Regulating the Microstructure of Sb ₂ Se ₃ Films via a MoO x Nanocrystal Interfacial Layer for Efficient Photoelectrochemical Hydrogen Production

Sb₂Se₃ photocathodes are promising candidates for photoelectrochemical hydrogen production, but their performance is often limited by insufficient light harvesting and severe charge recombination. Here, we introduce a MoOx nanocrystal interfacial layer to regulate the microstructure and interfacial properties of Sb₂Se₃ films. When grown on Mo/MoOx substrates, Sb₂Se₃ develops a nanocolumnar crystal structure with improved crystallographic orientation compared to films deposited directly on Mo, forming a light-trapping morphology that reduces reflectance and enhances absorption. In addition, MoOx functions as a hole transport layer, creating proper band alignment with Sb₂Se₃ to facilitate interfacial carrier transfer and mitigate charge accumulation and recombination losses. Transient absorption spectroscopy confirms that the presence of MoOx accelerates photogenerated carrier separation and prolongs carrier lifetime. Benefiting from these synergistic effects, the optimized Mo/MoOx/Sb₂Se₃/Pt photocathode achieves an approximately 40% enhancement in maximum photocurrent and a positive shift in onset potential relative to Mo/Sb₂Se₃/Pt. This work demonstrates an effective strategy to boost the performance of Sb₂Se₃-based photoelectrodes and provides valuable insights for interface and structural engineering in semiconductor devices.