Investigation of Optical, Structural, Morphological and Electrical Properties of Electrodeposited Cobalt Doped Copper Selenide (Cu_(1-x) Co_x Se) Thin Films

Abstract

Undoped and cobalt doped copper selenide thin films have been successfully prepared unto fluorine tin oxide (FTO) substrates by electrodeposition method using copper acetate, cobalt nitrate and selenium (IV) oxide as precursors for copper, cobalt and selenium ions respectively. Deposited thin films were subjected to optical, structural, morphological, compositional and electrical analysis using spectrophotometer, x-ray diffractometer, scanning electron microscope (SEM), energy dispersive x-ray spectroscopy (EDS) and 4-point probe. Optical results observed between the wavelength range of 300 nm and 1,000 nm showed that the films have good optical responses. Absorbance values ranged between 0.1 and 0.81 while transmittance lies between 15.59 and 78.68 %. Energy band gap of the films was found to vary from 2.10 to 2.28 eV. These results showed that cobalt as a dopant could be used to modify properties of copper selenide thin films. Structural analysis showed that the deposited films are polycrystalline in nature with hexagonal structural phase. Crystallite sizes of range 27.56 to 34.27 nm were obtained while dislocation density lied between and . Microstrain ranged between and . Micrograph images showed flake-like particles that increased in size as percentage of cobalt increased. Energy dispersive spectroscope (EDS) results confirmed the incorporation of cobalt on the deposited copper selenide films. Electrical resistivity of the films increased from to while conductivity decreased from to as a result of variation in cobalt ion concentration. These properties of the deposited thin films positioned them for solar cell and optoelectronics device applications.
 HIGHLIGHTS
 
 Energy band gap of electrosynthesized cobalt doped copper selenide ranged from 2.10 to 2.28 eV
 Film thickness values ranged from 48.41 and 176.79 nm. Thickness values of the films were found to increase as concentration of cobalt increase
 Increase in dopant concentration resulted to shift in diffraction peaks towards larger angles
 Increase in crystallite size from 27.56 - 34.27 nm was observed as dopant concentration increases
 SEM images of the films revealed flake - like particles of different sizes
 
 GRAPHICAL ABSTRACT