Temperature dependence of photoluminescence properties in a thermally activated delayed fluorescence emitter

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

doi:10.1063/1.4878397

Cited by 55 publications

(59 citation statements)

References 18 publications

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“…This result implies that the 4CN34BCz host effectively induces delayed emission of the 4CzIPN dopant. The TADF behaviour of 4CzIPN was confirmed in several papers by monitoring delayed emission of 4CzIPN at different temperatures and this result agrees with other group's investigation [17][18][19].…”

Section: Resultssupporting

confidence: 90%

Bicarbazole based donor–acceptor compound as a host for thermally activated delayed fluorescent emitter

et al. 2015

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Section: Resultssupporting

confidence: 90%

Bicarbazole based donor–acceptor compound as a host for thermally activated delayed fluorescent emitter

et al. 2015

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“…A correction factor, R , defined in Equation , can be deduced from PL quantum efficiencies at very low and room temperatures. In the case of 4CzIPN, the PL quantum efficiencies at 300 and 10 K are almost the same, although the ratio of the Ph in the measured PL varied greatly with temperature . Therefore, we determine

R = 1

for 4CzIPN at 10 K. In contrast, the PL quantum efficiency of 2CzPN at 10 K is slightly higher than that at 300 K .…”

Section: Resultsmentioning

confidence: 89%

Intersystem Crossing Rate in Thermally Activated Delayed Fluorescence Emitters

Kobayashi

Kawate

Niwa

et al. 2019

Physica Status Solidi (a)

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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.

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“…High temperature facilitates this endothermic transition. At low temperature (< 100 K), the PLQYs of TADF emitters are largely suppressed and strong photoexcitation intensity dependence of the emission appears, which are regarded as characteristic features of TADF molecules . The dependence of k RISC on temperature can be expressed in a Boltzmann distribution relation:

k_{RISC} \propto e x p (\frac{Δ E_{ST}}{k_{normalB} T})

where k B is the Boltzmann constant, T is the temperature, and Δ E ST is the singlet‐triplet energy splitting.…”

Section: Key Tadf Processesmentioning

confidence: 99%

Thermally Activated Delayed Fluorescence Materials Towards the Breakthrough of Organoelectronics

et al. 2014

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The design and characterization of thermally activated delayed fluorescence (TADF) materials for optoelectronic applications represents an active area of recent research in organoelectronics. Noble metal-free TADF molecules offer unique optical and electronic properties arising from the efficient transition and interconversion between the lowest singlet (S1 ) and triplet (T1 ) excited states. Their ability to harvest triplet excitons for fluorescence through facilitated reverse intersystem crossing (T1 →S1 ) could directly impact their properties and performances, which is attractive for a wide variety of low-cost optoelectronic devices. TADF-based organic light-emitting diodes, oxygen, and temperature sensors show significantly upgraded device performances that are comparable to the ones of traditional rare-metal complexes. Here we present an overview of the quick development in TADF mechanisms, materials, and applications. Fundamental principles on design strategies of TADF materials and the common relationship between the molecular structures and optoelectronic properties for diverse research topics and a survey of recent progress in the development of TADF materials, with a particular emphasis on their different types of metal-organic complexes, D-A molecules, and fullerenes, are highlighted. The success in the breakthrough of the theoretical and technical challenges that arise in developing high-performance TADF materials may pave the way to shape the future of organoelectronics.

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Temperature dependence of photoluminescence properties in a thermally activated delayed fluorescence emitter

Cited by 55 publications

References 18 publications

Bicarbazole based donor–acceptor compound as a host for thermally activated delayed fluorescent emitter

Bicarbazole based donor–acceptor compound as a host for thermally activated delayed fluorescent emitter

Intersystem Crossing Rate in Thermally Activated Delayed Fluorescence Emitters

Thermally Activated Delayed Fluorescence Materials Towards the Breakthrough of Organoelectronics

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