Thiophene-Fused Butterfly-Shaped Polycyclic Arenes with a Diphenanthro[9,10- b:9',10'- d]thiophene Core for Highly Efficient and Stable Perovskite Solar Cells

Two polycyclic heteroarene derivatives, namely, V-1 and V-2, with a diphenanthro[9,10-b:9',10'-d]thiophene (DPT) core tethered with two diphenylaminophenyl or diphenylamino groups were first synthesized and used as hole-transporting materials (HTMs) in perovskite solar cell (PSC) fabrication. The novel HTMs exhibit appropriate energy-level alignment with the perovskite so as to ensure efficient hole transfer from the perovskite to HTMs. V-2 with the diphenylamino substituent on DPT exhibited impressive photovoltaic performance with a power conversion efficiency of 19.32%, which was higher than that of V-1 (18.60%) and the benchmark 2,2',7,7'-tetrakis-(N,N-di-p-methoxyphenyl-amine)-9,9'-spirobifluorene (spiro-OMeTAD) (17.99%), presumably because of a better hole extraction, higher hole mobility, and excellent film-forming ability, which were supported by steady-state photoluminescence (PL), time-resolved PL, the hole mobility experiment, scanning electron microscopy, and atomic force microscopy measurements. Meanwhile, V-2-based PSCs exhibited better long-term durability than that with V-1 and the state-of-the-art spiro-OMeTAD, which is ascribable to the excellent surface morphology and hydrophobicity of the film. This systematic study suggests that DPT-based molecules are good potential candidates as HTMs for achieving high-performance PSCs.