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Zaima T, Ota W, Haruta N, Uejima M, Ohkita H, Sato T. Spontaneous-Symmetry-Breaking Charge Separation Induced by Pseudo-Jahn-Teller Distortion in Organic Photovoltaic Material. J Phys Chem Lett 2023; 14:9706-9712. [PMID: 37877625 DOI: 10.1021/acs.jpclett.3c02527] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2023]
Abstract
The driving force of charge separation in the initial photovoltaic conversion process is theoretically investigated using ITIC, a nonfullerene acceptor material for organic photovoltaic devices. The density functional theory calculations show that the pseudo-Jahn-Teller (PJT) distortion of the S1 excimer state induces spontaneous symmetry-breaking charge separation between the identical ITIC molecules even without the asymmetry of the surrounding environment. The strong PJT effect arises from the vibronic coupling between the pseudodegenerate S1 and S2 excited states with different irreducible representations (irreps), i.e., Au for S1 and Ag for S2, via the asymmetric vibrational mode with the Au irrep. The vibrational mode responsible for the spontaneous polarization, which is opposite in one ITIC monomer and the other, is the intramolecular C-C stretching vibration between the core IT and terminal IC units. These results suggest that controlling the PJT effect can improve the charge separation efficiency of the initial photovoltaic conversion process.
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Affiliation(s)
- Takeaki Zaima
- Fukui Institute for Fundamental Chemistry, Kyoto University, Takano Nishibiraki-cho 34-4, Sakyo-ku, Kyoto 606-8103, Japan
- Department of Molecular Engineering, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan
| | - Wataru Ota
- Fukui Institute for Fundamental Chemistry, Kyoto University, Takano Nishibiraki-cho 34-4, Sakyo-ku, Kyoto 606-8103, Japan
- Department of Molecular Engineering, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan
| | - Naoki Haruta
- Fukui Institute for Fundamental Chemistry, Kyoto University, Takano Nishibiraki-cho 34-4, Sakyo-ku, Kyoto 606-8103, Japan
- Department of Molecular Engineering, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan
| | - Motoyuki Uejima
- MOLFEX, Inc., Takano Nishibiraki-cho 34-4, Sakyo-ku, Kyoto 606-8103, Japan
| | - Hideo Ohkita
- Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan
| | - Tohru Sato
- Fukui Institute for Fundamental Chemistry, Kyoto University, Takano Nishibiraki-cho 34-4, Sakyo-ku, Kyoto 606-8103, Japan
- Department of Molecular Engineering, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan
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Wei F, Chen J, Zhao X, Wu Y, Wang H, Chen X, Xiong Z. High-Performance Hot-Exciton OLEDs via Fully Harvesting Triplet Excited States from Both the Exciplex Co-Host and the TBRb Emitter. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2023; 10:e2303192. [PMID: 37587760 PMCID: PMC10582462 DOI: 10.1002/advs.202303192] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Revised: 07/12/2023] [Indexed: 08/18/2023]
Abstract
The high-level reverse intersystem crossing (HL-RISC, T2 → S1 ) process from triplet to singlet exciton, namely the "hot exciton" channel, has recently been demonstrated in the traditional fluorescent emitter of TBRb. Although it is a potential pathway to improve the utilization of non-radiative triplet exciton energy, highly efficient fluorescent organic light emitting diodes (FOLEDs) based on this "hot exciton" channel have not been developed. Herein, high-efficiency and low-efficiency roll-off FOLEDs are achieved through doping TBRb molecules into an energy-level matched exciplex co-host. Combining the low-level RISC (LL-RISC, EX3 → EX1 ) process in the exciplex co-host with the HL-RISC process of hot excitons in TBRb to fully harvest the triplet energy, a record-high external quantum efficiency (EQE) of 20.4% is obtained via a proper Dexter energy transfer of triplet excitons, realizing the efficiency breakthrough from fully fluorescent material-based OLEDs with TBRb as an end emitter. Furthermore, the fingerprint Magneto-electroluminescence (MEL) as a sensitive measuring tool is employed to visualize the "hot exciton" channel in TBRb, which also directly verifies the effective energy confinement and the full utilization of hot excitons. Obviously, this work paves a promising way for further fabricating high-efficiency TBRb-based FOLEDs for lighting and flat-panel display applications.
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Affiliation(s)
- Fuxian Wei
- Chongqing Key Laboratory of Micro & Nano Structure Optoelectronics, School of Physical Science and TechnologySouthwest UniversityChongqing400715P. R. China
| | - Jing Chen
- Chongqing Key Laboratory of Micro & Nano Structure Optoelectronics, School of Physical Science and TechnologySouthwest UniversityChongqing400715P. R. China
| | - Xi Zhao
- Chongqing Key Laboratory of Micro & Nano Structure Optoelectronics, School of Physical Science and TechnologySouthwest UniversityChongqing400715P. R. China
| | - Yuting Wu
- Chongqing Key Laboratory of Micro & Nano Structure Optoelectronics, School of Physical Science and TechnologySouthwest UniversityChongqing400715P. R. China
| | - Huiyao Wang
- Chongqing Key Laboratory of Micro & Nano Structure Optoelectronics, School of Physical Science and TechnologySouthwest UniversityChongqing400715P. R. China
| | - Xiaoli Chen
- Chongqing Key Laboratory of Micro & Nano Structure Optoelectronics, School of Physical Science and TechnologySouthwest UniversityChongqing400715P. R. China
| | - Zuhong Xiong
- Chongqing Key Laboratory of Micro & Nano Structure Optoelectronics, School of Physical Science and TechnologySouthwest UniversityChongqing400715P. R. China
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Nandi RP, Kalluvettukuzhy NK, Pagidi S, Thilagar P. Molecular Persistent Room-Temperature Phosphorescence from Tetraarylaminoboranes. Inorg Chem 2023; 62:1122-1134. [PMID: 36630685 DOI: 10.1021/acs.inorgchem.2c03386] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Herein, we report the synthesis, molecular structure, and optical features of tetrarylaminoboranes 1 (Mes2B-N(Ph)(C10H7)) and 2 (Mes2B-N(Ph)(C14H9)). In the solution state, 1 shows aggregation-induced emission enhancement and color switching, while 2 displays emission color switching and aggregation-caused quenching. At 77 K, frozen solutions of 1 show delayed fluorescence (DF) and phosphorescence, whereas 2 display only DF. Pristine solids of 1 and 2 showed delayed fluorescence under ambient conditions; however, crystals of both compounds show no phosphorescence under similar conditions. Polymethyl methacrylate thin films of 1 (1 wt % doping concentration) exhibit persistent room-temperature phosphorescence (pRTP) lasting for ∼0.5 s. In contrast, 2 does not show phosphorescence under similar conditions. Systematic photophysical studies and theoretical (DFT and TD-DFT) calculations are performed on these molecules to rationalize their intriguing optical characteristics.
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Affiliation(s)
- Rajendra Prasad Nandi
- Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore 560012, India
| | - Neena K Kalluvettukuzhy
- Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore 560012, India
| | - Sudhakar Pagidi
- Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore 560012, India
| | - Pakkirisamy Thilagar
- Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore 560012, India
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Nandi RP, Ghosh S, Venkatasubbaiah K, Kumbhar D, Thilagar P. Tribophosphorescence from a Simple Boronic Ester. CHEMPHOTOCHEM 2022. [DOI: 10.1002/cptc.202200026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
| | | | | | | | - Pakkirisamy Thilagar
- IISc: Indian Institute of Science Inorganic and Physical Chemistry Indian Institute of Science Bangalore 560012 Bangalore INDIA
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Park J, Kim W, Aggawal Y, Shin K, Choi EH, Park B. Highly Efficient and Stable Organic Light-Emitting Diodes with Inner Passivating Hole-Transfer Interlayers of Poly(amic acid)-Polyimide Copolymer. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2022; 9:e2105851. [PMID: 35088585 PMCID: PMC8948599 DOI: 10.1002/advs.202105851] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Indexed: 06/02/2023]
Abstract
Ensuring the long-term stability of high-performance organic light-emitting diodes (OLEDs) has remained a great challenge due to their limited lifetime and durability. Herein, a novel functional interlayer consisting of a poly(amic acid)-polyimide copolymer is introduced for use in OLEDs. It is shown that an OLED sample with a polyimide-copolymer interlayer exhibits high peak brightness of nearly 96 000 cd m-2 and efficiency of ≈92 cd A-1 , much higher than those (≈73 000 cd m-2 and ≈83 cd A-1 ) of a well-organized reference OLED. Moreover, the growth of dark spots is strongly suppressed in the sample OLED and the device lifetime is extended considerably. Further, highly stable and uniform large-area OLEDs are successfully produced when using the interlayer. These improvements are ascribed not only to the excellent film-forming and hole-transferring properties but also to the inner passivating capability of the polyimide-copolymer interlayer. The results here suggest that the introduction of an inner passivating/encapsulating hole-transferable polyimide-copolymer interlayer together with conventional external encapsulation technology represents a promising breakthrough that enhances the longevity of high-performance next-generation OLEDs.
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Affiliation(s)
- Jaewoo Park
- Department of Electrical and Biological PhysicsKwangwoon UniversityWolgye‐DongSeoul01897South Korea
- Department of Plasma‐Bio DisplayKwangwoon UniversityWolgye‐DongSeoul01897South Korea
| | - Wonsun Kim
- Department of Electrical and Biological PhysicsKwangwoon UniversityWolgye‐DongSeoul01897South Korea
| | - Yushika Aggawal
- Department of Electrical and Biological PhysicsKwangwoon UniversityWolgye‐DongSeoul01897South Korea
| | - Kichul Shin
- Department of Electrical and Biological PhysicsKwangwoon UniversityWolgye‐DongSeoul01897South Korea
| | - Eun Ha Choi
- Department of Electrical and Biological PhysicsKwangwoon UniversityWolgye‐DongSeoul01897South Korea
- Department of Plasma‐Bio DisplayKwangwoon UniversityWolgye‐DongSeoul01897South Korea
| | - Byoungchoo Park
- Department of Electrical and Biological PhysicsKwangwoon UniversityWolgye‐DongSeoul01897South Korea
- Department of Plasma‐Bio DisplayKwangwoon UniversityWolgye‐DongSeoul01897South Korea
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Li J, Li T, Zhang M, Guo D, Zhang H. Rational designs of structurally similar TADF and HLCT emitters with benzo- or naphtho-carbazole units as electron donors. Phys Chem Chem Phys 2022; 24:25937-25949. [DOI: 10.1039/d2cp03500f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Structurally similar D–A type molecules with the combination of benzo- or naphtho-carbazole units as electron donors and tunable electron acceptors with different electron-withdrawing ability are designed to realize HLCT and TADF emissions.
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Affiliation(s)
- Jiaqi Li
- State Key Laboratory of Supramolecular Structure and Materials, Institute of Theoretical Chemistry, College of Chemistry, Jilin University, Changchun 130012, P. R. China
| | - Tingyu Li
- State Key Laboratory of Supramolecular Structure and Materials, Institute of Theoretical Chemistry, College of Chemistry, Jilin University, Changchun 130012, P. R. China
| | - Mingfan Zhang
- State Key Laboratory of Supramolecular Structure and Materials, Institute of Theoretical Chemistry, College of Chemistry, Jilin University, Changchun 130012, P. R. China
| | - Dongxue Guo
- State Key Laboratory of Supramolecular Structure and Materials, Institute of Theoretical Chemistry, College of Chemistry, Jilin University, Changchun 130012, P. R. China
| | - Houyu Zhang
- State Key Laboratory of Supramolecular Structure and Materials, Institute of Theoretical Chemistry, College of Chemistry, Jilin University, Changchun 130012, P. R. China
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Li TY, Djurovich PI, Thompson ME. Phosphorescent monometallic and bimetallic two-coordinate Au(I) complexes with N-heterocyclic carbene and aryl ligands. Inorganica Chim Acta 2021. [DOI: 10.1016/j.ica.2020.120188] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Xu Y, Xu P, Hu D, Ma Y. Recent progress in hot exciton materials for organic light-emitting diodes. Chem Soc Rev 2020; 50:1030-1069. [PMID: 33231588 DOI: 10.1039/d0cs00391c] [Citation(s) in RCA: 139] [Impact Index Per Article: 34.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
According to Kasha's rule, high-lying excited states usually have little effect on fluorescence. However, in some molecular systems, the high-lying excited states partly or even mainly contribute to the photophysical properties, especially in the process of harvesting triplet excitons in organic electroluminescent devices. In the current review, we focus on a type of organic light-emitting diode (OLED) materials called "hot exciton" materials, which can effectively harness the non-radiative triplet excitons via reverse intersystem crossing (RISC) from high-lying triplet states to singlet states (Tn→ Sm; n≥ 2, m≥ 1). Since Ma and Yang proposed the hot exciton mechanism for OLED material design in 2012, there have been many reports aiming at the design and synthesis of novel hot exciton luminogens. Herein, we present a comprehensive review of the recent progress in hot exciton materials. The developments of the hot exciton mechanism are reviewed, the fundamental principles regarding molecular design are discussed, and representative reported hot exciton luminogens are summarized and analyzed, along with their structure-property relationships and OLED applications.
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Affiliation(s)
- Yuwei Xu
- Institute of Polymer Optoelectronic Materials and Devices, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, P. R. China.
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Chen WC, Cheng YC. Elucidating the Magnitude of Internal Reorganization Energy of Molecular Excited States from the Perspective of Transition Density. J Phys Chem A 2020; 124:7644-7657. [PMID: 32864966 DOI: 10.1021/acs.jpca.0c06482] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Quantifying vibronic couplings in molecular excited states is crucial for the elucidation of a broad range of photophysical phenomena. In this study, we compare different theoretical approaches for the calculation of reorganization energy, a measure of vibronic coupling strength, and provide a rigorous derivation to show that molecular transition density characterizing electron-hole excitation could be used to quantify the magnitude of reorganization energy. The theory enables a descriptor based on molecular-orbital coefficients and atomic transition densities to quantify the magnitude of reorganization energies in molecular excited states. Applying the approach to low-lying excited states of polyacenes, we demonstrate that transition density distribution explains the difference in the magnitude of the reorganization energy of different excited states. Furthermore, to clarify the applicability of the transition density descriptor in molecular design for small-reorganization energy molecules, we investigate a broad range of molecular chromophores to show the effectiveness of the proposed theory. With this perspective on the relationship between reorganization energy and transition density, we successfully provide a quantitative rule to identify π-conjugated systems with small reorganization energy in the excited state, which should be useful for the development of novel optoelectronic materials.
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Affiliation(s)
- Wei-Chih Chen
- Department of Chemistry and Center for Quantum Science and Engineering, National Taiwan University, Taipei City 106, Taiwan, R.O.C
| | - Yuan-Chung Cheng
- Department of Chemistry and Center for Quantum Science and Engineering, National Taiwan University, Taipei City 106, Taiwan, R.O.C
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