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

Abstract

We propose a recently discovered material, namely, β-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, β-CuGaO2 is ferroelectric with a remarkably large remanent polarization of 83.80 μC/cm2, even exceeding that of the prototypic FPV material, BiFeO3. Quantitative theoretical analysis further indicates the asymmetric Ga 3dz2–O 2pz hybridization as the origin of the Pna21 ferroelectricity. In addition to the large displacive polarization, unusually small band gap (1.47 eV) and resultantly strong optical absorptions additionally differentiate β-CuGaO2 from conventional ferroelectrics; this material is expected to overcome critical limitations of currently available FPVs.