Carbon-based inorganic perovskite solar cells (C-IPSCs) with promising efficiency, good thermal stability, and low cost have emerged as important candidates for photovoltaic device commercialization. However, the relatively poor phase stability of CsPbI3 perovskite in humid conditions and the mismatched energy level at the perovskite/carbon interface hinder the efficiency and stability of CsPbI3 C-IPSCs. Herein, a facile molecular modification strategy is employed to solve the current issues using a multifunctional molecule, ethyl thioacetate (ES). Post-treatment enhances the hydrophobicity of CsPbI3 films due to the relatively small polarity of ES molecules. The C═O and C–S groups in ES form Lewis acid–base coordination interactions with uncoordinated Pb2+ in perovskite, effectively passivating surface defects in perovskite films. In addition, ES treatment optimizes the energy level arrangement, facilitating hole extraction at the perovskite/carbon interface. Thus, ES post-treatment yields a champion PCE of 17.07% for carbon-based CsPbI3 solar cells. The ES-treated C-IPSCs also show enhanced stability, which retains 80% of the initial PCE after 1360 h at 20% RH, surpassing the untreated counterparts by 19%.
Wang et al. (Mon,) studied this question.