Intersystem Crossing Rate in Thermally Activated Delayed Fluorescence Emitters

Takashi Kobayashi, Daisuke Kawate, Akitsugu Niwa, Takashi Nagase, Kenichi Goushi, Chihaya Adachi, Hiroyoshi Naito

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)


For a better understanding of the exciton decay process in thermally activated delayed fluorescence (TADF) emitters, the intersystem crossing rate, kISC, is one of the important physical constants that have to be determined. Herein, a method to calculate the kISC value from photoluminescence (PL) measurements is reconsidered. The kISC 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 kISC 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, kISC 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.

Original languageEnglish
Article number1900616
JournalPhysica Status Solidi (A) Applications and Materials Science
Issue number3
Publication statusPublished - Feb 1 2020

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films
  • Electrical and Electronic Engineering
  • Materials Chemistry


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