Terthiophene‐Based Dopant‐free Hole‐transporting Materials for Inverted Perovskite Solar Cells

The interfaces of perovskite solar cells are essential for high power conversion efficiency and long‐term stability. This study showcases two innovative materials, WZ40 and WZ102, triarylamine end‐capped functionalized terthiophene derivatives. These materials serve as hole‐transporting materials (HTMs), enabling the production of efficient mixed‐halide inverted perovskite solar cells. Both HTMs exhibit impressive thermal stability with decomposition temperatures over 415°C, making them suitable for developing stable perovskite solar cells. Their sulfur‐rich terthiophene core enhances perovskite stability through Pb‐S interactions, promoting uniform crystal growth. By adjusting the electron density in WZ40 and WZ102 through donor and acceptor group modifications, we optimize energy level alignment at the HTM/perovskite interface, facilitating efficient hole transfer. The donor‐rich WZ102‐based solar cell achieves an outstanding open‐circuit voltage of 1.09 V and a power conversion efficiency of close to 20%, thanks to effective hole transport and low series resistance. This work introduces a promising class of terthiophene‐based small molecules as HTMs, paving the way for dopant‐free interface materials and advancing the commercialization of perovskite solar cells.