24September2017

Materials and Electronics Engineering

Property dependence of CuxZnSnS4 thin films on the Cu composition ratio deposited by a sol–gel method

Kailiang Fua, Ping Liub, Chao Liua, Fang Yanga, Yongsheng Chena,*, Jingxiao Lua, Shi-e Yanga

Abstract
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aKey Lab of Material Physics, Department of Physics, Zhengzhou University, Zhengzhou 450052, PR China
bSchool of Electric and Information Engineering, Zhongyuan University of Technology, Zhengzhou 450007, PR China

Materials and Electronics Engineering 2014,1:7

Publication Date (Web): December 18, 2014 (Article)

DOI:10.11605/mee-1-7

*Corresponding author. E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

 

Abstract 


Figure 8 Optical absorption coefficient at Cu/(Zn+Sn)=0.8 (a) and plots of (αhν)2 at different Cu/(Zn+Sn) ratios (b) versus the incident photon energy.

      We report the relation between secondary-phase formation and Cu composition ratio in a precursor solution for Cu2ZnSnS4 (CZTS) thin films. The films were prepared by a sol–gel method from the methanolic solution of a metal–thiourea complex, followed by annealing processes with elemental sulfur under protective N2 gas. With decreased Cu/(Zn+Sn) in solution, the secondary phase transformed from Cu2SnS3 (CTS) to Sn2S and ZnS, resulting in decreased conductivity and irregularly varied optical bandgap. This phenomenon indicated that decreasing the Cu composition ratio contributed to the elimination of the formation of CTS and Sn2S phases to obtain Zn-rich film. The optimum kesterite structure of CZTS film was synthesized at Cu/(Zn+Sn) = 0.80 and Zn/Sn = 1.2, with the conductivity of 0.02 S/cm and the bandgap of 1.47 eV.


 

Keywords

Cu2ZnSnS4 thin films; Sol–gel method; Kesterite