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 (CO), sulfur (S), and –CF₃ groups act as Lewis bases, coordinating with undercoordinated Pb²⁺ ions. This coordination passivates defects and regulates the perovskite crystallization process, promoting larger grain formation and stabilizing the [PbI₆]⁴⁻ octahedral framework. This controlled crystallization also reduces the 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.