Band gap Engineering of BaTi1-x (Ni1/3Nb2/3)xO3 Ceramics for Ferro-Photovoltaic Applications

Abstract

A lot of interest has recently been paid in the field of photovoltaics, to the ferroelectric perovskite oxides, because of their special qualities, which include the availability of these materials in large quantities, the potential for charge carrier separation caused by polarization, high open circuit voltages, and chemical stability. However, ferroelectric perovskite oxides have a broad band gap due to which only slightly absorb solar light. In this study, we demonstrate how the optical band gap of BaTiO3 can be lowered by doping this perovskite oxide with Ni and Nb at the Ti-sites. The structural, optical, and ferroelectric properties of BaTi1-x (Ni1/3Nb2/3)xO3 ceramics are investigated. X-ray diffraction studies confirm the formation of phase-pure perovskites of BaTi1-x (Ni1/3Nb2/3)xO3. A coexistence of the tetragonal and orthorhombic structures was observed for the developed compositions and their fraction varies with changing Ni and Nb doping concentrations. All the studied compositions show ferroelectricity at room temperature. The band gap of BaTiO3 reduces from 3.2 eV to 2.06 eV for x = 0.07 composition for BaTi1-x (Ni1/3Nb2/3)xO3 ceramics. There is an additional secondary band gap obtained for this composition. The presence of secondary band gap provides more light absorption sites and thus can be more useful for photo-absorbing layer in solar cells. Thus the new low band gap composition of BaTi0.93 (Ni1/3Nb2/3)0.07O3 can be highly useful as ferro-photovoltaic material. © 2023 IEEE.