Optical and electrical characterization of AgInS2 thin films deposited by spray pyrolysis

Silver indium sulfide (AgInS2) thin films have been prepared by spray pyrolysis (SP) technique using silver acetate, indium acetate, and N, N-dimethylthiourea as precursor compounds. Films were deposited onto glass substrates at different substrate temperatures (Ts) and Ag:In:S ratios in the starting solutions. Optical transmission and reflection as well as electrical measurements were performed in order to study the effect of deposition parameters on the optical and electrical properties of AgInS2 thin films. X-ray diffraction measurements were used to identify the deposited compounds. It was found that different compounds such as AgInS2, Ag2S, In2O3, and In2S3 can be grown only by changing the Ag:In:S ratio in the starting solution and Ts. So that, by carefully selecting the deposition parameters, single phase AgInS2 thin films can be easily grown. Thin films obtained using a molar ratio of Ag:In:S = 1:1:2 and Ts = 400 °C, have an optical band gap of 1.9 eV and n-type electrical conductivity with a value of 0.3 Ω−1 cm−1 in the dark.