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

Abstract

We have designed and synthesized fluorinated indolo[3,2-<i>b</i>]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, <i>p</i>,<i>p</i>-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 <b>IDIDF</b> as compared to that of <i>p</i>,<i>p</i>-spiro-OMeTAD. As a consequence, the device fabricated using <b>IDIDF</b> shows superior photovoltaic properties compared to that using <i>p</i>,<i>p</i>-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.