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

Sb 2 Se 3 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 MoO x nanocrystal interfacial layer to regulate the microstructure and interfacial properties of Sb 2 Se 3 films. When grown on Mo/MoO x substrates, Sb 2 Se 3 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, MoO x functions as a hole transport layer, creating proper band alignment with Sb 2 Se 3 to facilitate interfacial carrier transfer and mitigate charge accumulation and recombination losses. Transient absorption spectroscopy confirms that the presence of MoO x accelerates photogenerated carrier separation and prolongs carrier lifetime. Benefiting from these synergistic effects, the optimized Mo/MoO x /Sb 2 Se 3 /Pt photocathode achieves an approximately 40% enhancement in maximum photocurrent and a positive shift in onset potential relative to Mo/Sb 2 Se 3 /Pt. This work demonstrates an effective strategy to boost the performance of Sb 2 Se 3 -based photoelectrodes and provides valuable insights for interface and structural engineering in semiconductor devices.