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

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

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Theoretical Study of Phenoxaphosphine-Based Blue Organic Light-Emitting Diode Exhibiting Thermally Activated Delayed Fluorescence

Journal of Nanoscience and Nanotechnology ◽

10.1166/jnn.2020.18855 ◽

2020 ◽

Vol 20 (11) ◽

pp. 7187-7190

Author(s):

JaMin Lee ◽

Sae Won Lee ◽

Young Sik Kim

Keyword(s):

Density Functional ◽

Light Emitting Diode ◽

Energy Difference ◽

Delayed Fluorescence ◽

Functional Theory ◽

Thermally Activated Delayed Fluorescence ◽

Light Emitting ◽

Organic Light Emitting Diode ◽

Thermally Activated ◽

Organic Light

We designed novel thermally activated delayed fluorescence (TADF) materials by combining the electron donors spiro[acridine-9,9′-fluorene] (D1) and 9,9-diphenyl acridan (PAC) with the electron acceptor phenoxaphosphine (OPO) unit (2D1-OPO and 2PAC-OPO) and used those property to compare it with that of the reference material using dimethylacridan (Ac) as an electron donor (Ac-OPO) for blue organic light-emitting diodes (OLEDs). To calculate electron distribution of highest occupied molecular orbitals (HOMO), lowest occupied molecular orbital (LUMO), lowest singlet (S1) energy and lowest triplet (T1) excitation states, density functional theory (DFT) and time-dependent DFT calculation have been used. The calculated energy difference (ΔEST) between the S1 and T1 states of 2D1-OPO (0.125 eV) and 2PAC-OPO (0.153 eV) were as small as that of Ac-OPO (0.127 eV). The results showed that 2D1-OPO is a good candidate for blue OLED emitter because it has an emission wavelength of 441.0 nm as well as a sufficiently small ΔEST value and large oscillator intensity value.

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

Molecules ◽

10.3390/molecules26041125 ◽

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%.

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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

Journal of Materials Chemistry C ◽

10.1039/d1tc02624k ◽

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...

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

Beilstein Journal of Organic Chemistry ◽

10.3762/bjoc.14.18 ◽

2018 ◽

Vol 14 ◽

pp. 282-308 ◽

Cited By ~ 84

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.

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Organic Molecules with Inverted Gaps between First Excited Singlet and Triplet States and Appreciable Fluorescence Rates

10.26434/chemrxiv.13087319.v1 ◽

2020 ◽

Author(s):

Robert Pollice ◽

Pascal Friederich ◽

Cyrille Lavigne ◽

Gabriel dos Passos Gomes ◽

Alan Aspuru-Guzik

Keyword(s):

Excited State ◽

Energy Difference ◽

Delayed Fluorescence ◽

Triplet States ◽

Electron Hole ◽

Thermally Activated Delayed Fluorescence ◽

Light Emitting ◽

Thermally Activated ◽

Singlet And Triplet States

One of the recent proposals for the design of state-of-the-art emissive materials for organic light emitting diodes (OLEDs) is the principle of thermally activated delayed fluorescence (TADF). The underlying idea is to enable facile thermal upconversion of excited state triplets, which are generated upon electron-hole recombination, to excited state singlets by minimizing the corresponding energy difference resulting in devices with up to 100% internal quantum efficiencies (IQEs). Ideal emissive materials potentially surpassing TADF emitters should have both negative singlet-triplet gaps and appreciable fluorescence rates to maximize reverse intersystem crossing (rISC) rates from excited triplets to singlets while minimizing ISC rates and triplet state occupation leading to long-term operational stability. However, molecules with negative singlet-triplet gaps are extremely rare and, to the best of our knowledge, not emissive. In this work, based on computational studies, we describe the first molecules with negative singlet-triplet gaps and considerable fluorescence rates and show that they are more common than hypothesized previously.

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Organic Molecules with Inverted Gaps between First Excited Singlet and Triplet States and Appreciable Fluorescence Rates

10.26434/chemrxiv.13087319 ◽

2020 ◽

Author(s):

Robert Pollice ◽

Pascal Friederich ◽

Cyrille Lavigne ◽

Gabriel dos Passos Gomes ◽

Alan Aspuru-Guzik

Keyword(s):

Excited State ◽

Energy Difference ◽

Delayed Fluorescence ◽

Triplet States ◽

Electron Hole ◽

Thermally Activated Delayed Fluorescence ◽

Light Emitting ◽

Thermally Activated ◽

Singlet And Triplet States

One of the recent proposals for the design of state-of-the-art emissive materials for organic light emitting diodes (OLEDs) is the principle of thermally activated delayed fluorescence (TADF). The underlying idea is to enable facile thermal upconversion of excited state triplets, which are generated upon electron-hole recombination, to excited state singlets by minimizing the corresponding energy difference resulting in devices with up to 100% internal quantum efficiencies (IQEs). Ideal emissive materials potentially surpassing TADF emitters should have both negative singlet-triplet gaps and appreciable fluorescence rates to maximize reverse intersystem crossing (rISC) rates from excited triplets to singlets while minimizing ISC rates and triplet state occupation leading to long-term operational stability. However, molecules with negative singlet-triplet gaps are extremely rare and, to the best of our knowledge, not emissive. In this work, based on computational studies, we describe the first molecules with negative singlet-triplet gaps and considerable fluorescence rates and show that they are more common than hypothesized previously.

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

Journal of Nanoscience and Nanotechnology ◽

10.1166/jnn.2020.18858 ◽

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.

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