Hole Boosted Cu(Cr,M)O2 Nanocrystals for All‐Inorganic CsPbBr3 Perovskite Solar Cells

: The all-inorganic CsPbBr3 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)O2 (M=Ba2+ , Ca2+ , or Ni2+ ) nanocrystals with enhanced hole-transporting characteristics by increasing interstitial oxygen effectively extract holes from perovskite. The all-inorganic CsPbBr3 PSC with a device structure of FTO/c-TiO2 /m-TiO2 /CsPbBr3 /Cu(Cr,M)O2 /carbon achieves an efficiency up to 10.18 % and it increases to 10.79 % by doping Sm3+ ions into perovskite halide, which is much higher than 7.39 % for the hole-free device. The unencapsulated Cu(Cr,Ba)O2 -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.