Triphenylamine-based hole transporting materials with thiophene-derived bridges for perovskite solar cells

A triphenylamine-based compound containing benzoyl[1,2-b:4,5-b’]dithiophene (BDT) derivative (BTPA-2) has been synthesized and employed in FA0.85MA0.15PbI3 perovskite solar cells (PSCs) as the hole transporting material (HTM). The reference BTPA-1 containing thiophene bridge was also prepared for a comparative study. Compared to the thiophene unit in BTPA-1, the hexyloxy substituted BDT unit in BTPA-2 made the HOMO energy level lower. The more conjugated system with the BDT unit can improve the conductivity and hole mobility. The BTPA-1 and BTPA-2 based FA0.85MA0.15PbI3 PSCs showed the best power conversion efficiencies (PCE) of 12.76 % and 13.97 %, respectively. Larger Voc and higher Jsc for the BTPA-2 based PSC were attributed to its reduced interfacial recombination and more conjugated system compared to the BTPA-1 based PSCs. More hydrophobic property of BTAP-2 made its PSC exhibit better environmental stability than BTPA-1.