Post‐Treated Polycrystalline SnO2 in Perovskite Solar Cells for High Efficiency and Quasi‐Steady‐State‐IV Stability

Abstract The prominent chemical bath deposition (CBD) method leverages tin dioxide (SnO 2 ) as an electron transport layer (ETL) in perovskite solar cells (PSCs), achieving exceptional efficiency. The deposition of SnO 2 , however, can lead to the formation of oxygen vacancies and surface defects, which subsequently contribute to performance challenges such as hysteresis and instability under light‐soaking conditions. To alleviate these issues, it is crucial to address heterointerface defects and ensure the uniform coverage of SnO 2 on fluorine‐doped tin oxide substrates. Herein, the efficacy of tin(IV) chloride (SnCl 4 ) post‐treatment in enhancing the properties of the SnO 2 ‐ETL and the performances of PSCs are presented. The treatment with SnCl 4 not only removes undesired agglomerated SnO 2 nanoparticles from the surface of CBD SnO 2 but also improves its crystallinity through a recrystallization process. This leads to an optimized interface between the SnO 2 ‐ETL and perovskite, effectively minimizing defects while promoting efficient electron transport. The resultant PSCs demonstrate improved performance, achieving an efficiency of 25.56% (certified with 24.92%), while retaining 95.84% of the initial PCE under ambient storage conditions. Additionally, PSCs treated with SnCl 4 endure prolonged light‐soaking tests, particularly when subjected to quasi‐steady‐state‐IV measurements. This highlights the potential of SnCl 4 treatment as a promising strategy for advancing PSC technology.