Thermal Annealing Influence over Optical Properties of Thermally Evaporated SnS/CdS Bilayer Thin Films

Subject Areas : Journal of Optoelectronical Nanostructures

Zahra Dehghani Tafti ¹ , Mahmood Borhani Zarandi ² , Hojjat Amrollahi Bioki ³

1 - Department of Physics, Faculty of Basic Sciences, Payame Noor University, Tehran, Iran
2 - Atomic and Molecular Group, Faculty of Physics, Yazd University, Yazd, Iran
3 - Department of Physics, Tarbiat Modares University, Tehran, Iran

Received: 2018-10-13 Accepted : 2019-04-21 Published : 2019-01-01

Keywords: CdS, Thin Film, Optical Properties, SnS, Thermal Annealing, Vacuum Evaporation,

Abstract :

Thin films of tin sulfide/cadmium sulfide (SnS/CdS) were prepared by
thermal evaporation method at room temperature on a glass substrate and then annealed
at different temperature with the aim of optimizing the optical properties of the material
for use in photovoltaic solar cell devices. The effect of annealing on optical properties
of SnS/CdS film was studied in the temperature range of 100 to 400 °C with steps of
100 °C. The films were characterized by optical absorption spectra. The optical
constants such as band gap, refractive index (n) and extinction coefficient (k) were
calculated on different annealing temperature and in the wavelength range of 250 nm to
750 nm. Analysis of the optical absorption coefficient demonstrated the presence of
direct optical transition and the corresponding band gap values showed enhancement as
deposition annealing temperature increased. The energy band gap in the range 2.20 eV –
3.18 eV has been obtained for a film as-deposited which increases clearly with
increasing annealing temperature. The refractive index and extinction coefficient both
decrease notably with increasing annealing temperature.

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