Degradation of quantum dot light emitting diodes, the case under a low driving level,Journal of Materials Chemistry C

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Degradation of quantum dot light emitting diodes, the case under a low driving level
Journal of Materials Chemistry C ( IF 5.7 ) Pub Date : 2019/12/17 , DOI: 10.1039/c9tc04107a
Xulan Xue _{1,

2,

3,

4} , Jiayi Dong _{5,

6,

7,

8} , Shuangpeng Wang _{5,

6,

7,

8} , Hanzhuang Zhang _{1,

2,

3,

4} , Han Zhang _{1,

2,

3,

4} , Jialong Zhao _{4,

9,

10,

11,

12} , Wenyu Ji _{1,

2,

3,

4}

Affiliation

Quantum dot light emitting diodes (QLEDs) have been emerging with unique photoelectrical properties and their efficiency is rapidly approaching the commercialization requirement. However, the device operation lifetime is still one of the biggest obstacles facing the QLED applications. Here, we investigate the case of degradation of red QLEDs by a low driving level (7.5 mA cm⁻²) because devices can commonly achieve a luminance of ∼500–2000 cd m⁻² (that is required in display applications) under this driving current. Based on the photoelectrical characteristics of QLEDs with different aging times, we find that the device stability is dominantly affected by the interfaces between QDs and adjacent charge transport layers. Some of the QDs stay in the permanent dark states (lightless states) due to the aging process, which may result from the generation of nonradiative sites in the hole-transport layer (HTL). The electron leakage should be responsible for the degradation of the HTL, leading to a highly resistive HTL and the rise of the operation voltage for the aged devices. Therefore, suppressing the interactions between QDs and charge transport layers and confining the charges within the QDs are feasible ways to boost the operation stability of QLEDs.

中文翻译：

量子点发光二极管的退化，驱动水平低的情况下

量子点发光二极管（QLED）不断涌现，具有独特的光电性能，其效率正迅速接近商业化要求。但是，器件的使用寿命仍然是QLED应用面临的最大障碍之一。在这里，我们研究了红色QLED在低驱动电平（7.5 mA cm ^-2）下退化的情况，因为设备通常可以达到约500-2000 cd m ^-2的亮度。（在显示应用中需要）在此驱动电流下。基于不同老化时间的QLED的光电特性，我们发现器件的稳定性主要受QD与相邻电荷传输层之间的界面影响。由于老化过程，某些QD保持在永久的黑暗状态（无光状态），这可能是由空穴传输层（HTL）中产生非辐射位点引起的。电子泄漏应导致HTL的劣化，从而导致高电阻HTL以及老化设备的工作电压升高。因此，抑制量子点与电荷传输层之间的相互作用并将电荷限制在量子点内是提高量子点发光二极管的工作稳定性的可行方法。

更新日期：2020-02-13

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