Optimization of the deposition and annealing conditions of fluorine-doped indium oxide films for silicon solar cells

Fluorine-doped indium oxide (IFO) films are deposited onto $(pp^+)$Si and $(n^+nn^+)$Si structures made of single-crystal silicon by ultrasonic spray pyrolysis. The effect of the IFO deposition time and annealing time in an argon atmosphere with methanol vapor on the IFO chemical composition, the photovoltage and fill factor of the Illumination-$U_{\mathrm{oc}}$ curves of IFO/$(pp^+)$Si structures, and the sheet resistance of IFO/$(n^+nn^+)$Si structures, correlating with the IFO/$(n^+)$Si contact resistance, is studied. The obtained features are explained by modification of the properties of the SiO$_x$ transition layer at the IFO/Si interface during deposition and annealing. Analysis of the results made it possible to optimize the fabrication conditions of solar cells based on IFO/$(pp^+)$Si heterostructures and to increase their efficiency from 17% to a record 17.8%.