Dual-Doping Strategy of Metal Chlorides in Ambient Air with High Humidity for Achieving Highly Air-Stable All-Inorganic Perovskite Solar Cells

Abstract

It is fundamentally challenging to achieve stable and efficient all-inorganic perovskite solar cells (PSCs) in ambient air conditions for low-cost commercial manufacturing, as the crystallinity, surface morphology, and optical activity of all-inorganic perovskites exhibit high sensitivity to environmental factors such as moisture and illumination. Herein, a dual-doping strategy is presented to prepare high-quality dual-doping CsPbI₂Br films under ambient air with relative humidity of 70% (70% RH) by introducing CaCl₂ and InCl₃ additives into precursor solution. The results from the experiments and calculations reveal that the CaCl₂ additive can isolate moisture by forming hydrates at the surface and grain boundary of perovskites. Meanwhile, the addition of InCl₃ can significantly improve the optoelectronic properties via the heterovalent substitution of Pb²⁺ by a small amount of In³⁺. Moreover, the phase segregation can be significantly suppressed in the dual-doping CsPbI₂Br films owing to decreasing the electron–phonon coupling strength and increasing the activation energy of ion migration. The unencapsulated dual-doping CsPbI₂Br PSC with the power conversion efficiency (PCE) of 15.51% (70% RH) demonstrates high humidity storage and long-term optical stability, remaining 90% of the original PCE after aging 2400 h under ambient air (50% RH) and 1500 h under continuous illumination, respectively.