Solution-processed CuO_x as an efficient hole-extraction layer for inverted planar heterojunction perovskite solar cells

A solution-processed CuO_x film has been successfully integrated as the hole-transporting layer (HTL) for inverted planar heterojunction perovskite solar cells (PVSCs). The CuO_x layer is fabricated by simply spin-coating a copper acetylacetonate (Cu(acac)₂) chloroform solution onto ITO glass with high transparency in the visible range. The compact and pinhole-free perovskite film with large grain domains is grown on the CuO_x film. The inverted PVSCs with the structure of ITO/CuO_x/MAPbI₃/PC₆₁BM/ZnO/Al are fabricated and show a best PCE of 17.43% under standard AM 1.5G simulated solar irradiation with a V_OC of 1.03 V, a J_SC of 22.42 mA cm⁻², and a fill factor of 0.76, which is significantly higher and more stable than that fabricated from the often used hole-transporting material PEDOT:PSS (11.98%) under the same experimental conditions. The enhanced performance is attributed to the efficient hole extraction through the CuO_x layer as well as the high-quality CH₃NH₃PbI₃ films grown on the CuO_x. Our results indicate that low-cost and solution-processed CuO_x film is a promising HTL for high performance PVSCs with better stability.