Additives for Pb defect passivation and FA immobilization: towards efficient and stable perovskite solar cells

Abstract

Perovskite solar cells (Pero-SCs) are rapidly emerging as a promising photovoltaic technology, yet their performance and stability are significantly hampered by defects and ion migration. This work introduces ethyl 4-methyl-2-(4-(trifluoromethyl)phenyl)thiazole-5-carboxylate (EMTC) as a multifunctional additive to mitigate these issues. The trifluoromethyl (-CF3) group of EMTC forms hydrogen bonds with the formamidinium cation (FA+), effectively anchoring it and suppressing ion migration. Simultaneously, the carbonyl (C=O), sulfur (S), and -CF3 groups act as Lewis bases, coordinating with undercoordinated Pb2+ ions. This coordination passivates defects, regulates the perovskite crystallization process, promoting larger grain formation and stabilizing the [PbI6]4− octahedral framework. This controlled crystallization also reduces pathways for organic cation volatilization. Consequently, EMTC-treated devices exhibit a significantly enhanced power conversion efficiency (PCE) from 21.68% to 23.57%. Remarkably, these devices retain over 96% of their initial PCE after 2832 hours of storage under dark, inert (N2) conditions at room temperature, demonstrating significantly improved stability.