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Injection lasing in organic thin films

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Disposable plastic transistors that light up

Easy processing, mechanical flexibility and low cost drive the intense research carried out in the field of organic semiconductors. Organic light emitting diodes can already be found in cell phone displays and now an organic light-emitting field effect transistor has been demonstrated for the first time.


Semiconductors are compounds with electrical conductivity midway between that of metals and that of insulators. Diodes and transistors that are the building blocks of modern electronics are made out of semiconducting materials. Until the 50's, plastics, i.e. organic compounds, were thought to be good insulators. After the first reports of conductivity in organic polymers, intense and very fruitful research has started in this area. Organic semiconductor devices have been advanced rapidly over the last few years. Laptop displays, cell phone displays and photovoltaic cells are only a few of the applications these materials have. Organic semiconducting materials have tremendous potential for certain electronics applications and unique properties such as ease of processing, compatibility with mechanically flexible substrates and optoelectronic properties tuned by chemical synthesis. A European research group is the first that has developed an organic light emitting field effect transistor. On a thin film of silicon oxide, tetracene was deposited under ultra high vacuum conditions. The transistor's source and drain electrodes were made out of gold. During operation of the transistor, light emission and the tetracene electroluminescence spectrum were observed. The discovery was made while the group was attempting to tackle the very difficult and still unresolved problem of realizing an organic injection laser. In contrast to the easily produced optically pumped laser diode, the injection laser diode is powered by electric current. The group's six European institutions are closer than ever to fabricating the organic semiconductor able to withstand the high current density required. The consortium has already applied for patents and is seeking support to further develop its research and to explore possible applications.

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8 June 2020