Exciton Quenching Behavior of Thermally Activated Delayed Fluorescence Molecules by Charge Carriers

The quenching of singlet excitons by injected charge carriers in molecules that display thermally activated delayed fluorescence (TADF) was investigated using time-resolved transient photoluminescence (PL) techniques. Injected electrons did not affect the excitons; however, injected holes caused significant quenching. Using a rate-equation analysis, the hole-induced exciton quenching rate was determined to be between 10(-11) and 10(-12) cm(3) s(-1). Interestingly, the TADF emission component was enhanced in the presence of injected holes, plausibly due to a reduction of the singlet-exciton energy level.