Metallurgical mechanism and optical properties of CuSnZnSSe powders using a 2-step sintering process

Abstract

Cu2SnZn(S + Se)4 is an excellent absorber material for solar cells. This study obtained Cu2SnZn(S + Se)4 powders through solid state reaction by the ball milling and sintering processes from elemental Cu, Zn, Sn, S, and Se without using either polluting chemicals or expensive vacuum facilities. Ratios of S/S + Se in CuSnZnSSe were controlled from 0 to 1. The results showed that the 2-step sintering process (400°C for 12 hrs and then 700°C for 1 hr) was able to stabilize the composition and structure of the CuSnZnSSe powders. The crystallized intensity of the CuSnZnS matrix decreased with increasing the Se content. Raising the Se content restrained the SnS phase and reduced the resistance of the absorber layer. In addition, Raman data confirmed that Se caused a Raman shift in the CuSnZnSSe matrix and enhanced the optical properties of the CuSnZnSSe powders. For the interface of CuSnZnSSe film and Mo substrate, Mo could diffuse into CuSnZnSSe matrix after 200°C annealing. The interface thermal diffusion of CuSnZnSSe/ZnS improved the effects of stack to enhance the stability of structure. © 2014 Tai-Hsiang Liu et al.