Quantum dots bring LECs closer to practical use
The downside of LECs is that at the present stage of development, only LECs that emit yellow light are to some extend usable. While in theory it should be possible to create LECs capable of emitting all colors of the visible spectrum, the reality is not quite that far. LECs in other colors than yellow are either slow or inefficient or instable – any combination of these three.
Researchers from the Center for Nanointegration of the University of Duisburg and Essen (UDE) now for the first time succeeded in changing the color. At the same time, they increased the efficiency. The goal of the researchers is generating white light out of the LECs – and of course increase stability and efficiency to an acceptable level. Julia Frohleiks, doctorate student in the UDE had the idea to attach quantum dots to the surface of the LECs. Due to the specific physical properties of quantum dots, the LECs indeed emitted light in different colors at low voltage. In addition, the light emitting intensity starts immediately after applying the voltage; the highest intensity is reached after some five minutes. In contrast, LECs without quantum dots but under the same voltage takes several minutes to start emitting low light; its maximum is reached only after about an hour.
Still, the new prototype is not perfect. The color changes back to yellow if the voltage is increased. “This is certainly something we have to work on”, concludes Frohleiks.
The results have been published recently. See J. Frohleiks, S. Wepfer, Y. Kelestemur, H. V. Demir, G. Bacher, and E. Nannen. Quantum Dot/Light-Emitting Electrochemical Cell Hybrid Device and Mechanism of Its Operation. ACS Applied Materials & Interfaces 2016 8 (37), 24692-24698 DOI: 10.1021/acsami.6b06833
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