ANNEALING EFFECT ON THE STRUCTURAL, MORPHOLOGICAL, AND PHOTOVOLTAIC PROPERTIES OF ZNO-CNTS NANOCOMPOSITE THIN FILMS

摘要

ZnO-CNTs thin films were prepared by chemical bath deposition (CBD) method. X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM) and electrochemical impedance spectroscopy (EIS) were employed to analyze the influence of annealing temperature effects on the morphological, structural and photovoltaic properties of the ZnO-CNTs thin films. XRD measurement indicated that the crystallite size of ZnO-CNTs hexagonal wurtzite structure varies from 18 nm to 34 nm. FESEM image shows porous structures of ZnO-CNTs thin film annealed at 250, 300 and 350 °C. The CNTs like fibre appeared in the porous structure of the thin film annealed at 250 °C. Photovoltaic performances measured the power conversion efficiency, η, photocurrent density, J_(sc), open-circuit voltage, V_(oc) and fill factor, FF of the ZnO-CNTs photoanodes. The highest power conversion efficiency of 1.07 % was achieved for the photoanode annealed at 350 °C. The electron transport parameters such as electron lifetime, τ_(eff), electron recombination lifetime, κ_(eff), effective electron diffusion coefficient, D_(eff), effective electron diffusion length, L_n series resistance, R_s, charge transport resistance, R_(ct) and transport resistance, R_t of the ZnO-CNTs photoanode were analyzed accordingly. The annealing temperature of 350 °C can be proposed as a suitable heat treatment effect to obtain a good structural, morphological and photovoltaic properties although with a bad electron transport properties.