Three benzene-arylamine hole-transporting materials (HTMs) with different numbers of terminal groups were prepared. It is noted that the molecule with three arms (H-Tri) shows a lower highest occupied molecular orbital level and a better film morphology on perovskite layer than the molecules with two or four arms (H-Di, H-Tetra). When these molecules were applied to the perovskite solar cells, the H-Tri-based one showed better performance compared with the H-Di- or H-Tetra-based ones. Photoluminescence and impedance spectroscopy demonstrate that H-Tri can improve the hole-electron separation efficiency and decrease the charge recombination, thus leading to a better performance. Moreover, the H-Tri-based device shows a comparable performance and a much less materials cost than the conventional spiro-OMeTAD. Therefore, we have presented a new low-cost and high-performance HTM through simple molecular engineering.
Keywords: hole-transporting materials; low cost; molecular engineering; perovskite solar cell; three arms.