Enhanced SnO2 electron transport layers by Eu3+ doping for efficient and stable perovskite solar cells†

Chemical bath deposition (CBD) is a promising way to fabricate SnO₂ electron transport layers (ETLs) for efficient and stable perovskite solar cells (PSCs). Here, europium chloride hexahydrate (EuCl₃·6H₂O) was introduced into the CBD process to optimize the properties of SnO₂ for high-efficiency and stable PSCs. The incorporation of Eu³⁺ ions into the SnO₂ lattice effectively enhances its electrical properties, mitigates surface trap defects, and reduces interfacial non-radiative recombination. More importantly, Eu³⁺ ions serve as effective protectants, improving the UV resistance of perovskite films. As a result, the PSCs based on the Eu-SnO₂ ETL exhibit a notable improvement in power conversion efficiency (PCE), increasing from 22.02% to 24.50%. Additionally, the devices demonstrate excellent stability, retaining 96.9% and 86% of their initial efficiency after 2600 h in ambient air and 130 h under continuous UV illumination, respectively. This strategy provides a valuable approach for further improving the film quality of SnO₂, offering great potential for high-efficiency and stable PSCs.