The effect of dopant concentration on properties of transparent conducting Al-doped ZnO thin films for efficient Cu2ZnSnS4 thin-film solar cells prepared by electrodeposition method

摘要

Al-doped ZnO (AZO) thin films were potentiostatically deposited on indium tin oxide substrates. The influence of the doping level of the ZnO:Al films was investigated. The results of the X-ray diffraction and scanning electron microscopy analysis revealed that the structural properties of the AZO films were found polycrystalline with a hexagonal wurtzite-type structure along the (002) plane. The grain size of the AZO films was observed as approximately 3?μm in the film doping with 4?mol% ZnO:Al concentration. The thin films also exhibited an optical transmittance as high as 90?% in the wavelength range of 100–1,000?nm. The optical band gap increased from 3.33 to 3.45?eV. Based on the Hall studies, the lowest resistivity (4.78?×?10?3?Ω?cm) was observed in the film doping with 3?mol% ZnO:Al concentration. The sheet resistant, carrier concentration and Hall mobility values were found as 10.78?Ω/ square, 9.03?×?1018?cm?3 and 22.01?cm2/v?s, respectively, which showed improvements in the properties of AZO thin films. The ZnO:Al thin films were used as a buffer layer in thin-film solar cells with the structure of soda-lime glass/Mo/Cu₂ZnSnS₄/ZnS/ZnO/Al grid. The best solar cell efficiency was 2.3?% with V _OC of 0.430?V, J _SC of 8.24?mA?cm?2 and FF of 68.1?%