Effect of Morphology of Solution-Processed Precursor Films on Cu2ZnSnS4 Thin Film Solar Cells

Abstract

Solution-processed Cu2ZnSnS4 (CZTS) thin films are generally fabricated by sulfurization of CZTS precursor films. Therefore, the sulfurized CZTS thin films are closely affected by the thin film properties of the CZTS precursor films. In this work, we have investigated the correlation between the thin film properties of the CZTS precursor films prepared using a spin coating process and the morphology and photovoltaic properties of the sulfurized CZTS films. The morphology and thickness of spin-coated CZTS precursor films are controlled by a stepwise pre-annealing treatment, and are then varied according to the difference between the decomposition temperature of each component of the CZTS precursor solution and the temperature of the stepwise pre-annealing treatment. This can be attributed to the different removal behaviors of the components of the CZST precursor solution during the stepwise pre-annealing treatment. The morphology and thickness of the CZTS precursor films are closely related to the final properties of CZTS thin films after the sulfurization process. We also investigated the photovoltaic properties of the CZTS solar cells prepared from the CZTS precursor films with different thicknesses and morphologies. In this case, the size and density of CZTS grains are decisive factors for determining the photovoltaic properties of CZTS solar cells.