Time-resolved photoluminescence study on concentration quenching of a red emitting tetraphenylchlorin dye for organic electroluminescent devices

摘要

Time-resolved photolurninescence (PL) of a red emitting dye, tetraphenylchlorin (TPC), doped in poly(methylmethacrylate) (PMMA) at various concentrations was studied to clarify the mechanism of concentration quenching often observed in organic electroluminescence devices. At doping concentrations lower than 10~(-2)mol/L, PL lifetimes of TPC were relatively constant (approx 10ns) and equal to that of TPC in dilute solution. At doping concentrations higher than 10~(-2) mol/L, PL lifetime decreased rapidly with increasing concentration, down to 2ns at 8 x 10~(-2) mol/L. This decrease in PL lifetime was related to the concentration quenching of TPC monomer emission by the increasing number of TPC dimer sites formed at such higher concentrations. Our experimental results of concentration-dependence trapping agree fairly well with the theoretical model of trapping by dimers reported in literature.