STRATEGIES FOR IMPROVING THE EFFICIENCY OF RED ORGANIC ELECTROLUMINESCENCE

摘要

To date organic electroluminescence has only found commercial use in simple passive matrix displays. Due to the triplet-triplet annihilation luminescence limit, it is more difficult to implement large passive matrix displays using phosphors than comparable displays using fluorescent materials. But as organic materials are applied to more sophisticated applications requiring active matrix drivers, the case for phosphorescent materials becomes overwhelming; their intrinsic advantages have already enabled them to set remarkable efficiency standards in the red and green, and the development of blue phosphors appears to be technically feasible. However, it is not clear whether optimal devices will use phosphorescent dyes as the emissive medium or use a phosphorescent material to sensitize fluorescence. Both techniques have advantages: using a host/phosphorescent guest combination is simpler, easier to fabricate, and may exhibit lower energy transfer losses due to the one step process; but sensitized fluorescence adds the efficiency advantages of phosphors to the broad field of fluorescent molecules, and the depth of fluorescent materials knowledge may facilitate more precise color tuning and higher photoluminescent efficiencies. In any case, the design flexibility now available is an encouraging sign for the burgeoning field of organic electrophosphorescence.