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Intersystem Crossing Rate in Thermally Activated Delayed Fluorescence Emitters
Author(s) -
Kobayashi Takashi,
Kawate Daisuke,
Niwa Akitsugu,
Nagase Takashi,
Goushi Kenichi,
Adachi Chihaya,
Naito Hiroyoshi
Publication year - 2020
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.201900616
Subject(s) - intersystem crossing , exciton , fluorescence , atmospheric temperature range , photoluminescence , range (aeronautics) , atomic physics , materials science , physics , analytical chemistry (journal) , optoelectronics , chemistry , excited state , optics , condensed matter physics , thermodynamics , singlet state , chromatography , composite material
For a better understanding of the exciton decay process in thermally activated delayed fluorescence (TADF) emitters, the intersystem crossing rate, k ISC , is one of the important physical constants that have to be determined. Herein, a method to calculate the k ISC value from photoluminescence (PL) measurements is reconsidered. The k ISC value can be determined at very low temperatures where delayed fluorescence (DF) is completely suppressed, as well as around room temperature where triplet excitons mainly decay into the ground state by emitting DF. However, there is a temperature range where the k ISC value cannot be determined accurately because the influences of nonradiative decay paths can be neither ignored nor corrected. For such a temperature range, an alternative approach, which utilizes the temperature dependence of an observed PL decay rate, is presented. In this way, k ISC values from 300 to 10 K are determined for thin films of two TADF emitters, i.e., 1,2,3,5‐tetrakis(carbazol‐9‐yl)‐4,6‐dicyanobenzene and 1,2‐bis(carbazol‐9‐yl)‐4,5‐dicyanobenzene, which are known as 4CzIPN and 2CzPN, respectively.