Preparation And Characterization Of Fluorine-doped Tin Dioxide Conductive Thin Films Deposited By Spray Pyrolysis

Transparent conductive thin films of F:SnO2 (fluorine-doped tin dioxide,FTO) with high optical transmittance and low electrical resistivity are key elements for thin-film solar cells and display devices.FTO were deposited on preheated microscopic glass slides using pentahydrate stannic chloride(SnCl4·5H2O) and ammonium fluoride (NH4F) or 3-ethyl-1-methylimidazolium trifluoroacetate (EMITA) as sources for tin and fluorine, ethanol/isopropanol and water as solvents by an intermittent spray pyrolysis method.The FTO thin films were characterized by X-ray diffractometer, scanning electron microscope,ultraviolet-visible spectrometry and four-point-probe setup.The effects of spray times,substrate temperature,concentration of SnCl4, NH4F/EMITA,H2O2 and volume ratio of ethanol/isopropanol to water on the optical and electrical characteristics of FTO thin films were investigated.The results show that the sheet resistance and the average transmittance of the FTO thin films prepared with the solution with 0.81 mol/L SnCl4,0.1 mol/L NH4F, at a volume ratio of ethanol to water of 8:2 for 100 times at 500℃are 13Ω/□and 76%,respectively.The results show that the transmittance of the FTO thin films can be improved due to a moderate concentration of H2O2 (-0.05 mol/L) in the spraying solution, and the sheet resistance is unchanged. The sheet resistance and the average transmittance of the FTO thin films prepared with the solution with 0.8 mol/L SnCl4,0.1 mol/L NH4F and 0.05 mol/L of H2O2,at a volume ratio of isopropanol to water of 8:2 for 100 times at 500℃are 15Ω/□and 84%, respectively. The FTO thin film has uniform grain size and a compact morphology.The results show that the sheet resistance and the average transmittance of the FTO thin films prepared with the solution with 0.4 mol/L SnCl4,0.3 mol/L EMITA, at a volume ratio of ethanol to water of 8:2 for 100 times at 500℃are 173Ω/□and 73%,respectively.