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, energy level alignment at the HTM/perovskite interface is optimized, 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.