Optimized fabrication of sputter deposited Cu2ZnSnS4 (CZTS) thin films

Abstract

An effective synthesis strategy is employed to fabricate Cu2ZnSnS4 (CZTS) thin films using radio frequency (rf) magnetron sputtering technique on soda lime glass substrates. The as-grown films are annealed at different temperatures ranging between 350 and 550 degrees C, and their chemical compositions and structural properties are investigated. The as-grown films have poor Cu/(Zn + Sn) ratios ranging between 0.39 and 0.44 and S/(Cu + Zn + Sn) ratios ranging between 0.97 and 1.21. The Cu/(Zn + Sn) ratio is improved by growing a thin additional Cu-capping layer on the as-grown film followed by annealing. An improved Cu/(Zn + Sn) ratio of similar to 0.71 is obtained and the S/(Cu + Zn + Sn) ratio is slightly reduced to similar to 0.85. The formation of a kesterite type CZTS is confirmed using X-ray diffraction and Raman spectroscopy measurements. Absorption measurements and band-gap energy determination of the CZTS films are carried out in order to confirm applicability to solar cells. (C) 2013 Elsevier Ltd. All rights reserved.