deposited, monitored by a quartz crystal microbalance, to complete the perovskite solar cell device. Environmental simulation and characterization To investigate the effects of coupled vacuum-thermal cycling on the microstructural and performance characteristics of perovskite thin films, this study employed a combined ultrahigh vacuum (UHV) interconnected system and glovebox for contamination-free sample transfer under vacuum conditions (detailed protocol in Supporting Information S1). The experimental setup integrated an X-ray photoelectron spectrometer (XPS) with a thermal programmed desorption chamber equipped with a cryogenic sample stage, enabling simultaneous exposure to UHV conditions (~10 -8 Pa) and periodic thermal cycling (150 K-430 K). Real-time monitoring of chemical structural evolution and gaseous decomposition products during thermal cycling was achieved through synchronized in situ XPS and quadrupole mass spectrometry (QMS). Complementary ex situ characterization—including rapid encapsulation transfer for morphology analysis (SEM), crystallographic evaluation (XRD), and carrier lifetime measurements—was performed to correlate degradation mechanisms. To elucidate the structure-property relationship in perovskite solar cells, depth-resolved elemental profiling was performed via in situ Ar⁺ ion sputtering, enabling quantitative tracking of elemental redistribution across functional layers during thermal cycling. Cross-sectional SEM imaging further visualized the microstructural evolution of devices pre- and post-thermal stress. Finally, current-voltage (J-V) characteristics under AM0 illumination (1366 W m -2 ) were systematically evaluated to quantify performance degradation. The active area (0.11 cm 2 ) is defined by the overlap of Ag and ITO without using mask. Supplementary Figures Figure S1. Photograph of the actual in-situ research platform Figure S2 . Pb 4f photoelectron spectra of the perovskite absorber layer after different numbers of thermal cycles: (a) one cycle; (b) two cycles; (c) three cycles Figure S3 . N 1s photoelectron spectra of the perovskite absorber layer after different thermal cycling durations: (a) one cycle; (b) two cycles; (c) three cycles. Figure S4 . C 1s photoelectron spectra of the perovskite absorber layer after different thermal cycling durations: (a) one cycle; (b) two cycles; (c) three cycles. Figure S5 . SEM morphology evolution of formamidinium lead iodide absorber layer under single high vacuum and different numbers of thermal cycles: (a) pristine absorber layer; (b) after one thermal cycle; (c) after two thermal cycles; (d) after three thermal cycles. Figure S6 . AFM surface roughness evolution of formamidinium lead iodide absorber layer during vacuum-thermal cycling numbers of thermal cycles: (a) pristine absorber layer; (b) after one thermal cycle; (c) after two thermal cycles; (d) after three thermal cycles. Figure S7 . Cross-sectional SEM images of perovskite devices during vacuum-thermal cycling: (a) pristine device; (b) device after three thermal cycles. Information & Authors Information Version history Copyright This work is licensed under a Non Exclusive No Reuse License.

Authors Metrics & Citations Metrics Article Usage 410views 180downloads Citations Download citation Xianchao Lu, Zhiyong Wang, Qianru Lin, et al. In-Situ Investigation of Perovskite Solar Cells Under Coupled Vacuum-Thermal Cycling in Extreme Space Environments. Authorea. 17 August 2025. DOI: https://doi.org/10.22541/au.175547361.10502563/v1 DOI: https://doi.org/10.22541/au.175547361.10502563/v1 If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download. For more information or tips please see 'Downloading to a citation manager' in the Help menu. Cited by - Perovskite Solar Cells for Space Applications: Progress, Perspectives, and Remaining Challenges, Energies, 19, 6, (1432), (2026).https://doi.org/10.3390/en19061432 - Perovskites beyond efficiency: stability challenges from space to Earth, Energy Advances, 5, 5, (632-644), (2026).https://doi.org/10.1039/D5YA00315F Loading...