Triplet-Triplet Upconversion in Organic Light- Emitting Diodes: Implications to Injection Lasing

Abstract While significant progress has been made over last few years in the field of organic solid-state lasers, achieving lasing action from organic semiconductors under electrical excitation still remains a big challenge. One of the major barriers towards electrically pumped organic lasers are optical losses due to triplet excitons. In this work, we report both experimental and theoretical results that confirm positive contribution of triplet excitons for the scope of electrically driven organic laser. We studied a model fluorescence material, 9-(9-phenylcarbazole-3-yl)-10(naphthalene-1-yl) anthracene and reveals that the threshold current densities required to achieve lasing emission under electrical injection can be significantly reduced with the aid of triplet-triplet exciton upconversion processes. Furthermore, we demonstrate that, to achieve the best performance, the singlet-triplet exciton annihilation must be minimized. These results are unprecedented and provide a pathway towards development of new class of triplet-triplet upconversion materials for injection laser.