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Brighter And Lighter

An innovation in LED lighting achieved through the use of quantum dots has greatly increased the efficiency, brightness, lifetime and low turn-on voltage of this energy source.

A research team at Seoul National University, South Korea has published their research in a recent issue of Nano Letters.

They found that the key to improving the brightness and efficiency of the QLEDs (Quantum Light Emitting Diode) comes from improving the injection of current-carrying electrons and holes into the quantum dots.

The more efficiently the electrodes can inject electrons and holes into the quantum dots, the more efficiently QLED can emit light.

The anodes of LEDs are usually made of indium tin oxide whose transparency allows light to escape. But in this research, the researchers inverted the device by making the indium tin oxide the cathode, with the help of zinc oxide nanoparticles as an electron transport layer; this made the carrier injection better and in turn increased the overall efficiency.

“The most important cause of the low performance of QLEDs is the poor injection of holes into the quantum dots (QDs) from the anode and neighboring hole transport layer due to a huge potential energy barrier,” Changhee Lee said in a press conference.

“Because of that, the electron-hole balance is not achieved, resulting in low quantum efficiency and low maximum brightness. Furthermore, the excess electrons or holes, which do not recombine in the QD layer and enter the neighboring organic hole-transport or electron-transport layers (HTL or ETL), can cause leakage current and device degradation, resulting in poor efficiency and stability. Therefore, good carrier injection is a key factor for realizing high-performance QLEDs” he added.

It is anticpated that these quantum LEDs will be ideal for the display market, as energy efficiency and brightness are crucial in display technology.

Source
http://pubs.acs.org/doi/abs/10.1021/nl3003254

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