Efficient and Stable All-Inorganic Perovskite Solar Cells Prepared with ABX3-Like Precursors

Abstract

Despite the fact that inorganic perovskites with supreme thermal stability are attractive photo-absorbers for emerging photovoltaic cells, intrinsic phase-instable issues pose challenges for obtaining satisfactory photovoltaic efficiencies and long-term device stability. Herein, we demonstrate an all-solution approach based on a series of perovskite-like products (PLP), namely NH₄PbX₃ (X = halogen) as the reactant for preparing inorganic perovskites featuring a heterojunction-resembling structure (HRS) and high material robustness. The creation of HRS is enabled by a self-migration and assembly process facilitated by the volatile characteristics of PLPs, as affirmed by joint experiential and theoretical investigations. We highlight that the particular structure of HRS is a key to the boost in material robustness, which translates to long-term device stability. Engaging compositional engineering on the PLPs allows us to regulate the energetics of surface components within the HRS, leading to gradient energy alignments to promote carrier transport and extraction in the device. Based on an optimized PLP (NH₄PbCl_2.8Br_0.2) to form the HRS, the resultant solar cell yields a power conversion efficiency (PCE) exceeding 20%, showing excellent operational stability under illumination (the efficiency remains over 95% of its initial value after 1000 hours of continuous illumination). The described PLP-based approach can be readily applied to a range of inorganic perovskite materials for receiving gains in photovoltaic performance.