Concentration Dependence of Photoluminescence and Electroluminescence in 2,5 bis2'-(4'-hydroxyhexanol benzyl)-1 '-ethyl3,4-dibutyl th1ophenes

摘要

A new thiophene-based compound 2,5 bis[2'-(4"-hydroxyhexanol benzyl)-1'-ethyl]3,4-dibu-tyl thiophene (HBDT) as well as a copolymer (HBDT-PU) consisting of alternating HBDT and urethane spacer units were synthesized. Absorption and luminescence properties of both compounds were studied in solution and in different polymer matrices. Absorption and luminescence spectra of HBDT and HBDT-PU coincide indicating that emission in HBDT-PU occurs from the thiopene containing unit. Photoluminescence (PL) is emitted in the blue-green region of the visible spectrum with a maximum at 460 nm. The PL efficiency of both compounds is strongly enhanced when dispersed in a PVK or PMMA matrix indicating that concentration quenching occurs in the pure material. Light emitting devices were fabricated utilizing a PVK/PBD blend doped with HBDT and HBDT-PU at different concentrations as emitter material. The electroluminescence (EL) spectra coincided with the PL spectra of HBDT indicating that EL emission originates from the dopant molecules. The dependence of the EL efficiency on the doping concentration was measured and found to be close to the concentration dependence of the PL quantum yield.