期刊
NATURE NANOTECHNOLOGY
卷 7, 期 6, 页码 369-373出版社
NATURE PUBLISHING GROUP
DOI: 10.1038/NNANO.2012.63
关键词
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资金
- National Science Foundation (NSF) [EEC-0646547]
- New York State Foundation for Science, Technology and Innovation (NYSTAR)
- Cornell Center for Materials Research
- IGERT of the NSF [DGE-0654193]
- King Abdullah University of Science and Technology (KAUST) [KUS-C1-018-02]
Infrared light-emitting diodes are currently fabricated from direct-gap semiconductors using epitaxy, which makes them expensive and difficult to integrate with other materials. Light-emitting diodes based on colloidal semiconductor quantum dots, on the other hand, can be solution-processed at low cost, and can be directly integrated with silicon(1). However, so far, exciton dissociation and recombination have not been well controlled in these devices, and this has limited their performance(2-8). Here, by tuning the distance between adjacent PbS quantum dots, we fabricate thin-film quantum-dot light-emitting diodes that operate at infrared wavelengths with radiances (6.4 Wsr(-1) m(-2)) eight times higher and external quantum efficiencies (2.0%) two times higher than the highest values previously reported. The distance between adjacent dots is tuned over a range of 1.3 nm by varying the lengths of the linker molecules from three to eight CH2 groups, which allows us to achieve the optimum balance between charge injection and radiative exciton recombination. The electroluminescent powers of the best devices are comparable to those produced by commercial InGaAsP light-emitting diodes. By varying the size of the quantum dots, we can tune the emission wavelengths between 800 and 1,850 nm.
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