基于电荷传输层优化的量子点发光二极管

Study on Quantum-dot Light Emitting Diode Based on Charge Transport Layer Optimization

摘要:

采用溶液法旋涂薄膜、真空蒸镀铝电极,制备了ITO/PEDOT∶PSS/空穴传输材料/量子点/纳米氧化锌(ZnO Nanoparticles)/Al结构的量子点发光二极管(QLED)器件。对比了不同纳米氧化锌分散剂对器件性能的影响。当用乙醇和乙醇胺分散氧化锌时,对量子点层破坏较小,器件的亮度最高达22 940cd/m2,电流效率达28.9cd/A。研究了在聚乙烯咔唑(PVK)中掺杂不同比例4,4′-环己基二[N,N-二(4-甲基苯基)苯胺](TAPC)器件的发光特性。在PVK中掺杂TAPC材料能够促进器件空穴传输以及电子空穴注入平衡,当PVK∶TAPC=3∶1时,器件的空穴传输层形貌较为平整,亮度较高;当PVK∶TAPC=1∶1时,器件的开启电压最低。通过对器件膜层表面形貌以及电学、光学性能的对比,分析了电荷传输层优化对器件特性改善的原因。

Abstract:

Quantum dot light emitting diodes (QLED) with the structure of ITO/PEDOT∶PSS/Hole transport material/quantum dot/ZnO nanoparticles/Al were fabricated by spin coating and electrode vacuum evaporation. Firstly, different effects on the performance of QLED devices of dispersant of ZnO nanoparticles were compared. When ZnO nanoparticles were dispersed in ethanol with ethanolamine, they made less damage to quantum dot layer and lead to high performance, thus the luminance of QLED and the current efficiency can be up to 22940cd/m2 and 28.9cd/A, respectively. Then the influence of different ratios of 4,4′-cyclohexylidenebis[N,N-bis(4-methylphenyl)aniline] (TAPC) in the poly(9-vinylcarbazole) (PVK) was investigated. High charge mobility of TAPC materials can enhance hole transportation, thus improve the balance of hole and electron recombination. When PVK∶TAPC=3∶1, the morphology of hole transport layer is relatively smooth, and the device can get a higher luminance. When PVK∶TAPC=1∶1, QLED gets the minimum turn-on voltage. The reasons of charge transport layer optimization is analyzed by comparing the surface morphology and the electrical and optical properties of the devices.