Scientists in Taiwan have recently produced white light-emitting diodes (LEDs) using a composite film of zinc oxide (ZnO)/blue light organic materials. They succeeded in growing an array of inorganic ZnO nanorods on a blue organic light-emitting film using a hydrothermal method. This technology is different from the traditional LED epitaxial growth method. It is not only simple in method but also low in temperature. It is very attractive for the future development of white light source.
Generally, white light emitting diodes can be classified into inorganic and organic types. In the past, the production of inorganic white light-emitting components has to consider the problem of material lattice matching, and requires high vacuum and high temperature process equipment, so the manufacturing cost is high; and the organic white light-emitting components require expensive and complicated chemical reactions in the development of white light materials, if White light components composed of three layers of RGB organic materials also need to be concerned about the problem of inconsistent luminous intensity and lifetime of each layer of materials.
Luminescent nanocomposites
Professor Lin Qingfu from Taiwan University Optoelectronics Institute and his doctoral student Li Junyu successfully integrated n-type inorganic ZnO nano-pillar arrays and p-type blue-light organic materials into pn-type white light-emitting diodes using low-temperature solution process technology. The inorganic/organic composite film has both The advantages of ZnO high carrier mobility, as well as the high fluorescence efficiency of organic materials and the benefits of large-area fabrication, do not have the problem of lattice matching of different materials, and do not require expensive vacuum and high temperature equipment.
According to the research of Professor Lin Qingfu's laboratory, the ZnO nanocolumn will bond with the organic film during the growth process and form Zn(OH)2, which is the source of the surface of the zinc oxide, so when the component is biased The electron-hole pairs are easily recombined between the surface of the ZnO nano-pillar/organic molecular interface, and photons are formed which cover a large number of wavelengths of the zinc oxide surface defects and the wavelength of the blue organic material, thereby obtaining white light.
The team used the Fourier-Transform Infrared Spectrometer (FTIR) to observe that the spectrum of the ZnO/blue organic composite film prepared by hydrothermal method has a strong peak at 3410 cm-1 corresponding to the hydroxyl group. It was confirmed that the composite film did contain a large amount of Zn(OH)2.
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