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

While perovskite solar cells (PSCs) are attractive for space applications, assessing their radiation tolerance requires adequate testing protocols. The primary criterion is that protons normally incident on a PSC during ground-based testing should create a uniform damage profile, mimicking the effect of the omnidirectional and polyenergetic proton spectrum in space orbit. However, given the low thicknesses of PSCs, proton energies >0.05 MeV can meet this criterion, leading to ambiguity regarding the precise energy needed for testing. Here, we highlight another major criterion: the optimal proton energy should also closely mimic the elemental vacancy distribution created in the perovskite by space protons. Using Monte Carlo ion-solid simulations, we first calculate the elemental vacancies in a PSC due to the low-Earth orbit (LEO) proton spectrum. We then show that only ∼0.07 MeV protons can result in a similar distribution during ground-based testing. Higher energies (∼1 MeV) lead to 25% more iodine, 33% more lead, and 50% fewer hydrogen vacancies, failing to represent the space radiation environment accurately. Our results offer precise guidelines for PSC radiation testing, paving the way for more accurate, reliable, and comparable assessments.