Bi-Doped SnO2 Transparent Conducting Thin Films Deposited By Spray Pyrolysis: Structural, Electrical, Optical And Photo-Thermoelectric Properties

Abstract

In this research, light and heavy Bi-doped SnO2 thin films were prepared on glass substrates by spray pyrolysis technique. The effect of heavy doped-Bi on the structural, morphological, electrical, photo-thermo-electrical, optical properties of SnO2 films has been investigated. The Bi/Sn atomic ratios (x = [Bi/Sn]) were varied from 0 to 0.30 in the spray solution. X-ray diffraction analysis showed the formation of SnO2 tetragonal rutile structure in low doped deposited films and amorphous structure for heavy Bi-doped SnO2. Also, the SnO2-Bi2O3 binary thin films were formed for x= [Bi/Sn] =0.05. Scanning electron microscopy (SEM) images indicated that nanostructure of the condensed films has a rectangular-particle growth toward particle- spherical growth. The Hall effect measurements have shown n-type conductivity in all deposited films. The lowest sheet resistance of 39.3 MΩ/□ and highest carrier concentration of n=4.53 × 1018 cm−3 were obtained for the thin film deposited with x = 0.10. The maximum of the Seebeck coefficient (S)=325 μVK−1 and figure of merit (ZT) = 1.85 was obtained for the thin film deposited with x = 0.20. The average transmittance of films varied over the range of T=72%-84%. The band gap values of samples were obtained in the range of Eg=3.52–3.88 eV for direct band gap. From the photoconductivity studies, the sample prepared with x = 0.20 exhibited the highest photoconductivity among the SnO2: Bi thin films.