Electroluminescence properties of systematically derivatized organic chromophores containing electron donor and acceptor groups

We present electroluminescent (EL) properties of new blue-green organic dyes. The molecular structures of these dyes are based on 2,7-divinyl-9,9-bis(tert-butyl)fluorene, a pi-electron bridge, end-capped with electron donor (D) and/or electron acceptor (A) group(s) to form D-pi-A, D-pi-D, and A-pi-A structures. The donor group is a triphenylamine, and the acceptor group is a diphenyloxadiazole. We studied EL properties of these dyes in a single-layer EL device having the following structure: ITO/PVK:DYE/Ca/Al. We found that both the wavelength of maximum emission and the threshold of EL depend on the structure and the concentration of the dye. Among the structure reported here, the D-pi-A dye shows the highest EL performance, exhibiting a brightness of 498 ed/m(2) at an applied voltage of 25 V.