Solar energy has become the essential energy source in space for facilitating the expanding human scientific and exploratory endeavours. Space is a hostile environment characterized by a high vacuum, energetic particles, and radiation from solar winds and cosmic galactic rays and intergalactic rays. The Earth, due to its geomagnetism, possesses natural shielding; this magnetic field filters out high-energy particles. The Geometric extends to 10 R_E (Radius of Earth). Beyond that, any electronic device is subjected to harsh deep space conditions. Therefore, comprehending deep space and its effects on solar cells is essential for the deployment of space photovoltaics. In space, the Moon's environment is characterized by extreme conditions, including a tenuous exosphere, exposure to cosmic radiation, due to absence of substantial atmosphere and its slow rotational period leads to the significant temperature fluctuations on the lunar surface [1]. It is devoid of a magnetic field leading to unmediated interactions with solar and cosmic events [2]. The lunar equatorial regions can attain peak temperatures ranging from approximately 387 K to 397 K (114°C to 124°C) during the day, closely corresponding to the solar flux at the surface, while nighttime temperatures plummet significantly, with equatorial areas experiencing minima as low as approximately 100 K (-173°C) [3]. This pressure is so low that it is effectively a vacuum, with gas molecules being sparse and not colliding as they do in Earth's atmosphere.​ This primordial atmosphere would have been ephemeral, fading away over roughly 70 million years because of the Moon's minimal gravity and absence of a shielding magnetic field [4]. The Moon might have undergone elevated atmospheric pressures. Some studies indicate that approximately 3.5 billion years ago, volcanic eruptions emitted considerable volumes of gases, forming a temporary atmosphere with surface pressures that could have approached 1 kPa and measurements indicate that the total mass of the lunar exosphere is approximately 25,000 kg, leading to a surface pressure around 3 × 10⁻¹⁵ bar (2 × 10⁻¹² torr) [5]. In space applications, various solar cell technologies are employed like silicon solar cell, multijunction solar cell, etc., but silicon solar cells susceptible to degrade the high-energy particles in space, leading to reduced efficiency over time and heavier due to material density, impacting launch costs and payload capacities [6]. Even though multi-junction solar cells are more radiation-resistant than silicon cells, extended exposure to radiation still degrades their performance and their extensive use in missions with tight budgets is restricted by high material and fabrication costs as well as weight considerations [7]. Among the myriad solar cell technologies, the ultra-thin perovskite solar cell is distinguished by an extraordinary specific power density of 50 W/g [8], which substantially exceeds that of both traditional and emerging alternatives. Considering the comparison, conventional silicon solar cells deliver a modest 1.9 W/g [9], ultra-thin GaAs solar cells offer 5.44 W/g [10], and transition metal dichalcogenides (TMDs) secure about 4.4 W/g [11]. Even multi-junction solar cells, recognized for their high efficiency and prevalent use in aerospace applications, typically produce around 10^–15 W/g [12], which is markedly inferior to the specific power of perovskite variants. This notable disparity renders ultra-thin perovskite solar cells an attractive option for our simulations, particularly in scenarios where space is limited or weight is a critical factor, such as in space missions. The combination of their lightweight characteristics and high-power output confers a transformative advantage in energy harvesting.

The numerical simulations in this study were carried out using the Solar Cell Capacitance Simulator (SCAPS-1D), a one-dimensional simulation software developed by the University of Ghent [18]. SCAPS solves Poisson’s equation and the continuity equations for electrons and holes across a defined multilayer device under steady-state or transient conditions. The simulator allows users to model semiconductor layers with customizable properties including bandgap energy, carrier mobilities, dielectric constant, electron affinity, doping concentrations, and defect distributions. SCAPS supports simulations under various environmental conditions such as different illumination spectra like AM0, AM1.5, temperature variations, and irradiation levels. It computes key output parameters such as current–voltage (I–V) characteristics, quantum efficiency (QE), electric field profiles, and recombination losses. Owing to its versatility, SCAPS-1D is widely used in the modelling of novel photovoltaic technologies, particularly perovskite-based solar cells. [18]

The fluence (Φ) values listed in Table 1 reflect expected cumulative exposure from natural solar and galactic sources in typical lunar or near-Earth environments. However, our choice to simulate up to 10¹⁵ cm^− 2 fluence. While the actual space environment near the Moon exposes materials to cumulative proton fluences in the range of 10⁹ − 10¹¹ cm^− 2 over typical mission durations [17] our simulations extended to 10¹⁵ cm^− 2 for radiation hardness qualification, comparative sensitivity analysis and predictive extrapolation. Proton fluence levels up to 10¹⁴ − 10¹⁵ cm^− 2 are commonly used in accelerated radiation testing protocols to evaluate device degradation margins and long-term survivability, particularly for high-reliability space missions [19]. By extending the fluence range, we were able to distinguish the radiation tolerance thresholds for different defect introduction rates (k). This helped us evaluate at what point performance degradation becomes critical for each material scenario. Simulating beyond nominal exposure levels allows us to model worst-case scenarios, such as solar proton events (SPEs) or prolonged mission timelines where cumulative fluence could significantly exceed average background levels. Therefore, while fluence levels > 10¹³ cm^− 2 may not be routinely encountered, they serve as a conservative boundary for stress testing photovoltaic materials under extreme space conditions.

In present case, the simulation methodology was designed to analyse the electrical performance and radiation stability of perovskite solar cells under both terrestrial and space environments. AM0 represents extraterrestrial solar irradiance (~ 1360 W/m²), free from atmospheric scattering and AM1.5G simulates terrestrial sunlight (~ 1000 W/m²). In moon orbit the spectrum is AM0 and its intensity is given by [20],

D_Eareth/D_moon*AM0 (1)

Where D_Earth is the distance of earth from Sun and D_Moon is the distance of moon from sun. At the ratio D_Earth/D_Moon is nearly equal to moon the intensity of moon orbit remains AM0. The impact of high energy photon radiation in space is analysed empirically as

N_def = N_i + k* Φ (2)

where N_def is the radiation induced defects in the absorber, N_i is the initial defect density in absorber and k is the defect introduction rate. The theoretical estimation of radiation generated defects in absorber provide an insight into the degradation of their performance in space environment. Figure 1 estimates the radiation generated defects for perovskite FAMACsPb(IBr)₃, under fluence ranging from 10¹⁰ to 10¹⁵ cm^− 2, for a k value of 10 cm^− 1. It could be seen that the N_def does not show any growth for low fluence and increases linearly with increasing fluence. Nguyen et al [21] reported that the radiation generated defects are donor -acceptor pair with donor energy level at 0.1 eV below conduction band and acceptor level at 0.1 eV above valence band level. The simulation outcomes presented above can be replicated utilizing the material parameters from Table 2 and the details specified in the relevant descriptions in Section 3.

The proposed perovskite solar cell was built with a planar architecture of ITO/SnO₂/FAMACsPb(IBr)₃/Spiro-OMeTAD/Au as schematically shown in Fig. 2. SnO₂ was used as the electron transport layer (ETL), FAMACsPb(IBr)₃ as the absorber, and Spiro-OMeTAD as the hole transport layer (HTL). The thicknesses and optoelectronic properties of each layer, such as bandgap, dielectric constant, electron affinity, doping concentration, and carrier mobilities, were assigned using the values shown in Table 2. These parameters were determined using validated experimental literature on high-efficiency perovskite devices [8, 22]. The structure was simulated in SCAPS-1D using both AM0 and AM1.5G spectra, with default interface conditions of flat-band alignment and negligible interface recombination. The model's calibration was verified by benchmarking against published J-V characteristics, as discussed in following section.

Figure 3 simulates the spectral irradiance distribution of two different solar insolation namely, Air Mass Zero (AM0) and Air Mass 1.5 (AM1.5G). The AM0 spectrum, with power density of ~ 1360W/m² [23], shown in black, represents above earth atmosphere solar radiation, which is space condition. It features a smooth curve without absorption dips, closely resembling the Sun’s theoretical blackbody radiation. This spectrum is particularly relevant for space applications, such as solar energy harvesting in satellites and spacecraft. In moon orbit the intensity of AM0 is given as per Eq. 1, The plot for AM1.5G highlights the impact of Earth's atmosphere on solar radiation, reducing the power insolation to ~ 1000 W/m² [24], which is essential for photovoltaic applications. The observed AM1.5G spectrum is rough with many dips in intensity due to the atmosphere’s absorption and scattering [24]. This reduction in spectral irradiance at certain wavelengths affects the efficiency of solar cells, as different photovoltaic materials have varying spectral responses. Understanding these spectral differences is crucial for optimizing solar cell design, especially for applications in space (AM0) environment [23].

Figure 4(a) simulates the J-V performance of Spiro-OMeTAD/ FAMACsPb(IBr)₃/SnO₂/ITO solar cells benchmarked with the experimentally reported device [22]. The benchmarking curve corresponds to the experimental results obtained from a high-efficiency perovskite device with similar material parameters and layer structure. The overlap between the simulated and experimental J–V curves show the model, and the input parameters used in SCAPS-1D simulation are reasonably reliable. The J-V plot overlaps, showing the good match of performance parameters such as V_OC, J_SC, FF and efficiency with reported device [22]. The QE plot of perovskite solar cells in space (AM0) and on the Earth's surface (AM1.5) are comparatively shown in Fig. 4(b). The lower J_SC values for AM1.5 in J-V characteristics even though the QE plot confirms the similar spectral response, highlights the effect of atmospheric scattering. QE is the fraction of incident photons that are involved in the generation of charge carriers inside the device. The QE curve is nearly identical for both AM0G and AM1.5G over the wavelength range, which means that the spectral response of the device is not noticeably dependent on the intensity but on the spectrum. The QE is close to 100% in the visible range (around 400–600 nm), which indicates high efficiency in photon-to-electron conversion. It is, however, drastically decreased at shorter and longer wavelengths due to material limitations and recombination losses.

Simulated plot in Fig. 5 shows the efficiency of solar cells as a function of the bandgap, comparing two different illumination or space conditions AM 0 and AM 1.5G. Simulated efficiency is consistent with the Shockley-Queisser limit, which predicts that single-junction solar cells achieve maximum efficiency at a bandgap of approximately ~ 1.4 eV under standard sunlight conditions [20, 25]. The efficiency maximizes at a bandgap of approximately 1.3 eV under AM0 spectrum, and in AM 1.5 spectrum optimal bandgap is 1.4 eV. It is highly relevant to the optimization of perovskite solar cells (PSCs), particularly those operating under space (AM0). These findings are useful to improve solar cell geometries for space and terrestrial use. Another observation from Fig. 5 is that the lower efficiency in AM0 than the AM1.5 illumination. Even though the power density is higher in AM0 (~ 1.3 kW/m²) as compared to AM1.5G (~ 1 kW/m²). Although AM0 has higher solar irradiance (~ 1366 W/m²) than AM1.5G (~ 1000 W/m²), the simulated efficiency under AM0 is lower, because the efficiency is given as the ratio of P_out/P_in, the denominator P_in is increased in AM0, thus lowering the efficiency numerical values. The power output will be higher in AM0 due to higher energy input.

To emulate radiation-induced degradation, the defect density N_def was expressed as a function of radiation fluence (Φ) and an introduction rate (k) according to Eq. 2. The empirical relation shows that the material dependent parameter k, is measure of matrial resutance hardness. We calculated N_def for three values of k (0.001, 10, 1000 cm^− 1) for FAMACsPb(IBr)₃ Fig. 6 shows that the N_def remain numerically equal to N₀ values irrespective of large variation in fluence ranging from 10¹⁰ to 10¹⁵ cm^− 2 for introduction rate (k) value of 10^− 3 cm^− 1. For k value of 10 cm^− 1, the radiation generated defects density N_def remain initial constant for low fluence up to 10¹¹ cm^− 2, beyond this fluence the N_def start to grow linearly as shown by the diamond line in Fig. 6. For large k values i.e. 10³ cm^− 1 N_def steeply grows with the fluence. The above simulated figure focused on how defect density changes with fluence and introduction rate (k). k is a material dependent parameter which shows the material inherent property toward radiation tolerance. In this study, the defect introduction rate coefficient (k) was used as a simulation parameter to model radiation-induced trap accumulation in a simplified linear form. While k values have been reported for materials like Si, CIGS, and GaAs under varying proton energies, no such experimental data currently exist for perovskites. Therefore, a range of k values was explored parametrically to study performance sensitivity. The values listed in Table 3 are collected from literature sources for comparative purposes but are not used as direct inputs for perovskite modeling. The some of the reported k values for solar cells are summarized in Table 3.

Figure 7(a) shows the overlapping J-V plot of perovskite solar cell under 1MeV proton fluence ranging from 10¹⁰ to 10¹⁵ cm^− 2. The impact of increasing fluence is not sheen due to the low k value, at lower k value N_def does not rises with fluence. Figure 7(b) shows the increasing degradation of perovskite solar cell J-V under increasing radiation fluence for k value of 10 cm^− 1. For fluence level of 10¹⁴ cm^− 2, J-V characteristics shows small decay in V_OC beyond this fluence level J_SC shows more degradation than V_OC. At high value of k, it is observed that the J_SC is completely diminished showing high sensitivity towards the radiation decay. The V_OC starts decaying as fluence grows, whereas the J_SC hold for initial rise in fluence and starts to completely vanish at higher fluence level. This theoretical observation is similar to the experimentally reported by Dabbabi, et al in literature [27].

This figure highlights the impact of increasing radiation-induced defect density on overall device performance and the normalised change in performance parameter of V_OC, J_SC, FF, Efficiency for different 1MeV proton fluence from 10¹⁰ to 10¹⁵ cm^− 2 are shown in Fig. 6. The normalised change calculated as the value of performance parameter (V_OC, J_SC, FF, Efficiency) divided by the performance parameters value at fluence values of 10¹⁰ cm^− 1. Figure 8 (a) shows the normalized changes in performance parameters values under the specified fluence range for k value of 10^− 3 cm^− 1. The overlapping of all the parameters like J_SC, V_OC, efficiency, FF show unchanged performance due low k. This is the desired scenario for a radiation resistance solar cell. Figure 8 (b) shows the degradation of efficiency with fluence at moderate k value. It shows J_SC is highly sensitive as it shows highest decays, followed by FF and V_OC. Figure 8 (c) shows the highest degradation in device performance when k = 10³ cm^− 1 with and efficiency almost decaying to zero. The simulated normalised plot highlights the fluence level which a practical device could tolerated and provide insight into device degradation mechanism.

The choice of 397 K in above mentioned figure was based on the practical simulation point to the lunar day peak temperature to explore the impact of elevated thermal stress. Simulated Fig. 9 represents the Current density–voltage (J–V) characteristics of the device measured at temperatures of 397 K, for varying particle fluence (ϕ) levels ranging from 10¹⁰ to 10¹⁵ particles/cm² for fixed introduction rate (k) of 10 cm^− 1 on perovskite solar cells. The measurements show that elevated temperature have significant impact on open circuit voltage V_OC, whereas short circuit current density J_SC increases slightly. Higher temperature decreases bandgap as per the Varshini equation [30] which increases absorption of incident spectrum thus increasing J_SC. V_OC decrease is higher than increase in J_SC, thus overall efficiency decreases. At elevated temperatures, the rate of carrier recombination increases due to enhanced phonon interactions and increased intrinsic carrier concentration, leading to a reduction in open-circuit voltage (V_OC) and overall device efficiency. These findings suggest a close relationship between temperature, radiation-induced defects, and the device's electrical performance.

The implications of 1MeV proton radiation on perovskite solar cell are examined for radiation-induced defects within the absorber. It was posited that the defects generated by radiation would correlate with the fluence, and these were simulated utilizing an appropriate defect model for the perovskite absorber. The simulation model employed here closely mirrored the experimental observations of significant reductions in short-circuit current density (J_SC) and minor decreases in open-circuit voltage (V_OC) with escalating fluence. It was observed that the performance degradation of the FAMACsPb(IBr)₃ material became evident for irradiation fluence exceeding 10¹³ particles/cm² under introduction rate of 10 cm^− 1, underscoring its robust performance in moon orbit environments. The simulated performance elucidated a pragmatic potential for perovskite solar cells in space applications.