光学学报, 2007, 27 (9): 1687, 网络出版: 2007-10-17
利用缓变结提高蓝色有机发光二极管的寿命
Lifetime Prolongation by Graded Junction for Blue Organic Light Emitting Diodes
光学器件 蓝色有机发光二极管 缓变结 半寿命 效率 optical device blue organic light emitting diode (OLED) graded junction half lifetime efficiency
摘要
在空穴传输层(HTL)和发光层(EML)界面加入缓变结的蓝色有机电致发光器件(Cell-GJ)。与传统的异质结结构的有机电致发光器件(Cell-HJ) 相比,寿命有了明显的提高:半寿命在初始亮度为100 cd/m2的条件下达到了8460 h,比Cell-HJ的半寿命长6倍。寿命的延长归功于穿过非突变界面的局部电场的消除,减少了焦耳热的产生从而提高了器件的寿命。但是实验证实Cell-GJ的效率比Cell-HJ的效率低。为了提高Cell-GJ的效率在其TBADN/AlQ交界处蒸镀GaQ薄层制得一种新型器件Cell-GJGaQ。由于GaQ的最低未占有轨道能级介于AlQ和TBADN之间,从AlQ到GaQ再到TBADN形成的多阶势垒可以极大地提高电子(少子)注入,从而使发光效率也有了明显改善。 研究结果表明Cell-GJGaQ的效率比Cell-GJ的效率高20%,半寿命同时也达到了6998 h,比Cell-HJ长5倍,整体性能有了较大提高。
Abstract
Blue organic light emitting diode (OLED) with a graded junction at hole transporting layer (HTL) and emitted layer (EML) interface was constructed (Cell-GJ). Compared with conventional heterojunction OLED (Cell-HJ), it exhibited significantly improved lifetime, and the half lifetime achieved 8460 h at initial luminance 100 cd/m2, more than 6 times longer than that of Cell-HJ. This improvement is attributed to the elimination of local electric field across the non-abrupt heterojunction, which thereby decreases the production of Joule heat and enhances the lifetime of device. However, the efficiency of Cell-GJ is lower than that of Cell-HJ. In order to redeem the decrease in efficiency of Cell-GJ, another device with a GaQ thin layer inserted in the TBADN/AlQ interface was made (Cell-GJGaQ). For the LUMO energy level of GaQ is between the energy level of AlQ and TBADN, the multi-step energy barrier between AlQ-GaQ-TBADN improves the electron (minority) injection greatly, so the luminescence efficiency is greatly improved. This Cell-GaQ shows efficiency 20% higher than that of Cell-GJ and also 5 times longer half lifetime than that of Cell-HJ. The whole performance is greatly improved.
刘善鹏, 白钰, 刘向, 朱文清, 蒋雪茵, 张志林. 利用缓变结提高蓝色有机发光二极管的寿命[J]. 光学学报, 2007, 27(9): 1687. 刘善鹏, 白钰, 刘向, 朱文清, 蒋雪茵, 张志林. Lifetime Prolongation by Graded Junction for Blue Organic Light Emitting Diodes[J]. Acta Optica Sinica, 2007, 27(9): 1687.