Dependence of Photovoltaic Properties of Spray-Pyrolyzed F-Doped SnO2 Thin Film on Spray Solution Preparation Method

Abstract

Spray pyrolysis deposition of SnCl2.2H2O- and NH4F-containing solution is an appropriate method for deposition of fluorine-doped tin oxide (FTO), which has extensive applications in photovoltaic devices. According to a literature review, several spray preparation methods have been studied. These methods lead to both precipitated and unprecipitated spray solutions. Precipitated and unprecipitated solutions were used for deposition of FTO thin films. FTO obtained from unprecipitated solution yielded the lowest sheet resistance and resistivity, which was due to its highest electron concentration (ne). However, precipitation had no influence on electron mobility. The x-ray diffraction patterns of precipitates showed the presence of Sn- and F-containing compounds, which implied partial depletion of F and Sn from solutions. As a result, a lower amount of F− ions was incorporated into FTO, which led to lower ne. In addition, partial depletion of Sn led to slightly smaller FTO thickness. Finally, FTO thin film deposited from unprecipitated solution gave the highest figure of merit. This means that precipitation in the precursor solution has deleterious effects on electrical and optical properties.