Entropy-driven strategy stabilizes photoactive halide perovskites for inverted solar cells
Xin Chen, Wei Hui, Qi Wang, Ping Xu, Zhilu Xu, Ben Fan, Lin Song, Xiaopeng Xu, Yihui Wu, Qiang Peng
Abstract
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. This work introduces a high FA+ configurational entropy strategy by adding 2NTD, tuning FA+ rotation dynamics and stabilizing photoactive phases to yield efficient, stable inverted perovskite devices with scalable potential.