Institute of Microelectronics, Peking University, Beijing, 100871, P. R. China.
Nanoscale. 2017 Jul 6;9(26):8962-8969. doi: 10.1039/c7nr02099f.
Efficient inverted quantum-dot (QD) light-emitting diodes (LEDs) are demonstrated by using 15% Mg doped ZnO (ZnMgO) as an interfacial modification layer. By doping Mg into ZnO, the conduction band level, the density of oxygen vacancies and the conductivity of the ZnO can be tuned. To suppress excess electron injection, a 13 nm ZnMgO interlayer with a relatively higher conduction band edge and lower conductivity is inserted between the ZnO electron transport layer and QD light-emitting layer, which improves the balance of charge injection and blocks the non-radiative pathway. Moreover, according to the electrical and optical studies of devices and materials, quenching sites at the ZnO surface are effectively reduced by Mg-doping. Therefore exciton quenching induced by ZnO nanoparticles is largely suppressed by capping ZnO with ZnMgO. Consequently, the red QLEDs with a ZnMgO interfacial modification layer exhibit superior performance with a maximum current efficiency of 18.69 cd A and a peak external quantum efficiency of 13.57%, which are about 1.72- and 1.74-fold higher than 10.88 cd A and 7.81% of the devices without ZnMgO. Similar improvements are also achieved in green QLEDs. Our results indicate that ZnMgO can serve as an effective interfacial modification layer for suppressing exciton quenching and improving the charge balance of the devices.
通过使用 15% Mg 掺杂 ZnO（ZnMgO）作为界面修饰层，展示了高效的倒置量子点（QD）发光二极管（LED）。通过在 ZnO 中掺杂 Mg，可以调整导带能级、氧空位密度和 ZnO 的电导率。为了抑制过量的电子注入，在 ZnO 电子传输层和 QD 发光层之间插入了一个 13nm 的 ZnMgO 界面层，其导带边缘较高，电导率较低，这改善了电荷注入的平衡并阻止了非辐射途径。此外，根据器件和材料的电学和光学研究，Mg 掺杂有效地减少了 ZnO 表面的猝灭位。因此，通过用 ZnMgO 覆盖 ZnO，ZnO 纳米颗粒引起的激子猝灭被大大抑制。因此，具有 ZnMgO 界面修饰层的红色 QLED 表现出优异的性能，最大电流效率为 18.69cdA，峰值外量子效率为 13.57%，分别比没有 ZnMgO 的器件的 10.88cdA 和 7.81%高 1.72-1.74 倍。绿色 QLED 也取得了类似的改进。我们的结果表明，ZnMgO 可以作为一种有效的界面修饰层，用于抑制激子猝灭并改善器件的电荷平衡。
