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Photoluminescence Quenching Probes Spin Conversion and Exciton Dynamics in Thermally Activated Delayed Fluorescence Materials
Author(s) -
Yurash Brett,
Nakanotani Hajime,
Olivier Yoann,
Beljonne David,
Adachi Chihaya,
Nguyen ThucQuyen
Publication year - 2019
Publication title -
advanced materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.707
H-Index - 527
eISSN - 1521-4095
pISSN - 0935-9648
DOI - 10.1002/adma.201804490
Subject(s) - intersystem crossing , exciton , materials science , photoluminescence , fluorescence , photon upconversion , phosphorescence , oled , photochemistry , singlet state , quenching (fluorescence) , diffusion , chemical physics , optoelectronics , luminescence , atomic physics , nanotechnology , excited state , chemistry , condensed matter physics , optics , physics , thermodynamics , layer (electronics)
Fluorescent materials that efficiently convert triplet excitons into singlets through reverse intersystem crossing (RISC) rival the efficiencies of phosphorescent state‐of‐the‐art organic light‐emitting diodes. This upconversion process, a phenomenon known as thermally activated delayed fluorescence (TADF), is dictated by the rate of RISC, a material‐dependent property that is challenging to determine experimentally. In this work, a new analytical model is developed which unambiguously determines the magnitude of RISC, as well as several other important photophysical parameters such as exciton diffusion coefficients and lengths, all from straightforward time‐resolved photoluminescence measurements. From a detailed investigation of five TADF materials, important structure–property relationships are derived and a brominated derivative of 2,4,5,6‐tetrakis(carbazol‐9‐yl)isophthalonitrile that has an exciton diffusion length of over 40 nm and whose excitons interconvert between the singlet and triplet states ≈36 times during one lifetime is identified.