Junction less thin-film ferroelectric oxides for photovoltaic energy production

Streaming Process for Electrode-less Electrochemical Deposition (SPEED) method is used to create complex thin-film structures, such as KBNNO, in a single step, in contrast to hydrothermal approaches with separate nanoparticle growth and deposition processes. This new ferroelearic oxide [KNbO3](1-x)[BaNi1/2Nb1/2O3-delta](x) or "KBNNO" has an alloy-tunable band gap as low as 1.1 eV, so that its absorption can be tailored to match the solar spectrum. At the same time, it has a reasonably large polarization allowing for charge separation across the bulk, sizeable photocurrents, and open-circuit voltages V-oc that exceed the band gap, potentially leading to efficiencies that exceed those possible for standard pn-junction cells. Physical characterization of KBNNO films demonstrate the microstructure and stoichiometry of SPEED-produced thin-films, ratio of elements needed to achieve an ideal band gap of similar to 1.39 eV, the effect on film chemistry, microstructure, and band gap of annealing, the practical separation of excited carriers at room temperature, the maximum achievable polarization and its temperature dependence, and the conditions for ideal poling. Photovoltaic characterization of KBNNO cells will determine the efficiency, the relative strengths of dark and photo currents, the open circuit voltage, the short circuit current, and cell fill factor (FF).