Improvement in the electronic quality of pulsed laser deposited CuIn_0.7Ga_0.3Se₂ thin films via post-deposition elemental sulfur annealing process

We synthesized CuIn_0.7Ga_0.3Se₂ thin films on soda lime glass substrates using pulsed laser deposition and post-annealing under different conditions. Increasing substrate temperature during deposition and vacuum annealing after deposition both increased grain size but had negligible effect on the electronic properties of the films. As-deposited films demonstrated P-type conductivities with high carrier concentrations and low Hall mobilities, but annealing in elemental sulfur environment significantly improved the electronic properties of the films. We found that the incorporation of even small quantities of sulfur into the films reduced carrier concentrations by over three orders of magnitude and increased Hall mobilities by an order of magnitude. This resulted in films with resistivity ∼ 5 Ω·cm suitable for photovoltaic applications.