A NOVEL FABRICATION TECHNIQUE AND NEW CONJUGATED POLYMERS FOR MULTILAYER POLYMER LIGHT-EMITTING-DIODES

We report a novel fabrication technique for multilayer light-emitting diodes composed of new polyoxadiazole, POD, conjugated polymers for th e first time. The fabrication technique called vapor deposition polyme rization is described. Chemical modification of monomers brought about the enhancement of reactivity and the production of high molecular we ight of POD. Emission color with photoexcitation was controllable from violet-blue to green by varying the chemical structures of PODs. It w as found that PODs could be employed as either electroluminescent or c arrier-injecting layers by the optimization of the device structure. T wo types of bilayer devices, which are constructed with POD/tris (8-qu inolinoato) aluminum, Alq(3), and with two POD layers with different c hemical structures, were investigated. Carrier injection begins in the POD/Alq(3), bilayer device near 7 V, and the device emitted green lig ht from Alq(3),. The maximum luminance of the POD/Alq(3), device reach ed 3500 cd/m(2). The POD/POD bilayer device emitted blue light with ma ximum luminance of 21 cd/m(2). Electroluminescence spectra of the devi ces coincided with photoluminescence spectra of each emitting material used. (C) 1997 by John Wiley & Sons, Ltd.