High transparency and conductivity of heavily In-doped ZnO thin films deposited by dip-coating method

Heavily In doped zinc oxide (IZO) thin films were deposited on glass substrates by dip-coating method with different concentrations of indium. The effect of heavy In doping on the structural, morphological, optical and electrical properties of ZnO was discussed on the basis of XRD, AFM, UV-Vis spectra and Hall effect measurements. The diffraction patterns of all deposited films were indexed to the ZnO wurtzite structure. However, high In doping damaged the films crystallinity. The highest optical transmittance observed in the visible region (>93 %) exceeded that of ITO: the absolute rival of the most commercial TCOs. The grain size significantly decreased from 140 nm for undoped ZnO to 17.1 nm for IZO with the greatest In ratio. The roughness decreased with increasing In atomic ratio, indicating an improvement in the surface quality. Among all synthesized films, the sample obtained with 11 at.% indium showed the best TCO properties: the highest transmittance (93.5 %) and the lowest resistivity (0.41 Ωcm) with a carrier concentration of 2.4 × 10¹⁷ cm⁻³. These results could be a promising solution for possible photonic and optoelectronic applications.