Optimizing the perovskite/SnO2 interface: Defect passivation and energy level alignment for high-efficiency perovskite solar cells

Achieving proper alignment of energy levels, efficient charge extraction, and minimizing non-radiative recombination at the interface is critical for advancing the performance of perovskite solar cells (PSCs). In this work, we present a facile and scalable strategy for enhancing PSC efficiency through the modification of the SnO 2 electron transport layer (ETL) using a lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) interlayer. The LiTFSI treatment effectively passivates interfacial defects—primarily by reducing oxygen vacancies—and optimizes the energy level alignment between the perovskite active layer and the ETL, thereby improving electrical conductivity and charge carrier extraction. As a result, devices with the modified ETL exhibit a significant performance enhancement, achieving an optimal power conversion efficiency (PCE) of 20.84 % compared to 18.55 % in control devices. This study demonstrates that the LiTFSI-mediated modification of SnO 2 not only mitigates hysteresis effects but also offers a promising route toward the development of high-efficiency, stable PSCs suitable for practical applications. • Oxygen vacancy reduction in SnO 2 film was observed by LiTFSI treatment on the ETL. • LiTFSI-modified cells showed improved energy alignment, boosting charge extraction. • Enhanced stability and scalability of PSC were achieved via LiTFSI treatment.