Long lived photo- and electroluminescence from a side-chain polymer/porphyrin blend

We utilised the technique of combining electroluminescent polymers with photo-emissive molecular dopants to create a blend that has an absorption spectrum and electrical transport properties dominated by the polymer, but photoluminescence and electroluminescence spectra dominated by the dopant. The dopant molecule, platinum octaethyl porphyrin, is well known as a solid state phosphor [1], and we have succeeded in creating a system with a luminescence lifetime of the order of tens of microseconds. In addition, although some photoluminescence quantum efficiency is inevitably lost in the energy transfer process, the blended system is still found to be 29% efficient. When the polymer-dopant blend is used to make light-emitting diodes (LEDs) which are tested in pulsed mode, the light emission from the device is seen to decay after the voltage pulse with the same lifetime as the photoluminescence. The long-lived emission is a strong indication that the blend emits from the triplet manifold of the dopant molecule.