Room temperature lifetime of triplet excitons in fluorescent host/guest systems

► Strong triplet exciton lifetime stabilization in the fluorescent host/guest systems F8BT/MEH-PPV and Alq3/DCM is shown, in comparison to the pristine materials. ► A waveguide structure is used for highly sensitive measurements of triplet absorption at room temperature in amorphous thin films. ► Triplet-triplet annihilation rates of 10−12 cm3 s−1 for the pristine materials down to 10−15 cm3 s−1 for Alq3/DCM were determined. ► The significantly longer triplet lifetime in the host/guest systems is attributed to a substantially lowered mobility of the localized triplet excitons.