The Interface Characteristics And Carrier Transmission Mechanism Study Of "ZnO Nanorods Array/Polymer" Devices

Compared with the gallium nitride, ZnO has a shorter emitting wavelength and a higher energy. It is a new star in the field of short wavelength light-emitting device. But the p-type doping of ZnO has remained a worldwide challenge. So its research progress of electroluminescent diode has been slow. By contrast, nano-material has special structural characteristics and excellent performance in optics, electricity, magnetics, mechanics, etc. More and more people are devoted to the synthesis and application of ZnO nanostructures. Our group has already developed a ZnO ultraviolet light-emitting devices using ZnO nanorods array combined with organic materials. But this work there are several problems:The influence factors of hydrothermal synthesis of ZnO nanorods array will still need to improve; The surface roughness of ZnO nanorods array is very large, so we can’t form a good film on the top of the array; Little research on organic inorganic interface, leading to the carrier transport and luminescence mechanism of the device is not clear. This paper makes the following research works to solve these problems.Firstly, by observing the hydrothermal growth process we found that a slow heating speed in initial reaction stage is advantageous to the ZnO nanorods array’s orientation, and it will not run out of a large number of nutrient solution at the beginning, the ZnO nanorods array will has a good monodispersity, and a longer length. Study also found that placing the seed surface down in a small angle, can eliminate the large scale ZnO which are free nucleation grown deposited on the top surface of the array, and can get rid of the gas adsorption which is generated from precursor solution’s reaction process, made the array surface clean, smooth, and good to film-forming.Secondly, we choose organic polymer combined with ZnO nanorods array to fabricate an ultraviolet electroluminescent device. Results found that if you want the polymer completely coverage the top of ZnO array, then polymer’s single molecule chain size is the best as far as possible long, and need it put into each other easily. So we choose the polymer MEH-PPV, and the device whose structure is "ITO/ZnO film/ZnO nanorods array/MEH-PPV/Al" achieved electroluminescent. Its main spectrum centered at380nm which belong to the band edge emission of ZnO. According to the charge density distribution diagram of the device, it is concluded that the carrier transmission mechanism is the tip tunneling, and every top of nanorod is a tip. Finally, we did some preliminary study on the surface of ZnO nanorods array. We have two film-forming method to make a film on the top of array. Method one is forming film derectly, method two is forming film after filled dielectric between the nanorods. The calculation results show that the method one can increase the area effective contact of device, method two can’t. In method two, milder hydrochloric acid etching technology, like gaseous fumigation and spin technology, can remove the exposed top of array, then reduce the surface roughness of array, improve the performance of device.