Lewis-Base Containing Spiro Type Hole Transporting Materials for High-Performance Perovskite Solar Cells with Efficiency Approaching 20%
Owing to excellent performance and dopability, spiro-OMeTAD remains an irreplaceable hole transporting material (HTM) in perovskite solar cells (PSCs). In order to further improve the performance of spiro-OMeTAD based PSCs, Lewis base can be introduced into the structure of spiro-OMeTAD wisely, which can keep the advantages of spiro-OMeTAD while adding the functionality of Lewis base in passivating the surface of perovskite. Therefore, spiro-type HTMs (spiro-CN-OMeTAD with dicyano group and spiro-PS-OMeTAD with thiocarbonyl group) were synthesized and confirmed by density functional theory (DFT) calculation and single-crystal X-ray diffraction. The spiro-CN-OMeTAD as HTM is certified with a suitable interfacial band alignment with perovskite, good film quality and effective defect passivation, which facilitate the resulting device to achieve an efficiency of 19.90 % with high open-circuit voltage, low hysteresis, and improved stability. This study provides an alternative strategy for the molecular design of better HTMs in high-performance PSC.