scholarly journals Not the Sum of their Parts: Understanding Multi-Donor Interactions in Symmetric and Asymmetric TADF Emitters

2021 ◽  
Author(s):  
Andrew Danos ◽  
Dalius Gudeika ◽  
Nadzeya Kukhta ◽  
Ramunas Lygaitis ◽  
Marco Colella ◽  
...  
Keyword(s):  
Photoluminescence Spectrum ◽  
Delayed Fluorescence ◽  
Quantum Yields ◽  
Thermally Activated Delayed Fluorescence ◽  
Thermally Activated

A pair of thermally activated delayed fluorescence (TADF) emitters with symmetric and asymmetric D-A-D structure are investigated. Despite displaying near-identical photoluminescence spectrum and quantum yields, the symmetric material possesses significantly...

scholarly journals Solution-Processed OLEDs Based on Thermally Activated Delayed Fluorescence Copper(I) Complexes with Intraligand Charge-Transfer Excited State

Molecules ◽  
2021 ◽  
Vol 26 (4) ◽  
pp. 1125
Author(s):  
Teng Teng ◽  
Jinfan Xiong ◽  
Gang Cheng ◽  
Changjiang Zhou ◽  
Xialei Lv ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Density Functional ◽  
Delayed Fluorescence ◽  
Quantum Yields ◽  
Functional Theory ◽  
Solution Processed ◽  
Thermally Activated Delayed Fluorescence ◽  
Light Emitting ◽  
Thermally Activated ◽  
Wide Range

A new series of tetrahedral heteroleptic copper(I) complexes exhibiting efficient thermally-activated delayed fluorescence (TADF) in green to orange electromagnetic spectral regions has been developed by using D-A type N^N ligand and P^P ligands. Their structures, electrochemical, photophysical, and electroluminescence properties have been characterized. The complexes exhibit high photoluminescence quantum yields (PLQYs) of up to 0.71 at room temperature in doped film and the lifetimes are in a wide range of 4.3–24.1 μs. Density functional theory (DFT) calculations on the complexes reveal the lowest-lying intraligand charge-transfer excited states that are localized on the N^N ligands. Solution-processed organic light emitting diodes (OLEDs) based on one of the new emitters show a maximum external quantum efficiency (EQE) of 7.96%.

Outstanding blue delayed fluorescence and significant processing stability of cuprous complexes with functional pyridine–pyrazolate diimine ligands

2015 ◽  
Vol 44 (15) ◽  
pp. 6706-6710 ◽  
Author(s):  
Qing Zhang ◽  
Jun Chen ◽  
Xiao-Yuan Wu ◽  
Xu-Lin Chen ◽  
Rongmin Yu ◽  
...  
Keyword(s):  
Delayed Fluorescence ◽  
Quantum Yields ◽  
Thermally Activated Delayed Fluorescence ◽  
Thermally Activated ◽  
Diimine Ligands ◽  
Processing Stability

Five cuprous complexes display outstanding blue thermally activated delayed fluorescence (TADF) with quantum yields near 1 and significant processing stability from the solid to the solvent states.

scholarly journals Regioisomeric Effect on the Excited-State Fate Leading to Room-Temperature Phosphorescence or Thermally Activated Delayed Fluorescence in a Dibenzophenazine-Cored Donor–Acceptor–Donor System

2021 ◽  
Author(s):  
Takumi Hosono ◽  
Nicolas Oliveira Decarli ◽  
Paola Zimmermann Crocomo ◽  
Tsuyoshi Goya ◽  
Leonardo Evaristo de Sousa ◽  
...  
Keyword(s):  
Excited State ◽  
Room Temperature ◽  
Delayed Fluorescence ◽  
Quantum Yields ◽  
Room Temperature Phosphorescence ◽  
Thermally Activated Delayed Fluorescence ◽  
Light Emitting ◽  
Thermally Activated ◽  
Donor Acceptor ◽  
Emission Behavior

Exploring design principle for switching thermally activated dealyed fluorescecne (TADF) and room temperature phosphorescence (RTP) is a fundamentally imporant research in developing triplet-mediated photofunctional organic materials. Herein systematic studies on the regioisomeric and substituents effects in a twisted donor–acceptor–donor (D–A–D) scaffold (A = dibenzo[a,j]phenazine; D = dihydrophenazasiline) on the fate of the excited state have been performed. The study revealed that the regiosiomerism clearly affects the emission behavior of the D–A–D compounds. Distinct difference in TADF, dual TADF & RTP, and dual RTP were observed, depending on the host used. Furthermore, OLED organic light-emitting diodes (OLEDs) fabricated with the developed emitters achieved high external quantum yields for RTP-based OLEDS up to 7.4%.

A red thermally activated delayed fluorescence emitter employing dipyridophenazine with a gradient multi-inductive effect to improve radiation efficiency

2019 ◽  
Vol 7 (25) ◽  
pp. 7525-7530 ◽  
Author(s):  
Huiqin Wang ◽  
Bingjie Zhao ◽  
Peng Ma ◽  
Zhe Li ◽  
Xinyu Wang ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Inductive Effect ◽  
Intramolecular Charge Transfer ◽  
Radiative Transition ◽  
Delayed Fluorescence ◽  
Radiation Efficiency ◽  
Quantum Yields ◽  
Thermally Activated Delayed Fluorescence ◽  
Thermally Activated ◽  
Electro Luminescence

Red TADF emitter oTPA-DPPZ employs dipyridophenazine with gradient multi-inductive effect as acceptor, which enhances intramolecular charge transfer and radiative transition, resulting photo- and electro-luminescence quantum yields of 75% and 18.5%.

scholarly journals Substitution Effects on a New Pyridylbenzimidazole Acceptor for Thermally Activated Delayed Fluorescence and Their Use in Organic Light-Emitting Diodes

2021 ◽  
Author(s):  
David Hall ◽  
P Rajamalli ◽  
Eimantas Duda ◽  
Subeesh Madayanad Suresh ◽  
Francesco Rodella ◽  
...  
Keyword(s):  
Light Emitting Diodes ◽  
Conformational Dynamics ◽  
Delayed Fluorescence ◽  
Organic Light Emitting Diodes ◽  
Quantum Yields ◽  
Substitution Effects ◽  
Thermally Activated Delayed Fluorescence ◽  
Light Emitting ◽  
Thermally Activated ◽  
Organic Light

<p>In this work we introduce a new acceptor for use in thermally activated delayed fluorescence (TADF) emitters, pyridylbenzimidazole, which when coupled with phenoxazine, allows efficient TADF occurs. <i>N</i>-functionalization of the benzimidazole using methyl, phenyl and <i>tert</i>-butyl groups permits colour tuning and adjustment of the optoelectronic properties and suppression of aggregation-caused quenching (ACQ) with minimal impact on the TADF mechanism. Good photoluminescence quantum yields, F<sub>PL</sub>, (49% - 68%) in mCP-doped films are reported for the emitters. The functionalized derivatives support a higher doping of 7 wt% before a fall-off in F<sub>PL</sub> is observed, in contrast with the parent compound, which undergoes ACQ at doping concentrations greater than 1 wt%. We find complex conformational dynamics, reflected in the time-resolved decay profile. D<i>E</i><sub>ST</sub> is modulated by N-substituents of the benzimidazole and ranges of between 0.22 eV and 0.32 eV in doped films. Density Functional Theory (DFT) calculations suggest the importance of intermediate triplet excited states to enhance the RISC rate. Vacuum-deposited organic light-emitting diodes (OLEDs), prepared using three of the four analogs show maximum external quantum efficiencies, EQE<sub>max</sub>, of 23.9%, 22.2% and 18.6% for <b>BIm(Me)PyPXZ</b>, <b>BIm(Ph)PyPXZ</b> and <b>BImPyPXZ</b>, respectively, with a correlated and modest efficiency roll-off at 100 cd m<sup>-2</sup> of 19% 13%, and 24% of the EQE<sub>max</sub>, respectively; higher maximum luminance values of 21,000 cd m<sup>-2</sup> and 18,000 cd m<sup>-2 </sup>are also obtained for <b>BIm(Ph)PyPXZ</b> and <b>BIm(Me)PyPXZ</b>, respectively, compared to 8,000 cd m<sup>-2</sup> for <b>BImPyPXZ</b>.</p>

scholarly journals Carbene-metal complexes as molecular scaffolds for construction of through-space TADF emitters

2021 ◽  
Author(s):  
Armands Ruduss ◽  
Baiba Turovska ◽  
Sergey Belyakov ◽  
Kitija Stucere ◽  
Aivars Vembris ◽  
...  
Keyword(s):  
Delayed Fluorescence ◽  
Organometallic Complexes ◽  
Quantum Yields ◽  
Design Strategies ◽  
Molecular Scaffolds ◽  
Triplet Energy ◽  
Spin Orbital ◽  
Thermally Activated Delayed Fluorescence ◽  
Thermally Activated ◽  
Spin Orbital Coupling

Through-space charge transfer (CT) process is observed in Cu(I) carbene-metal-amide complexes, where conventional imidazole or imidazoline N-heterocyclic (NHC) carbene fragments act as inert linkers and CT proceeds between a metal-bound carbazole donor and a distantly situated carbene-bound phenylsulfonyl acceptor. The resulting electron transfer gives a rise to efficient thermally activated delayed fluorescence (TADF), characterized with high photoluminescence quantum yields (ΦPL up to 90 %) and radiative rates (kr) up to 3.32×105 s-1. TADF process is aided by fast reverse intersystem crossing (rISC) rates of up to 2.56×107 s-1. Such emitters can be considered as hybrids of two existing TADF emitter design strategies, combining low singlet-triplet energy gaps (ΔEST) met in all-organic exciplex-like emitters (0.0062−0.0075 eV) and small, but non-negligible spin-orbital coupling (SOC) provided by Cu atom, like in TADF-active organometallic complexes.

Isomerization enhanced quantum yield of dibenzo[a,c]phenazine-based thermally activated delayed fluorescence emitters for highly efficient orange OLEDs

2020 ◽  
Vol 8 (28) ◽  
pp. 9639-9645
Author(s):  
Changjiang Zhou ◽  
Wen-Cheng Chen ◽  
He Liu ◽  
Xiaosong Cao ◽  
Nengquan Li ◽  
...  
Keyword(s):  
Quantum Yield ◽  
Delayed Fluorescence ◽  
Quantum Yields ◽  
Thermally Activated Delayed Fluorescence ◽  
Thermally Activated ◽  
Highly Efficient

Highly efficient orange/red OLED emitters are obtained with isomerization enhanced quantum yields.

scholarly journals Multichromophore Molecular Design for Efficient Thermally Activated Delayed Fluorescence Emitters with Near-Unity Photoluminescence Quantum Yields

2021 ◽  
Author(s):  
Dongyang Chen ◽  
Yu Kusakabe ◽  
Yongxia Ren ◽  
Dianming Sun ◽  
P Rajamalli ◽  
...  
Keyword(s):  
Molecular Design ◽  
Light Emitting Diode ◽  
Blue Emission ◽  
Delayed Fluorescence ◽  
Quantum Yields ◽  
Thermally Activated Delayed Fluorescence ◽  
Light Emitting ◽  
Organic Light Emitting Diode ◽  
Thermally Activated ◽  
Organic Light

Three multichromophore thermally activated delayed fluorescence (TADF) molecules, <b><i>p</i>-di2CzPN</b>, <b><i>m</i>-di2CzPN</b>, and<b> 1,3,5-tri2CzPN</b>, were synthesized and characterized. These molecules were designed by connecting the TADF moiety 4,5-di(9<i>H</i>-carbazol-9-yl)phthalonitrile (<b>2CzPN</b>) to different positions of a central benzene ring scaffold. Three highly soluble emitters all exhibited near quantitative photoluminescence quantum yields (<i></i><sub>PL</sub>) in toluene. High <i></i><sub>PL</sub>s were also achieved in doped films, 59% and 70% for <b><i>p</i>-di2CzPN</b> and <b><i>m</i>-di2CzPN</b> in 10 wt% DPEPO doped films, respectively, and 54% for <b>1,3,5-tri2CzPN</b> in 20 wt% doped CBP film. The rate constant of reverse intersystem crossing (<i>k</i><sub>RISC</sub>) for <b><i>p</i>-di2CzPN</b> and <b><i>m</i>-di2CzPN</b> in DPEPO films reached 1.1 × 10<sup>5</sup> s<sup>−1</sup> and 0.7 × 10<sup>5</sup> s<sup>−1</sup>, respectively, and <i>k</i><sub>RISC</sub> for <b>1,3,5-tri2CzPN</b> in CBP film reached 1.7 × 10<sup>5</sup> s<sup>−1</sup>. A solution-processed organic light-emitting diode based on <b>1,3,5-tri2CzPN </b>exhibited a sky-blue emission with CIE coordinate of (0.22, 0.44), and achieved a maximum external quantum efficiency of 7.1%.

Sign in / Sign up

Export Citation Format

Share Document