The initial luminescence loss of fluorescent OLEDs utilizing triplet–triplet annihilation is not only caused by quenching of singlet exciton with neutral quenchers but also by that of triplet excitons with positively charged quenchers.
ABSTRACTThe transient electroluminescence (EL) of phosphorescent organic
light-emitting diodes (OLEDs) was investigated. The behaviors of the
transient characteristics are analyzed using the triplet-triplet
annihilation model. The device exhibited a gradual decrease in quantum
current efficiency owing to the triplet-triplet annihilation at a high
current density. At a higher current density, the reduced rise and decay
times are due to high-density triplet excitons related to the enhanced
triplet-triplet annihilation and the increase of the nonradiative process.
The modulation speed of the devices is mainly limited by the phosphorescent
recombination lifetime.
The contribution of triplet–triplet annihilation to the lifetime and efficiency of fluorescent polymer organic light emitting diodes