scholarly journals Exceptionally fast radiative decay of a dinuclear platinum complex through thermally activated delayed fluorescence

2021 ◽  
Author(s):  
Piotr Pander ◽  
Ruth Daniels ◽  
Andrey V. Zaytsev ◽  
Ashleigh Horn ◽  
Amit Sil ◽  
...  
Keyword(s):  
Decay Rate ◽  
Radiative Decay ◽  
Platinum Complex ◽  
Delayed Fluorescence ◽  
Significant Enhancement ◽  
Thermally Activated Delayed Fluorescence ◽  
Radiative Decay Rate ◽  
Thermally Activated ◽  
Dinuclear Platinum ◽  
Dinuclear Platinum Complex

Efficient thermally activated delayed fluorescence (TADF) in a brightly luminescent diplatinum(ii) complex results in significant enhancement of the radiative decay rate.

scholarly journals Thermally Activated Delayed Fluorescence from Locally Excited State: Theoretical Prediction and Experimental Validation

2020 ◽  
Author(s):  
Xiaoxiao Xiao ◽  
Shuai Li ◽  
Hua Geng ◽  
Yuai Duan ◽  
Guo Wang ◽  
...  
Keyword(s):  
Radiative Decay ◽  
Delayed Fluorescence ◽  
Intersystem Crossing ◽  
Decay Rate Constant ◽  
Thermally Activated Delayed Fluorescence ◽  
Locally Excited ◽  
Thermally Activated ◽  
Boron Difluoride ◽  
Novel Design ◽  
Prompt And Delayed Fluorescence

<div>As is well known, the thermally activated delayed fluorescence (TADF) is always generated from charge-transfer (CT) excited states in electron-donor (D) – electron-acceptor (A) systems. Here, a novel design strategy is proposed for realizing TADF from a locally excited (LE) state through controlling the intersystem crossing (ISC) and reverse intersystem crossing (RISC) processes between the LE singlet and higher triplet CT states. Based on the strategy, a boron difluoride derivative is theoretically predicted to emit TADF from the LE state, whose radiative decay rate constant is much larger kr (S<sub>1</sub> →S<sub>0</sub> )=1.12 * 10<sup>8</sup> s <sup>-1</sup> , two orders of magnitude larger than those of common TADF systems. And its lifetimes of the prompt and delayed fluorescence are experimentally validated to be 0.44 ns and 0.7 μs, respectively. This work is a breakthrough in the understanding of TADF and opens a new avenue for extending the TADF materials.</div>

scholarly journals Thermally Activated Delayed Fluorescence from Locally Excited State: Theoretical Prediction and Experimental Validation

2020 ◽  
Author(s):  
Xiaoxiao Xiao ◽  
Shuai Li ◽  
Hua Geng ◽  
Yuai Duan ◽  
Guo Wang ◽  
...  
Keyword(s):  
Radiative Decay ◽  
Delayed Fluorescence ◽  
Intersystem Crossing ◽  
Decay Rate Constant ◽  
Thermally Activated Delayed Fluorescence ◽  
Locally Excited ◽  
Thermally Activated ◽  
Boron Difluoride ◽  
Novel Design ◽  
Prompt And Delayed Fluorescence

<div>As is well known, the thermally activated delayed fluorescence (TADF) is always generated from charge-transfer (CT) excited states in electron-donor (D) – electron-acceptor (A) systems. Here, a novel design strategy is proposed for realizing TADF from a locally excited (LE) state through controlling the intersystem crossing (ISC) and reverse intersystem crossing (RISC) processes between the LE singlet and higher triplet CT states. Based on the strategy, a boron difluoride derivative is theoretically predicted to emit TADF from the LE state, whose radiative decay rate constant is much larger kr (S<sub>1</sub> →S<sub>0</sub> )=1.12 * 10<sup>8</sup> s <sup>-1</sup> , two orders of magnitude larger than those of common TADF systems. And its lifetimes of the prompt and delayed fluorescence are experimentally validated to be 0.44 ns and 0.7 μs, respectively. This work is a breakthrough in the understanding of TADF and opens a new avenue for extending the TADF materials.</div>

scholarly journals Top-emitting thermally activated delayed fluorescence organic light-emitting devices with weak light-matter coupling

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Chunxiu Zang ◽  
Shihao Liu ◽  
Mengxin Xu ◽  
Ruifang Wang ◽  
Chen Cao ◽  
...  
Keyword(s):  
Radiative Decay ◽  
Delayed Fluorescence ◽  
Strong Light ◽  
Thermally Activated Delayed Fluorescence ◽  
Light Emitting ◽  
Thermally Activated ◽  
Matter Coupling ◽  
Organic Light ◽  
Weakly Coupled ◽  
Weak Light

AbstractResonance interaction between a molecular transition and a confined electromagnetic field can lead to weak or strong light-matter coupling. Considering the substantial exciton–phonon coupling in thermally activated delayed fluorescence (TADF) materials, it is thus interesting to explore whether weak light-matter coupling can be used to redistribute optical density of states and to change the rate of radiative decay. Here, we demonstrate that the emission distribution of TADF emitters can be reshaped and narrowed in a top-emitting organic light-emitting device (OLED) with a weakly coupled microcavity. The Purcell effect of weak microcavity is found to be different for TADF emitters with different molecular orientations. We demonstrate that radiative rates of the TADF emitters with vertical orientation can be substantial increased in weakly coupled organic microcavity. These observations can enhance external quantum efficiencies, reduce efficiency roll-off, and improve color-purities of TADF OLEDs, especially for emitters without highly horizontal orientation.

scholarly journals Extracting Design Principles for Efficient Thermally Activated Delayed Fluorescence (TADF) from a Simple Four-State Model

2019 ◽  
Author(s):  
Piotr de Silva ◽  
Changhae Andrew Kim ◽  
Tianyu Zhu ◽  
Troy Van Voorhis
Keyword(s):  
Parameter Space ◽  
Radiative Decay ◽  
Delayed Fluorescence ◽  
Single Model ◽  
Thermally Activated Delayed Fluorescence ◽  
Thermally Activated ◽  
Simple Quantum ◽  
Donor Acceptor ◽  
New Guidelines ◽  
Significant Region

<p>We introduce a simple quantum-mechanical model for thermally activated delayed fluorescence (TADF). The Hamiltonian is represented in the basis of four spin-mixed diabatic states representing pure charge transfer (CT) and local excitations (LE). The model predicts that it is possible to realize lowest-lying adiabatic singlet (S1) and triplet (T1) states with a small singlet triplet gap, differing CT/LE contributions, and appreciable LE component in the S1 state. These characteristics can explain the coexistence of fast T1→S1 reverse intersystem crossing and S1→S0 radiative decay in some chromophores. Through the sampling of the parameter space and statistical analysis of the data, we show which parameter combinations contribute the most to the TADF efficiency. We also show that conformational fluctuations of a single model donor-acceptor system sample a significant region of the parameter space and can enhance the TADF rate by almost three orders of magnitude. This study provides new guidelines for optimization of TADF emitters by means of electronic structure and conformation engineering. <br></p>

scholarly journals Extracting Design Principles for Efficient Thermally Activated Delayed Fluorescence (TADF) from a Simple Four-State Model

2019 ◽  
Author(s):  
Piotr de Silva ◽  
Changhae Andrew Kim ◽  
Tianyu Zhu ◽  
Troy Van Voorhis
Keyword(s):  
Parameter Space ◽  
Radiative Decay ◽  
Delayed Fluorescence ◽  
Single Model ◽  
Thermally Activated Delayed Fluorescence ◽  
Thermally Activated ◽  
Simple Quantum ◽  
Donor Acceptor ◽  
New Guidelines ◽  
Significant Region

<p>We introduce a simple quantum-mechanical model for thermally activated delayed fluorescence (TADF). The Hamiltonian is represented in the basis of four spin-mixed diabatic states representing pure charge transfer (CT) and local excitations (LE). The model predicts that it is possible to realize lowest-lying adiabatic singlet (S1) and triplet (T1) states with a small singlet triplet gap, differing CT/LE contributions, and appreciable LE component in the S1 state. These characteristics can explain the coexistence of fast T1→S1 reverse intersystem crossing and S1→S0 radiative decay in some chromophores. Through the sampling of the parameter space and statistical analysis of the data, we show which parameter combinations contribute the most to the TADF efficiency. We also show that conformational fluctuations of a single model donor-acceptor system sample a significant region of the parameter space and can enhance the TADF rate by almost three orders of magnitude. This study provides new guidelines for optimization of TADF emitters by means of electronic structure and conformation engineering. <br></p>

Solvent Dependence of Structural Dynamics and Spin-flip Processes in 3,4,5-tri(9H-carbazole-9-yl)benzonitrile (ortho-3CzBN)

2020 ◽  
Author(s):  
Masaki Saigo ◽  
Kiyoshi Miyata ◽  
Hajime Nakanotani ◽  
Chihaya Adachi ◽  
Ken Onda
Keyword(s):  
Dft Calculations ◽  
Excited States ◽  
Structural Changes ◽  
Photophysical Properties ◽  
Delayed Fluorescence ◽  
Time Resolved ◽  
Thermally Activated Delayed Fluorescence ◽  
Thermally Activated ◽  
Solvent Dependence ◽  
Acetonitrile Solutions

We have investigated the solvent-dependence of structural changes along with intersystem crossing of a thermally activated delayed fluorescence (TADF) molecule, 3,4,5-tri(9H-carbazole-9-yl)benzonitrile (o-3CzBN), in toluene, tetrahydrofuran, and acetonitrile solutions using time-resolved infrared (TR-IR) spectroscopy and DFT calculations. We found that the geometries of the S1 and T1 states are very similar in all solvents though the photophysical properties mostly depend on the solvent. In addition, the time-dependent DFT calculations based on these geometries suggested that the thermally activated delayed fluorescence process of o-3CzBN is governed more by the higher-lying excited states than by the structural changes in the excited states.<br>

New hole transport styrene polymers bearing highly π-extended conjugated side-chain moieties for high-performance solution-processable thermally activated delayed fluorescence OLEDs

2021 ◽  
Vol 12 (11) ◽  
pp. 1692-1699
Author(s):  
Ji Hye Lee ◽  
Jinhyo Hwang ◽  
Chai Won Kim ◽  
Amit Kumar Harit ◽  
Han Young Woo ◽  
...  
Keyword(s):  
High Performance ◽  
High Efficiency ◽  
Delayed Fluorescence ◽  
Hole Transport ◽  
Side Chain ◽  
Solution Processed ◽  
Thermally Activated Delayed Fluorescence ◽  
Thermally Activated ◽  
Turn On ◽  
Solution Processable

New polystyrene-based polymers with high π-extended hole transport pendants were synthesized to obtain a low turn-on voltage and high efficiency in solution-processed green TADF-OLEDs.

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