Surface etching of CZTS absorber layer by Br-related solution.

Cu₂ZnSnS₄ (CZTS) material has many advantages for high-efficiency thin-film solar cell absorber layer. A detailed study of the surface of the CZTS and the hetero-interface of the CZTS/buffer layer is important to improve the conversion efficiency of CZTS thin film solar cells. We investigated the surface condition of the CZTS films by carrying out the surface treatment using bromine solution. The activation energy of the etching using bromine solution was estimated from the slope of the line fitting the graph of the temperature dependence of the etching rate. The activation energy is about 0.35 eV. This value suggests that etching mechanism of CZTS using bromine solution is diffusion-limited process. There were no significant changes in the structural characteristics after surface treatment by X-ray diffraction and Raman spectroscopy. From the results of X-ray photoelectron spectroscopy measurements, a relative surface composition was shifted to Cu- and Zn-rich phase after surface treatment. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]