Feng Huwei, Song Jiaojiao, Song Bin, Lin Qingli, Shen Huaibin, Li Lin Song, Wang Hongzhe, Du Zuliang
Key Lab for Special Functional Materials, Ministry of Education, National and Local Joint Engineering Research Center for High-Efficiency Display and Lighting Technology, School of Materials Science and Engineering, Collaborative Innovation Center of Nano Functional Materials and Applications, Henan University, Kaifeng, China.
Front Chem. 2020 Apr 17;8:266. doi: 10.3389/fchem.2020.00266. eCollection 2020.
Quantum dot light-emitting diodes (QLEDs) have been considered as the most promising candidate of light sources for the new generation display and solid-state lighting applications. Especially, the performance of visible QLEDs based on II-VI quantum dots (QDs) has satisfied the requirements of the above applications. However, the optoelectronic properties of the corresponding near-infrared (NIR) QLEDs still lag far behind the visible ones. Here, we demonstrated the highly efficient NIR QLEDs based on chloride treated CdTe/CdSe type-II QDs. The maximum radiant emittance and peak external quantum efficiency (EQE) increased by 24.5 and 26.3%, up to 66 mW/cm and 7.2% for the corresponding devices based on the chloride treated CdTe/CdSe QDs with the PL peak located at 788 nm, respectively, compared with those of devices before chloride treatment. Remarkably, the EQE of > 5% can be sustained at the current density of 0.3-250 mA/cm after the chloride treatment. Compared with NIR LEDs based on transition metal complex, the efficiency roll-off has been suppressed to some extent for chloride treated CdTe/CdSe based NIR QLEDs. Based on the optimized conditions, the peak EQE of 7.4, 5.0, and 1.8% can be obtained for other devices based on chloride treated CdTe/CdSe with PL peak of 744, 852, and 910 nm, respectively. This improved performance can be mainly attributed to the chloride surface ligand that not only increases the carrier mobility and reduces the carrier accumulation, but also increases the probability of electron-hole radiative efficiency within QD layers.
量子点发光二极管（QLED）被认为是新一代显示和固态照明应用中最有前途的光源候选者。特别是，基于II-VI族量子点（QD）的可见QLED的性能已满足上述应用的要求。然而，相应的近红外（NIR）QLED的光电特性仍远远落后于可见QLED。在此，我们展示了基于氯化物处理的CdTe/CdSe II型量子点的高效近红外QLED。与氯化物处理前的器件相比，基于氯化物处理的CdTe/CdSe量子点且PL峰位于788nm的相应器件的最大辐射发射率和峰值外量子效率（EQE）分别提高了24.5%和26.3%，达到66mW/cm²和7.2%。值得注意的是，氯化物处理后，在0.3-250mA/cm²的电流密度下，EQE可维持在>5%。与基于过渡金属配合物的近红外LED相比，氯化物处理的基于CdTe/CdSe的近红外QLED的效率滚降在一定程度上得到了抑制。基于优化条件，对于基于氯化物处理的CdTe/CdSe且PL峰分别为744、852和910nm的其他器件，峰值EQE可分别达到7.4%、5.0%和1.8%。这种性能的提高主要归因于氯化物表面配体，它不仅增加了载流子迁移率并减少了载流子积累，还增加了量子点层内电子-空穴辐射效率的概率。
