Fast, Bright OLEDs Enable an Electrically Driven Polymer Laser

Organic semiconductors are attractive optoelectronic materials. However, the low mobility of light-emitting materials, and high capacitance of the OLED structure has generally led to them being considered slow. We have shown that the limitations of RC time constant and mobility can be overcome to make very fast and bright OLEDs. This opens up new directions for OLEDs, including communications and the potential to make electrically driven lasers. Organic semiconductors are suitable as laser gain media, but direct electrical pumping is exceptionally difficult because of losses due to charges, triplets and contacts. We have explored an alternative approach of separating charges and light generation from the gain medium to address these challenges. This in turn brings its own challenges as it requires the development of OLEDs giving world record intensity of light output, and efficient transfer of the light generated to the laser structure. We show that such an OLED can excite lasing in a polymer distributed feedback laser. The gain medium was the polymer BBEHP-PPV deposited by spin-coating. Measurements of threshold, beam and spectral narrowing will be presented.