Real-time beam shaping without additional optical elements

Providing artificial light and enhancing the quality of the respective light sources is of continued interest in the fields of solid state, condensed matter, and semiconductor physics. Much research has been carried out to increase the luminous efficiency, lifetime and colour stability of such devices. However, the emission characteristics of a given light source do not necessarily comply with today’s often sophisticated applications. Here, beam shaping addresses the transformation of a given light distribution into a customized form. This is typically achieved by secondary optical elements often sporting elaborate designs, where the actual light source takes up only a small fraction of the system’s volume. Such designs limit the final light source to a single permanent operation mode, which can only be overcome by employing mechanically adjustable optical elements. Here we show that organic light-emitting diodes (OLEDs) can enable real-time regulation of a beam shape without relying on secondary optical elements and without using any mechanical adjustment. For a red light-emitting two-unit OLED architecture, we demonstrate the ability to continuously tune between strongly forward and strongly sideward emission, where the device efficiency is maintained at an application-relevant level ranging between 6 and 8% of external quantum efficiency for any chosen setting. In combination with additional optical elements, customizable and tuneable systems are possible, whereby the tuning stems from the light source itself rather than from the use of secondary optics.Organic Light-Emitting Diodes: Promising beam-shaping properties uncoveredA simple, efficient design incorporating organic light-emitting diodes could enable the development of customized, adjustable light sources for many applications. The ability to manipulate the shape of a beam of light emitted by a device is useful in many scenarios, for example switching between normal and private screen display modes on a mobile phone. However, current beam-shaping designs require extra components, making devices bulkier and more complex. Now, Felix Fries, Sebastian Reineke and co-workers at the Technische Universität Dresden, Germany, have used organic light-emitting diodes (OLEDs) to generate real-time beam shaping simply by manipulating the input power signal. The team’s design comprises two red-emitting OLEDs; by sending a carefully-modulated power signal through both OLEDs simultaneously they could customize the resulting beam of light. They hope to expand their research into full red-green-blue colour displays.