Photo-, and electroluminescence studies of 2,5-bis[2 '-(4 ''-(6-hexoxy benzyl))-1 '-ethenyl]-3, 4-dibutyl thiophenes

We have synthesized a thiophene-based compound 2,5-bis[2'-(4 "-(6-hexoxy be nzyl))-1'-ethenyl]-3, 4-dibutyl thiophene (HBDT) and a copolymer poly(2,5-b is(2'-(4 "-(6-hexoxy benzyl))-1'-ethenyl)-3,4-dibutyl thiophene-1,6-diisocy anatohexane) (HBDT-PU) consisting of alternating HBDT and urethane spacer u nits. Absorption and photoluminescence (PL) spectra of the compounds coinci de indicating that emission in HBDT-PU occurs from the thiophene containing unit. PL is emitted in the blue-green region with a maximum at 460 nm. Con centration quenching occurs in pure materials: PL efficiency is strongly en hanced when the compounds are dispersed in a polymer matrix like poly(N-vin yl carbozole) (PVK) or poly(methyl metacrylate) (PMMA). Light emitting devi ces were fabricated using a PVK:2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3 ,4-oxadiazole (PBD) blend doped with HBDT as the emitter material. Efficien t energy transfer from PVK:PBD to HBDT molecules takes place in blended fil ms. The electroluminescence (EL) spectra coincided with the PL spectra of H BDT indicating that EL emission comes solely from HBDT molecules. The influ ence of the doping concentration on the EL efficiency was found to coincide with the concentration dependence of the PL quantum yield. (C) 1999 Elsevi er Science S.A. All rights reserved.