1] Chemistry Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA [2] Photo-Electronic Hybrid Research Center, Korea Institute of Science and Technology, Seoul 136-791, Korea [3].
Nat Commun. 2013;4:2661. doi: 10.1038/ncomms3661.
Development of light-emitting diodes (LEDs) based on colloidal quantum dots is driven by attractive properties of these fluorophores such as spectrally narrow, tunable emission and facile processibility via solution-based methods. A current obstacle towards improved LED performance is an incomplete understanding of the roles of extrinsic factors, such as non-radiative recombination at surface defects, versus intrinsic processes, such as multicarrier Auger recombination or electron-hole separation due to applied electric field. Here we address this problem with studies that correlate the excited state dynamics of structurally engineered quantum dots with their emissive performance within LEDs. We find that because of significant charging of quantum dots with extra electrons, Auger recombination greatly impacts both LED efficiency and the onset of efficiency roll-off at high currents. Further, we demonstrate two specific approaches for mitigating this problem using heterostructured quantum dots, either by suppressing Auger decay through the introduction of an intermediate alloyed layer, or by using an additional shell that impedes electron transfer into the quantum dot to help balance electron and hole injection.
基于胶体量子点的发光二极管 (LED) 的发展受到这些荧光团的诱人特性的驱动，例如光谱狭窄、可调谐发射以及通过基于溶液的方法进行易处理。提高 LED 性能的当前障碍是对外部因素（例如表面缺陷处的非辐射复合）与内在过程（例如多载流子俄歇复合或由于施加的电场引起的电子-空穴分离）的作用的理解不完整。在这里，我们通过将结构工程化量子点的激发态动力学与其在 LED 中的发射性能相关联的研究来解决这个问题。我们发现，由于额外电子对量子点的显著充电，俄歇复合极大地影响了 LED 的效率以及在高电流下效率下降的开始。此外，我们展示了使用异质结构量子点来缓解此问题的两种具体方法，一种是通过引入中间合金层来抑制俄歇衰减，另一种是使用额外的壳层来阻止电子转移到量子点中，以帮助平衡电子和空穴注入。
