Optoelectronic Properties of ZnO:TiO2 Nanocomposite Thin Films

Abstract

Solutions containing ZnO:TiO₂ composite nanoparticles were produced in 1:5 and 1:2 molar rates using sol gel method. ZnO doped TiO₂ solutions were drop cast and spin coated on Si wafer and thin films were obtained. Optical characteristics of the composite thin film structures were characterized using visible UV spectra. Energy bandgap of photodiodes were calculated as 3.32 eV, 3.19 eV and 3.16 eV for undoped TiO₂, 1:5 ZnO doped TiO₂ and 1:2 ZnO doped TiO₂ composites, respectively. Enhanced ZnO doping reduced the band gap energy of TiO₂ photodiodes. Photoresponsive characteristics of the diodes revealed that thin films show photoresponsive characteristics that increased illumination intensities increased the measured diode photocurrent. Barrier height of the undoped TiO₂, 1:5 ZnO doped TiO₂ and 1:2 ZnO doped TiO₂ diodes were found to be 0.478 eV, 0.470 eV and 0.493 eV while ideality factors of the diodes were calculated as 6.04, 5.92 and 6.58, respectively.