Sensitive triplet exciton detection in polyfluorene using Pd-coordinated porphyrin

We developed a sensitive spectroscopic method to probe triplet concentration in thin films of polyfluorene (PF) at room temperature. The energy of photoexcited triplet excitons is transferred to the guest metal-organic complex, meso-tetratolylporphyrin-Pd (PdTPP), and detected as phosphorescent emission. The phosphorescence intensity of PdTPP-PF blends is proportional to the independently measured triplet concentration using photoinduced absorption experiments. The high sensitivity of this method allows room temperature detection of triplet excitons in spin-coated polymer films as thin as 10 nm. We found that the triplet lifetime is independent of PdTPP concentration and therefore this method is nearly non-perturbing for the triplet population.