The effects of the planarity of the core building block and peripheral donor groups on the photovoltaic performance of triarylated amine-based hole transport materials

Precise design of the molecular configuration of hole transport materials (HTMs) is crucial to achieve highly efficient perovskite solar cells (PSCs). Herein, by combining the core units of triphenylamine and carbazole with different peripheral groups, three small molecular HTMs termed TPA-DF, CZ-DF and CZ-DM are designed and synthesized. The effects of the configuration of the core building block and the donating ability of the terminal group on the optical, electro-chemical and photovoltaic properties are systemically examined. The research results demonstrate that the material CZ-DF with a planar carbazole core unit and N-(4-methoxyphenyl)-9,9-dimethyl-9H-fluoren-2-amine as the terminal donor group shows the most suitable energy level and the highest hole mobility and conductivity among these three HTMs. Applied in PSCs, the CZ-DF based device achieves a power conversion efficiency (PCE) of 21.5%, and can retain 79.5% of its the initial PCE after aging at 65 ?, 45-60% relative humidity (RH) in an air atmosphere.