Silver indium sulfide (AgInS2) thin films have been prepared by the spray pyrolysis technique using silver acetate, indium acetate and N-N dimethyl thiourea as precursor compounds. Depending on the film preparation conditions AgInS2 thin films are obtained, which are candidates to be used in photovoltaic devices. The films formed at different substrate temperatures (Ts) and Ag:In:S ratios in the starting solution have been electrically and optically characterized. Changes in the Ag:In:S ratio and Ts affect the optical as well as the electrical properties.
In all cases, it was found that the electrical conductivity measured in the dark (σD) increases and the optical band gap decreases as Ts increases. For a ratio Ag:In:S=1:1:1, σD varies from 10-6 to 1 (Ωcm)-1, and the optical band gap (Eg) decreases from 1.73 to 1.67, when Ts increases from 250 to 450° C. If the ratio Ag:In:S=1:0.25:2, σD changes from 10-5 to 10-2 (Ωcm)-1, and Eg decreases from 1.85 to 1.66 eV, when Ts increases from 300 to 450° C. In thin films formed with a ratio Ag:In:S=1:1:2 in the starting solution, σD goes from 10-5 to 1 (Ωcm)-1, and Eg changes from 1.85 to1.69 eV, when Ts increases from 300 to 450° C. In any case it was observed an n-type electrical conductivity behavior. |