Investigations on structural, optical and thermoelectric parameters of spray deposited bismuth selenide thin films with different substrate temperature

• Influence of substrate temperature on the deposition of Bi2Se3 has been shown.
• Bi2Se3 SEM microstructure strongly depends upon the change in substrate temperature.
• Seebeck measurements at 300 °C–500 °C confirms n-type conductivity.
• Improved Seebeck coefficient has been observed at high temperature deposited film.

A series of Bi2Se3 films was deposited at different substrate temperature in 150–500 °C temperature range using spray pyrolysis technique, in order to study the effect of substrate temperature on structural and thermoelectric properties. The crystallinity of the as-synthesized sample has been analyzed by X-ray diffraction, which shows the formation of hexagonal Bi2Se3. Scanning electron microscopy examination indicates that the Bi2Se3 microstructure strongly depends upon the change in substrate temperature. The optical absorption study shows that the direct band gap of the film decreases with increase in substrate temperature. The thermoelectrical measurements have shown n-type conductivity in as deposited films and the magnitude of Seebeck coefficient for films has been found to be increasing with increasing deposition temperature. Improved thermoelectric properties at higher substrate temperature shows promising aspect and Bi2Se3 films could be a good thermoelectric material at lower temperature range.