互混型有机电致发光器件

Mixed Organic Thin Films for Organic Light-emitting Diodes

通过共蒸镀空穴传输材料TPD和电子传输材料Alq3,在普通双层器件的异质结界面引入了均匀互混层,并研究了互混层的厚度变化对器件光电性能的影响。互混层的引入在一定程度上改善了普通双层器件的异质结界面由于高浓度载流子积聚导致的高电场和界面缺陷对器件主要性能(效率和寿命)的负面影响。我们发现一定厚度的互混层使器件的性能有所提高。

The most common used structure of organic light-emitting diodes is the double layer heterojunction structure. By softening the high local electric field and partly eliminating the non-radiative recombination traps at the heterojunction interface, OLEDs with bipolar transport/emitting layer （BTEL） showed improved stability. However, the detail mechanisms of this structure are still undefined. The performance of OLEDs with uniformly mixed organic layer, which was formed by co-evaporating a hole transport material TPD, and an electron transport/emissive material Alq3 was studied. We observed that the performances of OLEDs with uniformly mixed layer were strongly dependent on the thickness of the mixed-layer, and there exists an optimized thickness of mixed layer. The devices with 5 nm （thickness） mixed layer showed improved lifetime and current efficiency, while the devices with 10 nm or 20 nm（thickness） mixed layers demonstrated similar performance compared to the heterojunction devices. The single layer devices with 100 nm totally mixed layer exhibited a very poor efficiency and stability. A primary discussion on the results was given.