Copper(I)-Based <i>p</i>-Type Oxides for Photoelectrochemical and Photovoltaic Solar Energy Conversion

Abstract

Recent research efforts have been growing into p-type copper(I) based oxides for development of their use in solar energy applications. The oxides of interest include the binary Cu2O and a number of new ternary CuxMyOz oxides. Both the binary and ternary Cu(I)-based oxides have many advantages when compared to other well-known p-type oxides such as NiO, III–V, and II–VI semiconductors. The benefits found within the diverse group of Cu(I)-containing oxides include bandgap sizes that can be tuned from ∼1.2 to >3.0 eV, high charge carrier mobility, and favorable band energies relative to fuel-producing redox couples. These properties give them potential utility in a variety of different solar applications, such as in dye-sensitized solar cells and suspended powder photocatalysis. Research efforts into surface modifications and changes in their chemical compositions and structures have allowed for greater stability and greater efficiency in aqueous solutions, both of which have represented two key barriers for this class of materials. Presented in this review are the currently known binary and ternary Cu(I)-oxides and relationships of their syntheses and structures with their visible-light and ultraviolet bandgap sizes, band energies, and photoelectrochemical properties. As their constituent elements are relatively abundant and nontoxic, they represent an attractive class of materials that can be used in the conversion of sunlight to electricity or solar fuels.