Two-stage growth of Cu3BiS3 thin films: Influence of the Cu/Bi ratio

Thin films composed of Cu3BiS3 have shown significant promise as light-harvesting materials because of their suitable optoelectronic properties and abundant, non toxic constituent elements. A large-grained, highly crystalline Cu3BiS3 films is a prerequisite for application of these layers in solar cells. We have grown large-grained, highly crystalline Cu3BiS3 films by a two-stage process via thermally evaporating Cu/Bi/Cu metallic layers and sulfurization at 400 & DEG;C for 30 min. The influence of the Cu/Bi ratio on the growth of Cu3BiS3 thin films was investigated by varying the Bi precursor thickness. The Cu/Bi ratio significantly influenced the structural, microstructural, optical, and electrical properties of Cu3BiS3 thin films. The Cu3BiS3 film synthesized with a Cu/Bi ratio of 4.35 contained Cu1.8S spurious phase, a non-uniform grain morphology, a direct optical bandgap of 1.41 eV, and an electrical resistivity of 75.5 Ucm. Upon decreasing the Cu/Bi ratio from 3.38 to 2.77, the Cu1.8S spurious phase was eliminated, and phase-pure Cu3BiS3 was crystallized with a uniform grain morphology, particle size of 2-4 mm, direct bandgap of 1.42 eV, and electrical resistivity of 53.5 Ucm. A further decrease in the Cu/Bi ratio from 2.77 to 2.54 resulted in a slight decrease in the grain size and electrical resistivity of the Cu3BiS3 films. This study demonstrates that Cu3BiS3 films synthesized with near-stoichiometric composition possess better structural, microstructural, optical, and electrical properties than those synthesized with Cu-rich composition and are suitable for use as solar cell absorber layer.& COPY; 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

In this study, Cu3BiS3 thin films with different properties were synthesized by controlling the Cu/Bi ratio, and it was found that films with near-stoichiometric composition exhibited better performance and were suitable for use as absorber layers in solar cells.