β-CuGaO2 as a Strong Candidate Material for Efficient Ferroelectric Photovoltaics

We propose a recently discovered material, namely, beta-CuGaO2 [T. Omata et al., J. Am. Chem. Soc. 2014, 136, 3378] as a strong candidate material for efficient ferroelectric photovoltaics (FPVs). According to first-principles predictions exploiting hybrid density functional, beta-CuGaO2 is ferroelectric with a remarkably large remanent polarization of 83.80 mu C/cm(2), even exceeding that of the prototypic FPV material, BiFeO3. Quantitative theoretical analysis further indicates the asymmetric Ga 3d(z)(2)-O 2p(z) hybridization as the origin of the Pna2(1) ferroelectricity. In addition to the large displacive polarization, unusually small band gap (1.47 eV) and resultantly strong optical absorptions additionally differentiate beta-CuGaO2 from conventional ferroelectrics; this material is expected to overcome critical limitations of currently available FPVs.