Jain Ankit, Voznyy Oleksandr, Korkusinski Marek, Hawrylak Pawel, Sargent Edward H
Department of Electrical and Computer Engineering, University of Toronto , 10 King's College Road, Toronto, Ontario M5S 3G4, Canada.
National Research Council of Canada , Ottawa, Ontario K1A 0R6, Canada.
J Phys Chem Lett. 2017 Jul 20;8(14):3179-3184. doi: 10.1021/acs.jpclett.7b01503. Epub 2017 Jun 28.
It has previously been found that Auger processes can lead to femtosecond carrier trapping in quantum dots, limiting their performance in optoelectronic applications that rely on radiative recombination. Using atomistic simulations, we investigate whether a shell can protect carriers from Auger-assisted trapping. For these studies we investigate CdSe/CdS core-shell quantum dots having total diameters reaching up to 10 nm. We find trapping lifetimes as fast as 1 ps for 2 nm shells, and we report that shells as thick as 6 nm are required to suppress trapping fully. The most efficient recombination mechanism is found to proceed through shallow empty traps, suggesting it can be suppressed by filling the traps through doping or external electrochemical potential. Our findings suggest that to achieve efficient light emission, surface traps have to be completely eliminated, even in thick-shell quantum dots.
此前已发现，俄歇过程可导致量子点中的飞秒载流子俘获，限制了它们在依赖辐射复合的光电子应用中的性能。通过原子模拟，我们研究了一个壳层是否能保护载流子免受俄歇辅助俘获。对于这些研究，我们考察了总直径达10 nm的CdSe/CdS核壳量子点。我们发现，对于2 nm厚的壳层，俘获寿命快至1 ps，并且我们报告，需要6 nm厚的壳层才能完全抑制俘获。发现最有效的复合机制是通过浅的空陷阱进行的，这表明可以通过掺杂或外部电化学势填充陷阱来抑制它。我们的研究结果表明，为了实现高效发光，即使在厚壳量子点中，表面陷阱也必须被完全消除。
