Room temperature lifetime of triplet excitons in fluorescent host/guest systems
Abstract We studied the triplet decay dynamics in the fluorescent polymer–polymer host/guest system F8BT/MEH-PPV and in the small molecule host/guest system Alq 3 /DCM. The triplet lifetime was determined by a highly sensitive time-resolved measurement of the triplet state absorption via a pump and probe experiment in a waveguide structure. We were able to identify triplet–triplet annihilation as a major decay mechanism of triplet states in the pristine amorphous organic materials at room temperature (rate constant: k TT  ≈ 10 −12  cm 3  s −1 ). On the contrary, the host/guest systems showed a significantly increased triplet lifetime caused by a reduced triplet–triplet annihilation rate which we attribute to a substantially lowered mobility of the localized triplet excitons. Our results are expected to be of paramount importance for organic light emitting devices based on fluorescent emitters (e.g. organic lasers and organic light emitting diodes).