The contribution of triplet-triplet annihilation to the lifetime and efficiency of fluorescent polymer organic light emitting diodes.

We demonstrate that the fast initial decay of a prototypical fluorescent polymer based organic light emitting diode device is related to the contribution that triplet-triplet annihilation makes to the device efficiency. We show that, during typical operating conditions, approximately 20% of the device efficiency originates from the production of singlet excitons by triplet-triplet annihilation. During prolonged device operation, the triplet excitons are quenched much more easily than the emissive singlets; thus, the contribution to the efficiency from triplet-triplet annihilation is lost during the early stages of the device lifetest. The fast initial decay of the device luminance can be removed by incorporating a triplet quenching additive into the active layer to remove any effect of triplet-triplet annihilation; this yields an increase in the device lifetime of greater than 3x and an even more significant improvement in the initial luminance decay. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3561430