Blue electroluminescence in blend of polymers containing carbazole and 1,3,4-oxadiazole units

The electro-optical properties of novel polymers such as poly(2,5-dihexyl phenylene-alt N-ethyl-3,6-carbazolevinylene) (PDPCVz) and poly[1',4'-phenylene-1 ",4 "-(2 "-(2''''-ethylhexyloxy))phenylene-2,5-(1"',4'"-phenylene)-1,3,4-oxadiazolyl] (PPEPPO) were characterized. The photoluminescence and electroluminescence spectra of the blend films composed of PDPCVz and PPOPPD were mainly contributed from the luminance of PDPCVz even at low PDPCVz ratios. Remarkably enhanced blue EL was shown, which probably results form the energy transfer in the exited state from PPEPPO, with a larger bandgap, to PDPCVz with a smaller bandgap. Furthermore, by incorporation of Alq(3) as the electron transporting layer to the EL devices, remarkable improvements in charge injection and EL efficiency were observed. (C) 2000 Published by Elsevier Science S.A.