Entropy-driven strategy stabilizes photoactive halide perovskites for inverted solar cells

The phase instability of perovskite materials remains a significant obstacle to their practical application in photovoltaics. Herein, we present a high-configurational-entropy strategy based on formamidinium ion (FA⁺) to fabricate the photoactive phase-stable halide perovskites through incorporating 2-amino-1,3,4-thiadiazole (2NTD). 2NTD optimally balances interactions with the [PbI₆]^4– octahedral frameworks while enhancing the rotational freedom of FA⁺. This synergistic effect amplifies FA⁺ anisotropy and elevates configurational entropy. Moreover, 2NTD effectively inhibits the formation of I₂/I₃^– species and passivates the associated trap-state, thereby reducing the self-degradation behavior within perovskite films caused by undesirable iodine species. This improvement significantly enhances the crystallization and phase-stability of the perovskites under I₂-rich conditions. Consequently, efficiencies of 26.63% (certified 26.40%) for a 0.09-cm² inverted PSCs, 25.34% for a 1-cm² device, and 23.08% for a 12.96-cm² mini-module were obtained. Moreover, the target device exhibits a minimized non-radiative voltage loss of 69 mV and an improved long-term operational stability.