Optical and electrical characterization of In2S3 buffer layer for photovoltaics applications

In2S3 thin films have been synthesized by annealing indium thin films under sulfur pressure. The indium thin films have been deposited by evaporation onto glass substrates. The sample is then introduced, with small grains of sulfur into a Pyrex tube. The latter is sealed under vacuum and then annealed for two hours at temperatures ranging from 280 ∘C to 400 ∘C in a step of 40 ∘C.This simple and economic technique allows the elaboration of In2S3 thin films crystallized in the β structure. Optical density (O.D.) measurements were made for In2S3 thin films synthesized at different temperatures. The optical spectra show that the threshold value of optical absorption is approximately 610 nm. By increasing the synthesis temperature this threshold value moved towards higher wavelength values. The gap is around 3 eV and the electrical resistivity measurements at room temperature, show that the films are highly resistive with an electric conductivity σ around 10−1 (Ωcm)−1.