CuI-Derived CuxO Thin Films Development via Thermal Oxidation for Lead-Free Perovskite Solar Cells

Abstract The development of low-cost, stable, and efficient hole transport layers (HTLs) is crucial to the advancement of lead-free perovskite solar cells. In this work, a solution-based oxidation process is employed to convert spin-coated copper iodide (CuI) films into mixed-phase copper oxide (Cu x O) thin films comprising Cu₂O and CuO. Oxidation occurs under moderate temperatures (200–300°C), leading to uniform, compact, and highly conductive p-type films with tunable bandgaps. Structural, morphological, and optical analysis confirms successful phase transformation, and measurements of Hall effect reveal maximum mobility of holes of 26.7 cm 2 V −1 s −1 for double-coated films annealed at 300°C. Device simulations via SCAPS-1D using these measured properties predict that Cu x O HTLs can make high-efficiency lead-free perovskite solar cells with Cs₂AgBi ₁−x SbₓBr₆ absorbers. While experimental device integration is yet to be demonstrated, this research lays the foundation for oxidized CuI-derived Cu x O as a potential candidate inorganic HTL for green photovoltaics and offers thoughtful guidance for subsequent experimentation.