Visualization of Frontier Molecular Orbital Separation of a Single Thermally Activated Delayed Fluorescence Emitter by STM

2021 ◽  
pp. 7512-7518
Author(s):  
Inhae Zoh ◽  
Miyabi Imai-Imada ◽  
Jaehyun Bae ◽  
Hiroshi Imada ◽  
Youichi Tsuchiya ◽  
...  
Keyword(s):  
Molecular Orbital ◽  
Delayed Fluorescence ◽  
Frontier Molecular Orbital ◽  
Thermally Activated Delayed Fluorescence ◽  
Thermally Activated

scholarly journals Constructing Narrowband Thermally Activated Delayed Fluorescence Materials with Emission Maxima Beyond 560 nm Based on Frontier Molecular Orbital Engineering

2021 ◽  
Author(s):  
Xinliang Cai ◽  
Yincai Xu ◽  
Qingyang Wang ◽  
Chenglong Li ◽  
Yue Wang
Keyword(s):  
Molecular Orbital ◽  
Wavelength Region ◽  
Coupling Reaction ◽  
Spatial Separation ◽  
Delayed Fluorescence ◽  
Frontier Molecular Orbital ◽  
Esterification Reaction ◽  
Thermally Activated Delayed Fluorescence ◽  
Suzuki Coupling Reaction ◽  
Thermally Activated

<p>The development of purely organic materials with narrowband emission in long wavelength region beyond 560 nm still remains a great challenge. Herein, we present a modification approach of multiple resonance (MR) skeleton with electron donor based on frontier molecular orbital engineering (FMOE), resulting in significant red-shift emission of target molecules. Subsequently, the parent MR skeleton is functionalized by boron esterification reaction and changed into a universal building block, namely, the key intermediate BN-Bpin, for molecular structure optimizations. BN-Bpin has been employed to construct a series of highly efficient thermally activated delayed fluorescence (TADF) materials with high color purity through one-step Suzuki coupling reaction. The target molecule perfectly integrates the inherent advantages of MR skeleton and spatial separation typical donor–acceptor (D–A) structure. The results demonstrate that the ingenious modulation of the acceptor is an effective approach to achieve bathochromic emission and narrowband emission simultaneously.</p>

scholarly journals Constructing Narrowband Thermally Activated Delayed Fluorescence Materials with Emission Maxima Beyond 560 nm Based on Frontier Molecular Orbital Engineering

2021 ◽  
Author(s):  
Xinliang Cai ◽  
Yincai Xu ◽  
Qingyang Wang ◽  
Chenglong Li ◽  
Yue Wang
Keyword(s):  
Molecular Orbital ◽  
Wavelength Region ◽  
Coupling Reaction ◽  
Spatial Separation ◽  
Delayed Fluorescence ◽  
Frontier Molecular Orbital ◽  
Esterification Reaction ◽  
Thermally Activated Delayed Fluorescence ◽  
Suzuki Coupling Reaction ◽  
Thermally Activated

<p>The development of purely organic materials with narrowband emission in long wavelength region beyond 560 nm still remains a great challenge. Herein, we present a modification approach of multiple resonance (MR) skeleton with electron donor based on frontier molecular orbital engineering (FMOE), resulting in significant red-shift emission of target molecules. Subsequently, the parent MR skeleton is functionalized by boron esterification reaction and changed into a universal building block, namely, the key intermediate BN-Bpin, for molecular structure optimizations. BN-Bpin has been employed to construct a series of highly efficient thermally activated delayed fluorescence (TADF) materials with high color purity through one-step Suzuki coupling reaction. The target molecule perfectly integrates the inherent advantages of MR skeleton and spatial separation typical donor–acceptor (D–A) structure. The results demonstrate that the ingenious modulation of the acceptor is an effective approach to achieve bathochromic emission and narrowband emission simultaneously.</p>

Lowest unoccupied molecular orbital managing function of CN-substituted dibenzofuran in high triplet energy hosts for blue thermally-activated delayed fluorescent organic light-emitting diodes

2021 ◽  
Author(s):  
Sung Yong Byun ◽  
Kyung Hyung Lee ◽  
Jun Yeob Lee
Keyword(s):  
Molecular Orbital ◽  
Light Emitting Diodes ◽  
Delayed Fluorescence ◽  
Organic Light Emitting Diodes ◽  
Triplet Energy ◽  
Thermally Activated Delayed Fluorescence ◽  
Light Emitting ◽  
Thermally Activated ◽  
Organic Light ◽  
Lowest Unoccupied Molecular Orbital

The effect of lowest unoccupied molecular orbital (LUMO) management of high triplet energy electron transport type hosts on the device performance of blue thermally-activated delayed fluorescence (TADF) organic light-emitting diodes...

scholarly journals Recent advances on organic blue thermally activated delayed fluorescence (TADF) emitters for organic light-emitting diodes (OLEDs)

2018 ◽  
Vol 14 ◽  
pp. 282-308 ◽  
Author(s):  
Thanh-Tuân Bui ◽  
Fabrice Goubard ◽  
Malika Ibrahim-Ouali ◽  
Didier Gigmes ◽  
Frédéric Dumur
Keyword(s):  
Molecular Orbital ◽  
Light Emitting Diodes ◽  
Molecular Design ◽  
Delayed Fluorescence ◽  
Organic Light Emitting Diodes ◽  
Thermally Activated Delayed Fluorescence ◽  
Light Emitting ◽  
Thermally Activated ◽  
Organic Light ◽  
Recent Advances

The design of highly emissive and stable blue emitters for organic light emitting diodes (OLEDs) is still a challenge, justifying the intense research activity of the scientific community in this field. Recently, a great deal of interest has been devoted to the elaboration of emitters exhibiting a thermally activated delayed fluorescence (TADF). By a specific molecular design consisting into a minimal overlap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) due to a spatial separation of the electron-donating and the electron-releasing parts, luminescent materials exhibiting small S1–T1 energy splitting could be obtained, enabling to thermally upconvert the electrons from the triplet to the singlet excited states by reverse intersystem crossing (RISC). By harvesting both singlet and triplet excitons for light emission, OLEDs competing and sometimes overcoming the performance of phosphorescence-based OLEDs could be fabricated, justifying the interest for this new family of materials massively popularized by Chihaya Adachi since 2012. In this review, we proposed to focus on the recent advances in the molecular design of blue TADF emitters for OLEDs during the last few years.

Theoretical Study on Benzazole Derivatives for Use in Blue Thermally Activated Delayed Fluorescence Emitters

2015 ◽  
Vol 15 (10) ◽  
pp. 7819-7822 ◽  
Author(s):  
Dong Yuel Kwon ◽  
Geon Hyeong Lee ◽  
Young Sik Kim
Keyword(s):  
Density Functional Theory ◽  
Molecular Orbital ◽  
Density Functional ◽  
Light Emitting Diode ◽  
Energy Difference ◽  
Delayed Fluorescence ◽  
Functional Theory ◽  
Thermally Activated Delayed Fluorescence ◽  
Organic Light Emitting Diode ◽  
Thermally Activated

Four novel thermally activated delayed fluorescence (TADF) materials with 9,10-dihydro-9,9- dimethylacridine (DMAC) and phenylindolo(2,3-a)carbazole (PIC) as electron donors and benzazole derivatives (BO, and BT) as electron acceptors (DMAC-BO, DMAC-BT, PIC-BO, and PIC-BT) were designed and theoretically investigated for use as a blue organic light emitting diode (OLED) emitter. Using density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations, we calculated the electron distribution of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), and the energy of the lowest singlet (S1) and the lowest triplet (T1) excited states. All the dyes had a small spatial overlap between the HOMO and LUMO because of the relatively large dihedral angle between the phenyl ring and the acceptor moiety. In terms of the energy difference (ΔEST) between the S1 state and the T1 state, DMAC-BO and DMAC-BT showed the small ΔEST (0.18 eV and 0.21 eV, respectively). However, PIC-BO and PIC-BT showed the large ΔEST (0.62 eV and 0.61 eV, respectively). Among the TADF materials, we showed that DMAC-BO would have the best TADF properties in terms of small ΔEST and blue OLED emitters

Designing Noble Benzimidazole-Based Bipolar Hosts for Blue Organic Light-Emitting Diodes Using Thermally Activated Delayed Fluorescence Materials

2020 ◽  
Vol 20 (11) ◽  
pp. 7196-7200
Author(s):  
Ja Min Lee ◽  
Sae Won Lee ◽  
Young Sik Kim
Keyword(s):  
Dft Calculations ◽  
Molecular Orbital ◽  
Light Emitting Diodes ◽  
Delayed Fluorescence ◽  
Organic Light Emitting Diodes ◽  
Thermally Activated Delayed Fluorescence ◽  
Light Emitting ◽  
Thermally Activated ◽  
Organic Light ◽  
Td Dft

We designed a novel thermally activated delayed fluorescence (TADF) host molecules for blue elec-trophosphorescence by combining the electron acceptor benzimidazole (BI) unit and the electron donor acridine derivatives into a single molecular unit based on density functional theory (DFT). We obtained the energies of the first singlet (S1) and the first triplet (T1) excited states of the TADF materials by performing DFT and time-dependent DFT (TD-DFT) calculations on the ground state using dependence on charge transfer amounts for the optimal Hartree–Fock percentage in the exchange-correlation of TD-DFT. The DFT and TD-DFT calculations showed that the large separation between the highest occupied molecular orbital and the lowest unoccupied molecular orbital caused a small difference in energy (ΔEST) between the S1 and T1 states. The host molecules retained a high triplet energy and demonstrated a great potential for use in blue phosphorescent organic light-emitting diodes. The results showed that these molecules are promising host materials for TADF OLEDs because they have a low barrier to hole and electron injection, a balanced charge transport for both holes and electrons, and a small ΔEST.

The effect of frontier orbital distribution of the core structure on the photophysics and device performances of thermally activated delayed fluorescence emitters

2019 ◽  
Vol 7 (25) ◽  
pp. 7760-7767 ◽  
Author(s):  
Mina Jung ◽  
Kyung Hyung Lee ◽  
Wan Pyo Hong ◽  
Jun Yeob Lee
Keyword(s):  
Molecular Orbital ◽  
Delayed Fluorescence ◽  
Core Structure ◽  
Frontier Orbital ◽  
Thermally Activated Delayed Fluorescence ◽  
Thermally Activated ◽  
The Core ◽  
Highest Occupied Molecular Orbital ◽  
Lowest Unoccupied Molecular Orbital

The effect of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) distribution of the core structure on the thermally activated delayed fluorescence (TADF) behavior of the TADF emitters was investigated.

Theoretical Study of Triphenylphosphine Oxide Derivatives for Blue Thermally Activated Delayed Fluorescence

2021 ◽  
Vol 21 (8) ◽  
pp. 4508-4511
Author(s):  
Sae Won Lee ◽  
Young Sik Kim
Keyword(s):  
Molecular Orbital ◽  
Electron Donor ◽  
Density Functional ◽  
Energy Difference ◽  
Triphenylphosphine Oxide ◽  
Delayed Fluorescence ◽  
Thermally Activated Delayed Fluorescence ◽  
Light Emitting ◽  
Thermally Activated ◽  
Electron Distributions

We designed novel thermally activated delayed fluorescence (TADF) materials by combining the electron donor 10,10-diphenyl-5,10-dihydrodibenzo[b,e][1,4]azasiline (DDA) with the electron acceptor triphenylphosphine oxide (PO) unit (mDDA-PO and o-mDDA-PO) and compared their characteristics with those of a reference material using 1,3-Bis(N-carbazolyl)benzene (mCP) as an electron donor (mCP-PO) for blue organic light-emitting diodes (OLEDs). Using density functional theory (DFT) and time-dependent DFT calculations, we obtained the electron distributions of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) as well as the energies of the lowest singlet (S1) and lowest triplet (T1) excited states. The calculated energy difference (ΔEST) between the S1 and T1 states of mDDA-PO (0.16 eV) and o-mDDA-PO (0.07 eV) were smaller than that of mCP-PO (0.48 eV). The results showed that o-mDDA-PO is a suitable blue OLED emitter because it has sufficiently small ΔEST values, which is favorable in a reverse-intersystem process crossing from the T1 state to S1 states, as well as an emission wavelength of 446.7 nm.

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>

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