Preparation of AgIn1−xGaxSe2 films from sol–gel derived precursors via a coating method

Abstract

AgIn1−xGaxSe2 films were prepared via coating the pastes that contained sol–gel derived precursors and selenium powders, followed by the normal heating process without using H2Se. Pure-phased AgIn1−xGaxSe2 films were successfully obtained after heating in a reducing atmosphere (H2/N2) at 500 °C for 0.5 h. As the flow rate of the carrier gas was reduced, In2O3 and Ag2Se phases in the obtained films disappeared owing to prolonged residence time for selenium vapor to react with the precursors. In the paste-coating process, the gallium-ion content of the prepared films was effectively adjusted using the sol–gel route. The lattice constants of AgIn1−xGaxSe2 decreased with increasing the gallium-ion contents. The uniformity throughout AgIn1−xGaxSe2 films was confirmed by using the grazing incident X-ray diffraction analysis. The band gap energy increased nonlinearly from 1.27 to 1.63 eV as the molar ratio of gallium ions to IIIA ions (indium ions and gallium ions) increased from 0.2 to 0.8.