Molecular "Flower" as the High-Mobility Hole-Transport Material for Perovskite Solar Cells.

To develop novel hole-transport materials (HTMs) with less synthetic steps is still a great challenge. Here, a small molecule hexakis[4-(N,N-di-p-methoxyphenylamino)phenyl]benzene (F-1) was successfully synthesized by a relatively simple scenario. F-1 exhibits a deep highest occupied molecular orbital energy level of -5.31 eV. Notably, F-1 also features 2 times higher hole mobility of 4.98 × 10-4 cm2 V-1 s-1 than that of the mostly used 2,2',7,7'-tetrakis(N,N-bis(4-methoxyphenyl)amino)-9,9'-spirobifluorene (spiro-OMeTAD). Consequently, F-1-based perovskite solar cells (PSCs) show markedly improved performance compared with spiro-OMeTAD-based ones. These results indicate such a material can be a promising HTM candidate to boost the overall performance of the PSC.