Low-Temperature Processing All-Inorganic Carbon-Based Perovskite Solar Cells up to 11.78% Efficiency via Alkali Hydroxides Interfacial Engineering

All-inorganic carbon-based perovskite solar cells (C-PSCs) have attracted massive attention owing to their low-cost fabrication and superior stability. However, the low power conversion efficiency (PCE; <10%), serious hysteresis, and relatively high-temperature fabrication process (>250 °C) largely hinder their great potential for commercialization. Herein, we demonstrate a simple and efficient interfacial engineering strategy with alkali hydroxides (KOH, NaOH) to enable the low-temperature (∼150 °C) fabrication of high-quality CsPbI2Br perovskite films and C-PSC device (ITO/SnO2/MOH/CsPbI2Br/carbon), in which a thin layer of alkali hydroxide interfacial modifier leads to reduced work function and surface tension force of SnO2, full SnO2/CsPbI2Br interface contact, and facile electron transfer from CsPbI2Br to ETL. Importantly, K+ cations can effectively suppress the halide ion migration and the vacancy defect formation by forming KBr-like compounds, thus leading to significant improvement in current–voltage hysteresis and stability together with stabilized PCE of 11.22% under contious illumination (the champion PCE in the reverse scan direction up to 11.78% (0.09 cm2) and 9.34% (1.00 cm2)), which represent the highest level for the low-temperature-processing all-inorganic C-PSCs. Our work represents an advance in construction of a highly efficient inorganic perovskite/ETL interface that can significantly improve the photovoltaic performance and stability of PSCs.