Polymethine dyes as novel efficient infrared electroluminescence materials

We examined the electroluminescence (EL) characteristics of four polymethine dyes to evaluate both their advantages and limitations as infrared (IR) EL materials. The IR EL intensity showed a marked dependence on the IR dye, and an IR EL quantum efficiency of 3.6 x 10(-2)% photons/electron was measured for the most efficient IR EL dye, 2-[2-[2-chloro-3-[2-(1-dodecyl-1,2-dihydro-benzo[c,d ]-indol-2-ylidene)-ethylidene]-1-cyclohexen-1-yl]-ethenyl]-1-dodecyl-benzo[c,d]indolium chloride (SO447). We discuss the IR EL characteristics of these dyes in terms of photoluminescence efficiency, competitive visible/near-IR EL and dimer EL, and trapping efficiency.