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Cai W, Zhong C, Ma ZW, Cai ZY, Qiu Y, Sajid Z, Wu DY. Machine-learning-assisted performance improvements for multi-resonance thermally activated delayed fluorescence molecules. Phys Chem Chem Phys 2023; 26:144-152. [PMID: 38063043 DOI: 10.1039/d3cp04441f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2023]
Abstract
With favorable colour purity, multi-resonance thermally activated delayed fluorescence (MR-TADF) molecules exhibit enormous potential in high-definition displays. Due to the relatively small chemical space of MR-TADF molecules, it is challenging to improve molecular performance through domain-specific expertise alone. To address this problem, we focused on optimizing the classic molecule, DABNA-1, using machine learning (ML). Molecular morphing operations were initially employed to generate the adjacent chemical space of DABNA-1. Subsequently, a machine learning model was trained with a limited database and used to predict the properties throughout the generated chemical space. It was confirmed that the top 100 molecules suggested by machine learning present excellent electronic structures, characterized by small reorganization energy and singlet-triplet energy gaps. Our results indicate that the improvement in electronic structures can be elucidated through the view of the molecular orbital (MO). The results also reveal that the top 5 molecules present weaker vibronic peaks of the emission spectrum, demonstrating higher colour purity when compared to DABNA-1. Notably, the M2 molecule presents a high RISC rate, indicating its promising future as a high-efficiency MR-TADF molecule. Our machine-learning-assisted approach facilitates the rapid optimization of classical molecules, addressing a crucial requirement within the organic optoelectronic materials community.
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Affiliation(s)
- Wanlin Cai
- State Key Laboratory of Physical Chemistry of Solid Surface, Collaborative Innovation Center of Chemistry for Energy Materials, and Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, P. R. China.
| | - Cheng Zhong
- Hubei Key Lab on Organic and Polymeric Optoelectronic Materials, Department of Chemistry, Wuhan University, Wuhan, Hubei, 430072, P. R. China
| | - Zi-Wei Ma
- State Key Laboratory of Physical Chemistry of Solid Surface, Collaborative Innovation Center of Chemistry for Energy Materials, and Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, P. R. China.
| | - Zhuan-Yun Cai
- State Key Laboratory of Physical Chemistry of Solid Surface, Collaborative Innovation Center of Chemistry for Energy Materials, and Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, P. R. China.
| | - Yue Qiu
- Grimwade Centre for Cultural Materials Conservation, School of Historical and Philosophical Studies, Faculty of Arts, University of Melbourne, Parkville, VIC 3052, Australia
| | - Zubia Sajid
- State Key Laboratory of Physical Chemistry of Solid Surface, Collaborative Innovation Center of Chemistry for Energy Materials, and Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, P. R. China.
| | - De-Yin Wu
- State Key Laboratory of Physical Chemistry of Solid Surface, Collaborative Innovation Center of Chemistry for Energy Materials, and Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, P. R. China.
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Xie X, Troisi A. Identification via Virtual Screening of Emissive Molecules with a Small Exciton-Vibration Coupling for High Color Purity and Potential Large Exciton Delocalization. J Phys Chem Lett 2023; 14:4119-4126. [PMID: 37129191 PMCID: PMC10165648 DOI: 10.1021/acs.jpclett.3c00749] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
A sequence of quantum chemical computations of increasing accuracy was used in this work to identify molecules with small exciton reorganization energy (exciton-vibration coupling), of interest for light emitting devices and coherent exciton transport, starting from a set of ∼4500 known molecules. We validated an approximate computational approach based on single-point calculations of the force in the excited state, which was shown to be very efficient in identifying the most promising candidates. We showed that a simple descriptor based on the bond order could be used to find molecules with potentially small exciton reorganization energies without performing excited state calculations. A small set of chemically diverse molecules with a small exciton reorganization energy was analyzed in greater detail to identify common features leading to this property. Many such molecules display an A-B-A structure where the bonding/antibonding patterns in the fragments A are similar in HOMO and LUMO. Another group of molecules with small reorganization energy displays instead HOMO and LUMO with a strong nonbonding character.
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Affiliation(s)
- Xiaoyu Xie
- Department of Chemistry, University of Liverpool Liverpool L69 3BX, U.K
| | - Alessandro Troisi
- Department of Chemistry, University of Liverpool Liverpool L69 3BX, U.K
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Wu CC, Li EY, Chou PT. Reducing the internal reorganization energy via symmetry controlled π-electron delocalization. Chem Sci 2022; 13:7181-7189. [PMID: 35799804 PMCID: PMC9214956 DOI: 10.1039/d2sc01851a] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Accepted: 05/24/2022] [Indexed: 12/30/2022] Open
Abstract
The magnitude of the reorganization energy is closely related to the nonradiative relaxation rate, which affects the photoemission quantum efficiency, particularly for the emission with a lower energy gap toward the near IR (NIR) region. In this study, we explore the relationship between the reorganization energy and the molecular geometry, and hence the transition density by computational methods using two popular models of NIR luminescent materials: (1) linearly conjugated cyanine dyes and (2) electron donor–acceptor (D–A) composites with various degrees of charge transfer (CT) character. We find that in some cases, reorganization energies can be significantly reduced to 50% despite slight structural modifications. Detailed analyses indicate that the reflection symmetry plays an important role in linear cyanine systems. As for electron donor–acceptor systems, both the donor strength and the substitution position affect the relative magnitude of reorganization energies. If CT is dominant and creates large spatial separation between HOMO and LUMO density distributions, the reorganization energy is effectively increased due to the large electron density variation between S0 and S1 states. Mixing a certain degree of local excitation (LE) with CT in the S1 state reduces the reorganization energy. The principles proposed in this study are also translated into various pathways of canonically equivalent π-conjugation resonances to represent intramolecular π-delocalization, the concept of which may be applicable, in a facile manner, to improve the emission efficiency especially in the NIR region. The reorganization energies may be significantly reduced by molecular symmetry effect.![]()
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Affiliation(s)
- Chi-Chi Wu
- Department of Chemistry, National Taiwan Normal University, No. 88, Section 4, Tingchow Road, Taipei 116, Taiwan
| | - Elise Y. Li
- Department of Chemistry, National Taiwan Normal University, No. 88, Section 4, Tingchow Road, Taipei 116, Taiwan
| | - Pi-Tai Chou
- Department of Chemistry, National Taiwan University, No. 1, Section 4, Roosevelt Road, Taipei 106, Taiwan
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Liu F, Cheng Z, Wan L, Feng Z, Liu H, Jin H, Gao L, Lu P, Yang W. Highly Efficient Multi-Resonance Thermally Activated Delayed Fluorescence Material with a Narrow Full Width at Half-Maximum of 0.14 eV. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2022; 18:e2106462. [PMID: 34862733 DOI: 10.1002/smll.202106462] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2021] [Indexed: 06/13/2023]
Abstract
Multi-resonance thermally activated delayed fluorescence (MR-TADF) material, which possesses the ability to achieve narrowband emission in organic light-emitting diodes (OLEDs), is of significant importance for wide color gamut and high-resolution display applications. To date, MR-TADF material with narrow full width at half-maximum (FWHM) below 0.14 eV still remains a great challenge. Herein, through peripheral protection of MR framework by phenyl derivatives, four efficient narrowband MR-TADF emitters are successfully designed and synthesized. The introduction of peripheral phenyl-based moieties via a single bond significantly suppresses the high-frequency stretching vibrations and reduces the reorganization energies, accordingly deriving the resulting molecules with small FWMH values around 20 nm/0.11 eV and fast radiative decay rates exceeding 108 s-1 . The corresponding green OLED based on TPh-BN realizes excellent performance with the maximum external quantum efficiency (EQE) up to 28.9% without utilizing any sensitizing host and a relatively narrow FWHM of 0.14 eV (28 nm), which is smaller than the reported green MR-TADF molecules in current literatures. Especially, the devices show significantly reduced efficiency roll-off and relatively long operational lifetimes among the sensitizer-free MR-TADF devices. These results clearly indicate the promise of this design strategy for highly efficient OLEDs with ultra-high color purity.
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Affiliation(s)
- Futong Liu
- State Key Laboratory of Supramolecular Structure and Materials, Department of Chemistry, Jilin University, Changchun, 130012, P. R. China
| | - Zhuang Cheng
- State Key Laboratory of Supramolecular Structure and Materials, Department of Chemistry, Jilin University, Changchun, 130012, P. R. China
| | - Liang Wan
- State Key Laboratory of Supramolecular Structure and Materials, Department of Chemistry, Jilin University, Changchun, 130012, P. R. China
| | - Zijun Feng
- State Key Laboratory of Supramolecular Structure and Materials, Department of Chemistry, Jilin University, Changchun, 130012, P. R. China
| | - Hui Liu
- State Key Laboratory of Supramolecular Structure and Materials, Department of Chemistry, Jilin University, Changchun, 130012, P. R. China
| | - Haixu Jin
- State Key Laboratory of Supramolecular Structure and Materials, Department of Chemistry, Jilin University, Changchun, 130012, P. R. China
| | - Lei Gao
- State Key Laboratory of Supramolecular Structure and Materials, Department of Chemistry, Jilin University, Changchun, 130012, P. R. China
| | - Ping Lu
- State Key Laboratory of Supramolecular Structure and Materials, Department of Chemistry, Jilin University, Changchun, 130012, P. R. China
| | - Wensheng Yang
- Institute of Molecular Plus, Tianjin University, Tianjin, 300072, P. R. China
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Tseng S, Chao C, Chang K, Wen C, Chou T, Tsai T, Wu T, Haung X, Liu J, Hung C, Liu K, Chou P. Substituent Effects in Six(Anilido)‐Five(Thiazole) Membered Ring Boron Difluoride Dyes. CHEMPHOTOCHEM 2021. [DOI: 10.1002/cptc.202100188] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Sheng‐Ming Tseng
- Department of Chemistry National Taiwan University Taipei 10617 Taiwan (Republic of China)
| | - Chi‐Min Chao
- Department of Medical Applied Chemistry Chung Shan Medical University
- Department of Medical Education Chung Shan Medical University Hospital Taichung 40201 Taiwan (Republic of China)
| | - Kai‐Hsin Chang
- Department of Chemistry National Taiwan University Taipei 10617 Taiwan (Republic of China)
| | - Chi‐Sheng Wen
- Department of Medical Applied Chemistry Chung Shan Medical University
- Department of Medical Education Chung Shan Medical University Hospital Taichung 40201 Taiwan (Republic of China)
| | - Tai‐Che Chou
- Department of Chemistry National Taiwan University Taipei 10617 Taiwan (Republic of China)
| | - Tsung‐Lun Tsai
- Department of Medical Applied Chemistry Chung Shan Medical University
- Department of Medical Education Chung Shan Medical University Hospital Taichung 40201 Taiwan (Republic of China)
| | - Ting‐Wen Wu
- Department of Medical Applied Chemistry Chung Shan Medical University
- Department of Medical Education Chung Shan Medical University Hospital Taichung 40201 Taiwan (Republic of China)
| | - Xiao‐Ci Haung
- Department of Medical Applied Chemistry Chung Shan Medical University
- Department of Medical Education Chung Shan Medical University Hospital Taichung 40201 Taiwan (Republic of China)
| | - Jun‐Qi Liu
- Department of Medical Applied Chemistry Chung Shan Medical University
- Department of Medical Education Chung Shan Medical University Hospital Taichung 40201 Taiwan (Republic of China)
| | - Cheng‐Hsien Hung
- Department of Medical Applied Chemistry Chung Shan Medical University
- Department of Medical Education Chung Shan Medical University Hospital Taichung 40201 Taiwan (Republic of China)
| | - Kuan‐Miao Liu
- Department of Medical Applied Chemistry Chung Shan Medical University
- Department of Medical Education Chung Shan Medical University Hospital Taichung 40201 Taiwan (Republic of China)
| | - Pi‐Tai Chou
- Department of Chemistry National Taiwan University Taipei 10617 Taiwan (Republic of China)
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Chen WC, Chang YC. Rational design of organic semiconductors with low internal reorganization energies for hole and electron transport: position effect of aza-substitution in phenalenyl derivatives. Phys Chem Chem Phys 2021; 23:18163-18172. [PMID: 34612279 DOI: 10.1039/d1cp02902a] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Amphoteric-redox phenalenyl radical (PLY) is a suitable candidate used to design ambipolar organic materials. Because the singly occupied nonbonding molecular orbital (NBMO) of PLY has a perfect local nonbonding character, its internal reorganization energy (λ) for transporting holes (λ+) or electrons (λ-) is known to be small. Herein, PLY is employed to study the position effect of the aza group on the λ. By adding or extracting an electron from the NBMO, the bond length alterations can be minute. Therefore, the PLY derivatives are also an excellent candidate to study the contributions from the bond angle alterations to the λ. Substituting the aza groups at the β- or α-positions of PLY shows two different trends. When consecutively substituting the aza group at the three β-positions of PLY, the λs are consistently decreased. Contrarily, a series of double functionalization of aza groups at the four α-positions of PLY, the λs are increased. It is because the local bonding or antibonding character in frontier orbitals (FMO) is observed in α2N-PLY and α4N-PLY. As the FMOs of the three β-substituted PLYs and α6N-PLY have perfect local nonbonding character, we found the bond angle alterations are the main contributors of λ. The λs for most aza-PLYs were smaller than 100 meV. Thus, we propose a design rule for substituting aza groups on the parent molecules with strong local nonbonding character in their FMOs. Based on the adiabatic ionization potential and electron affinity, two π-extended PLY derivatives with small λ were recommended for fabricating air-stable ambipolar OFET.
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Affiliation(s)
- Wei-Chih Chen
- Department of Chemistry, National Taiwan University, Taipei City 10617, Taiwan
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