Development of homogenous n-TiO2/ZnO bilayer/p-Cu2O heterostructure thin film

Abstract

Metal oxide semiconductor materials have shown a great potential in the fabrication of heterojunction thin film due to its improved properties for photovolatic mechanism in solar cell application. In this work, p-(111)-Cu 2 O based heterostructure was successfully developed with uniformity and highly oriented n-TiO 2 /(002)-ZnO bilayer thin film in order to overcome improper electron mobility between the heterointerface of n and p-type layer by optimizing several properties. n-TiO 2 /ZnO bilayer acts as window layer deposited on FTO substrate by using sol-gel spin coating method. The crystallize size and transmittance spectrum of n-TiO 2 thin film was improved after n-ZnO was coated onto TiO 2 thin film. Meanwhile, cyclic voltammetry (CV) measurement was carried out and potential deposition of −0.4 V vs Ag/Cl at 40 °C was acquired. p-Cu 2 O which acts as absorbing layer was deposited onto n-TiO 2 /ZnO bilayer by using electrodeposition technique. The successful fabrication of n-TiO 2 /ZnO/p-Cu 2 O heterostructure were confirmed by the existence of all peaks on the XRD spectrum. Two strong absorption edges observed and the merged shape of p-Cu 2 O grain with other layer leads to the surface flatness improvement. The optical energies of n-TiO 2 /ZnO bilayer and p-Cu 2 O thin film are estimated as 3.15 and 1.75 eV, respectively. The structural, morphological, optical, and topological properties of thin films were characterized using X-ray diffraction, Field emission-scanning electron microscope, Ultraviolet-visible spectroscopy, and Atomic force microscopy, respectively.

Annealing Treatment on Homogenous n-TiO2/ZnO Bilayer Thin Film Deposition as Window Layer for p-Cu2O-Based Heterostructure Thin Film

“…Previously, we have studied the effect of annealing temperature on n-TiO 2 /ZnO bilayer thin film by using sol-gel spin coating method. The results showed high crystallinity of thin film with significant modification in morphological and optical properties when the annealing temperature reached up to 500 • C [20]. In this present work, the n-TiO 2 /ZnO bilayer thin film proposed as window layer was constructed with different annealing time.…”

“…The intensity was increased as the annealing time increased. However, the preferred (002)-orientation of ZnO thin film appeared at 34.28 • when the annealing time was up to 2 h. This highly oriented (002)-ZnO as window layer is essential for the next deposition of p-Cu 2 O thin film due to the low lattice mismatch of 7.6% exhibited in atomic arrangement of p-n heterojunction thin film [20]. Based on the results, other peaks except TiO 2 and ZnO were undetected.…”

“…Consequently, it will improve the minimum energy required tion. The electron will become easily excited from the valence band to [20]. Moreover, transmittance spectra (T) of the annealed n-TiO 2 /ZnO bilayer thin films is related to absorbance coefficient (α) in Equation ( 2) as follows [25]:…”

“…Consequently, it will improve the minimum energy required for an electron excitation. The electron will become easily excited from the valence band to the conduction band [20].…”

The Impact of Spinning Speed on n-TiO2/ZnO Bilayer Thin Film Fabricated through Sol–Gel Spin-Coating Method

“…To examine its structural properties, X-ray diffraction spectroscopy was employed, utilizing a 2θ range spanning from 20 to 80 • , and Cu Kα radiation with a 1.54056 Å wavelength was used to analyze the crystal structure. The crystallite size of the n-TiO 2 /ZnO bilayer thin film was calculated using Scherrer Equation (1) [24].…”