European researchers have devised a method for tuning the color emitted by light emitting diodes (LEDs). Color control is achieved by modifying the size of crystals in semi-conducting materials used to produce the light-emitting layer.
Semi-conducting nanocrystals of defined size based on perovskite grown on nanoporous silicon and alumina thin films were produced by researchers from Johannes Kepler University Linz (Austria) and Ludwig-Maximilians-University München (Germany). A blue-shifted photoluminescence emission was achieved by reducing the pore size. The stability of these crystals ensures that the LEDs exhibit high color fidelity—an important criterion of quality. The resulting semiconductors can be printed on suitable surfaces, and are appropriate for the manufacture of LEDs for use in displays.
The crucial element in the new method is a thin wafer, patterned like a waffle and only a few nanometers thick. The depressions serve as tiny reaction vessels, whose shape and volume ultimately determine the final size of the nanocrystals. The wafers are produced by means of an economical electrochemical process, and can be fashioned directly into LEDs.
The researchers plan to enhance the efficiency of these diodes and explore their potential use in other applications, such as flexible displays.