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2. High‐Efficiency Deep Red Electroluminescence via a Spiro‐Based Pure Hydrogen Carbon Host.

Author

Yu, You‐Jun, Qu, Zhi‐Hao, Ding, Ling‐Yi, Wang, Xue‐Qi, Meng, Xin‐Yue, Li, Meng‐Tian, Zhou, Dong‐Ying, Jiang, Zuo‐Quan, and Liao, Liang‐Sheng

Subjects
*DELAYED fluorescence, *QUANTUM efficiency, *BAND gaps, *ORGANIC light emitting diodes, *ACTIVATED carbon, *ELECTROLUMINESCENCE
Abstract

Deep‐red and near‐infrared emitters with twisted donor–acceptor (D–A) structures often exhibit suboptimal performance in organic light‐emitting diodes (OLEDs) due to constraints imposed by the energy gap law. In this work, a pure hydrogen carbon (PHC) host material named SBF‐DTP is purposefully tailored for deep‐red OLEDs. The excellent capacity of SBF‐DTP to support D–A type DR emitters effectively arises from its distinctive attributes: localized excitation states, 3D configuration, and low polarity. When employing SBF‐DTP as the host for the fluorescence emitter DCPA‐TPA and the thermally activated delayed fluorescence emitter APDC‐DTPA, doped films exhibit substantially enhanced photoluminescence quantum yields. This improvement leads to high‐efficiency OLEDs with external quantum efficiencies of 5.47% for DCPA‐TPA and 20.03% for APDC‐DTPA, respectively, which is about twice as high as the initial reports. This findings underscore the paramount significance of developing efficient host materials in the pursuit of high‐performance deep red and even near‐infrared OLEDs. [ABSTRACT FROM AUTHOR]

Published
2024
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3. Modulating the Locally Excited States with a Regulating Substituent for Highly Efficient Red/Near‐Infrared Thermally Activated Delayed Fluorescence Emitters.

Author

Feng, Zi‐Qi, Yu, You‐Jun, Song, Zi‐Yu, Song, Min, Zuo, Peng, Jiang, Zuo‐Quan, Zhou, Dong‐Ying, and Liao, Liang‐Sheng

Subjects
*DELAYED fluorescence, *EXCITED states, *QUANTUM efficiency, *REDUCED instruction set computers, *ORGANIC light emitting diodes, *DIODES
Abstract

Developing highly efficient red/near‐infrared (NIR) thermally activated delayed fluorescence (TADF) materials is important for organic light‐emitting diodes (OLEDs). Here, two TADF emitters, APTT and APTI, which have the same D/A backbone but different attaching groups at acenaphtho‐[1,2‐b]pyrazine‐8,9‐dicarbonitrile (APDC) core, are reported. The appended regulating groups can not only suppress the D/A rotation due to the space confinement effects but also modulate the locally excited triplet state (3LE). The improved molecular rigidity suppresses the non‐radiative process, accounting for the improved photoluminescence quantum yields (PLQYs), while the modulated 3LE promotes the reverse intersystem crossing (RISC) process due to the high utilization efficiency of triplets. Consequently, both APTT and APTI demonstrate high PLQY and fast RISC process, thereby enhancing TADF efficiency. The doped devices based on APTT and APTI achieve maximum external quantum efficiency (EQEmax) values of 20.5% and 25.4% with emission peaks at 664 and 670 nm, respectively. The non‐doped devices of APTT and APTI achieve the EQEmax of 2.8% and 2.9% with emission peaks at 788 and 794 nm, respectively. Encouragingly, the non‐doped devices of APTI have set new records for near‐infrared TADF OLEDs based on the APDC core. This study provides an efficient approach to modulating the optoelectronic properties of highly efficient NIR TADF OLEDs. [ABSTRACT FROM AUTHOR]

Published
2024
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4. Enhancing Light Outcoupling Efficiency via Anisotropic Low Refractive Index Electron Transporting Materials for Efficient Perovskite Light‐Emitting Diodes

Author

Sun, Shuang‐Qiao, primary, Tai, Jing‐Wen, additional, He, Wei, additional, Yu, You‐Jun, additional, Feng, Zi‐Qi, additional, Sun, Qi, additional, Tong, Kai‐Ning, additional, Shi, Kefei, additional, Liu, Bo‐Chen, additional, Zhu, Min, additional, Wei, Guodan, additional, Fan, Jian, additional, Xie, Yue‐Min, additional, Liao, Liang‐Sheng, additional, and Fung, Man‐Keung, additional

Published
2024
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9. A red thermally activated delayed fluorescence emitter with mitigated efficiency roll-off via a π-stacked multiple donor–acceptor structure.

Author

Song, Min, Yu, You-Jun, Feng, Zi-Qi, Qu, Zhi-Hao, Zuo, Peng, Yan, Hong-Yan, Jiang, Zuo-Quan, Zhou, Dong-Ying, and Liao, Liang-Sheng

Abstract

Red to near-infrared organic light-emitting diodes (OLEDs) utilizing thermally activated delayed fluorescence (TADF) emitters continue to exhibit significant external quantum efficiency (EQE) roll-off at high luminance levels exceeding 1000 cd m−2, attributed to the relatively modest reverse intersystem crossing rate constant (kRISC) of approximately 103–104 s−1. This study presents a novel TADF molecule, TCPP-DTPA, featuring a structurally rigid π-stacked multiple donor/acceptor design. The enhanced donor/acceptor interactions minimize the energy gap between the singlet and triplet states of the TCPP-DTPA, allowing for an efficient RISC process with a high rate constant of 4.67 × 106 s−1. The OLED utilizing TCPP-DTPA demonstrates a peak EQE of 23.5% at a wavelength of 618 nm. Additionally, notable EQE values of 7.8% and 14.9% are observed at a luminance of 1000 cd m−2 for OLEDs without and with an energy-transfer assistant dopant in the emissive layer, respectively. This research contributes to enhancing the efficiency of high-brightness red TADF OLEDs, while also offering valuable insights for the optimization of molecular design and device engineering to mitigate the electroluminescence efficiency roll-off. [ABSTRACT FROM AUTHOR]

Published
2024
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15. Bifunctional Electron-Transporting Agent for Red Colloidal Quantum Dot Light-Emitting Diodes

Author

Wang, Ya-Kun, primary, Wan, Haoyue, additional, Xu, Jian, additional, Zhong, Yun, additional, Jung, Eui Dae, additional, Park, So Min, additional, Teale, Sam, additional, Imran, Muhammad, additional, Yu, You-Jun, additional, Xia, Pan, additional, Won, Yu-Ho, additional, Kim, Kwang-Hee, additional, Lu, Zheng-Hong, additional, Liao, Liang-Sheng, additional, Hoogland, Sjoerd, additional, and Sargent, Edward H., additional

Published
2023
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16. Multidentate Molecule Anchoring Halide Perovskite Surface and Regulating Crystallization Kinetics toward Efficient Light‐Emitting Diodes (Small 11/2023)

Author

Sun, Shuang‐Qiao, primary, Sun, Qi, additional, Ji, Yu‐Jin, additional, Xu, Yan‐Lin, additional, He, Wei, additional, Zhu, Min, additional, Zhou, Jun‐Gui, additional, Yu, You‐Jun, additional, Feng, Dan‐Dan, additional, Xie, Yue‐Min, additional, Li, You‐Yong, additional, and Fung, Man‐Keung, additional

Published
2023
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17. Toward narrowband emission: the chemical strategies for modifying boron-based luminescent materials.

Author

Liu, Fu-Ming, Ding, Ling-Yi, Yu, You-Jun, Li, Meng-Tian, Liao, Liang-Sheng, and Jiang, Zuo-Quan

Abstract

Organic light-emitting diodes (OLEDs) with high-definition displays require narrowband emission from each pixel. Recently, boron-based thermally activated delayed fluorescence (TADF) emitters have gained broad attention in the OLED research field. They can effectively utilize both singlet and triplet excitons for electroluminescence, resulting in a small full width of half maximum (FWHM). The fused nitrogen/boron (N/B) system, known as the multi-resonance TADF (MR-TADF) system, has been making rapid progress. In this review, we summarize the current research progress in both traditional and MR-type boron derivatives with TADF characteristics from a molecular construction perspective. We discuss the molecular design strategy involved in maintaining high device efficiency and simultaneously achieving a narrowband emission profile. This review aims to provide insight and guidance for future developments for improving the stability, color purity, and performance of boron-based materials. [ABSTRACT FROM AUTHOR]

Published
2023
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20. Multidentate Molecule Anchoring Halide Perovskite Surface and Regulating Crystallization Kinetics toward Efficient Light‐Emitting Diodes

Author

Sun, Shuang‐Qiao, primary, Sun, Qi, additional, Ji, Yu‐Jin, additional, Xu, Yan‐Lin, additional, He, Wei, additional, Zhu, Min, additional, Zhou, Jun‐Gui, additional, Yu, You‐Jun, additional, Feng, Dan‐Dan, additional, Xie, Yue‐Min, additional, Li, You‐Yong, additional, and Fung, Man‐Keung, additional

Published
2022
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23. Controlling Morphological Dimensions of Organic Charge‐Transfer Cocrystal by Manipulating the Growth Kinetics for Optical Waveguide Applications.

Author

Wu, Bin, Zhuo, Ming‐Peng, Chen, Song, Su, Yang, Yu, You‐Jun, Fan, Jian‐Zhong, Wang, Zuo‐Shan, and Wang, Xue‐Dong

Subjects
OPTOELECTRONIC devices, KINETIC control, OPTICAL losses, LIGHT transmission, OPTICAL waveguides
Abstract

Precise fabrication of organic micro/nanostructures with regular morphology has gained a considerable concern in developing high‐performance optoelectronic devices, which is still a huge challenge to realize tunable morphology without the dependence on molecule packing arrangement. Herein, a thermodynamic/kinetic controlled self‐assembly for triphenylene‐7,7,8,8‐tetracyanoquinodimethane (TP‐TCNQ) cocrystal, with well‐defined microwires and microplates based on the same crystal structure, is proposed. With the low solution concentration of C = 5 mm, the comparable growth rates along [011] driven by π–π interaction and along [100] driven by charge‐transfer (CT) interaction facilitate the formation of thermodynamically favored shape of microplates. In contrast, the prominent CT interaction along [100] leads to the construction of microwires at kinetic state under high‐concentration solution of C = 10 mm. Furthermore, the prepared TP‐TCNQ microwires and microplates demonstrate isotropic photonic transmissions with the low optical loss coefficient of 0.033 and 0.042 dB µm−1, respectively. This strategy provides a novel avenue to finely construct the organic microcrystals with desired morphology for potential optoelectronics. [ABSTRACT FROM AUTHOR]

Published
2023
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27. In Situ Inorganic Ligand Replenishment Enables Bandgap Stability in Mixed‐Halide Perovskite Quantum Dot Solids

Author

Wang, Ya‐Kun, primary, Singh, Kamalpreet, additional, Li, Jiao‐Yang, additional, Dong, Yitong, additional, Wang, Xue‐Qi, additional, Pina, Joao M., additional, Yu, You‐Jun, additional, Sabatini, Randy, additional, Liu, Yang, additional, Ma, Dongxin, additional, Liu, Jun, additional, Liu, Zeke, additional, Gao, Yiyuan, additional, Voznyy, Oleksandr, additional, Ma, Wanli, additional, Fung, Man‐Keung, additional, Liao, Liang‐Sheng, additional, and Sargent, Edward H., additional

Published
2022
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32. Efficient and Spectrally Stable Blue Perovskite Light-Emitting Diodes Employing a Cationic π-Conjugated Polymer

Author

Yuan, Shuai, Cui, Lin-Song, Dai, Linjie, Liu, Yun, Liu, Qing-Wei, Sun, Yu-Qi, Auras, Florian, Anaya, Miguel, Zheng, Xiaopeng, Ruggeri, Edoardo, Yu, You-Jun, Qu, Yang-Kun, Abdi-Jalebi, Mojtaba, Bakr, Osman M, Wang, Zhao-Kui, Stranks, Samuel D, Greenham, Neil C, Liao, Liang-Sheng, Friend, Richard H, Cui, Lin-Song [0000-0001-6577-3432], and Apollo - University of Cambridge Repository

Subjects
ion migrations, blue emissions, high efficiencies, stabilities, perovskite light-emitting diodes
Abstract

Metal halide perovskite semiconductors have demonstrated remarkable potentials in solution-processed blue light-emitting diodes (LEDs). However, the unsatisfied efficiency and spectral stability responsible for trap-mediated non-radiative losses and halide phase segregation remain the primary unsolved challenges for blue perovskite LEDs. In this study, it is reported that a fluorene-based π-conjugated cationic polymer can be blended with the perovskite semiconductor to control film formation and optoelectronic properties. As a result, sky-blue and true-blue perovskite LEDs with Commission Internationale de l'Eclairage coordinates of (0.08, 0.22) and (0.12, 0.13) at the record external quantum efficiencies of 11.2% and 8.0% were achieved. In addition, the mixed halide perovskites with the conjugated cationic polymer exhibit excellent spectral stability under external bias. This result illustrates that π-conjugated cationic polymers have a great potential to realize efficient blue mixed-halide perovskite LEDs with stable electroluminescence.

Published
2021

33. Indirect Control of Donor/Acceptor Interactions for Highly Efficient Space‐Confined Thermally Activated Delayed Fluorescence Emitters.

Author

Feng, Zi‐Qi, Yang, Sheng‐Yi, Kong, Fan‐Cheng, Qu, Yang‐Kun, Meng, Xin‐Yue, Yu, You‐Jun, Zhou, Dong‐Ying, Jiang, Zuo‐Quan, and Liao, Liang‐Sheng

Subjects
DELAYED fluorescence, SPACE charge, MOLECULAR shapes, QUANTUM efficiency, CHARGE transfer
Abstract

Conformational engineering is essential to further reinforce the luminescent properties of thermally activated delayed fluorescence (TADF) materials featuring through‐space charge transfer (TSCT) characteristics. Herein, two TSCT‐TADF emitters (8MeDM‐B and 8FDM‐B) with the methyl and fluorine moieties substituted at the C8 site of the rigid spiro‐fluorene bridge is reported. Derivation of the C8 site is first proposed to control the molecular configuration with the ability to indirectly tune the intramolecular interaction between donor and acceptor groups. As a result, 8MeDM‐B and 8FDM‐B both present small singlet‐triplet energy gaps, fast reverse intersystem crossing rates, and high photoluminescence quantum yields. Interestingly, the smaller fluorine atom not the bigger methyl group exhibits more evident electrostatic repulsive force onto the central donor and thus rectifies the central spiro structure. Consequently, the high external quantum efficiency values of 28.8% and 31.7% for 8MeDM‐B and 8FDM‐B‐based electroluminescence devices are achieved, respectively. This study offers a measure for enhancing TSCT‐TADF emitters without directly modifying the donor or acceptor. [ABSTRACT FROM AUTHOR]

Published
2023
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34. Carbonyl‐Containing Thermally Activated Delayed Fluorescence Emitters for Narrow‐Band Electroluminescence.

Author

Yu, You‐Jun, Liu, Fu‐Ming, Meng, Xin‐Yue, Ding, Ling‐Yi, Liao, Liang‐Sheng, and Jiang, Zuo‐Quan

Subjects
*DELAYED fluorescence, *ELECTROLUMINESCENCE, *KETONE derivatives
Abstract

Carbonyl‐containing derivatives show enduring vitality in the field of thermally activated delayed fluorescence (TADF) materials; they can realize high device efficiency by using both singlet and triplet excitons for electroluminescence. Recently, a system based on fused ketone/amine exhibited huge potential for constructing multi‐resonance TADF (MR‐TADF) emitters, which exhibit higher narrow‐band emission than conventional TADF emitters with twisted donor‐acceptor (D‐A) structure. Herein, we summarize current research progress in both traditional and MR‐type ketone derivatives with TADF characteristics for introducing the molecular design strategy of maintaining high device efficiency while keeping narrow‐band emission profile. We hope this review can inspire the emergence of more high‐performance narrow‐band materials. [ABSTRACT FROM AUTHOR]

Published
2023
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35. Efficient and Spectrally Stable Blue Perovskite Light‐Emitting Diodes Employing a Cationic π‐Conjugated Polymer

Author

Yuan, Shuai, primary, Cui, Lin‐Song, additional, Dai, Linjie, additional, Liu, Yun, additional, Liu, Qing‐Wei, additional, Sun, Yu‐Qi, additional, Auras, Florian, additional, Anaya, Miguel, additional, Zheng, Xiaopeng, additional, Ruggeri, Edoardo, additional, Yu, You‐Jun, additional, Qu, Yang‐Kun, additional, Abdi‐Jalebi, Mojtaba, additional, Bakr, Osman M., additional, Wang, Zhao‐Kui, additional, Stranks, Samuel D., additional, Greenham, Neil C., additional, Liao, Liang‐Sheng, additional, and Friend, Richard H., additional

Published
2021
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41. Circularly Polarized Thermally Activated Delayed Fluorescence Emitters in Through-Space Charge Transfer on Asymmetric Spiro Skeletons

Author

Yang, Sheng-Yi, primary, Wang, Ya-Kun, additional, Peng, Chen-Chen, additional, Wu, Zheng-Guang, additional, Yuan, Shuai, additional, Yu, You-Jun, additional, Li, Hao, additional, Wang, Tong-Tong, additional, Li, Hong-Cheng, additional, Zheng, You-Xuan, additional, Jiang, Zuo-Quan, additional, and Liao, Liang-Sheng, additional

Published
2020
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