效率增强的新型蓝色有机发光器件

使用一种新型空穴传输材料J003制备了不同结构、不同发光层厚度的两组蓝色发光器件,其结构为:ITO/CuPc/J003/JBEM:perylene/Al_q3/LiF/Al和ITO/CuPc/J003/JBEM:perylene/TPBi/Al_q3/LiF/Al,这里CuPc(Copper phthalocyanine)和LiF分别为空穴注入层(HIL)和电子注入层(EIL),J003为空穴传输层(HTL),JBEM(9,10-bis(3,5'-diaryl)phenylylanthracene)为发光层(EML),TPBj(1,3,5-tri(phenyl-2-benzimidazole)-benzene)为空穴阻挡层(HBL),Al_q3(tris(8-quinolinolato)aluminium complex)为电子传输层(ETL).两种结构中前者为无阻挡层的普通型结构,后者在发光层和电子传输层中加入了空穴阻挡层,是新型阻挡层结构.研究了空穴阻挡层的引入在不同厚度发光层时对器件发光性能的影响,结果表明,新型阻挡层结构能明显提高器件的亮度和效率,但依赖于发光层厚度,利用能级图分析了其中的原因.

Blue Organic Electroluminescent Devices with Enhanced Efficiency on a Novel Structure Basis

Blue organic electroluminescent devices with a novel structure by using a new hole transporting material have been fabricated. The structure is ITO/CuPc/J0503/JBEM:perylene/TPBi/Alq₃/LiF/Al, in which a (hole-blocking) layer was inserted between electron-transporting layer and emitting layer. For comparison, devices with a conventional structure have also been made, and the structure is ITO/CuPc/J0503/JBEM:perylene/Alq₃/LiF/Al. Here CuPc(Copper phthalocyanine)and LiF are hole and electron injection layers,respectively,J0503 hole-transporting layer(HTL), JBEM(9,10-bis(3’5’-diaryl)phenyl anthracene)emitting-layer(EML), TPBi(1, 3, 5-tri(pheny1-2-benzimidazole)-benzene)hole-blocking layer(HBL), and Alq₃(tris(8-quinolinolato)aluminium complex)electron-transporting layer(ETL). Devices with different EML thickness of each structure have also been prepared in order to investigate the effect of EML thickness on the performance. The results indicate that the devices with the novel structure show improved efficiency and luminance as compared to the conventional ones. However, the improvements depend on the thickness of EML. Small differences are found in both structures with the EML thickness larger than the diffusion length of excitons because the blocking-effect from HBL has little effect on the increasing density of excitons.While the novel devices with thickness approximate to the diffusion length of excitons show much higher efficiency and luminance than that of the conventional ones having the same EML thickness because of the good confinement to both charge carriers and excitons. When the thickness of EML is too small, probably, strong interface effect leads to break the performances of the novel devices.