Improved extraction performance of SnO₂ ETL for perovskite solar cells by a combined hydrolysis oxidation and sol-gel method

SnO₂ is widely used in perovskite solar cells (PSCs) due to its high electron mobility, suitable conduction band and low-temperature preparation characteristics. Currently, the two most commonly used methods for preparing SnO₂ are SnCl₂ hydrolysis oxidation or SnO₂ sol-gel preparation. However, although SnCl₂ hydrolysis oxidation can produce well-crystallized SnO₂, its controllability is poor, resulting in low device performance repeatability. On the other hand, the devices based on SnO₂ electronic transport layer prepared by the sol-gel method have good repeatability, but usually have poor crystallinity, leading to a decrease in electron transport performance. In this study, a combination of hydrolysis oxidation and sol-gel methods was used to prepare SnO₂ electronic transport layers. The results of the study demonstrate that using SnCl₂ hydrolysis oxidation to prepare high-quality SnO₂ crystalline layers can serve as a pre-growth template to improve the crystalline quality of sol-gel generated SnO₂. Additionally, covering the hydrolysis oxidation-based SnO₂ layer with sol-gel prepared SnO₂ crystalline layer can improves the repeatability of device preparation. The electron transport layers prepared by this method can effectively enhance the quality of thin film crystal growth and charge extraction capability, ultimately contributing to improving the efficiency, stability, and reducing hysteresis of the devices.