title: Wurtzite CuGaO2: a new direct and narrow band gap oxide semiconductor applicable as a solar cell absorber.
abstract: An oxide semiconductor β-CuGaO2 with a wurtzite-derived β-NaFeO2 structure has been synthesized. Structural characterization has been carried out by Rietveld analysis using XRD and SAED, and it was shown that the lattice size is very close to that of zinc oxide. The optical absorption spectrum indicated that the band gap is 1.47 eV, which matches the band gap required to achieve the theoretical maximum conversion efficiency for a single-junction solar cell. The thermoelectromotive force indicated p-type conduction in its intrinsic state. Density functional theory calculations were performed to understand the electronic structure and optical properties of the semiconductor. These calculations indicated that β-CuGaO2 is a direct semiconductor and intense absorption of light occurs near the band edge. These properties render this new material promising as an absorber in solar cells.
authors.affiliation: Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University , Suita, Osaka 565-0871, Japan.
authors.forename: Takahisa
authors.initials: T
authors.lastname: Omata
authors.forename: Hiraku
authors.initials: H
authors.lastname: Nagatani
authors.forename: Issei
authors.initials: I
authors.lastname: Suzuki
authors.forename: Masao
authors.initials: M
authors.lastname: Kita
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Yanagi
authors.forename: Naoki
authors.initials: N
authors.lastname: Ohashi