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, a Lewis base can be introduced into the structure of spiro OMeTAD wisely, which can keep the advantages of spiro OMeTAD while incorporating the functionality of a Lewis base in passivating the surface of the perovskite. Therefore, spiro type HTMs (spiro CN OMeTAD with a dicyano group and spiro PS OMeTAD with a thiocarbonyl group) were synthesized and confirmed by density functional theory (DFT) calculations and X ray single crystallographic diffraction. Spiro CN OMeTAD as an HTM is certified to have a suitable interfacial band alignment with the perovskite, good film quality and effective defect passivation, which facilitate the resulting device to achieve an efficiency of 19.90% with a 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 PSCs.
Nanoscale