IN2S3:Ag, an ideal buffer layer for thin film solar cells

Silver diffusion enhanced the properties of Indium sulfide (In2S3) films making it highly suitable buffer layer for photovoltaic applications. Thin layer of silver deposited over In2S3 films diffused into In2S3 films in ‘as-deposited’ condition itself creating doping effect. A significant enhancement in crystallinity and grain size could be obtained up to an optimum percentage of doping concentration. This optimum value showed dependence on thickness and atomic ratio of indium and sulfur in the film. Band gap decreased up to the optimum value of doping and thereafter it increased. Electrical studies showed a decrease in resistivity due to doping. Sample having the optimum doping was found to be more photosensitive and low resistive when compared with the pristine sample. These results proved that silver diffused indium sulfide surpasses pristine sample for crystallinity and photosensitivity. Doping β-In2S3 film with optimum amount of silver modified the structural and electrical properties of the films favorably so that the Ag electrodes given to the ITO/CuInS2/In2S3 cell structure itself acted as a doping agent for the In2S3 layer, enhancing the cell efficiency to 9.5% (John et al. Sol Energy Mater Sol Cells 89:27, 2005).