New hole transport materials with 1,2-dimethoxyphenyl as the terminal groups

Two new compounds (J1 and J2) are synthesized and used as hole transport materials (HTMs) for perovskite solar cells (PSCs). In J1 and J2, 1,2-dimethoxyphenyl is used as the terminal group, with tetraphenyl ethylene and 9,​9′-​spirobi[9H-​fluorene] ring as the core structure, respectively. Compared to the commonly used methoxyl end group, there are two methoxyl units on 1,2-dimethoxyphenyl, which enhances the electron-donating ability of the end groups. Additionally, the introduced phenyl ring could extend π conjugation of the whole molecule, which is favorable for electron delocalization and charge transporting. Planar PSCs are fabricated, and J2-based device shows a power conversion efficiency (PCE) of 15.07%, with a short-circuit current density (Jsc) of 20.37 mA cm−2, an open-circuit voltage (Voc) of 1020 mV and a fill factor (FF) of 0.73.