Influence of Excimer Behavior on Photoluminescence and Electroluminescence of a Novel Conjugated Molecule Doped in Polymer

Influence of excimer formation on photoluminescence and electroluminescence of a novel conjugated molecule, 1-(9anthrylethynyl)-4-chloromethyl-2,5-dimethoxybenzene (ACDB), doped in polystyrene was investigated. The monomer emission decreased and the excimer emission increased when the concentration of ACDB in the doped film was increased for photoluminescence. This resulted from the energy migration to the trapping sites of excimer. The electroluminescent device with lower concentration of ACDB in the emitting layer exhibited only the exciton emission independent of the applied voltage. The device with higher concentration exhibits exciton emission at high drive voltages but excimer emission at low drive voltages. The electric field strength dependent electroluminescent behavior with higher concentration of ACDB was explained according to the fluorescence quenching effects caused by the field-enhanced thermal dissociation of excimer. Doping polymer is helpful in suppressing the formation of excimer.