期刊
ACS NANO
卷 8, 期 5, 页码 4893-4901出版社
AMER CHEMICAL SOC
DOI: 10.1021/nn500852g
关键词
quantum dots; electroluminescence; current efficiency
类别
资金
- National Research Foundation of Korea (NRF) - Korea government (MSIP) [2013R1A2A2A01068158]
- Converging Research Center Program through the Ministry of Science, ICT and Future Planning, Korea [2013K000182]
- Samsung Display Co., Ltd.
- National Research Foundation of Korea [2013R1A2A2A01068158] Funding Source: Korea Institute of Science & Technology Information (KISTI), National Science & Technology Information Service (NTIS)
Green CdSe@ZnS quantum dots (QDs) of 9.5 nm size with a composition gradient shell are first prepared by a single-step synthetic approach, and then 12.7 nm CdSe@ZnS/ZnS QDs, the largest among ZnS-shelled visible-emitting QDs available to date, are obtained through the overcoating of an additional 1.6 nm thick ZnS shell. Two QDs of CdSe@ZnS and CdSe@ZnS/ZnS are incorporated into the solution-processed hybrid QD-based light-emitting diode (QLED) structure, where the QD emissive layer (EMI) is sandwiched by poly (9-vinlycarbazole) and ZnO nanoparticles as hole and electron-transport layers, respectively. We find that the presence of an additional ZnS shell makes a profound impact on device performances such as luminance and efficiencies. Compared to CdSe@ZnS QD-based devices the efficiencies of CdSe@ZnS/ZnS QD-based devices are overwhelmingly higher, specifically showing unprecedented values of peak current efficiency of 46.4 cd/A and external quantum efficiency of 12.6%. Such excellent results are likely attributable to a unique structure in CdSe@ZnS/ZnS QDs with a relatively thick ZnS outer shell as well as a well-positioned intermediate alloyed shell, enabling the effective suppression of nonradiative energy transfer between closely packed EMI QDs and Auger recombination at charged QDs.
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