Ultra-thin and high transparent Cu2ZnSnSe4/NiOx double-layered inorganic hole-transporting layer for inverted structure CH3NH3PbI3 perovskite solar cells

Abstract Inorganic hole transporting layer (HTL) plays the most important role to fabrication of low cost and stable in perovskite solar cells. Herein, we present low cost highly transparent and ultra-thin sputtered Cu2ZnSnSe4 (CZTSe) combined with solution-processed NiOx films as a double-layered inorganic HTL applied in inverted CH3NH3PbI3 perovskite solar cells, which is beneficial to enhance hole extraction and suppress electron transport. Sputtered CZTSe films have high transmittance (>85%), high hole mobility (15.1 cm2 v-1 s-1), low resistivity (0.33 Ω-cm), earth-abundant elemental constituents, and non-toxic properties, which is one of the promising p-type inorganic hole-transporting material. An obvious enhancement of open-circuit voltage (Voc), short-circuit current density (Jsc), fill factor (FF), and power conversion efficiency (PCE) of a 600°C-annealed-CZTSe/NiOx double-layered HTL based inverted perovskite solar cell was observed, and final Voc, Jsc, FF, and PCE of 1.03 V, 17.9 mA cm-2, 73%, and 13.46% were achieved, respectively. Importantly, the ultra-thin CZTSe/NiOx double-layer HTL makes the perovskite solar cell exhibit improved stability, of which this device remains 73% of the initial PCE value after 350 h’ storage in the nitrogen-filled glove box.