Structural and Optical Properties Investigation of Sn doped ZnTe Thin Film

Neha Pandey; Brijesh Kumar; D. K. Dwivedi

Abstract

To increase the efficiency of a single-junction solar cell the Intermediate Band Solar Cell (IBSC) is proposed, where, IBSC designed to provide extra optical transitions that enable sub-band gap energy photons to participate in current generation through pumping of electrons from the valence band (VB) to the Intermediate Band (IB) and further from the IB to the conduction band (CB) hence it provide high conversion efficiency. Thin film of undoped and Sn (Tin) -doped ZnTe (Zinc-Telluride) is fabricated on glass substrate made of glass by using thermal evaporation technique under vacuum. Subsequently, thin film characterization is performed through XRD measurement, SEM and EDAX analysis along with UV-Vis NIR spectrophotometer. From XRD measurement, it is observed that nature of the film changes from polycrystalline to amorphous after addition of Sn dopants in ZnTe thin film. The EDAX analysis confirms the existence of elements Sn, Zn and Te in both samples. The absorption spectrum of the films obtained by UV-Vis NIR spectrophotometer, used to determine optical constants such as absorption coefficient (α), optical band gap (Eg) and extinction coefficient (k) in wavelength range of 400-1000nm. Besides this, Band gap of Sn doped ZnTe thin film is found to be decreased due to the formation of intermediate band in band gap of ZnTe host material that significantly improves the efficiency of solar cell.

Abstract

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