掺杂对OLED发光效率的影响

概述了掺杂发光的种类、掺杂发光提高OLED发光效率的机制。

Investigation on Electroluminescent Efficiency of Doped OLED

e electroluminescent efficiency of OLED can be greatly improved by doping light-emitting layer with fluorescent or phosphorescent dye. The category and the mechanism of improving electroluminescent efficiency of doped OLED are summarized. OLED can be doped with fluorescent, phosphorescent or mixed. The quantum efficiency of OLED doped with fluorescent dye can be significantly improved due to the high fluorescent efficiency of dopant. But as for fluorescent dye, only single exciton contribute to the electroluminescence, the max theoretical value of inter-quantum efficiency was limited to 25% due to the spin of electrons. When OLED doped with phosphorescent dye, the theoretical value of quantum efficiency can reach 100% , and the experimental value has already reached nearly 100%. This is because phosphorescent dye makes use of triple excitons to give off light. In all kinds of doped system, exciton first formed in the host and then transferred to guest, giving off light. So the process of energy transfer from host to guest will greatly affect the electroluminescent efficiency of doped OLED. There are two kinds of energy transfer processes in doped OLED, Forster energy transfer and Dexter energy transfer. In addition, the current and the doped concentration will affect the electroluminescent efficiency of doped OLED. Especially for phosphorescent dye doped OLED, the half-life of phosphorescent will significantly affect the electroluminescent efficiency of phosphorescent dye doped OLED.