The effect of solvents on the growth and key properties of tin oxide thin films deposited via chemical spray pyrolysis

The influence of solvents on various properties of SnO2 thin films deposited by spray pyrolysis technique is reported in this work. Six different solvents viz. isopropanol, 1-propanol, ethanol, methanol, water and H2O2 were used for making the precursor solution for spraying. The impact of these solvents on the crystal structure, surface morphology, optical and electrical properties of the prepared thin films is investigated using XRD, FESEM, PL, UV-Vis spectra and Hall measurement analysis. X-ray diffraction analysis revealed that samples prepared with alcoholic solvents are more crystalline compared to the samples prepared with water or H2O2 precursor solvents. Samples prepared with alcoholic solvents produced nanostructured thin films while mat-like morphology was observed for films prepared with water and H2O2 precursor solvents. Thin film samples prepared with alcoholic solvents exhibited good optical transmittance (>75%) in the visible region compared to the samples deposited using water or H2O2 solvents. Photoluminescence measurements revealed enhanced UV and violet emissions in the samples prepared with alcoholic solvents, while the emissions were very weak in the samples deposited using water or H2O2 solvents. The effect of precursor solvents on thickness, band gap, carrier concentration, mobility, resistivity and figure of merit of the samples are also explored. Based on the results obtained we recommend methanol as a precursor solvent followed by ethanol for preparing SnO2 thin films for TCO applications and isopropanol, 1-propanol or ethanol for depositing nanostructured SnO2 thin films.