Perovskites allow for color-controlled LEDs

Researchers from Ludwig-Maximilians-Universitaet (LMU) in Munich and the Johannes Kepler University (JKU) in Austria have designed a method to tune the color of the light emitted by a LED by altering the size of its semiconductor crystals.

The method enables the production of semi-conducting nanocrystals of defined size based on perovskites. The crystals are extremely stable, which ensures that the LEDs exhibit high color fidelity ' an important criterion of quality. Moreover, the resulting semiconductors can be printed on various surfaces, and are thus promising for the manufacture of LEDs for use in displays.

To achieve this, the scientists made use of a thin wafer, only a few nanometers thick, which is patterned like a waffle. The depressions serve as tiny reaction vessels, whose shape and volume ultimately determine the final size of the nanocrystals. 'Optimal measurements of the size of the crystals were obtained using a fine beam of high-energy X-radiation at the Deutsche Elektronen-Synchrotron (DESY) in Hamburg', say LMU researchers.

Moreover, the wafers are produced by means of an economical electrochemical process, and can be fashioned directly into LEDs. 'Our nanostructure oxide layers also prevent contact between the semiconductor crystals and deleterious environmental factors such as free oxygen and water, which would otherwise limit the working lifetime of the LEDs,' as the team explains. In the next step, the aim will be to enhance the efficiency of these diodes further, and explore their potential for use in other applications.