Modulating donor assemblies of D-π-D type hole transport materials for perovskite solar cells

Abstract

Donor-π-donor (D-π-D) type organic semiconductors have been demonstrated to be excellent hole transporting materials (HTMs) in perovskite solar cells (PSCs). However, a systematic understanding of the impact from peripheral donors on the physicochemical properties and photovoltaic performance of HTMs is still scarce. Herein, through a synergistic modulation of the donor inner/outer arms, a series of novel D-π-D type HTMs are designed, synthesized and successfully applied in PSCs. It is found that substituting phenothiazine with carbazole as the inner arm could well improve the structural planarity and charge delocalization of HTMs. Moreover, via introducing fluorene units into the outer arm of the donor structure, HTM YT-KMPF exhibits excellent film morphology and hydrophobicity, making PSCs achieve a power conversion efficiency of 21.40% as well as excellent long-term stability. This work reveals the significance of donor modulation for designing efficient and stable HTMs.