Synthesis and characterization of thermally evaporated copper bismuth sulphide thin films

Non-toxic copper containing chalcogenides are considered as promising alternate materials for the absorber layer in thin film solar cells and visible-light harvesting devices. In this paper, we reported synthesis of Cu3BiS3 thin films using a two-step thermal evaporation method for the first time. A Cu2S layer of 0.4 μm thickness was firstly evaporated onto glass substrate at room temperature, followed by evaporation of a Bi2S3 layer of 0.8 μm thickness. The Cu3BiS3 thin films were formed by thermally annealing and diffusing the two evaporated layers in a vacuum furnace. This method resulted in the improved crystallinity and phase purity of the grown Cu3BiS3 films. Effects of annealing temperature on different properties of the fabricated samples were investigated. The obtained low band-gap (1.45 eV) and good optical properties such as low transmittance (10-30%) and reflectance (~ 10%) of the Cu3BiS3 films demonstrated it as a suitable material for the absorber layer of solar cells.