Chemical bath deposition of SnS thin films on ZnS and CdS substrates

Journal of Materials Science: Materials in Electronics,  2014, Volume 25, Issue 7, pp 3160-3165.

Safonova, P. K. Nair, E. Mellikov, A. R. Garcia, K. Kerm, N. Revathi, T. Romann, V. Mikli, O. Volobujeva.

1. Department of Materials Science, Tallinn Technical University, Ehitajate tee 5, 19086, Tallinn, Estonia and

2. Department of Solar Energy Materials, Instituto de Investigación en Energía, Universidad Nacional Autónoma de México, 62580, Temixco, Morelos, Mexico and

3. Institute of Chemistry, University of Tartu, Ülikooli 18, 50090, Tartu, Estonia.

 

Abstract

 We illustrate that Tin sulfide (SnS) thin films of 110–500 nm in thickness may be deposited on ZnS and CdS substrates to simulate the requirement in developing window-buffer/SnS solar cells in the superstrate configuration. In the chemical bath deposition reported here, tin chloride and thiosulfate are the major constituents and the deposition is made at 25 °C. In a single deposition, film thickness of 110–170 nm is achieved and in two more successive depositions, the film thickness is 450–500 nm. The thicker films are composed of vertically stacked flakes, 100 nm across and 10–20 nm in thickness. The Sn/S elemental ratio is ~1 for the films 110–170 nm in thickness, but it slightly increases for thicker films. The crystalline structure is orthorhombic, similar to the mineral herzenbergite, and with crystallite diameters 13 nm (110–170 films) and 16 nm (450–500 nm films). The Raman bands at 94, 172 and 218 cm⁻¹ further confirm the SnS composition of the films. The optical band gap of SnS is 1.4–1.5 eV for the thinner films, but is 1.28–1.39 eV for the thicker films, the decrease being ascribed to the increase in the crystallite diameter. Uniform pin-hole free SnS thin films were successfully grown on two different substrates and can be applied in solar cell structures.

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