Indolo[3,2- b ]indole-based crystalline hole-transporting material for highly efficient perovskite solar cells

We have designed and synthesized fluorinated indolo[3,2- ]indole (IDID) derivatives as crystalline hole-transporting materials (HTM) for perovskite solar cells. The fluorinated IDID backbone enables a tight molecular arrangement stacked by strong π-π interactions, leading to a higher hole mobility than that of the current HTM standard, , -spiro-OMeTAD, with a spherical shape and amorphous morphology. Moreover, the photoluminescence quenching in a perovskite/HTM film is more effective at the interface of the perovskite with as compared to that of , -spiro-OMeTAD. As a consequence, the device fabricated using shows superior photovoltaic properties compared to that using , -spiro-OMeTAD, exhibiting an optimal performance of 19%. Thus, this remarkable result demonstrates IDID core-based materials as a new class of HTMs for highly efficient perovskite solar cells.