Effects of Fe concentration on properties of ZnO nanostructures and their application to photocurrent generation

Abstract

Fe-doped zinc oxide nanorods were electrochemically deposited at low temperature on ITO substrates. The synthesized ZnO arrayed layers were investigated by using X-ray diffraction, scanning electron microscopy, UV–vis transmittance, electrochemical impedance spectroscopy and photocurrent spectroscopy. X-ray diffraction analysis demonstrated that the electrodeposited films are crystalline and present the hexagonal Würtzite ZnO phase with preferential (002) orientation. The resulting ZnO films present different structural form from aligned hexagonal nanorods in the absence of Fe dopand to vertical aligned nanoflakes arrays in the presence of high Fe concentration. The addition of Fe dopand up to 4 at. %, induces variations of the optical band gap from 3.26 to 3.28 eV, the blue shift in the band gap energy being attributed to the Burstein-Moss effect. It was found that the carrier density of Fe-doped ZnO thin films varied between 2.81 × 1018 to 4.29 × 1018 cm−3 when the Fe concentration was increased between 0 and 2 at. %. The presence of Fe doping in the thin films also influenced the photovoltaic properties of the materials as shown by the photocurrent response and the electronic disorder.