Effect of copper ratio and sulfurization process on optical, structural and electrical properties of ultrasonic spray pyrolysed CZTS thin films

Kermadi, S., Ait Ameur, F., Sali, S., Zougar, L., Bahfir, A., Boumaour, M., Toumiat, A., Melnik, N.N., Hewak, D.W. and Anca, D. (2015) Effect of copper ratio and sulfurization process on optical, structural and electrical properties of ultrasonic spray pyrolysed CZTS thin films. 29th European Photovoltaic Energy Conference and Exhibition (EU PVSEC), Amsterdam, Netherlands. 13 - 17 Sep 2015.

Abstract

Ultrasonic spray pyrolysed CuxZnSnS4 (CZTS) thin films with different copper ratios (x = 1.6, 2, 2.4 and 2.8) were successfully deposited on microscopic glass substrates from an aqueous solution of CuCl2 2H2O, ZnCl2, SnCl2 and thiourea. The deposited films at substrate temperature of 310 °C were heat treated up to 500 °C under N2 gas flows with and without sulfurization process (under sulfur vapor flow ). The effect of the both copper ratio and sintering atmosphere on structure, morphology, optical and electrical properties was studied by Raman scattering, AFM observations, ultraviolet-visible absorbance spectroscopy and Four Point Probe. Results showed that after sulfurization, the crystallization of samples with x=2 and 2.8 in CZTS kesterite structure is improved while the Cu- enriched film featuring larger grains in the range of 100 nm in size. The optical band gap ranges from 1.4 to 2 eV while the film with the stoichiometric composition (x=2) showed the lowest value. The sheet resistance drops significantly in all sulfurized samples and the lowest value of 131 Ohms was reached with the stoichiometric composition (x=2).

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Contributors

Author: D.W. Hewak

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