Planar GaN/Cu₂O Microcrystal Composite Junction Photoanode for Efficient Solar Water Splitting

Abstract

Cu 2 O microcrystals are electrodeposited on an epitaxial GaN layer on a Si(111) substrate to improve the solar water splitting efficiency of a GaN photoanode. The performance of the GaN/Cu 2 O composite junction photoanode is investigated as a function of the Cu 2 O deposition amount for Cu 2 O microcrystal formation. For optimum Cu 2 O deposition amount, the photocurrent density is significantly enhanced compared to that of the bare GaN photoanode. The improved water splitting performance is attributed to the builtin electric field and band offsets of the n-GaN/p-Cu 2 O heterostructure, promoting the separation of photogenerated electrons and holes and the transport of the hole to the surface.