Enhanced photoelectrochemical water splitting performance of GaN nanowires on textured Si (100) platforms: The role of texturing in 3.69 % STH conversion efficiency

Abstract

Nanostructured GaN semiconductors, including 0D quantum wells and 1D nanowires (NWs), as well as 3D nanoporous structures, have the potential to enhance the efficiency of photoelectrochemical (PEC) cells due to their shorter charge carrier transfer paths, accelerated separation of photogenerated carriers, and enhanced sunlight absorption. However, their practical applicability is limited due to poor stability and low solar-to-hydrogen conversion efficiency. To address these issues, one approach is to load a passivation layer and cocatalyst onto the GaN surfaces to protect against oxidation and corrosion and promote the oxidation of water, respectively. Another strategy is to design these structures on textured platforms to enhance light management, resulting in broader absorption of wavelengths and reduced sensitivity to incident angle and light polarization. In this study, we present a novel comparison of PEC-WS performance among 120 CdS/ZnO/GaN nanowires fabricated on different substrates, including planar Si (120 CdS/ZnO/GaN NWs-Si), textured 3D pyramids (120 CdS/ZnO/GaN-Si PNWs), and NWs Si (120 CdS/ZnO/GaN-Si HNWS). Compared to the other substrates, 120 CdS/ZnO/GaN-Si HNWS photoanode showed a 1.14 and 1.26-fold increase in photocurrent density and 3.69 % solar to hydrogen conversion efficiency under 1-Sun illumination. Our Si texturing approach, in-depth understanding of charge transportation, and demonstration of a co-catalyst-loaded core-shell passivated structure offer promising opportunities for achieving highly efficient PEC-WS performance in GaN-based photoanodes.