Regulating the Microstructure of Sb ₂ Se ₃ Films via a MoO _<i>x</i> 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 MoO_<i>x</i> nanocrystal interfacial layer to regulate the microstructure and interfacial properties of Sb₂Se₃ films. When grown on Mo/MoO_<i>x</i> 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, MoO_<i>x</i> 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 MoO_<i>x</i> accelerates photogenerated carrier separation and prolongs carrier lifetime. Benefiting from these synergistic effects, the optimized Mo/MoO_<i>x</i>/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.