Energy and Charge Transfer in Electroluminescent Polymer/Porphyrin Blends

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Abstract
We present a study of the effects of blending electroluminescent polymers with platinum (II) octaethylporphyrin (PtOEP). We find that in the case of polymers which are measured to have HOMO and LUMO levels respectively below and above those of the PtOEP, and which have emission spectra overlapping the PtOEP absorption spectra, energy transfer occurs as expected. We find further evidence, in the form of steady state and time-resolved electroluminescence and photoluminescence measurements, which indicates additional transfer of triplet excitons between polymer and porphyrin. Where the polymers have emission spectra overlapping the absorption spectra of PtOEP, but which are measured to have a HOMO or LUMO level between those of the porphyrin, quenching of the photoluminescence efficiency occurs. We propose this is due to charge separation between the porphyrin and the polymer, and show evidence for this in the form of photoinduced absorption measurements.