Abstract
Recent studies of frequency resolved DF due to T-T annihilation to singlet excitons (1S*) in π-conjugated polymers are reviewed, and the significance of this process is compared to that of other long-lived processses affecting the PL, in particular the nonradiative quenching of 1S* by polarons or triplet excitons. While the DF studies suggest that T-T annihilation typically accounts for up to ∼3% of the total PL, PLDMR and other studies suggest that singlet quenching by polarons and triplets may be a very significant process in the films and organic light emitting devices (OLEDs), especially at high excitation densities.