Bright, multicoloured light-emitting diodes based on quantum dots

Abstract

Quantum-dot-based LEDs are characterized by pure and saturated emission colours with narrow bandwidth, and their emission wavelength is easily tuned by changing the size of the quantum dots. However, the brightness, efficiency and lifetime of LEDs need to be improved to meet the requirements of commercialization in the near future. Here, we report red, orange, yellow and green LEDs with maximum luminance values of 9,064, 3,200, 4,470 and 3,700 cd m−2, respectively, the highest values reported so far. Solution-processable core–shell quantum dots with a CdSe core and a ZnS or CdS/ZnS shell were used as emissive layers in the devices. By optimizing the thicknesses of the constituent layers of the devices, we were able to develop quantum-dot-based LEDs with improved electroluminescent efficiency (1.1–2.8 cd A−1), low turn-on voltages (3–4 V) and long operation lifetimes. These findings suggest that such quantum-dot-based LEDs will be promising for use in flat-panel displays.

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Figure 1: Structures, images and HOMO and LUMO energy levels of the QD-LEDs.
Figure 2: Electroluminescence performance of the QD-LEDs.
Figure 3: Lifetime characteristics of a red-emitting QD-LED.
Figure 4: Effect of QD layer thickness on EL performance of the QD-LEDs.
Figure 5: EL efficiency versus current plots of the red-emitting QD-LEDs with an HTL of 45 nm, a QD layer of 2 ML and different ETL thicknesses.

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Acknowledgements

This work was supported by the Ministry of Science and Technology of China (973 project, No. 2002CB613404) and NSFC (No. 20421101 and 50633050). Y.A.W. acknowledges funding from the National Science Foundation SBIR program (award number: 0638209). We thank Ghassan Jabbour for the calculation of the CIE of the QD-LED emission.

Author information

Q.J.S., C.H.Y. and Y.F.L. designed, fabricated and characterized the devices. Y.A.W., L.S.L. and D.Y.W. designed and synthesized the quantum dots. T.Z. and J.X. measured the device lifetimes and calculated the thicknesses of the QD layers.

Correspondence to Y. Andrew Wang or Yongfang Li.

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Supplementary Information

Supplementary information and figures S1-S3 (PDF 104 kb)

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Sun, Q., Wang, Y., Li, L. et al. Bright, multicoloured light-emitting diodes based on quantum dots. Nature Photon 1, 717–722 (2007) doi:10.1038/nphoton.2007.226

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