Taiwanese scientists developed zinc oxide white light emitting diode (LED)

Taiwanese scientists have recently used zinc oxide (ZnO)/blue light organic material composite films to produce white light emitting diodes (LEDs). They used the hydrothermal method to successfully grow an inorganic ZnO nanorod array on a blue light organic light emitting film. This technology is different from the traditional epitaxial growth method of LEDs. Not only is the method simple and low-temperature throughout the process, it is very attractive for the future development of white light sources.

White light emitting diodes can be generally divided into two categories: inorganic and organic. In the past, the production of inorganic white light emitting components had to consider the problem of material lattice matching, and required high vacuum and high temperature process equipment, so the manufacturing cost was high; while the development of organic white light emitting components requires expensive and complex chemical reactions in the development of white light materials. If the white light component is composed of three layers of RGB organic materials, it is also necessary to consider the problem of inconsistent luminous intensity and life of each layer of materials.

Luminescent nanocomposites

Professor Qingfu Lin of the Institute of Optoelectronics at National Taiwan University and his doctoral student Junyu Li have successfully integrated n-type inorganic ZnO nanorod arrays and p-type blue light organic materials into pn-type white light emitting diodes using low-temperature solution process technology. This inorganic/organic composite film has the advantages of high carrier mobility of ZnO and the benefits of high fluorescence efficiency and large-area production of organic materials. There is no problem of lattice matching of different materials, and no need to use expensive vacuum and high-temperature equipment.

According to research from Professor Lin Qingfu's laboratory, ZnO nanopillars will bond with organic films during their growth and generate Zn(OH)2, which is the source of zinc oxide surface luminescence. Therefore, when a bias is applied to the component, electron-hole pairs can easily recombine at the ZnO nanopillar surface/organic molecule interface, generating photons that cover a large number of zinc oxide surface defect luminescence wavelengths and blue light organic material luminescence wavelengths, thereby obtaining white light.

The team used a Fourier-Transform Infrared Spectrometer (FTIR) to observe and found that the spectrum of the ZnO/blue light organic material composite film produced by the hydrothermal method had a strong peak at 3410cm-1 corresponding to the hydroxyl group, proving that the composite film does contain a large amount of Zn(OH)2.