Center for Functional Nanomaterials Seminar

Solar energy is a promising long-term solution for future energy requirements; however, current solar energy conversion devices are plagued by low efficiency. The use of ferroelectric ABO3 perovskite oxides is one approach for boosting conversion efficiency. Ferroelectric oxides possess spontaneous polarization and have been shown to produce a bulk photovoltaic effect, in which charged carriers, specifically electrons and holes, separate to prevent recombination. Once separated, the high-energy electrons are available for electrical work or for the catalytic splitting of water into hydrogen and oxygen. Currently, most solid oxide ferroelectrics have a band gap of at least 3 eV, absorbing primarily in the ultra-violet (UV) region. Since UV light comprises only 8% of the solar spectrum, new materials with a decreased band gap and large polarization would be highly desirable. PbTiO3 is a well known solid oxide ferroelectric which is used as an end-member in a variety of solid solutions. Using density functional theory, we substitute the B-site of PbTiO3 with group 10 metals Ni, Pd and Pt, stabilized by an accompanying O vacancy. We predict that the new PbTiO3-derived perovskites display significantly lower band gaps while maintaining, or even enhancing the polarization of the parent PbTiO3 material.