Abstract
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.