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. (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)