Critical Role\nof Low-Energy Protons in Radiation Testing\nof Perovskite Space Solar Cells

While\nperovskite solar cells (PSCs) are attractive for space applications,\nassessing their radiation tolerance requires adequate testing protocols.\nThe primary criterion is that protons normally incident on a PSC during\nground-based testing should create a uniform damage profile, mimicking\nthe effect of the omnidirectional and polyenergetic proton spectrum\nin space orbit. However, given the low thicknesses of PSCs, proton\nenergies >0.05 MeV can meet this criterion, leading to ambiguity\nregarding\nthe precise energy needed for testing. Here, we highlight another\nmajor criterion: the optimal proton energy should also closely mimic\nthe elemental vacancy distribution created in the perovskite by space\nprotons. Using Monte Carlo ion-solid simulations, we first calculate\nthe elemental vacancies in a PSC due to the low-Earth orbit (LEO)\nproton spectrum. We then show that only ∼0.07 MeV protons can\nresult in a similar distribution during ground-based testing. Higher\nenergies (∼1 MeV) lead to 25% more iodine, 33% more lead, and\n50% fewer hydrogen vacancies, failing to represent the space radiation\nenvironment accurately. Our results offer precise guidelines for PSC\nradiation testing, paving the way for more accurate, reliable, and\ncomparable assessments.