Optimizing indium concentration in ZnO thin films for enhanced optical, electronic, and thermoelectric applications

In this work, ZnO and In-doped ZnO (IZO) thin films with varying indium concentrations (1–5 at. %) on glass substrates via reactive radio frequency magnetron sputtering were studied. The effect of In concentration on various aspects such as crystal structures, surface morphology, compositional analysis, optical, electrical, and thermal properties has been investigated. We investigated an in-depth examination linking structural and chemical states to thermoelectric performance. X-ray photoelectron spectroscopy reveals that the In-doped ZnO samples show clear core level spectra for In 3d, Zn 2p, and O 1s regions, which confirm the existence and ionized state of indium, zinc, and oxygen. The Hall effect measurements indicate that the IZO thin films exhibited a carrier concentration of 1021 cm−3, with mobility values varying from 4.46 to 8.57 cm−2 V−1 s−1. The Seebeck coefficient is 199.1 μV K−1 for ZnO thin films, while it ranges between 30.1 and 62.2 μV K−1 for In-doped ZnO thin films. Additionally, the power factor for In-doped ZnO thin films reaches a maximum of 530.0 μW m−1 K−2. Our results demonstrate a synergistic balance among electrical conductivity, thermoelectric efficiency, and optical transparency at the optimum doping level of 2 at. %. These results are highly promising for applications in optical, electronic, and thermoelectric devices.