Department of Electrical and Electronic Engineering , Southern University of Science and Technology , Shenzhen 518055 , P. R. China.
ACS Appl Mater Interfaces. 2018 Jul 11;10(27):23218-23224. doi: 10.1021/acsami.8b08470. Epub 2018 Jun 27.
The effect of postannealing on the device characteristics is systematically investigated. The external quantum efficiency (EQE) of blue quantum-dot light-emitting diodes (QLEDs) is significantly improved from 5.22 to 9.81% after postannealing. Similar results are obtained in green and red QLEDs, whose EQEs are enhanced from 11.47 and 13.60 to 15.57 and 16.59%, respectively. The annealed devices also exhibit a larger current density. The origin of efficiency improvement is thoroughly investigated. Our finding indicates that postannealing promotes the interfacial reaction of Al and ZnMgO and consequently leads to the metallization of the AlZnMgO contact and the formation of the AlO interlayer. Because of the metallization of AlZnMgO, the contact resistance is effectively reduced, and thus the electron injection is enhanced. On the other hand, the formation of the AlO interlayer can effectively suppress the quenching of excitons by the metal electrode. Because of the enhancement of electron injection and suppression of exciton quenching, the annealed blue, green, and red QLEDs exhibit a 1.9-, a 1.3-, and a 1.2-fold efficiency improvement, respectively. We envision the results offer a simple yet effective method to enhance the charge injection and the efficiency of QLED devices, which would promote the practical application of QLEDs.
系统研究了后退火对器件性能的影响。蓝色量子点发光二极管（QLED）的外量子效率（EQE）在后退火后从 5.22%显著提高到 9.81%。绿色和红色 QLED 也得到了类似的结果，其 EQE 分别从 11.47%和 13.60%提高到 15.57%和 16.59%。退火后的器件还表现出更大的电流密度。彻底研究了效率提高的原因。我们的发现表明，后退火促进了 Al 和 ZnMgO 的界面反应，从而导致 AlZnMgO 接触的金属化和 AlO 中间层的形成。由于 AlZnMgO 的金属化，接触电阻得到有效降低，从而增强了电子注入。另一方面，AlO 中间层的形成可以有效地抑制金属电极对激子的猝灭。由于电子注入的增强和激子猝灭的抑制，退火后的蓝色、绿色和红色 QLED 分别表现出 1.9 倍、1.3 倍和 1.2 倍的效率提高。我们预计，这些结果提供了一种简单而有效的方法来提高 QLED 器件的电荷注入和效率，这将促进 QLED 的实际应用。
