Energy-transfer pumping of semiconductor nanocrystals using an epitaxial quantum well


As a result of quantum-confinement effects, the emission colour of semiconductor nanocrystals can be modified dramatically by simply changing their size1,2. Such spectral tunability, together with large photoluminescence quantum yields and high photostability, make nanocrystals attractive for use in a variety of light-emitting technologies—for example, displays, fluorescence tagging3, solid-state lighting and lasers4. An important limitation for such applications, however, is the difficulty of achieving electrical pumping, largely due to the presence of an insulating organic capping layer on the nanocrystals. Here, we describe an approach for indirect injection of electron–hole pairs (the electron–hole radiative recombination gives rise to light emission) into nanocrystals by non-contact, non-radiative energy transfer from a proximal quantum well that can in principle be pumped either electrically or optically. Our theoretical and experimental results indicate that this transfer is fast enough to compete with electron–hole recombination in the quantum well, and results in greater than 50 per cent energy-transfer efficiencies in the tested structures. Furthermore, the measured energy-transfer rates are sufficiently large to provide pumping in the stimulated emission regime, indicating the feasibility of nanocrystal-based optical amplifiers and lasers based on this approach.

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Figure 1: Schematic and optical properties of the hybrid quantum-well/nanocrystal structure.
Figure 2: Pump- and time-dependent emission from an isolated quantum well.
Figure 3: Experimental observations of QW–NC energy transfer.
Figure 4: Carrier relaxation and energy-transfer processes in the hybrid quantum-well/nanocrystal structure and a schematic of an electrically driven energy-transfer device.


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This work was supported by Los Alamos LDRD Funds and the Office of Basic Energy Sciences, Office of Science, US Department of Energy. Sandia National Laboratories is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the Department of Energy.

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Correspondence to Marc Achermann or Victor I. Klimov.

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The authors declare that they have no competing financial interests.

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Supplementary Information

Calculation of the QW-NC energy transfer rate. (PDF 128 kb)

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Achermann, M., Petruska, M., Kos, S. et al. Energy-transfer pumping of semiconductor nanocrystals using an epitaxial quantum well. Nature 429, 642–646 (2004).

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