摘要
Quantum dot light-emitting diodes(QLEDs)have attracted considerable attention in displays owing to their high color purity,wide gamut,narrow emission band,and solution-processed characteristics.However,a major problem of the unbalanced carrier(electrons and holes)injection in QLEDs deteriorates their performance.Here,we balanced the charge injection in QLEDs by optimizing the carrier transport layers.Different organic hole transport layers(HTLs)with a suitable thickness were employed to match the electron transport layer(ETL)of ZnO.Mg^(2+) was doped into the ZnO(MZO)ETL to decrease the electron mobility and match the hole mobility of the HTL.Consequently,the QLEDs exhibited an excellent external quantum efficiency(EQE)of 21.10%at a luminance of 4661 cd m^(-2).In the luminance range of 100–30,000 cd m^(-2),EQE roll-off was considerably low,and more than 80%of the initial EQE value could be maintained,indicating less Auger recombination because of the balanced carrier injection.This work reveals that compared with energy level matching,the charge transfer capability of the transport layers is more instrumental in the charge balance regulation of QLED devices.
量子点发光二极管具有高色纯度、宽色域、窄带发射和低成本溶液制备工艺等优点,在显示领域引起了广泛关注.然而,量子点发光二极管内部的不平衡载流子(电子和空穴)注入导致器件性能下降,是一个一直存在的重要问题.我们通过优化载流子传输层对器件中的电荷注入进行了平衡调节.利用不同厚度的有机空穴传输层来匹配ZnO电子传输层的电子传输速率.与此同时,在ZnO电子传输层中掺杂了Mg^(2+)以降低电子迁移速率,进一步匹配较慢的空穴迁移速率.通过对量子点发光二极管器件中电荷平衡传输的调节,实现外量子效率超过21%,对应亮度为4,661 cd m^(-2).在100-30,000 cd m^(-2)亮度范围内,外量子效率表现出较低的滚降,可保持初始效率的80%以上,这表明平衡载流子的注入减少了电荷俄歇复合.本工作表明,与器件结构中能级匹配相比,传输层的电荷传输能力对器件中电荷平衡的调节作用影响更为明显,这对量子点发光二极管的电荷平衡调节和性能改善具有重要的指导意义.
基金
supported by the National Natural Science Foundation of China(51774034,51961135107 and 51772026)
the National Key Research&Development Program of China(2017YFE0119700)。
