Morphology and structure controlled fabrication of Cu2ZnSnS4 thin films by convective assembly deposition

Abstract

Thin films of Cu2ZnSnS4 (CZTS) were prepared from colloidal solution and deposited by convective assembly deposition technique. This technique is capable to control the organization of thin layer on a substrate as a result of the evaporation-driven flow or the viscous-driven flow of colloids towards the edge of meniscus when the solution is dragged across the substrate. Then, capillary-driven forces bring particles into contact with each other and the substrate. In this approach, a variety of morphologies and structures of CZTS thin films could be obtained depending mainly on the controlled deposition conditions. This work aimed to incorporate the simple yet efficient technique with detailed investigation of effects of operating parameters, including velocity of the substrate (500–1250 µm/s), annealing temperature (340–550 °C) and substrate type (glass slide and molybdenum-coated soda lime glass, Mo-coated SLG), on the properties of resulting CZTS thin films. Different morphologies of CZTS films were derived due to the effect of velocity. Furthermore, higher velocity resulted in thicker films, implying that the mechanism of convective flow in the meniscus of colloidal solution and the subsequent film formation was predominantly driven by the viscous drag. Annealing temperature strongly influenced grain growth, composition variation and enhancement of crystallinity. A unique porous structure of CZTS thin film could be obtained by deposition at a controlled velocity using Mo-coated SLG as a substrate. The key advantage of this work is the control of morphology and structure of CZTS films for various desired applications including solar cells and photoelectrochemical devices.