CdS Quantum Dot Interlayer Engineering for Enhanced SnO₂/Perovskite Interfaces in Solar Cells

Interfacial defects at the buried junction between the electron transport layer (ETL) and perovskite absorber critically hinder the performance of perovskite solar cells (PSCs). We report herein that a CdS quantum dot (QD) interlayer, deposited onto SnO₂ via a successive ionic layer adsorption and reaction method, provides an effective strategy to improve charge transport across this interface. The CdS QD layer not only suppresses oxygen vacancies but also reacts with hydroxyl groups on the SnO₂ surface, thereby improving surface potential uniformity and enhancing the electron extraction rate. Impedance spectroscopy further confirms improved interface homogeneity and charge transport, correlating with higher fill factor and short-circuit current densities. As a result, CdS modification enables a ∼25% efficiency enhancement on PSCs, highlighting the potential of QD-based interfacial engineering towards high-performance PSCs.