Fabrication and characterization of ZnO/CuO
thin film heterojunction prepared by
spin-coating method
著者（英）
Aminudin Muhamad
Abstract of Master’s Thesis, 2019
Fabrication and characterization of ZnO/CuO
thin film heterojunction prepared by spin-coating method
Graduate School of Science and Technology, Kwansei Gakuin University Department of Physics, Akihiko Fujiwara Lab., Muhamad AMINUDIN
Toward building a sustainable society, demand for renewable energy has increased more and more. A solar cell, also known as a photovoltaic (PV) cell, is one of the most popular power generation devices. In order to improve energy conversion efficiency, many kinds of materials been studied. Oxide semiconductors are promising for the application of electronic devices including solar cells, because of low cost, chemically stable and non-toxic. They can be deposited on wide variation of substrate by solution-processed methods contributing to low-cost and high-throughput fabrication. On the other hand, precise control of properties of films, such as thickness, crystallinity, roughness of surface and interfaces is to be improved. In this study, fabrication and characterization of oxide thin film heterojunction by a solution-processed method have been studied in order to establish the fabrication method for high quality films by solution-processing methods.
As oxide materials, typical n- and p-type semiconductors, ZnO and CuO were used. ZnO/CuO films were fabricated on indium tin oxide (ITO) coated glass substrate by a spin-coating method using ethanol solution of zinc/copper acetates. The film quality and crystallinity of the films were characterized by X-ray reflectivity (XRR) and X-ray diffraction (XRD). Optical properties of visible light region were investigated by a UV-Vis spectrometer.
Figure 1 shows XRR profile of a series of ZnO(2)/CuO(n) films, where 2 and m refer the spin-coating times of ZnO and CuO layers, respectively. Although Kiessig fringes which originates from interference between scattering from surface and interfaces of the films were hardly modified form those of ITO layers, the ZnO(2)/CuO(8) showed new fringes. The result shows that the ZnO(2)/CuO(8) is a relatively uniform film with small roughness at the surface and interfaces. The estimated thicknesses were about 43 and 3 nm for ZnO and CuO layers, respectively.
Figure 2 shows the visible light absorption spectra of films without annealing, annealed at 350 °C
in air, and annealed at 350 °C under Ar/H2 flow. By annealing at 350 °C under Ar/H2 flow, absorbance
has been successfully increased.
In conclusion, fabrication and characterization of oxide thin film heterojunction by a spin-coating method have been studied, and ways for fabrication of uniform films and increase of visible light
absorption coefficient was proposed.
Fig. 1 X-ray reflectivity (XRR) profiles of ZnO(2)/CuO(n) films for n = 0, 2, 5 and 8. XRR profile of ITO coated substrate is also shown as a reference. Inset: fitting result.
1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06 1.E+07 1.E+08 1.E+09 1.E+10 1.E+11 1.E+12 1.E+13 1.E+14 1.E+15 1.E+16 1.E+17 0 1 2 3 4 5 6 In ten sit y ( cp s) 2θ ZnO(2)/CuO(8) ZnO(2)/CuO(5) ZnO(2)/CuO(2) ZnO(2) G/ITO substrate
Fig. 2 Visible light absorption spectra of films with different annealing condtions: without annealing,nnealed at 350 °C in air, and annealed at 350 °C under Ar/H2 flow.
Ambient
Ar/H2
Without Annealing
