典型有机发光二极管中载流子传输和复合模型

The Model of Carriers' Transport and Recombination on the Classical Bilayer OLEDs

提高载流子复合效率是改善有机发光二极管(OLED s)发光效率的重要方法。采用真空热蒸发成膜法制作了典型双层结构的OLED s(ITO/TPD/A lq3/A l)。二极管的性能测试结果表明器件的电流-电压关系与Fow ler-Nordhe im场发射载流子注入理论符合得较好。以Fow ler-Nordhe im场发射载流子的隧穿注入理论为基础,对OLED s的电流进行理论分析和数学推导,建立典型双层结构有机发光二极管中载流子传输、复合的理论模型。以此模型为依据,对载流子注入复合进行理论分析,探究载流子注入复合的效率的表达式。在外加电压和器件材料一定下,得出了载流子复合效率与阳极区一侧积累的空穴面密度和阴极区一侧积累的电子面密度的关系表达式。

OLED （organic light emitting diod various applications. Since Tang et al. reportede） is a very attractive candidate as display devices and for on organic electroluminescence devices,OLED has been widely studied by many researchers and developed as commercial products. Because OLED has a lot of merits from the viewpoint of mobile display such as low power consumption, light weight and thinness, many efforts are being made to develop a robust mobile display with OLED. At recent years, in order to improve OLEDs＇ luminescence-efficiency, much research has been done. However, improving carriers＇ recombination-efficiency is one of valid approach to improve OLEDs＇ luminescence-efficiency. Carriers＇ recombination-efficiency is connect with structures of devices and parameters of materials. So it is necessary to build a model of carriers＇ transport and recombination for finding out the relation between carriers＇ recombination-efficiency and the structure or parameters. In this paper, we attempt to build a model of carriers＇ transport and recombination on the classical bilayer OLEDs. In our experiments, a classical bilayer OLED （ITO/TPD/Alq3/Al） is fabricated by thermal evaporation method. We have test the property of the OLED. The result showed that the electricity-voltage relation accords with Fowler-Nordheim tunneling injection theory very well. Basing on Fowler-Nordheim＇s theory, analyzing the distribution of currents theoretically, and deducing mathematically, a model for carries transport and recombination on the classic OLEDs is presented. According to this model, we analyze carriers＇ transport and recombination process theoretically and probe into the expression of carriers＇ recombination-efficiency. Further more, under this model, a formula between the recombination-efficiency and the surface-density of charged carriers, including holes which congregate at the interface on the anode side and the electrons which congregate at the interface on the cathode side, is educed. In this formula, the macroscopic variable （carriers＇ recombination-efficiency） is expressed by microscopic variables （surface-density of charged cartiers）. It can offer some theoretical foundation for improving the efficiency of charged carriers recombination in OLEDs from microcoscopic mechanism.