Improvement of Cu2ZnSnS4 thin film properties by a modified sulfurization process

Abstract

In the solution-based preparation of CZTS (Cu2ZnSnS4) thin films followed by a sulfurization process, a layer of MoS2 is formed at the CZTS–Mo interface. Formation of this MoS2 layer is mainly governed by the sulfurization process in H2S ambient gas rather than diffusion of a sulfur source in the CZTS film. Growth of CZTS grain and grain boundaries facilitates the formation of a MoS2 layer in any sulfurization process. A decrease in the series resistance and an increase in the current density and solar cell efficiency were achieved through an increase in the temperature of the second sulfurization sequence in a two-step sulfurization sequence. The formation of a CZTS grain dominates the performance of CZTS thin film solar cells with a relatively thin MoS2 layer, but the performance is degraded by an increase in recombination rate and the hole barrier effect between CZTS and Mo when the MoS2 is sufficiently thick.