Nanocrystalline CuO thin films: synthesis, microstructural and optoelectronic properties

Abstract

Nanocrystalline copper oxide (CuO) thin films have been synthesized by a sol-gel method using cupric acetate Cu (CH 3 COO) as a precursor. The as prepared powder was sintered at various temperatures in the range of (300-700°C) and has been deposited onto a glass substrates using spin coating technique. The structural, compositional, morphological, electrical optical and gas sensing properties of CuO thin films have been studied by X-ray diffraction, Scanning Electron Microscopy (SEM), Four Probe Resistivity measurement and UV-visible spectrophotometer. The variation in annealing temperature affected the film morphology and optoelectronic properties. X-ray diffraction patterns of CuO films show that all the films are nanocrystallized in the monoclinic structure and present a random orientation. The crystallite size increases with increasing annealing temperature (40-45 nm). The room temperature dc electrical conductivity was increased from 10 -6 to 10 -5 (X cm) -1 , after annealing due to the removal of H 2 O vapor which may resist conduction between CuO grain. The thermopower measurement shows that CuO films were found of n-type, apparently suggesting the existence of oxygen vacancies in the structure. The electron carrier concentration (n) and mobility (l) of CuO films annealed at 400-700°C were estimated to be of the order of 4.6-7.2 9 10 19 cm -3 and 3.7-5.4 9 10 -5 cm 2 V -1 s -1 respectively. It is observed that CuO thin film annealing at 700°C after deposition provide a smooth and flat texture suited for optoelectronic applications. The optical band gap energy decreases (1.64-1.46 eV) with increasing annealing temperature. It was observed that the crystallite size increases with increasing annealing temperature. These modifications influence the morphology, electrical and optical properties.

Optimizing CuO p-type dye-sensitized solar cells by using a comprehensive electrochemical impedance spectroscopic study

“…Thus, we believe that our work may assist in understanding the full potential of CuO electrodes in p-type DSSCs. 17,18 Firstly, a new and comprehensive approach for the interpretation of EIS measurements, which was validated by a thorough comparison with different devices, is described. This is compared to already known models for EIS characterization of p-type DSSCs.…”

Studies on chemical bath deposited CuO thin films for solar cells application

“…In order to utilize CuO for electrochemical and photoelectrochemical applications, it needs to be prepared as nanostructured thin films. Thin films of cupric oxide have been prepared by a number of techniques including pulsed laser deposition [3], thermal oxidation [4], ultrasonics spray pyrolysis [5], chemical bath deposition [6], microwave [7], sol-gel [8], electro-deposition [9], hydrothermal [10], sputtering [11], solvothermal [12], and successive ionic layer adsorption and reaction method [13]. All these preparation techniques offer distinct advantages depending on the kind of application.…”

Combining Electron‐Accepting Phthalocyanines and Nanorod‐like CuO Electrodes for p‐Type Dye‐Sensitized Solar Cells

“…[3] A viable alternative is based on the long overlooked copper(II) oxide (CuO), whose films feature higher conductivity, better charge carrier mobility, and comparable valence band energy relative to NiO films. [4,5] Still, the most recent report on CuO based p-type DSSCs is dated from 2008. [6] Very likely, state-of-the-art efficiencies as low as 0.011% resulted in a moderate interest.…”