Toward efficient and air-stable carbon-based all-inorganic perovskite solar cells through substituting CsPbBr3 films with transition metal ions.

• Divalent transition metal ions are doped into the lattices of CsPbBr 3 perovskite. • The enlarged grain size and decreased energy differences reduce charge recombination. • The all-inorganic CsPbBr 3 PSC free of HTLs achieves a PCE up to 9.18%. • The optimal device shows excellent long-term stability over 760 h in 80% RH. The perovskite film with large grain size and low defect states density is technically important to improve the power conversion efficiency and environmental stability of perovskite solar cells (PSCs). In the present work, we raise a compositional engineering strategy of inorganic CsPbBr 3 perovskite films by substituting partial Pb2+ with divalent transition metal ions having smaller ionic radius (TM2+ = Mn2+, Ni2+, Cu2+ and Zn2+). The photovoltaic performances of hole transporting layer-free all-inorganic CsPbBr 3 PSCs are markedly improved through maximizing grain size with few grain boundaries as well as low trap states density and minimizing energy loss in charge carrier transfer. A champion power conversion efficiency as high as 9.18% is achieved for the all-inorganic CsPb 0.995 Zn 0.005 Br 3 PSC free of encapsulation, which shows a remarkable long-term stability over 760 h in 80% humidity air atmosphere at 25 °C. The high efficiency and improved stability demonstrate compositional engineering is a promising strategy to forward high-quality perovskite films and high-performance of all-inorganic CsPbBr 3 PSCs. [ABSTRACT FROM AUTHOR]