Spin-Coating-Free Deposition of ZnO and RGO@ZnO Nanolayers for Efficient, Economical Perovskite Solar Cells

In this study, ZnO nanoparticles (NPs) and RGO@ZnO nanocomposites (NCs) were integrated as electron transport layers (ETLs) using spin-coating-free deposition methods and cost-effective and scalable fabrication of planar perovskite solar cells was achieved. ZnO NPs and RGO@ZnO NCs were synthesized via a rapid hydrothermal process and characterized using XRD, SEM, UV-Vis, and FTIR techniques. Structural and optical analyses confirmed the formation of highly crystalline and uniform nanostructures, with RGO integration enhancing light absorption and narrowing the band gap. The films were deposited using the doctor blade technique, and the MAPbI₃ perovskite layer was formed by a simple drop-casting method. PCBM was used as the hole transport layer, and a silver (Ag) paste was applied as the top electrode. Photovoltaic performances of two device structures, ITO/ZnO/MAPbI₃/PCBM/Ag and ITO/RGO@ZnO/MAPbI₃/PCBM/Ag, were compared. Devices incorporating RGO@ZnO exhibited significantly improved efficiency up to threefold under standard solar illumination due to reduced charge recombination, improved energy level alignment, and enhanced carrier mobility. Moreover, these devices maintained high performance under indoor LED lighting, demonstrating superior low-light adaptability.