SrTiO3 based high temperature solid oxide solar cells: Photovoltages, photocurrents and mechanistic insight

High temperature solid oxide solar cells based on SrTiO3 (STO) are investigated. Schottky contacts between STO and different materials, including La1-xSrxCrO3, La0.8Sr0.2MnO3, La0.6Sr0.4CoO3 and metals like Au and Pt are illuminated by UV light with a wavelength of 365 nm at 350 °C in air and the resulting voltages and currents are measured. With certain material combinations, e.g. LaCrO3/STO or Au/STO heterojunctions, high photovoltages of more than 1.0 V are obtained. Current measurements reveal changes in the bulk STO due to stoichiometry polarization, leading to a self-enhancement effect of the photovoltaic cell. Mechanistic insight in the processes under UV light is gained by electrochemical impedance spectroscopy, especially regarding the space charge region at the heterojunction and bulk changes due to stoichiometry polarization. In addition to the electronic effects upon illumination, also photo-ionic effects of oxygen transport caused by chemical potential changes were observed.