Abstract
We use photo-induced absorption technique to investigate the change of the triplet excitons in conjugated polymer doped with transition-metal complexes. By comparing pure PFO with PFO doped with 10 wt% Ir(mppy)3, we find the population of the triplet excitons in PFO doped with 10 wt% Ir(mppy)3 increases by one order of magnitude. The average lifetime of the triplet excitons in PFO doped with 10 wt% Ir(mppy)3 decreases by one order of magnitude. Combining these two results and the measurement of photoluminescence quantum efficiency, we deduce that the rate constant of the inter-system crossing increases by two order of magnitude after doping with 10 wt% Ir(mppy)3 . Furthermore, we compare the results at different concentrations and different temperature. In accordance with our experimental results, we deduce that the change of the triplet excitons in PFO comes from heavy-atom effect from Ir(mppy)3.