Highly transparent Cu2O absorbing layer for thin film solar cells

Highly transparent Cu2O thin films on transparent conducting oxide on a glass substrate were fabricated using reactive sputtering by carefully controlling the O2 flow. The impurity dependence of transmittance was thoroughly investigated, and the transmittance was found heavily depending on impurities in Cu2O thin films as confirmed by x-ray diffraction analysis. A highly transparent Cu2O thin film was fabricated using precisely impurity-controlled Cu2O thin films. The effects of impurities in a Cu2O thin film on photovoltaic properties were studied. A maximum efficiency of 8.4% was observed in the lowest-impurity Cu2O thin film.