Electroluminescence Properties of Systematically Derivatized Organic Chromophores Containing Electron Donor and Acceptor Groups

Abstract

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 π-electron bridge, end-capped with electron donor (D) and/or electron acceptor (A) group(s) to form D−π−A, D−π−D, and A−π−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−π−A dye shows the highest EL performance, exhibiting a brightness of 498 cd/m 2 at an applied voltage of 25 V.