Study of multilayer ZnO/Al doped ZnO nanostructured thin films

Single layer (ZnO, ZnS and Al doped ZnO film), double layer (ZnO/Al doped ZnO film) and triple layer films (ZnO/Al doped ZnO/ZnO and ZnO/Al doped ZnO/ZnS film) were deposited on sodalime glass substrate by electroless process. Wet deposited thin films were dried in air and subsequently annealed in a muffle furnace in air atmosphere at 500 degrees C for 2 h. Significant characteristics of the thin films, such as crystallinity, surface roughness, as well as the optical properties in a large spectral range between 300 and 800 nm were analysed. Average grain size of the films was found 40-90 nm. The obtained sample of triple layer film of ZnO/Al doped ZnO/ZnS exhibits best, optimum optical characteristics, i.e. intermediate range of absorbance of spectra, lowest value of photoluminescence intensity, and has minimum recombination of electron-hole pairs. Triple layer film of ZnO/Al doped ZnO/ZnS is suitable in place of CdS/Al doped ZnO multilayer film as a transparent substrate in dye-sensitised solar cell.