FIRST-PRINCIPLES BASED DESIGN OF PEROVSKITE OXIDES FOR VISIBLE LIGHT ABSORPTION IN PHOTOVOLTAICS

Ferroelectric (FE) materials have recently attracted increased attention as a candidate class of materials for use in photovoltaic devices and for coupling of light absorption with functional properties. Their strong inversion symmetry breaking due to spontaneous polarization allows for excited carrier separation by the bulk of the material and voltages higher than the band gap (Eg), which may allow efficiencies beyond the Shockley-Queisser limit. Until recently, the use of FE oxides in PV devices has been blocked by the wide band gaps (Eg=2.7-4 eV) of FE oxides, which allow the use of only 8-20% of the solar spectrum and drastically reduce the upper limit of photovoltaic efficiency. Ab initio calculations and crystal chemical analysis are powerful tools for the investigation of oxide solid solutions and are well-suited for making the connection between the local, Angstrom-scale interactions and structural features and the macroscopic physical properties. In this presentation, I will
describe our computational studies of a variety of ferroelectric perovskite oxides and show that the physical behaviors of these materials are governed by the simple local structure and chemical bonding characteristics; these characteristics can then be modified to rationally design new materials with light absorption through the visible range that enables the use of these materials in photovoltaic applications.