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Exciton–Exciton Annihilation in Thermally Activated Delayed Fluorescence Emitter
Author(s) -
Hasan Monirul,
Shukla Atul,
Ahmad Viqar,
Sobus Jan,
Bencheikh Fatima,
McGregor Sarah K. M.,
Mamada Masashi,
Adachi Chihaya,
Lo ShihChun,
Namdas Ebinazar B.
Publication year - 2020
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.202000580
Subject(s) - intersystem crossing , annihilation , singlet state , materials science , singlet fission , exciton , excited state , quenching (fluorescence) , photochemistry , oled , triplet state , atomic physics , fluorescence , molecular physics , physics , chemistry , condensed matter physics , optics , nanotechnology , nuclear physics , layer (electronics)
Recent studies have demonstrated that in thermally activated delayed fluorescence (TADF) materials, efficient reverse intersystem crossing occurs from nonradiative triplet exited states to radiative singlet excited states due to a small singlet–triplet energy gap. This reverse intersystem crossing significantly influences exciton annihilation processes and external quantum efficiency roll‐off in TADF based organic light‐emitting diodes (OLEDs). In this work, a comprehensive exciton quenching model is developed for a TADF system to determine singlet–singlet, singlet–triplet, and triplet–triplet annihilation rate constants. A well‐known TADF molecule, 3‐(9,9‐dimethylacridin‐10(9 H )‐yl)‐9 H ‐xanthen‐9‐one (ACRXTN), is studied under intensity‐dependent optical and electrical pulse excitation. The model shows singlet–singlet annihilation dominates under optically excited decays, whereas singlet–triplet annihilation and triplet–triplet annihilation have strong contribution in electroluminescence decays under electrical pulse excitation. Furthermore, the efficiency roll‐off characteristics of ACRXTN OLEDs at steady state is investigated through simulation. Finally, singlet and triplet diffusion length are calculated from annihilation rate constants.