Organic semiconductors can be deposited at low cost over large areas using a variety of methods and are used commercially in consumer display technologies in the form of organic light-emitting diodes. However, developing electrically injected organic lasers remains challenging. This is due to several effects, including poor thermal stability, low charge-carrier mobility (and thus low current densities) and contact losses. Graham Turnbull, Ifor Samuel and colleagues now report an electrically driven lasing device that uses semiconducting layers made of only organic materials.

Credit: Adapted under a Creative Commons licence CC BY 4.0

The researchers — who are based at the University of St Andrews, the University of Glasgow and the Institute of Physical-Organic Chemistry and Coal Chemistry, Ukraine — developed a device consisting of an organic gain medium that is excited by electroluminescence emitted from an organic light-emitting diode integrated on top. By physically separating the regions where charge injection and laser population inversion occurs, the team were able to overcome losses related to the low charge-carrier mobility of organic semiconductors, which can lead to accumulation of injected charges and makes contact placement challenging. At injected current densities above 2.8 kA cm−2, a laser emission peak at 542.2 nm was observed and a slope efficiency of 2.1 ± 0.2 μW A−1 was calculated.

Original reference: Nature 621, 746–752 (2023)