Minimizing Efficiency\nRoll-Off in Organic Emitters\nvia Enhancing Radiative Process and Reducing Binding Energy: A Theory\nInsight

Organic solid-state lasers have received increasing attention\ndue\nto their great potential for realizing organic continuous-wave or\nelectrically driven lasers. Moreover, they exhibit significant promise\nfor optoelectronic devices due to their chemically tunable optoelectronic\nproperties and cost-effective self-assembly traits. Recently, a great\nprogress has been made in organic solid-state lasers via spatially\nseparated charge injection and lasing. However, making directly electrically\ndriven organic semiconductor lasers is very challenging. It is difficult\nbecause of a number of excitonic losses caused by the spin-forbidden\nnature as well as serious efficiency roll-off at a high current density.\nHere, a multifunction gain material, functioning both as a thermally\nactivated delayed fluorescence (TADF) emitter with exceptional optical\ngain and as a source of phosphorescence, was theoretically investigated.\nThe new molecule we designed exhibits a reduction of triplet accumulation\nthrough an effective exciton radiative process (5-fold boost in figure\nof merit) and significantly decreased exciton binding energy (dipole\nmoment from 5.77 to 14.03 D), which benefit amplified spontaneous\nemission and lasing emission. Our work provides theoretical insights\ninto organic solid-state lasers and may contribute to the development\nof new and efficient laser-gaining molecules.