UV-Inert ZnTiO₃ Electron Selective Layer for Photostable Perovskite Solar Cells

Although planar-structured perovskite solar cells (PSCs) have power conversion efficiencies exceeding 24%, the poor photostability, especially with ultraviolet irradiance (UV) severely limits commercial application. The most commonly-used TiO₂ electron selective layer has a strong photocatalytic effect on perovskite/TiO₂ interface when TiO₂ is excited by UV light. Here a UV-inert ZnTiO₃ is reported as the electron selective layer in planar PSCs. ZnTiO₃ is a perovskite-structured semiconductor with excellent chemical stability and poor photocatalysis. Solar cells are fabricated with a structure of indium doped tin oxide (ITO)/ZnTiO₃/Cs_0.05FA_0.81MA_0.14PbI_2.55Br_0.45/Sprio-MeOTAD/Au. The champion device exhibits a stabilized power conversion efficiency of 19.8% with improved photostability. The device holds 90% of its initial efficiency after 100 h of UV soaking (365 nm, 8 mW cm⁻²), compared with 55% for TiO₂-based devices. This work provides a new class of electron selective materials with excellent UV stability in perovskite solar cell applications.