Copper Thiocyanate Inorganic Hole-Transporting Material for High-Efficiency Perovskite Solar Cells

In this Letter we show that the mixed perovskite in the form of (FAPbI 3 ) 0.85 (MAPbBr 3 ) 0.15 in combination with CuNCS as p-type hole conductor leads to over 16% power conversion efficiency (PCE) under full sun illumination and yields a remarkable monochromatic incident photon-to-electron conversion efficiency of 85%. The devices displayed a short-circuit current density ( J sc ) of 21.8 mA/cm 2, open-circuit voltage ( V oc ) of 1100 mV, fill factor (FF) of 0.69, and a PCE of 16.6%. Under similar conditions, the device without CuSCN shows a PCE of 9.5%, with a significant decrease in the J sc (from 21.8 mA/cm 2 to 15.64 mA/cm 2 ) and V oc (from 1100 mV to 900 mV). The high J sc with CuSCN is mainly due to the effective charge transfer between perovskite and CuSCN, followed by the fast hole transport through CuSCN to the Au. In comparison, the spiro-OMeTAD reference cells showed efficiencies up to 19.65%. Different from most organic hole-transporting materials is the transparency and high hole mobility of CuSCN, which represent a paradigm shift in perovskite solar cells particularly for tandem solar cells.