Unravelling the Material Composition Effects on the Gamma Ray Stability of Lead Halide Perovskite Solar Cells: MAPbI₃ Breaks the Records

Abstract

In this work, we report a comparative study of the gamma ray stability of perovskite solar cells based on a series of perovskite absorbers including MAPbI 3 (MA = methylammonium), MAPbBr 3 , Cs 0.15 FA 0.85 PbI 3 (FA = formamidinim), Cs 0.1 MA 0.15 FA 0.75 PbI 3 , CsPbI 3 , and CsPbBr 3. We reveal that the composition of the perovskite material strongly affects the radiation stability of the solar cells. In particular, solar cells based on the MAPbI 3 were found to be the most resistant to gamma rays since this perovskite undergoes rapid self-healing due to the special gas-phase chemistry analyzed with ab initio calculations. The fact that the solar cells based on MAPbI 3 can withstand a 1000 kRad gamma ray dose without any noticeable degradation of the photovoltaic properties is particularly exciting and shifts the paradigm of research in this field toward designing more dynamic rather than intrinsically robust (e.g., inorganic) materials.

X-ray stability and degradation mechanism of lead halide perovskites and lead halides

“…On the contrary, the MAFA-Mix and CsFA-Mix samples show a decrease in the amount of Pb 0 during irradiation, not an increase, suggesting a reaction that consumes Pb 0 faster than it is formed. A similar process allowed encapsulated MAPbI 3 to reform after decomposition under gamma radiation as proposed by Boldyreva et al 15 The new nitrogen species observed during radiolysis of the organic cation are very likely, in part, responsible for this self-healing process. Radiolysis of ammonium halide salts and alkylammoium halide salts has been shown to result in the production of halide containing radicals.…”

“…damage) is required to initiate the degradation, which in turn appears to catalyse further degradation, meaning that degradation could be limited or avoided by reducing the X-ray fluence. Additionally, at 3.2x10 15 photons/s/cm 2 the formation of metallic lead is significantly slower than at higher intensities, indicating that the reaction behaves differently at lower X-ray flux densities. Therefore, the same total fluence can give less damage at lower X-ray flux densities suggesting that the X-ray stability is improved by limiting the maximum X-ray flux density.…”

“…The maximum intensity was estimated to 1.0x10 13 photons/s and the defocused beam forms a circle with a diameter of 300 μm, giving it an area of 70700 μm 2 . However, the beam hits the sample at a grazing angle of 11 degrees resulting in a spot size of 37000 μm 2 and an actual flux density of about 2.7x10 15 photons/s/cm 2 . The intensity was reduced by detuning the undulator gap, resulting in a lower X-ray intensity as measured by the mirror current, see Table S1.…”

“…Due to the small spot sizes used, no significant heating is expected as even the highest X-ray intensities (672 mW/cm 2 ) would increase the temperature by less than 3 o C, see SI for details. The excitation of charge carries from the X-rays and the secondary radiation could, however, be significant as the X-ray intensities approach or even exceed an irradiance of 100 mW/cm 2 (2.0x10 15 photons/s/cm 2 at 3000 eV), i.e. the same power as 1 sun illumination.…”

“…The perovskites demonstrated remarkable radiation resistance, often better than for the substrate and significantly better than for silicon, partially attributed the perovskites self-healing ability. [14][15][16][17] Boldyreva et.al. studied a large number of hybrid organic-inorganic and inorganic perovskites composition under up to 500 kRad of 662 keV gamma rays.…”