| ZnO is a new type of optoelectronic semiconductor material that can be used to realize blue and ultraviolet luminescence and even laser emission. Since the report on the near ultraviolet photoluminescence (PL) of ZnO thin film at room temperature in 1996, the research of the excitated luminescence of ZnO has become a hot topic around the world. Compared with PL, electroluminescence (EL) has many advantages, such as its simple apparatus, low. expense and power consumption, which make it more practical in application. Up to now, most of the researches in this field have been focused on the EL properties of ZnO thin film based on the doping method. While about ZnO nanometer powders, which are much simpler in preparation, few papers are reported on their EL properties. Besides, electrically driven luminescence based on well-designed nanostructures can provide an alternative and intriguing strategy for the mechanism analysis and application exploration. Thus, for the ZnO-based materials, it is necessary to investigate their EL properties under the electrically excitation based on their porous nanostructures.In this paper, we mainly focused on research of the preparation and the EL properties of several different ZnO nanostructure materials. Firstly, mesoporous ZnO precursor was prepared by an improved sol-gel method, in which ODA, Pluronic P123 (P123) and Pluronic F-127 (F-127) were chosen as the template agents respectively. From the N2 adsorption-desorption results, the pore distribution of the mesoporous precursors prepared by ODA, P123 and F-127 are 5.64nm, 6.61nm, and 5.70nm, respectively. And their surface areas are 100.78m2 /g, 69.21 m2/g and 103.57 m2/g. After calcining in air at 600℃ for 5h, ZnO nanocrystalline samples were obtained. Then the EL properties of these calcined samples were tested by a special apparatus. All the samples showed a green emission with a band around 510nm but with great diversity in emission intensity. By comparing the EL spectra of the pure ZnO sample prepared in the improved method and the sample from the former method, and the EL spectra from the two ZnO samples prepared with ODA but with different methods, a great phenomenon was found that by improving the preparation, the emission intensity could be greatly enhanced. At the same time, both samples from the improved method showed blue-shift in their ELspectra. On the other hand, by comparing the EL spectra of the samples prepared with the same method, the emission intensity of all the samples dealt with template agents were much higher than that of the sample dealt without surfactant. In detail, at the optimal dosages of each template agent, for the samples dealt with ODA, P123 and F-127, the enhanced degrees are 0.89, 2.03 and 3.3 times, respectively.Secondly, ZnO hollow sphere was prepared by template preparation method. In this period, electronegative polystyrene nanospheres with a diameter of 500nm were prepared by emulsion polymerization method. Then by using this nanosphere as the template and PVP as the dispersant, PSt/Zn5(CO3)2(OH)6 core-hell structure was obtained by physical adsorption method. In the end, by calcining in air at an enhanced temperature, PSt was eliminated. At the same time, the shell of Zn5(CO3)2(OH)6 precursor was converted into ZnO hollow sphere crystal. In contrast to the EL spectra of ZnO nanocrystalline grain, the emission band of the obtained ZnO hollow sphere blue-shifted to around 520nm. Besides, the emission intensity has markedly been increased. This might be caused by the difference of the micro structures of the two samples.Thirdly, two main improvements were made to the method of ZnO nanorods preparation. Those were the introduction of assistant surfactant and the modification to the dosage of its surfactant DBS. By these two improvements, ZnO nanorods with a diameter of 20nm were obtained. But there was no apparent change in the length of the rod.Therefore, the idea of well-designed microstructure for materials is an effective way for the EL properties research of ZnO nanometer powders and even for the realization of laser emission under electrical pump. |
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