Enhanced performance of perovskite solar cells via construction of benzothiadiazole-based hole transport materials utilizing an asymmetric strategy

Hole transport materials (HTMs) are essential for efficient and stable perovskite solar cells (PSCs). Thanks to their excellent photovoltaic properties, benzothiadiazole-based small molecule materials are used as HTMs. However, the structure-activity relationship of benzothiadiazole-based HTMs is still not well understood. In this work, the low-cost B-TPA HTM is constructed with diphenylamine and triphenyl amine derivatives as peripheral groups, utilizing an asymmetric strategy. The asymmetrical structure of B-TPA effectively lowers the hole recombination energy and suppresses charges accumulation at the interface of perovskite/hole transport layers. In addition, B-TPA exhibits excellent film formation properties and higher hole mobility. Consequently, the B-TPA based PSCs achieve a champion power conversion efficiency (PCE) of 23.2%. Meanwhile, the strong hydrophobicity of B-TPA greatly enhances the environmental stability of the PSCs. The PSCs based on B-TPA maintain 90.4% of their initial efficiency after 1000 hours of aging. Our work lays a solid foundation for the design and development of low-cost and high-performance HTMs.