Band structure and thermoelectric properties of inkjet printed ZnO and ZnFe2O4 thin films

The band structure and thermoelectric properties of inkjet printed ZnO and ZnFe2O4 thin films have been investigated. The bulk pellets were prepared by a solid-state method and thin films were deposited using an inkjet printing method. Multiple print cycles were required to fabricate homogeneous films and the composition of the thin films can be varied by varying the relative amounts of liquid deposited. It was possible to obtain high thermoelectric properties of ZnO by controlling the ratios of dopant added and the temperature of the heat treatments. XRD analysis showed that the fabricated samples have a wurtzite structure and an additional ZnAl2O4 phase was formed with increasing Al content and sintering temperature. It was found that the band gap of Al doped ZnO becomes smaller with increasing Al content and thus the electrical conductivity of Alx doped ZnO (x=0.04) thin films showed the highest electrical conductivity (114.10 S/cm). The ZnFe2O4 samples were compared against the ZnO samples. The formation of single phase cubic spinel structure of the sintered ZnFe2O4 samples was found and confirmed by X-ray diffraction technique. Secondary phase Fe2O3 was also detected for compositions with Zn (x≤0.4). Finally, we want to report that the electrical conductivity of ZnxFe3−xO4 was lower than the conductivity of the Al-doped ZnO.