Steric Switching for Thermally Activated Delayed Fluorescence by Controlling the Dihedral Angles between Donor and Acceptor in Organoboron Emitters

2019 ◽  
Vol 11 (11) ◽  
pp. 10768-10776 ◽  
Author(s):  
Tien-Lin Wu ◽  
Shih-Han Lo ◽  
Yu-Che Chang ◽  
Min-Jie Huang ◽  
Chien-Hong Cheng
Keyword(s):  
Delayed Fluorescence ◽  
Dihedral Angles ◽  
Thermally Activated Delayed Fluorescence ◽  
Thermally Activated ◽  
Donor And Acceptor

Study of an Oxadiazole Derivative for a Blue Thermally Activated Delayed Fluorescence Emitter

2015 ◽  
Vol 15 (10) ◽  
pp. 7828-7831 ◽  
Author(s):  
Dong Yuel Kwon ◽  
Geon Hyeong Lee ◽  
Young Sik Kim
Keyword(s):  
Excited States ◽  
Energy Gap ◽  
Delayed Fluorescence ◽  
Excited Singlet ◽  
Thermally Activated Delayed Fluorescence ◽  
Excited Triplet ◽  
Thermally Activated ◽  
Donor And Acceptor ◽  
Homo And Lumo ◽  
Dft And Tddft Calculations

Novel thermally activated delayed fluorescence (TADF) materials (ACR-OXD, 2ACR-OXD) with 9,10- dihydro-9,9-dimethylacridine (ACR) as an electron donor and oxadiazole derivative (OXD) as an electron acceptor were designed and theoretically investigated for blue OLED emitter. Using DFT and TDDFT calculations, we gained the electron distribution of HOMO and LUMO and the energy of the lowest singlet (S1) and the lowest triplet (T1) excited states. In comparison with the previously reported a xanthen derivative (ACR-XTN), ACR-OXD exhibits a promising blue TADF emitter because of destabilizing the LUMO of ACR-OXD by the change of the electron accepting group and maintaining the steric hindrance between donor and acceptor moieties which lead to efficient TADF due to the small energy gap between the lowest excited singlet (S1) state and the lowest excited triplet (T1) state.

scholarly journals Hot Exciplexes in U-Shaped TADF Molecules with Emission from Locally Excited States

2021 ◽  
Author(s):  
A. Lennart Schleper ◽  
Kenichi Goushi ◽  
Christoph Bannwarth ◽  
Bastian Haehnle ◽  
Philipp Welscher ◽  
...  
Keyword(s):  
Delayed Fluorescence ◽  
Organic Light Emitting Diodes ◽  
Intersystem Crossing ◽  
Thermally Activated Delayed Fluorescence ◽  
New Approach ◽  
Light Emitting ◽  
Thermally Activated ◽  
Donor And Acceptor ◽  
Low Efficiency ◽  
High Color Purity

Rapid reverse intersystem crossing and high color purity are vital characteristics of emitters with thermally activated delayed fluorescence in opto-electronic devices. We present a new approach, called “hot exciplexes” that enables access to both attributes at the same time. Hot exciplexes are produced by coupling facing donor and acceptor moieties to an anthracene bridge, yielding an exciplex with large T1 to T2 spacing. The hot exciplex model is investigated using optical spec-troscopy and quantum chemical simulations. Reverse intersystem crossing is found to occur preferentially from the T3 to the S1 state within only a few nanoseconds. Application and practi-cality of the model are shown by fabrication of organic light-emitting diodes with up to 32 % hot exciplex contribution and low efficiency roll-off.

scholarly journals A Novel Design Strategy for Suppressing Efficiency Roll-Off of Blue Thermally Activated Delayed Fluorescence Molecules through Donor–Acceptor Interlocking by C–C Bonds

Nanomaterials ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 1735 ◽  
Author(s):  
Tae Hui Kwon ◽  
Soon Ok Jeon ◽  
Masaki Numata ◽  
Hasup Lee ◽  
Yeon Sook Chung ◽  
...  
Keyword(s):  
Energy Gap ◽  
Delayed Fluorescence ◽  
Triplet Energy ◽  
Design Synthesis ◽  
Thermally Activated Delayed Fluorescence ◽  
Thermally Activated ◽  
Donor And Acceptor ◽  
Donor Acceptor ◽  
Display Performance ◽  
Commercial Applications

The short material lifetime of thermally activated delayed fluorescence (TADF) technology is a major obstacle to the development of economically feasible, highly efficient, and durable devices for commercial applications. TADF devices are also hampered by insufficient operational stability. In this paper, we report the design, synthesis, and evaluation of new TADF molecules possessing a sterically twisted skeleton by interlocking donor and acceptor moieties through a C–C bond. Compared to C–N-bond TADF molecules, such as CPT2, the C–C-bond TADF molecules showed a large dihedral angle increase by more than 30 times and a singlet–triplet energy-gap decrease to less than 0.22 eV because of the steric hindrance caused by the direct C–C bond connection. With the introduction of a dibenzofuran core structure, devices comprising BMK-T317 and BMK-T318 exhibited a magnificent display performance, especially their external quantum efficiencies, which were as high as 19.9% and 18.8%, respectively. Moreover, the efficiency roll-off of BMK-T318 improved significantly (26.7%). These results indicate that stability of the material can be expected through the reduction of their singlet–triplet splitting and the precise adjustment of dihedral angles between the donor–acceptor skeletons.

scholarly journals Triazine-Acceptor-Based Green Thermally Activated Delayed Fluorescence Materials for Organic Light-Emitting Diodes

Materials ◽  
2019 ◽  
Vol 12 (16) ◽  
pp. 2646 ◽  
Author(s):  
Ramanaskanda Braveenth ◽  
Kyu Yun Chai
Keyword(s):  
Light Emitting Diodes ◽  
Molecular Design ◽  
Delayed Fluorescence ◽  
Organic Light Emitting Diodes ◽  
Potential Candidate ◽  
Thermally Activated Delayed Fluorescence ◽  
Light Emitting ◽  
Thermally Activated ◽  
Organic Light ◽  
Donor And Acceptor

High-efficiency thermally activated delayed fluorescence (TADF) is leading the third-generation technology of organic light-emitting diodes (OLEDs). TADF emitters are designed and synthesized using inexpensive organic donor and acceptor derivatives. TADF emitters are a potential candidate for next-generation display technology when compared with metal-complex-based phosphorescent dopants. Many studies are being conducted to enhance the external quantum efficiencies (EQEs) and photoluminescent quantum yield of green TADF devices. Blue TADF reached an EQE of over 35% with the support of suitable donor and acceptor moieties based on a suitable molecular design. The efficiencies of green TADF emitters can be improved when an appropriate molecular design is applied with an efficient device structure. The triazine acceptor has been identified as a worthy building block for green TADF emitters. Hence, we present here a review of triazine with various donor molecules and their device performances. This will help to design more suitable and efficient green TADF emitters for OLEDs.

scholarly journals Molecular Design Realizing Very Fast Reverse Intersystem Crossing in Purely Organic Emitter

2019 ◽  
Author(s):  
yoshimasa wada ◽  
Hiromichi Nakagawa ◽  
Soma Matsumoto ◽  
Yasuaki Wakisaka ◽  
Hironori Kaji
Keyword(s):  
Energy Gap ◽  
Molecular Design ◽  
Delayed Fluorescence ◽  
Intersystem Crossing ◽  
Triplet States ◽  
Thermally Activated Delayed Fluorescence ◽  
Light Emitting ◽  
Thermally Activated ◽  
Donor And Acceptor ◽  
Spin Inversion

Reverse intersystem crossing (RISC), originally considered forbidden in purely organic materials, has been recently enabled by minimizing the energy gap between the lowest singlet excited state (S<sub>1</sub>) and lowest triplet state (T<sub>1</sub>) in thermally activated delayed fluorescence (TADF) systems. However, direct spin-inversion between S<sub>1</sub> and T<sub>1</sub> is still inefficient when both states are of the same charge transfer (CT) nature (i.e. <sup>1</sup>CT and <sup>3</sup>CT, respectively). Intervention of locally excited triplet states (<sup>3</sup>LE) between <sup>1</sup>CT and <sup>3</sup>CT is expected to trigger fast spin-flip. Here, we report on the systematic-design of the ideal TADF molecules with near-degenerate <sup>1</sup>CT, <sup>3</sup>CT and <sup>3</sup>LE states by controlling the through-space distance between the donor and acceptor segments in a molecule with tilted intersegment angles. The new system realizes very fast RISC with a rate constant (<i>k</i><sub>RISC</sub>) of 1.2×10<sup>7</sup> s<sup>−1</sup>. The large <i>k</i><sub>RISC</sub> of the emitter resulted in great device performance in the applications to blue TADF assisted fluorescence organic light-emitting diodes (OLEDs) as well as TADF-emitter OLEDs.<br>

Donor and acceptor interlock by a planar indolo[3,2,1-jk]carbazole for a suppressed non-radiative mechanism in thermally activated delayed fluorescent emitters

2020 ◽  
Vol 8 (41) ◽  
pp. 14490-14498
Author(s):  
Vilas Venunath Patil ◽  
Yun Hwan Park ◽  
Kyung Hyung Lee ◽  
Jun Yeob Lee
Keyword(s):  
Molecular Structure ◽  
Delayed Fluorescence ◽  
Thermally Activated Delayed Fluorescence ◽  
Thermally Activated ◽  
Donor And Acceptor ◽  
Donor Acceptor ◽  
Radiative Mechanism

In this work, we report a novel molecular structure of the thermally activated delayed fluorescence (TADF) emitters with the donor–acceptor structure interlocked by a planar indolo[3,2,1-jk]carbazole (ICz) unit to suppress a non-radiative mechanism.

scholarly journals Virtual Screening of TADF Emitters for Single-Layer OLEDs

2021 ◽  
Vol 9 ◽  
Author(s):  
Kun-Han Lin ◽  
Gert-Jan A. H. Wetzelaer ◽  
Paul W. M. Blom ◽  
Denis Andrienko
Keyword(s):  
Light Emitting Diode ◽  
Single Layer ◽  
Delayed Fluorescence ◽  
Hole Transport ◽  
Thermally Activated Delayed Fluorescence ◽  
Light Emitting ◽  
Organic Light Emitting Diode ◽  
Thermally Activated ◽  
Organic Light ◽  
Donor And Acceptor

Thermally-activated delayed fluorescence (TADF) is a concept which helps to harvest triplet excitations, boosting the efficiency of an organic light-emitting diode. TADF can be observed in molecules with spatially separated donor and acceptor groups with a reduced triplet-singlet energy level splitting. TADF materials with balanced electron and hole transport are attractive for realizing efficient single-layer organic light emitting diodes, greatly simplifying their manufacturing and improving their stability. Our goal here is to computationally screen such materials and provide a comprehensive database of compounds with a range of emission wavelengths, ionization energies, and electron affinities.

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