Development of a new hole transport material for perovskite solar cells

N,N-di(4-methoxyphenyl)amino-9,9' -spirobifluorene (spiro-OMeTAD) is a widely used hole transport layer (HTL) material for emerging lead halide hybrid perovskite solar cells (PSCs). Finding alternative HTL materials is required for the future development of more efficient and stable PSCs. Here, we developed a new HTL material of N-2,N-2,N,N-7(7)-tetrakis(4-methoxyphenyl)benzo[b]benzo[4,5]thieno[2,3-d]thiophene-2,7-diamine (TBTD). Chemically doped TBTD provided better hole extraction in PSCs than chemically doped spiro-OMeTAD due to higher electrical conductivity and a more suitable hole transport energy level. Thus, PSCs with the TBTD HTL showed higher power conversion efficiency (similar to 21%) than spiro-OMeTAD HTL (similar to 19%). The operational stability of TBTD-based PSCs was similar to that of spiro-OMeTAD-based PSCs. The findings discussed in this study will aid in the future development of high-performance PSCs.