A paper by Karl Leo has been published in the journal Nature Materials

Organic semicon­duc­tors have gained a strong reputa­tion as energy-saving materi­als in organic light-emitting diodes (OLEDs), which are used in large displays. Many of us hold them in our hands every day as we reach for a cell phone or tablet, for example.

In these and other appli­ca­tions, such as solar cells, the energy gap is a key parame­ter. The ability to adjust this energy gap as smoothly as possi­ble is a desir­able property of the mater­ial for its versa­tile techni­cal applicability.

In their latest publi­ca­tion, the group of researchers, which includes Hector Fellow Karl Leo, reports how they were able to realize the adjust­ment of the energy gap for the first time by means of blend­ing for organic semiconductors.

The researchers found an uncon­ven­tional way by blend­ing two semicon­duc­tors with similar molec­u­lar struc­ture but differ­ent molec­u­lar sizes. "The key insight is that all molecules arrange themselves in certain patterns deter­mined by their molec­u­lar shape and size," explains Frank Ortmann, profes­sor at TU Munich and group leader at the Center for Advanc­ing Electron­ics Dresden. "This leads to the desired change in the dielec­tric constant and the size of the band gap of the material."

Together with Peter Hegemann, Karl Leo is also currently conduct­ing research on the appli­ca­tion of organic light-emitting diodes (OLEDs) in optoge­net­ics as part of an inter­dis­ci­pli­nary project of the HFA. The aim is to use a new OLED technol­ogy that can imitate electri­cally switch­able differ­ent colors.