Two star-shaped TPA-based small-molecule materials (Z1012 and Z1013) were designed and synthesized in this paper. These molecules show high hole mobility and suitable energy levels for CH3NH3PbI3-based perovskite solar cells. Photovoltaic cells based on the Z1013 without any dopants or additives achieve an excellent power conversion efficiency (PCE) of 15.4%, which is comparable to devices based on state-of-art p-doped spiro-OMeTAD. Moreover, the devices based on these two HTMs show much better stability than that of devices based on spiro-OMeTAD when aging in ambient air both at room temperature and 80 °C. These results demonstrate that star-shape TPAs could be excellent dopant-free HTMs for perovskite solar cells and hold promise to replace the p-doped spiro-OMeTAD, which is important for the fabrication of cost-effective and stable devices.
Zhang, F., Zhao, X., Yi, C., Bi, D., Bi, X., Wei, P., … Grätzel, M. (2017). Dopant-free star-shaped hole-transport materials for efficient and stable perovskite solar cells. Dyes and Pigments, 136, 273–277. https://doi.org/10.1016/j.dyepig.2016.08.002