All-perovskite triple-junction solar cells for space: in operando response to proton irradiation

Monolithic all-perovskite triple-junction solar cells (3J-PSCs) promise the highest power-to-weight ratios, making them attractive candidates for space photovoltaics. Their stability under high-energy particle irradiation concurrent with illumination is, however, a crucial consideration for space photovoltaic applications. Here, we investigate for the first time 3J-PSCs under high-energy (68 MeV) proton irradiation using complementary in situ and in operando measurements in the dark and under AM0 illumination, respectively. In situ dark current density-voltage (J-V) evolution reveals no pronounced cumulative degradation under proton irradiation, with the PCE remaining factor, R(PCE), remaining above 0.99 at a fluence of 1 × 10¹³ p⁺ cm^-2. At the same time, stable radiation-induced current and voltage are observed, consistent with radiation-induced charge-carrier generation through ionizing energy loss. Under simultaneous AM0 illumination, both proton-irradiated and non-irradiated devices exhibit closely similar performance evolution, with stable open-circuit voltage (V_OC) and short-circuit current density (J_SC) alongside a gradual fill factor (FF) reduction, reaching comparable final R(PCE) values of approximately 0.87. This indicates that no pronounced additional proton-induced performance loss is resolved under the investigated conditions. Intensity-dependent photoluminescence quantum yield (iPLQY) measurements show that the quasi-Fermi level splitting (QFLS) of the individual subcells remains unchanged and pseudo-J-V (pJ-V) analysis further confirms preserved absorber-level performance potential after irradiation. Together, our experiments reveal a high tolerance of 3J-PSCs to radiation-induced degradation both in the dark and under simultaneous AM0 illumination, showing higher remaining performance than the III-V 3J solar cells under comparable proton energy and fluence, while also highlighting operational instabilities of today's 3J PSCs under continuous AM0 illumination.