Source: http://aoot.osa.org/oe/abstract.cfm?uri=oe-27-6-7935
Timestamp: 2019-04-19 02:41:27+00:00

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In this paper, we report the synthesis, the structural and optical characterization of CdSe/CdS//CdS nanorods (NRs) and their exploitation in nanorod-based light-emitting diodes (NR-LEDs). Two kinds of NRs of CdSe/CdS and CdSe/CdS//CdS were incorporated into the structure of solution-processed hybrid NR-LEDs. Compared to CdSe/CdS, the efficiencies of CdSe/CdS//CdS NR-based LEDs are overwhelmingly higher, specifically showing unprecedented values of peak current efficiency of 19.8 cd/A and external quantum efficiency of 15.7%. Such excellent results are likely attributable to a unique structure in CdSe/CdS//CdS NRs with a relatively high quantum yield, thick CdS outer shell, and rod structure which minimize nonradiative energy transfer between closely packed NRs in emitting layer.
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Fig. 1 (a) Schematic illustration of designed growth of CdS NRs over CdSe cores, and the growth of an additional CdS shell over the resulting CdSe/CdS NRs to form CdSe/CdS//CdS NRs. Evolution of UV-vis absorption spectra (b) and photoluminescence spectra of CdSe/CdS//CdS NRs upon shell growth (c).
Fig. 2 (a) TEM image of CdSe core QDs. (b) TEM image of F-NRs. (c) TEM image of S-NRs. (d, e) High-resolution TEM images corresponding to F-NRs and S-NRs, respectively.
Fig. 3 Powder X-ray diffraction patterns of CdSe, CdSe/CdS core/shell F-NRs, and CdSe/CdS//CdS S-NRs.
Fig. 4 (a) Comparison of PL QYs of F-NRs and S-NRs in the forms of solution versus solid film. Variations of PL lifetime in solution versus film states of (b) F-NRs and (c) S-NRs.
Fig. 5 (a) Schematic structure illustration of the multilayered NR-LEDs. (b) The cross-sectional STEM image of a hybrid NR-LEDs device. (c) Energy level diagram of the multilayered NR-LEDs.
Fig. 6 AFM characterizations of surface of F-NRs as the emitting layer without (a) and with (b) PMMA interlayer.
Fig. 7 (a) Variation of current-density (J) and luminance (L) versus driving voltage (V). (b) Current efficiency (ηA) and EQE (ηEQE) as a function of luminance for F-NRs versus S-NRs LEDs.
Fig. 8 (a) PL spectra of S-NRs solution versus corresponding EL spectra of devices. (b) Evolution of EL of S-NRs LEDs with increasing driving voltage. (c) CIE chromaticity coordinates of S-NRs LEDs.

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