Physical Properties of Silver Doped ZnSe Thin Films for Photovoltaic Applications

Closed space sublimation (CSS) technique was used to deposit pure (99.99%) zinc selenide(ZnSe) powder on to glass substrates for fabricating the ZnSe thin films. The temperatures of source, substrate and the deposition time were optimized to deposit thin films of different thicknesses. Silver (Ag) was used as a dopant by ion exchange process in the ZnSe thin films. The structural analysis showed that as-deposited ZnSe thin films were polycrystalline having preferred orientation [111] direction. Micro structural parameters such as crystallite size, lattice parameter were determined using X-rays diffraction (XRD). Grains boundaries, roughness on surface and the grain density of the thin film samples were measured by scanning electron and atomic force microscopy before and after Ag doping.As-deposited, Ag-doped ZnSe samples before and after annealing were optically characterized by spectrophotometer in ultra violet, visible and infrared regions. The energy band gap of as-deposited ZnSe thin films for varying thicknesses were ranging from 2.62-2.67 eV which was reduced after Ag doping.The electrical properties showed that as-deposited thin films were highly resistive of the order of 10 -cm and after Ag immersion, it was reduced to 1 -cm. Deposition parameters and Ag doping 8 influenced the structural, surface, optical and electrical properties.