Hole‐Boosted Cu(Cr,M)O 2 Nanocrystals for All‐Inorganic CsPbBr 3 Perovskite Solar Cells

The all‐inorganic CsPbBr 3 perovskite solar cell (PSC) is a promising solution to balance the high efficiency and poor stability of state‐of‐the‐art organic–inorganic PSCs. Setting inorganic hole‐transporting layers at the perovskite/electrode interface decreases charge carrier recombination without sacrificing superiority in air. Now, M‐substituted, p‐type inorganic Cu(Cr,M)O 2 (M=Ba 2+ , Ca 2+ , or Ni 2+ ) nanocrystals with enhanced hole‐transporting characteristics by increasing interstitial oxygen effectively extract holes from perovskite. The all‐inorganic CsPbBr 3 PSC with a device structure of FTO/c‐TiO 2 /m‐TiO 2 /CsPbBr 3 /Cu(Cr,M)O 2 /carbon achieves an efficiency up to 10.18 % and it increases to 10.79 % by doping Sm 3+ ions into perovskite halide, which is much higher than 7.39 % for the hole‐free device. The unencapsulated Cu(Cr,Ba)O 2 ‐based PSC presents a remarkable stability in air in either 80 % humidity over 60 days or 80 °C conditions over 40 days or light illumination for 7 days.