Excellent Performance of Perovskite Solar Cells With SnO ₂ Quantum Dots as Electron Transport Layer

Electron transport layer (ETL) is an important part of perovskite solar cells (PSCs), which has a direct effect on the performance of devices. Tin dioxide (SnO 2 ), known for its excellent conductivity and low photocatalytic activity, has emerged as a leading candidate for ETLs in PSCs. While the advanced SnO 2 layer is typically fabricated through chemical bath deposition, offering tunable properties, commercial SnO 2 (C‐SnO 2 ) nanocrystals with limited tunability still require further optimization. In this study, we present the synthesis and application of quantum dots SnO 2 (QD‐SnO 2 ) to create ETL. By optimizing different precursor concentrations, we prepared QD‐SnO 2 with a diameter of less than 3 nm. Compared with C‐SnO 2 particles, the PCE of ‐based devices is improved by 18.5% and shows good stability. Strikingly, in order to prove the universality of QD‐SnO 2 , the champion power conversion efficiency (PCE) of FA x MA 1‐ x PbI 3 ‐based and Cs 0.05 MA 0.1 FA 0.85 PbI 3 ‐based PSC devices reaches 20.70% and 22.04%, respectively. This work provides a new type of ETL for researchers to choose from, which is of great significance to the development of PSCs.