Binary copper oxides as photovoltaic absorbers: recent progress in materials and applications

Abstract Binary copper oxides are a promising class of p-type semiconductors for solar energy conversion applications due to their particular electrical and optical properties, elemental abundance, and non-toxicity. So far, three phases with different copper ion oxidation states, including cuprous Cu 2 O, paramelaconite Cu 4 O 3 , and cupric CuO, have already been successfully synthesized by thin-film deposition techniques. This work reviews recent progress in determining the physical properties of these three phases from the viewpoints of both experimental and theoretical calculations, including their thermodynamics, structure, microstructure, band structure, defects, and their optical and electrical properties. In particular, we discuss some undecided issues regarding the properties of these materials. In addition, we summarize recent advances in photovoltaic cells using copper oxides as absorbers, including correlations between device performance and material properties.