Flexible Large‐Area Light‐Emitting Devices Based on WS 2 Monolayers

Strong covalent in‐plane bonds and a tiny thickness in the nanometer range make two‐dimensional (2D) materials ideally suited for flexible electronic or optoelectronic applications. Despite this exciting perspective, only a few prototypes of such flexible devices—photodetectors and transistors—have been reported until now. The first large‐area flexible light‐emitting device (LED) based on 2D materials is realized by integrating a transition metal dichalcogenide (TMDC) monolayer synthesized by metal organic chemical vapor deposition (MOCVD) into a p–n architecture on conductive polymer foil. This flexible LED demonstrates homogeneous red light emission from a few square millimeter area in a scalable design. Uniquely, the electroluminescence can be tuned over 30 meV simply by bending the devices, i.e., by applying a defined strain. This approach combines the flexibility of organic semiconductor device concepts with the durability of inorganic semiconductor technology.