Tailoring the alkalinity of SnO2 colloidal suspension for high‐performance and stable perovskite solar cells

The commercial tin oxide (SnO 2 ) colloidal suspension is widely utilized as an electron transport layer (ETL) in high‐performance perovskite solar cells (PSCs) due to its favorable material properties and potential for large‐scale production. However, despite significant efforts have been proposed to address bulk transport and interface recombination issues through the introduction of additives or modifiers, the efficiency of PSCs based on commercial SnO 2 nanoparticles remains limited to around 25%. In this study, we highlight the crucial role of the physicochemical characteristics of the SnO 2 colloidal suspension in shaping the morphology, electrical properties and optical properties of the SnO 2 ETL. By controlling the pH value of the SnO 2 solution with weak acids such as carbonic acid, we successfully induced the reassembly of metal oxide nanoparticles into smaller sizes with more homogeneous dispersion and dense interconnections. Consequently, the resulting SnO 2 ETL exhibited enhanced crystallinity, high conductivity, low surface defects, and high optical transmittance. As a result, we achieved a significant improvement in the power conversion efficiency of the target PSCs, increasing it from 23.10% to 24.70%. This improvement was attributed to higher voltage, photocurrent, and fill factor compared to the relevant control samples. We observed a similar device improvement using phosphoric acid, indicating that our approach represents a universal technique to further enhance the quality of SnO 2 ETL for large‐area, high‐efficiency, and stable PSCs. This article is protected by copyright. All rights reserved.