| Light-emitting diode (LED) is a kind of solid light sources. LED owns a number of advantages over other types of light sources, like energy-saving, environmental-friendly, single color, long-life and widely used in the field of the LCD backlight and general lighting. The urgency of the worldwide demand for green lighting, LED lighting industry can bring huge economic benefits. At present, one of the reason which LED can not replace other types of light sources in a short term is that the light extraction efficiency of LED is still an awful problem which is needed to be further improved.At present, the methods to improve light extraction efficiency of LED are proceeded worldwidely, such as flip-chip structure, surface-roughening, nano-imprinting, the photonic crystal structure and so on. Most processes of these methods are complex, high production costs, energy consumption, or have long production period. Moreover, most of these methods need a on-the-chip etching processing, which will inevitably damage to the electrical properties of the material. Compared with these methods, this method which uses ZnO nanorod arrays to improve the extraction efficiency of LED will not cause any damage to the electrical properties of the material, and has a simple fabrication process, low production costs. The light extraction efficiency is improved significantly, which can be a new choice for the chip manufacturer. This research that relate to the production of zinc oxide nano-array, and the light extraction efficiency of light-emitting diodes, include the following aspects:1. We analyzed the mechanism of ZnO nanorod arrays improve of light extraction efficiency of GaN-based LEDs. After the production of zinc oxide nanorod arrays, the light extraction efficiency of LED can improve145%.2. We introduced the fabrication method of ZnO nanorod arrays and used liquid-phase-deposited ZnO nanorod arrays. Equimolar amounts of zinc acetate and hexamethylenetetramine were used as the deposition precursors of hydrothermal reaction solution.3. When we use RF magnetron sputtering to prepare the ZnO seed layer, the time of sputtering should not last long. With the increase of sputtering time, the ZnO seed layer thickness increases, the ZnO nanorod arrays will be so dense that light will not escape via the side walls of the ZnO nanorods. This will reduce the light extraction efficiency of LED.4. During the process of hydro thermal growth, the concentration of reaction solution and the time of hydrothermal growth are important issues which will affect the morphology of the ZnO nanorod arrays. Either when the concentration of hydrothermal reaction is0.025M, or the solution is heated by1hour or3hours, light extraction efficiency of LED will be blighted because zinc oxide nanowires are not conducive to it.5. We choose sol-gel method to prepare ZnO seed layer,. When the ZnO nanorod arrays are generated, the surface of the LED chip will form the "fold" structure which will absorb part of light.6. We choose RF magnetron sputtering method to prepare ZnO seed layer,. When the ZnO nanorod arrays are generated, the maximum value of EL intensities of GaN-based LED is79%. The optimized experimental parameters:sputtering for15seconds, the concentration of hydrothermal reaction solution is0.05M, the time of hydrothermal growth is2hours.7. On the basis of the above experiments, the light extraction efficiency of red light LED is demonstrated by utilizing sol-gel coating and the aqueous solution growth technique successively. With310mA current injection, and the light output efficiency of the LED with ZnO nanorod arrays was enhanced by about14.75%. |
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