Quantifying Exciton Annihilation Effects in Thermally Activated Delayed Fluorescence Materials

Important parameters for the design and performance of thermally activated delayed fluorescence (TADF) emitters are forward reverse intersystem crossing rates between singlet triplet states. The magnitude these is determined from prompt transient photoluminescence decay. It demonstrated that this decay strongly depends on initial photoexcited population density due to exciton–exciton annihilation processes. By kinetic modeling power-dependent time-resolved TADF emitter 9,10-bis(4-(9H-carbazol-9-yl)-2,6-dimethylphenyl)-9,10-diboraanthracene (CzDBA), singlet–triplet triplet–triplet identified as main loss processes with rate constants in order 10−17 m3 s−1. Neglecting quenching leads erroneous estimates (reverse) rates.