1
|
Kirch A, Wolansky J, Miri Aabi Soflaa S, Buchholtz SA, Werberger R, Kaiser C, Fischer A, Leo K, Edman L, Benduhn J, Reineke S. Tuning Charge-Transfer States by Interface Electric Fields. ACS APPLIED MATERIALS & INTERFACES 2024; 16:31407-31418. [PMID: 38841759 PMCID: PMC11194774 DOI: 10.1021/acsami.4c04602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2024]
Abstract
Intermolecular charge-transfer (CT) states are extended excitons with a charge separation on the nanometer scale. Through absorption and emission processes, they couple to the ground state. This property is employed both in light-emitting and light-absorbing devices. Their conception often relies on donor-acceptor (D-A) interfaces, so-called type-II heterojunctions, which usually generate significant electric fields. Several recent studies claim that these fields alter the energetic configuration of the CT states at the interface, an idea holding prospects like multicolor emission from a single emissive interface or shifting the absorption characteristics of a photodetector. Here, we test this hypothesis and contribute to the discussion by presenting a new model system. Through the fabrication of planar organic p-(i-)n junctions, we generate an ensemble of oriented CT states that allows the systematic assessment of electric field impacts. By increasing the thickness of the intrinsic layer at the D-A interface from 0 to 20 nm and by applying external voltages up to 6 V, we realize two different scenarios that controllably tune the intrinsic and extrinsic electric interface fields. By this, we obtain significant shifts of the CT-state peak emission of about 0.5 eV (170 nm from red to green color) from the same D-A material combination. This effect can be explained in a classical electrostatic picture, as the interface electric field alters the potential energy of the electric CT-state dipole. This study illustrates that CT-state energies can be tuned significantly if their electric dipoles are aligned to the interface electric field.
Collapse
Affiliation(s)
- Anton Kirch
- Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Institute of Applied Physics, Technische Universität Dresden, Nöthnitzer Straße 61, Dresden 01187, Germany
- The Organic Photonics and Electronics Group, Department of Physics, Umeå University, Umeå SE-90187, Sweden
| | - Jakob Wolansky
- Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Institute of Applied Physics, Technische Universität Dresden, Nöthnitzer Straße 61, Dresden 01187, Germany
| | - Shayan Miri Aabi Soflaa
- Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Institute of Applied Physics, Technische Universität Dresden, Nöthnitzer Straße 61, Dresden 01187, Germany
| | - Stephanie Anna Buchholtz
- Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Institute of Applied Physics, Technische Universität Dresden, Nöthnitzer Straße 61, Dresden 01187, Germany
| | - Robert Werberger
- Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Institute of Applied Physics, Technische Universität Dresden, Nöthnitzer Straße 61, Dresden 01187, Germany
| | - Christina Kaiser
- Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Institute of Applied Physics, Technische Universität Dresden, Nöthnitzer Straße 61, Dresden 01187, Germany
| | - Axel Fischer
- Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Institute of Applied Physics, Technische Universität Dresden, Nöthnitzer Straße 61, Dresden 01187, Germany
| | - Karl Leo
- Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Institute of Applied Physics, Technische Universität Dresden, Nöthnitzer Straße 61, Dresden 01187, Germany
| | - Ludvig Edman
- The Organic Photonics and Electronics Group, Department of Physics, Umeå University, Umeå SE-90187, Sweden
| | - Johannes Benduhn
- Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Institute of Applied Physics, Technische Universität Dresden, Nöthnitzer Straße 61, Dresden 01187, Germany
| | - Sebastian Reineke
- Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Institute of Applied Physics, Technische Universität Dresden, Nöthnitzer Straße 61, Dresden 01187, Germany
| |
Collapse
|
2
|
Fedorenko EV, Lyubykh NA, Khrebtov AA, Beloliptsev AY, Mirochnik AG. Exciplex luminescence of difluoroboron meta- and para-Nitrodibenzoylmethanates in solutions and polymer matrix. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2023; 303:123193. [PMID: 37515888 DOI: 10.1016/j.saa.2023.123193] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2023] [Revised: 07/17/2023] [Accepted: 07/22/2023] [Indexed: 07/31/2023]
Abstract
Molecular systems with intense exciplex luminescence are promising for the creation of OLEDs and light-transforming materials. The luminescent properties of difluoroboron meta- and para-nitrodibenzoylmethanates (1 and 2) were studied by the steady-state and time-resolved luminescence spectroscopy methods and quantum chemistry simulation. The influence of the position of the nitro group on the spectral properties of the complexes was revealed. The nitro group withdraws the electron density upon photoexcitation in the para-isomer in contrast to the meta-isomer. The bond order of the CC bond between the phenyl and chelate rings decreases in the excited relaxed state of 2, which leads to rotation of the substituent and a low quantum yield. Formation of exciplexes of 1 and 2 in benzene, toluene and polystyrene was found. The formation of the ground and excited-state electron donor-acceptor complexes based on difluoroboron nitrodibenzoylmethanates and benzene was revealed. The TDDFT method showed that the complexes are characterized by the presence of short contacts between the fluorine atom of the dye molecule and the hydrogen atoms of the aromatic hydrocarbon molecule. These contacts shorten during the transition from the ground state to the excited state. Polymeric compositions based on polystyrene (PS) and poly(methyl methacrylate) (PMMA) doped with 1 and 2 were obtained. The luminescence intensity of dyes 1 and 2 increases during the transition from PMMA to PS. A significant bathochromic shift of the luminescence maximum of 1 is observed, which is associated with the formation of exciplexes and triplexes. The obtained polymeric materials are promising for the development of optical smart materials.
Collapse
Affiliation(s)
- Elena V Fedorenko
- Institute of Chemistry, Far Eastern Branch, Russian Academy of Sciences, Vladivostok 690022, Russian Federation.
| | - Nikita A Lyubykh
- Institute of Chemistry, Far Eastern Branch, Russian Academy of Sciences, Vladivostok 690022, Russian Federation.
| | - Aleksandr A Khrebtov
- Institute of Chemistry, Far Eastern Branch, Russian Academy of Sciences, Vladivostok 690022, Russian Federation; Far Eastern Federal University, Vladivostok 690091, Russian Federation.
| | - Anton Yu Beloliptsev
- Institute of Chemistry, Far Eastern Branch, Russian Academy of Sciences, Vladivostok 690022, Russian Federation.
| | - Anatolii G Mirochnik
- Institute of Chemistry, Far Eastern Branch, Russian Academy of Sciences, Vladivostok 690022, Russian Federation.
| |
Collapse
|
3
|
Lee SH, Kim TJ, Lee E, Kwon D, Kim J, Joo J. Observation of aligned dipoles and angular chromism of exciplexes in organic molecular heterostructures. Nat Commun 2023; 14:7190. [PMID: 37938244 PMCID: PMC10632441 DOI: 10.1038/s41467-023-42976-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2023] [Accepted: 10/26/2023] [Indexed: 11/09/2023] Open
Abstract
The dipole characteristics of Frenkel excitons and charge-transfer excitons between donor and acceptor molecules in organic heterostructures such as exciplexes are important in organic photonics and optoelectronics. For the bilayer of the organic donor 4,4',4''-tris[(3-methylphenyl)phenylamino]triphenylamine and acceptor 2,4,6-tris(biphenyl-3-yl)-1,3,5-triazine molecules, the exciplexes form aligned dipoles perpendicular to the Frenkel excitons, as observed in back focal plane photoluminescence images. The angular chromism of exciplexes observed in the 100 meV range indicates possible delocalization and angle-sensing photonic applications. The blue shift of the peak position and increase in the linewidth of photoluminescene spectra with increasing excitation power are caused by the repulsive aligned exciplex dipole moments with a long lifetime (4.65 μs). Electroluminescence spectra of the exciplex from organic light-emitting diodes using the bilayer are blue-shifted with increasing bias, suggesting unidirectional alignment of the exciplex dipole moments. The observation of exciplex dipole moment alignments across molecular interfaces can facilitate the controlled coupling of exciton species and increase efficiency of organic light-emitting diodes.
Collapse
Affiliation(s)
- Sang-Hun Lee
- Department of Physics, Korea University, Seoul, 02841, Republic of Korea
| | - Taek Joon Kim
- Department of Physics, Korea University, Seoul, 02841, Republic of Korea
| | - Eunji Lee
- Department of Energy Science, Sungkyunkwan University, Suwon, 16419, Republic of Korea
| | - Dayeong Kwon
- Department of Physics, Korea University, Seoul, 02841, Republic of Korea
| | - Jeongyong Kim
- Department of Energy Science, Sungkyunkwan University, Suwon, 16419, Republic of Korea.
| | - Jinsoo Joo
- Department of Physics, Korea University, Seoul, 02841, Republic of Korea.
| |
Collapse
|
4
|
Deng Z, Zhao H, Cao X, Xiong S, Li G, Deng J, Yang H, Zhang W, Liu Q. Enhancing Built-in Electric Field via Molecular Dipole Control in Conjugated Microporous Polymers for Boosting Charge Separation. ACS APPLIED MATERIALS & INTERFACES 2022; 14:35745-35754. [PMID: 35914116 DOI: 10.1021/acsami.2c08747] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
The built-in electric field (BEF) has been considered as the key kinetic factor for facilitating efficient photoinduced carrier separation and migration of polymeric photocatalysts. Enhancing the BEF of the polymers could enable a directional migration of the photogenerated carriers to accelerate photogenerated charge separation and thus boost photocatalytic performances. However, achieving this approach remains a formidable challenge, which has never been realized in conjugated microporous polymers (CMPs). Herein, we developed a molecular dipole control strategy to modulate the BEF in CMPs by varying the nature of the core. As a result, a series of CMPs with a tunable BEF were designed and prepared via FeCl3-mediated coupling of bicarbazole with different acceptor cores. The optimized CbzCMP-9 featured the strongest BEF induced by its high molecular dipole, which grants it with a powerful driving force to accelerate exciton dissociation into electron-hole pairs and facilitates charge transfer along the backbone of CMPs to the surface, resulting in a remarkable photocatalytic performance toward thiocyano chromones and C-3 thiocyanation of indoles (up to 95 and 98% yields, respectively) and prominently surpassing many other reported photocatalysts. In brief, the proposed strategy highlights that enhancing the BEF by modulating molecular dipole can lead to a dramatic improvement in photocatalytic performance, which is expected to be employed for constructing other photocatalytic systems with high performance.
Collapse
Affiliation(s)
- Zhaozhang Deng
- Hunan Provincial Key Lab of Advanced Materials for New Energy Storage and Conversion, School of Materials Science and Engineering, Hunan University of Science and Technology, Xiangtan 411201, China
| | - Hongwei Zhao
- Hunan Provincial Key Lab of Advanced Materials for New Energy Storage and Conversion, School of Materials Science and Engineering, Hunan University of Science and Technology, Xiangtan 411201, China
| | - Xinxiu Cao
- Hunan Provincial Key Lab of Advanced Materials for New Energy Storage and Conversion, School of Materials Science and Engineering, Hunan University of Science and Technology, Xiangtan 411201, China
| | - Shaohui Xiong
- Hunan Provincial Key Lab of Advanced Materials for New Energy Storage and Conversion, School of Materials Science and Engineering, Hunan University of Science and Technology, Xiangtan 411201, China
| | - Gen Li
- Hunan Provincial Key Lab of Advanced Materials for New Energy Storage and Conversion, School of Materials Science and Engineering, Hunan University of Science and Technology, Xiangtan 411201, China
| | - Jiyong Deng
- Hunan Provincial Key Laboratory of Environmental Catalysis & Waste Recycling, School of Chemistry and Chemical Engineering, Hunan Institute of Engineering, Xiangtan 411104, China
| | - Hai Yang
- Hunan Provincial Key Laboratory of Environmental Catalysis & Waste Recycling, School of Chemistry and Chemical Engineering, Hunan Institute of Engineering, Xiangtan 411104, China
| | - Weijie Zhang
- Hunan Provincial Key Laboratory of Environmental Catalysis & Waste Recycling, School of Chemistry and Chemical Engineering, Hunan Institute of Engineering, Xiangtan 411104, China
| | - Qingquan Liu
- Hunan Provincial Key Lab of Advanced Materials for New Energy Storage and Conversion, School of Materials Science and Engineering, Hunan University of Science and Technology, Xiangtan 411201, China
| |
Collapse
|
5
|
Recent Advances of Interface Exciplex in Organic Light-Emitting Diodes. MICROMACHINES 2022; 13:mi13020298. [PMID: 35208422 PMCID: PMC8875368 DOI: 10.3390/mi13020298] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/22/2022] [Revised: 02/05/2022] [Accepted: 02/07/2022] [Indexed: 02/06/2023]
Abstract
The interface exciplex system is a promising technology for reaching organic light-emitting diodes (OLEDs) with low turn-on voltages, high efficiencies and long lifetimes due to its unique virtue of barrier-free charge transport, well-confined recombination region, and thermally activated delayed fluorescence characteristics. In this review, we firstly illustrate the mechanism frameworks and superiorities of the interface exciplex system. We then summarize the primary applications of interface exciplex systems fabricated by doping and doping-free technologies. The operation mechanisms of these OLEDs are emphasized briefly. In addition, various novel strategies for further improving the performances of interface exciplex-based devices are demonstrated. We believe this review will give a promising perspective and attract researchers to further develop this technology in the future.
Collapse
|
6
|
Shen D, Ma C, Ng TW, Chandran HT, Lo MF, Lee CS. Organic-Inorganic Charge Transfer Complex with Charge Modulation after Electrical Pre-biasing. ACS APPLIED MATERIALS & INTERFACES 2020; 12:37384-37390. [PMID: 32706573 DOI: 10.1021/acsami.0c09064] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Several breakthroughs in organic optoelectronic devices with new applications and performance improvement have been made recently by exploiting novel properties of charge transfer complexes (CTCs). In this work, a CTC film formed by coevaporating molybdenum(VI) oxide and pentacene (MoO3:pentacene) shows a strong dipole of 2.4 eV with direction controllability via pre-biasing with an external voltage. While CTCs are most widely known for their much red-shifted energy gaps, there is so far no report on their controllable dipoles. By controlling this dipole with an electrical pre-bias in a MoO3:pentacene CTC based device, current changes over 2 orders of magnitude can be achieved. Kelvin probe force microscopy further confirms that surface potential of the MoO3:pentacene film can be modulated by an external electric field. It is shown for the first time that a dipole of controllable direction can be set up inside a CTC layer by pre-biasing. This concept is further tested by incorporating the CTC layer in organic photovoltaic (OPV) devices. It was demonstrated that by pre-biasing the OPV devices in different directions, their open circuit voltages (Voc) can be significantly tuned via the built-in potentials.
Collapse
Affiliation(s)
- Dong Shen
- Center of Super-Diamond and Advanced Films (COSDAF), Department of Chemistry, City University of Hong Kong, Hong Kong SAR, People's Republic of China
| | - Chunqing Ma
- Center of Super-Diamond and Advanced Films (COSDAF), Department of Chemistry, City University of Hong Kong, Hong Kong SAR, People's Republic of China
| | - Tsz-Wai Ng
- Center of Super-Diamond and Advanced Films (COSDAF), Department of Chemistry, City University of Hong Kong, Hong Kong SAR, People's Republic of China
| | - Hrisheekesh Thachoth Chandran
- Center of Super-Diamond and Advanced Films (COSDAF), Department of Chemistry, City University of Hong Kong, Hong Kong SAR, People's Republic of China
| | - Ming-Fai Lo
- Center of Super-Diamond and Advanced Films (COSDAF), Department of Chemistry, City University of Hong Kong, Hong Kong SAR, People's Republic of China
| | - Chun-Sing Lee
- Center of Super-Diamond and Advanced Films (COSDAF), Department of Chemistry, City University of Hong Kong, Hong Kong SAR, People's Republic of China
| |
Collapse
|
7
|
Song X, Zhang D, Li H, Cai M, Huang T, Duan L. Exciplex System with Increased Donor-Acceptor Distance as the Sensitizing Host for Conventional Fluorescent OLEDs with High Efficiency and Extremely Low Roll-Off. ACS APPLIED MATERIALS & INTERFACES 2019; 11:22595-22602. [PMID: 31198026 DOI: 10.1021/acsami.9b05963] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Exciplex systems with efficient thermally activated delayed fluorescence as the sensitizing hosts for fluorescent organic light-emitting diodes (OLEDs) have been flourished recently, while the device performances are still lagging behind. Here, a donor molecule sterically encapsulated with tert-butyl units is designed and synthesized to increase the donor-acceptor separation in an exciplex system, leading to reduced singlet-triplet energy gap (Δ ESTs) and improved reverse intersystem crossing (RISC) efficiency. OLEDs utilizing exciplexes with increased donor-acceptor distance ( rDA) as the hosts for conventional fluorescent dopants exhibit a maximum external quantum efficiency (EQEmax) as high as 16.5%, benefiting from the enhanced RISC process and suppressed exciton loss by the Dexter interaction. Furthermore, extremely low efficiency roll-off is obtained with EQEs of 16.2% at 5000 cd/m2 and 15.2% at 10 000 cd/m2. The results here represent the state-of-the-art performances for devices based on exciplexes as the hosts for conventional fluorescent dopants, manifesting the superiority of exciplexes with increased rDA as the sensitizing hosts for fluorescent dopants.
Collapse
Affiliation(s)
| | | | - Haoyuan Li
- School of Chemistry and Biochemistry, Center for Organic Photonics and Electronics (COPE) , Georgia Institute of Technology , Atlanta , Georgia 30332-0400 , United States
| | | | | | | |
Collapse
|
8
|
Zhang B, Xie Z. Recent Applications of Interfacial Exciplex as Ideal Host of Power-Efficient OLEDs. Front Chem 2019; 7:306. [PMID: 31134183 PMCID: PMC6514091 DOI: 10.3389/fchem.2019.00306] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2019] [Accepted: 04/16/2019] [Indexed: 12/22/2022] Open
Abstract
Currently, exploring the applications of intermolecular donor-acceptor exciplex couple as host of OLEDs with phosphorescence, thermally activated delayed fluorescence (TADF) or fluorescence emitter as dopant is a hot topic. Compared to other host strategies, interfacial exciplex has the advantage in various aspects, such as barrier-free charge injection, unimpeded charge transport, and the energy-saving direct exciton formation process at the “Well”-like heterojunction interface region. Most importantly, due to a very fast and efficient reverse intersystem-crossing (RISC) process, such a host is capable of regulating singlet/triplet exciton populations in itself as well as in the dopant emitters both under photoluminescent (PL) and electroluminescent (EL) driving conditions. In this mini-review, we briefly summarize and comment on recent applications of this ideal host in OLEDs (including both thermal-evaporation OLEDs and solution-processed OLEDs) with diverse emitters, e.g., fluorescence, phosphorescence, delayed fluorescence, or others. Special attention is given to illustrate the peculiar achievement of high overall EL performance with superiorities of low driving voltages, slow roll-off rate, high power efficiencies and satisfied device lifetime using this host strategy, which is then concluded by personal perspectives on the relevant next-step in this field.
Collapse
Affiliation(s)
- Baohua Zhang
- Center for Advanced Analytical Science, School of Chemistry and Chemical Engineering, Guangzhou University, Guangzhou, China
| | - Zhiyuan Xie
- State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, China
| |
Collapse
|
9
|
Ullbrich S, Benduhn J, Jia X, Nikolis VC, Tvingstedt K, Piersimoni F, Roland S, Liu Y, Wu J, Fischer A, Neher D, Reineke S, Spoltore D, Vandewal K. Emissive and charge-generating donor-acceptor interfaces for organic optoelectronics with low voltage losses. NATURE MATERIALS 2019; 18:459-464. [PMID: 30936478 DOI: 10.1038/s41563-019-0324-5] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/25/2018] [Accepted: 02/19/2019] [Indexed: 06/09/2023]
Abstract
Intermolecular charge-transfer states at the interface between electron donating (D) and accepting (A) materials are crucial for the operation of organic solar cells but can also be exploited for organic light-emitting diodes1,2. Non-radiative charge-transfer state decay is dominant in state-of-the-art D-A-based organic solar cells and is responsible for large voltage losses and relatively low power-conversion efficiencies as well as electroluminescence external quantum yields in the 0.01-0.0001% range3,4. In contrast, the electroluminescence external quantum yield reaches up to 16% in D-A-based organic light-emitting diodes5-7. Here, we show that proper control of charge-transfer state properties allows simultaneous occurrence of a high photovoltaic and emission quantum yield within a single, visible-light-emitting D-A system. This leads to ultralow-emission turn-on voltages as well as significantly reduced voltage losses upon solar illumination. These results unify the description of the electro-optical properties of charge-transfer states in organic optoelectronic devices and foster the use of organic D-A blends in energy conversion applications involving visible and ultraviolet photons8-11.
Collapse
Affiliation(s)
- Sascha Ullbrich
- Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Institute for Applied Physics, Technische Universität Dresden, Dresden, Germany.
| | - Johannes Benduhn
- Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Institute for Applied Physics, Technische Universität Dresden, Dresden, Germany.
| | - Xiangkun Jia
- Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Institute for Applied Physics, Technische Universität Dresden, Dresden, Germany
| | - Vasileios C Nikolis
- Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Institute for Applied Physics, Technische Universität Dresden, Dresden, Germany
| | - Kristofer Tvingstedt
- Experimental Physics VI, Julius-Maximilian University of Würzburg, Würzburg, Germany
| | | | - Steffen Roland
- Institute of Physics and Astronomy, University of Potsdam, Potsdam, Germany
| | - Yuan Liu
- Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Institute for Applied Physics, Technische Universität Dresden, Dresden, Germany
| | - Jinhan Wu
- Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Institute for Applied Physics, Technische Universität Dresden, Dresden, Germany
| | - Axel Fischer
- Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Institute for Applied Physics, Technische Universität Dresden, Dresden, Germany
| | - Dieter Neher
- Institute of Physics and Astronomy, University of Potsdam, Potsdam, Germany
| | - Sebastian Reineke
- Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Institute for Applied Physics, Technische Universität Dresden, Dresden, Germany
| | - Donato Spoltore
- Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Institute for Applied Physics, Technische Universität Dresden, Dresden, Germany
| | - Koen Vandewal
- Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Institute for Applied Physics, Technische Universität Dresden, Dresden, Germany.
- Institute for Materials Research (IMO-IMOMEC), Hasselt University, Diepenbeek, Belgium.
| |
Collapse
|
10
|
Chapran M, Pander P, Vasylieva M, Wiosna-Salyga G, Ulanski J, Dias FB, Data P. Realizing 20% External Quantum Efficiency in Electroluminescence with Efficient Thermally Activated Delayed Fluorescence from an Exciplex. ACS APPLIED MATERIALS & INTERFACES 2019; 11:13460-13471. [PMID: 30864778 DOI: 10.1021/acsami.8b18284] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The investigation of nondoped exciplex blends of 2,4,6-tris[3-(diphenylphosphinyl)phenyl]-1,3,5-triazine (PO-T2T), working as the one-electron acceptor molecule, with different electron donors is reported. The emissions of these exciplexes span from the blue to orange-red regions, showing clear contribution from thermally activated delayed fluorescence (TADF) and delayed fluorescence originated from nongeminate recombination of charge carriers created by the dissociation of optically generated exciplexes. We focus our studies on the properties of TADF in these systems, covering in particular the physical meaning of the different transient components observed in their luminescence decays. Our results unravel the intricate role of reverse intersystem crossing due to spin-orbit coupling and possibly also due to hyperfine interactions and internal conversion, which affect the efficiency of the TADF mechanism. Remarkable performances are obtained in prototype organic light-emitting diodes fabricated with some of these blends. Green exciplex blends, in particular, exhibited the current efficiency of 60 cd A-1, power efficiency of 71 lm W-1, and external quantum efficiency of 20%. We believe that our results will contribute significantly to highlight the potential advantages of intermolecular exciplexes in the area of organic light-emitting diodes.
Collapse
Affiliation(s)
- Marian Chapran
- Department of Molecular Physics , Lodz University of Technology , Zeromskiego 116 , 90-924 Lodz , Poland
| | - Piotr Pander
- Physics Department , Durham University , South Road, Durham DH1 3LE , United Kingdom
| | - Marharyta Vasylieva
- Faculty of Chemistry , Silesian University of Technology , M. Strzody 9 , 44-100 Gliwice , Poland
| | - Gabriela Wiosna-Salyga
- Department of Molecular Physics , Lodz University of Technology , Zeromskiego 116 , 90-924 Lodz , Poland
| | - Jacek Ulanski
- Department of Molecular Physics , Lodz University of Technology , Zeromskiego 116 , 90-924 Lodz , Poland
| | - Fernando B Dias
- Physics Department , Durham University , South Road, Durham DH1 3LE , United Kingdom
| | - Przemyslaw Data
- Physics Department , Durham University , South Road, Durham DH1 3LE , United Kingdom
- Faculty of Chemistry , Silesian University of Technology , M. Strzody 9 , 44-100 Gliwice , Poland
- Centre of Polymer and Carbon Materials , Polish Academy of Science , M. Curie-Sklodowskiej 34 , 41-819 Zabrze , Poland
| |
Collapse
|
11
|
Jinnai K, Nishimura N, Kabe R, Adachi C. Fabrication-method Independence of Organic Long-persistent Luminescence Performance. CHEM LETT 2019. [DOI: 10.1246/cl.180949] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- Kazuya Jinnai
- Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395, Japan
- JST, ERATO, Adachi Molecular Exciton Engineering Project, Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395, Japan
| | - Naohiro Nishimura
- Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395, Japan
- JST, ERATO, Adachi Molecular Exciton Engineering Project, Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395, Japan
| | - Ryota Kabe
- Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395, Japan
- JST, ERATO, Adachi Molecular Exciton Engineering Project, Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395, Japan
| | - Chihaya Adachi
- Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395, Japan
- JST, ERATO, Adachi Molecular Exciton Engineering Project, Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395, Japan
- International Institute for Carbon Neutral Energy Research (WPI-I2NER), Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395, Japan
| |
Collapse
|
12
|
Colella M, Danos A, Monkman AP. Less Is More: Dilution Enhances Optical and Electrical Performance of a TADF Exciplex. J Phys Chem Lett 2019; 10:793-798. [PMID: 30726086 PMCID: PMC7005938 DOI: 10.1021/acs.jpclett.8b03646] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2018] [Accepted: 02/06/2019] [Indexed: 05/25/2023]
Abstract
A surprising yet highly practical approach to improve the performance of a TADF exciplex blend is reported. Using the TSBPA donor and PO-T2T acceptor to form an exciplex, we are able to blue shift the emission, increase PLQY from 58 to 80%, and increase the device EQE from 14.8 to 19.2% by simply diluting the exciplex with an inert high triplet energy host material-here either UGH-3 or DPEPO. These effects are explained in terms of an increasing donor-acceptor distance and associated charge separation, while different behaviors observed in the different hosts are attributed to different energy barriers to electron transfer through the host. We expect that the observed performance-enhancing effects of dilution will be general to different exciplex blends and host materials and offer a new way to optimize the electrical properties of exciplex emission layers with narrow blue emission.
Collapse
|
13
|
Wang X, Guo L, Feng L. A multi stimuli responsive material with rhodamine B and carbazole groups. NEW J CHEM 2019. [DOI: 10.1039/c8nj05716h] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
A facile material with multi stimuli responsive behaviors was developed. The chromic properties of the material can be observed by stimulating it with light, electricity and ions.
Collapse
Affiliation(s)
- Xiaoju Wang
- Institute of Molecular Science
- Chemical Biology and Molecular Engineering
- Laboratory of Education Ministry
- Shanxi University
- Taiyuan 030006
| | - Lixia Guo
- School of Chemistry and Chemical Engineering
- Shanxi University
- Taiyuan
- P. R. China
| | - Liheng Feng
- School of Chemistry and Chemical Engineering
- Shanxi University
- Taiyuan
- P. R. China
| |
Collapse
|
14
|
Siddiqui QT, Awasthi AA, Bhui P, Parab P, Muneer M, Bose S, Agarwal N. TADF and exciplex emission in a xanthone–carbazole derivative and tuning of its electroluminescence with applied voltage. RSC Adv 2019; 9:40248-40254. [PMID: 35542672 PMCID: PMC9076223 DOI: 10.1039/c9ra08227a] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2019] [Accepted: 11/26/2019] [Indexed: 11/21/2022] Open
Abstract
Materials showing white light emission have found applications in a variety of solid state devices especially in display technology. For white light emission, doping of red (R), green (G) and blue (B) emitters in a host matrix is commonly practised. However, finding RGB emitters of similar stability with homogenous doping is challenging. Furthermore, such devices suffer from color purity in the long run. Small organic light emitters, capable of colour tuning and having a broad emission spectrum are in high demand as they provide colour stability, reproducibility, a simple device geometry and high efficiency. Recently, it has been shown that the efficiency of OLEDs can be enhanced by employing thermally activated delayed fluorescence (TADF) materials. Here, we designed and synthesised a xanthone–carbazole based D-A-D material (Xan-Cbz) for TADF properties. Blue TADF emission, in neat thin films, at 470 nm was observed and further investigated by studying delayed fluorescence and lifetime measurements. In addition, a blend of Xan-Cbz with NPD shows exciplex emission at 525 nm in thin film. OLEDs based on Xan-Cbz were fabricated using several device configurations. OLEDs having the device configuration ITO/PEDOT:PSS/NPD/Xan-Cbz/Bphen/LiF-Al showed a luminance of 1.96 × 104 Cd m−2 (at a current density of 50 mA cm−2) and VON at ∼6 V. Electroluminescence showed the features of both neat emission (470 nm) of Xan-Cbz and its exciplex (525 nm) with NPD. Further, colour tuning was observed as a function of applied voltage and the ratio of light intensity (I525/I470) of neat and exciplex emission was found to decrease with increasing voltage. Greenish-blue emission (CIE coordinates: 0.202, 0.382) from Xan-Cbz OLEDs was obtained. Xan-Cbz showed its neat emission (at 470 nm) in ITO/PEDOT:PSS/CBP/Xan-Cbz/Bphen/LiF-Al and pure exciplex emission (at 525 nm) in ITO/PEDOT:PSS/NPD:Xan-Cbz/Bphen/LiF-Al device configurations. Thus in this article we showed blue TADF emission, exciplex emission and voltage dependent color tuning in OLEDs based on a small organic emitter. Xanthone–carbazole (Xan–Cbz) derivative is synthesized and its photophysical properties are explored. OLEDs of Xan–Cbz shows tunability of electro-luminescence with applied voltage.![]()
Collapse
Affiliation(s)
- Qamar T. Siddiqui
- School of Chemical Sciences
- UM-DAE, Centre for Excellence in Basic Sciences
- University of Mumbai
- Mumbai
- India
| | - Ankur A. Awasthi
- School of Chemical Sciences
- UM-DAE, Centre for Excellence in Basic Sciences
- University of Mumbai
- Mumbai
- India
| | - Prabhjyot Bhui
- School of Physical Sciences
- UM-DAE, Centre for Excellence in Basic Sciences
- University of Mumbai
- Mumbai
- India
| | - Pradnya Parab
- School of Physical Sciences
- UM-DAE, Centre for Excellence in Basic Sciences
- University of Mumbai
- Mumbai
- India
| | - Mohammad Muneer
- Department of Chemistry
- Aligarh Muslim University
- Aligarh
- India
| | - Sangita Bose
- School of Physical Sciences
- UM-DAE, Centre for Excellence in Basic Sciences
- University of Mumbai
- Mumbai
- India
| | - Neeraj Agarwal
- School of Chemical Sciences
- UM-DAE, Centre for Excellence in Basic Sciences
- University of Mumbai
- Mumbai
- India
| |
Collapse
|
15
|
Colella M, Pander P, Pereira DDS, Monkman AP. Interfacial TADF Exciplex as a Tool to Localize Excitons, Improve Efficiency, and Increase OLED Lifetime. ACS APPLIED MATERIALS & INTERFACES 2018; 10:40001-40007. [PMID: 30381946 DOI: 10.1021/acsami.8b15942] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
In this work, we employ a thermally activated delayed fluorescence (TADF) exciplex formed between the emissive layer (EML) host, 26DCzPPy, and the electron transport layer (ETL) 2,4,6-tris[3-(diphenylphosphinyl)phenyl]-1,3,5-triazine at the interface between the EML and the ETL to improve the stability and efficiency of a phosphorescence organic light-emitting diode based on Ir(dmpq)2acac. We show that the presence of the TADF exciplex at the EML-ETL interface induces an efficient localization of the recombination zone, which is confined within the 5 nm thick EML. Furthermore, the TADF exciplex allows harvesting of the holes and electrons that piled up at the EML-ETL interface and transfers the resultant excited state energy to the phosphorescent emitter through Förster and/or Dexter energy transfer. This approach effectively improves the LT90 of devices from <1 min to 6 h by limiting recombination processes outside of the 5 nm EML.
Collapse
Affiliation(s)
- Marco Colella
- Physics Department , Durham University , South Road , Durham DH1 3LE , United Kingdom
| | - Piotr Pander
- Physics Department , Durham University , South Road , Durham DH1 3LE , United Kingdom
| | - Daniel de Sa Pereira
- Physics Department , Durham University , South Road , Durham DH1 3LE , United Kingdom
| | - Andrew P Monkman
- Physics Department , Durham University , South Road , Durham DH1 3LE , United Kingdom
| |
Collapse
|
16
|
Pander P, Gogoc S, Colella M, Data P, Dias FB. Thermally Activated Delayed Fluorescence in Polymer-Small-Molecule Exciplex Blends for Solution-Processed Organic Light-Emitting Diodes. ACS APPLIED MATERIALS & INTERFACES 2018; 10:28796-28802. [PMID: 30044613 DOI: 10.1021/acsami.8b07554] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The photophysics of an exciplex state formed between a small molecule and a polymer is investigated in this work. The results obtained with this blend show the strong potential of polymer-small-molecule blends for triplet harvesting in organic light-emitting diodes (OLEDs) via thermally activated delayed fluorescence. The exciplex formed between poly( N-vinylcarbazole) (PVK) and 2,4,6-tris[3-(diphenylphosphinyl)phenyl]-1,3,5-triazine (PO-T2T) shows yellow-green emission and is applied in solution-processed OLEDs. The excellent film-forming properties in this blend allow easy spin coating and potential use in other solution-processing techniques, such as slot die coating. In this work, we critically address the reverse intersystem crossing mechanism in the presented exciplex system, including the role of local triplet states. Moreover, we bring a clear physical meaning to the decay components of the exciplex emission, including the decay occurring in a power-law fashion that is often ignored in the literature.
Collapse
Affiliation(s)
- Piotr Pander
- Department of Physics , Durham University , South Road , Durham DH1 3LE , United Kingdom
| | - Szymon Gogoc
- Faculty of Chemistry , Silesian University of Technology , Ks. M. Strzody 9 , 44-100 Gliwice , Poland
| | - Marco Colella
- Department of Physics , Durham University , South Road , Durham DH1 3LE , United Kingdom
| | - Przemyslaw Data
- Department of Physics , Durham University , South Road , Durham DH1 3LE , United Kingdom
- Faculty of Chemistry , Silesian University of Technology , Ks. M. Strzody 9 , 44-100 Gliwice , Poland
- Centre of Polymer and Carbon Materials , Polish Academy of Sciences , M. Sklodowskiej-Curie 34 , 41-819 Zabrze , Poland
| | - Fernando B Dias
- Department of Physics , Durham University , South Road , Durham DH1 3LE , United Kingdom
| |
Collapse
|
17
|
Sarma M, Wong KT. Exciplex: An Intermolecular Charge-Transfer Approach for TADF. ACS APPLIED MATERIALS & INTERFACES 2018; 10:19279-19304. [PMID: 29613766 DOI: 10.1021/acsami.7b18318] [Citation(s) in RCA: 116] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Organic materials that display thermally activated delayed fluorescence (TADF) are a striking class of functional materials that have witnessed a booming progress in recent years. In addition to pure TADF emitters achieved by the subtle manipulations of intramolecular charge transfer processes with sophisticated molecular structures, a new class of efficient TADF-based OLEDs with emitting layer formed by blending electron donor and acceptor molecules that involve intermolecular charge transfer have also been fabricated. In contrast to pure TADF materials, the exciplex-based systems can realize small Δ EST (0-0.05 eV) much more easily since the electron and hole are positioned on two different molecules, thereby giving small exchange energy. Consequently, exciplex-based OLEDs have the prospective to maximize the TADF contribution and achieve theoretical 100% internal quantum efficiency. Therefore, the challenging issue of achieving small Δ EST in organic systems could be solved. In this article, we summarize and discuss the latest and most significant developments regarding these rapidly evolving functional materials, wherein the majority of the reported exciplex forming systems are categorized into two subgroups, viz. (a) exciplex as TADF emitters and (b) those as hosts for fluorescent, phosphorescent and TADF dopants according to their structural features and applications. The working mechanisms of the direct electroluminescence from the donor/acceptor interface and the exciplex-forming systems as cohost for the realization of high efficiency OLEDs are reviewed and discussed. This article delivers a summary of the current progresses and achievements of exciplex-based researches and points out the future challenges to trigger more research endeavors to this growing field.
Collapse
Affiliation(s)
- Monima Sarma
- Department of Chemistry , National Taiwan University , Taipei 10617 , Taiwan
| | - Ken-Tsung Wong
- Department of Chemistry , National Taiwan University , Taipei 10617 , Taiwan
- Institute of Atomic and Molecular Science , Academia Sinica , Taipei 10617 , Taiwan
| |
Collapse
|
18
|
Zhang D, Song X, Li H, Cai M, Bin Z, Huang T, Duan L. High-Performance Fluorescent Organic Light-Emitting Diodes Utilizing an Asymmetric Anthracene Derivative as an Electron-Transporting Material. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2018; 30:e1707590. [PMID: 29774610 DOI: 10.1002/adma.201707590] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/29/2017] [Revised: 03/18/2018] [Indexed: 06/08/2023]
Abstract
Fluorescent organic light-emitting diodes with thermally activated delayed fluorescent sensitizers (TSF-OLEDs) have aroused wide attention, the power efficiencies of which, however, are limited by the mutual exclusion of high electron-transport mobility and large triplet energy of electron-transporting materials (ETMs). Here, an asymmetric anthracene derivative with electronic properties manipulated by different side groups is developed as an ETM to promote TSF-OLED performances. Multiple intermolecular interactions are observed, leading to a kind of "cable-like packing" in the crystal and favoring the simultaneous realization of high electron-transporting mobility and good exciton-confinement ability, albeit the low triplet energy of the ETM. The optimized TSF-OLEDs exhibit a record-high maximum external quantum efficiency/power efficiency of 24.6%/76.0 lm W-1 , which remain 23.8%/69.0 lm W-1 at a high luminance of even 5000 cd m-2 with an extremely low operation voltage of 3.14 V. This work opens a new paradigm for designing ETMs and also paves the way toward practical application of TSF-OLEDs.
Collapse
Affiliation(s)
- Dongdong Zhang
- Key Lab of Organic Optoelectronics and Molecular Engineering of Ministry of Education, Department of Chemistry, Tsinghua University, Beijing, 100084, China
| | - Xiaozeng Song
- Key Lab of Organic Optoelectronics and Molecular Engineering of Ministry of Education, Department of Chemistry, Tsinghua University, Beijing, 100084, China
| | - Haoyuan Li
- Key Lab of Organic Optoelectronics and Molecular Engineering of Ministry of Education, Department of Chemistry, Tsinghua University, Beijing, 100084, China
| | - Minghan Cai
- Key Lab of Organic Optoelectronics and Molecular Engineering of Ministry of Education, Department of Chemistry, Tsinghua University, Beijing, 100084, China
| | - Zhengyang Bin
- Key Lab of Organic Optoelectronics and Molecular Engineering of Ministry of Education, Department of Chemistry, Tsinghua University, Beijing, 100084, China
| | - Tianyu Huang
- Key Lab of Organic Optoelectronics and Molecular Engineering of Ministry of Education, Department of Chemistry, Tsinghua University, Beijing, 100084, China
| | - Lian Duan
- Key Lab of Organic Optoelectronics and Molecular Engineering of Ministry of Education, Department of Chemistry, Tsinghua University, Beijing, 100084, China
- Center for Flexible Electronics Technology, Tsinghua University, Beijing, 100084, P. R. China
| |
Collapse
|
19
|
Zhang D, Song X, Cai M, Kaji H, Duan L. Versatile Indolocarbazole-Isomer Derivatives as Highly Emissive Emitters and Ideal Hosts for Thermally Activated Delayed Fluorescent OLEDs with Alleviated Efficiency Roll-Off. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2018; 30:1705406. [PMID: 29315848 DOI: 10.1002/adma.201705406] [Citation(s) in RCA: 84] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2017] [Revised: 10/26/2017] [Indexed: 06/07/2023]
Abstract
Maintaining high efficiency at high brightness levels is an exigent challenge for real-world applications of thermally activated delayed fluorescent organic light-emitting diodes (TADF-OLEDs). Here, versatile indolocarbazole-isomer derivatives are developed as highly emissive emitters and ideal hosts for TADF-OLEDs to alleviate efficiency roll-off. It is observed that photophysical and electronic properties of these compounds can be well modulated by varying the indolocarbazole isomers. A photoluminescence quantum yield (ηPL ) approaching unity and a maximum external quantum efficiency (EQEmax ) of 25.1% are obtained for the emitter with indolo[3,2-a]carbazolyl subunit. Remarkably, record-high EQE/power efficiency of 26.2%/69.7 lm W-1 at the brightness level of 5000 cd m-2 with a voltage of only 3.74 V are also obtained using the same isomer as the host in a green TADF-OLED. It is evident that TADF hosts with high ηPL values, fast reverse intersystem crossing processes, and balanced charge transport properties may open the path toward roll-off-free TADF-OLEDs.
Collapse
Affiliation(s)
- Dongdong Zhang
- Key Lab of Organic Optoelectronics and Molecular Engineering of Ministry of Education, Department of Chemistry, Tsinghua University, Beijing, 100084, P. R. China
| | - Xiaozeng Song
- Key Lab of Organic Optoelectronics and Molecular Engineering of Ministry of Education, Department of Chemistry, Tsinghua University, Beijing, 100084, P. R. China
| | - Minghan Cai
- Key Lab of Organic Optoelectronics and Molecular Engineering of Ministry of Education, Department of Chemistry, Tsinghua University, Beijing, 100084, P. R. China
| | - Hironori Kaji
- Institute for Chemical Research, Kyoto University, Uji, Kyoto, 611-0011, Japan
| | - Lian Duan
- Key Lab of Organic Optoelectronics and Molecular Engineering of Ministry of Education, Department of Chemistry, Tsinghua University, Beijing, 100084, P. R. China
- Center for Flexible Electronics Technology, Tsinghua University, Beijing, 100084, P. R. China
| |
Collapse
|
20
|
Zhang D, Song X, Cai M, Duan L. Blocking Energy-Loss Pathways for Ideal Fluorescent Organic Light-Emitting Diodes with Thermally Activated Delayed Fluorescent Sensitizers. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2018; 30:1705250. [PMID: 29280207 DOI: 10.1002/adma.201705250] [Citation(s) in RCA: 82] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Revised: 10/08/2017] [Indexed: 06/07/2023]
Abstract
Organic light-emitting diodes (OLEDs) based on thermally activated delayed fluorescence-sensitized fluorescence (TSF) offer the possibility of attaining an ultimate high efficiency with low roll-off utilizing noble-metal free, easy-to-synthesize, pure organic fluorescent emitters. However, the performances of TSF-OLEDs are still unsatisfactory. Here, TSF-OLEDs with breakthrough efficiencies even at high brightnesses by suppressing the competitive deactivation processes, including direct charge recombination on conventional fluorescent dopants (CFDs) and Dexter energy transfer from the host to the CFDs, are demonstrated. On the one hand, electronically inert terminal-substituents are introduced to protect the electronically active core of the CFDs; on the other hand, delicate device structures are designed to provide multiple energy-funneling paths. As a result, unprecedentedly high maximum external quantum efficiency/power efficiency of 24%/71.4 lm W-1 in a green TSF-OLED are demonstrated, which remain at 22.6%/52.3 lm W-1 even at a high luminance of 5000 cd m-2 . The work unlocks the potential of TSF-OLEDs, paving the way toward practical applications.
Collapse
Affiliation(s)
- Dongdong Zhang
- Key Lab of Organic Optoelectronics and Molecular Engineering of Ministry of Education, Department of Chemistry, Tsinghua University, Beijing, 100084, China
| | - Xiaozeng Song
- Key Lab of Organic Optoelectronics and Molecular Engineering of Ministry of Education, Department of Chemistry, Tsinghua University, Beijing, 100084, China
| | - Minghan Cai
- Key Lab of Organic Optoelectronics and Molecular Engineering of Ministry of Education, Department of Chemistry, Tsinghua University, Beijing, 100084, China
| | - Lian Duan
- Key Lab of Organic Optoelectronics and Molecular Engineering of Ministry of Education, Department of Chemistry, Tsinghua University, Beijing, 100084, China
- Center for Flexible Electronics Technology, Tsinghua University, Beijing, 100084, P. R. China
| |
Collapse
|
21
|
Han HB, Wu ZG, Zheng YX. Efficient bluish green electroluminescence of iridium complexes with good electron mobility. NEW J CHEM 2018. [DOI: 10.1039/c8nj01726c] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Two efficient bluish green iridium complexes with good electron mobility were applied in efficient OLEDs, showing a maximum current efficiency of 71.18 cd A−1 and a maximum external quantum efficiency of 27.7%.
Collapse
Affiliation(s)
- Hua-Bo Han
- State Key Laboratory of Coordination Chemistry
- Jiangsu Key Laboratory of Advanced Organic Materials
- Collaborative Innovation Center of Advanced Microstructures
- School of Chemistry and Chemical Engineering
- Nanjing University
| | - Zheng-Guang Wu
- State Key Laboratory of Coordination Chemistry
- Jiangsu Key Laboratory of Advanced Organic Materials
- Collaborative Innovation Center of Advanced Microstructures
- School of Chemistry and Chemical Engineering
- Nanjing University
| | - You-Xuan Zheng
- State Key Laboratory of Coordination Chemistry
- Jiangsu Key Laboratory of Advanced Organic Materials
- Collaborative Innovation Center of Advanced Microstructures
- School of Chemistry and Chemical Engineering
- Nanjing University
| |
Collapse
|
22
|
Zhou YH, Xu J, Wu ZG, Zheng YX. Synthesis, photoluminescence and electroluminescence of one iridium complex with 2-(2,4-difluorophenyl)-4-(trifluoromethyl)pyrimidine and tetraphenylimidodiphosphinate ligands. J Organomet Chem 2017. [DOI: 10.1016/j.jorganchem.2017.07.039] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
|
23
|
Han C, Duan C, Yang W, Xie M, Xu H. Allochroic thermally activated delayed fluorescence diodes through field-induced solvatochromic effect. SCIENCE ADVANCES 2017; 3:e1700904. [PMID: 28929136 PMCID: PMC5600533 DOI: 10.1126/sciadv.1700904] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2017] [Accepted: 08/16/2017] [Indexed: 05/04/2023]
Abstract
Allochroic organic light-emitting devices (AOLEDs) characterized by field-dependent emissive color variation are promising as visible signal response units for intelligent applications. Most of the AOLEDs were realized by changing their recombination zones or inter- and intramolecular energy transfer, rendering the limited repeatability, stability, and electroluminescence (EL) performance. We report a novel thermally activated delayed fluorescence (TADF) diode that featured a successive and irreversible emission color change from bluish green to deep blue during voltage increase, which uses the significant influence of host polarity on the emission color of TADF dyes, namely, solvatochromic effect. Its host 3,6-di-tert-butyl-1,8-bis(diphenylphosphoryl)-9H-carbazole (tBCzHDPO) was designed with remarkable field-dependent polarity reduction from 7.9 to 3.3 D by virtue of hydrogen bond-induced conformational isomerization. This TADF device achieves the best EL performance among AOLEDs, to date, with, for example, an external quantum efficiency beyond 15%, as well as the unique irreversible allochroic characteristic for visible data storage and information security.
Collapse
|
24
|
Kautny P, Glöcklhofer F, Kader T, Mewes JM, Stöger B, Fröhlich J, Lumpi D, Plasser F. Charge-transfer states in triazole linked donor-acceptor materials: strong effects of chemical modification and solvation. Phys Chem Chem Phys 2017; 19:18055-18067. [PMID: 28671704 DOI: 10.1039/c7cp01664f] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
A series of 1,2,3-triazole linked donor-acceptor chromophores are prepared by Click Chemistry from ene-yne starting materials. The effects of three distinct chemical variations are investigated: enhancing the acceptor strength through oxidation of the sulphur atom, alteration of the double bond configuration, and variation of the triazole substitution pattern. A detailed photophysical characterization shows that these alterations have a negligible effect on the absorption while dramatically altering the emission wavelengths. In addition, strong solvatochromism is found leading to significant red shifts in the case of polar solvents. The experimental findings are rationalized and related to the electronic structure properties of the chromophores by time-dependent density functional theory as well as the ab initio algebraic diagrammatic construction method for the polarization propagator in connection with a new formalism allowing to model the influence of solvation onto long-lived excited states and their emission energies. These calculations highlight the varying degree of intramolecular charge transfer character present for the different molecules and show that the amount of charge transfer is strongly modulated by the conducted chemical modifications, by the solvation of the chromophores, and by the structural relaxation in the excited state. It is, furthermore, shown that enhanced charge separation, as induced by chemical modification or solvation, reduces the singlet-triplet gaps and that two of the investigated molecules possess sufficiently low gaps to be considered as candidates for thermally activated delayed fluorescence.
Collapse
Affiliation(s)
- Paul Kautny
- Institute of Applied Synthetic Chemistry, TU Wien, Getreidemarkt 9/163, A-1060 Vienna, Austria.
| | - Florian Glöcklhofer
- Institute of Applied Synthetic Chemistry, TU Wien, Getreidemarkt 9/163, A-1060 Vienna, Austria.
| | - Thomas Kader
- Institute of Applied Synthetic Chemistry, TU Wien, Getreidemarkt 9/163, A-1060 Vienna, Austria.
| | - Jan-Michael Mewes
- Centre for Theoretical Chemistry and Physics, The New Zealand Institute for Advanced Study (NZIAS), Massey University Albany, Private Bag 102904, Auckland 0745, New Zealand
| | - Berthold Stöger
- X-ray Center, TU Wien, Getreidemarkt 9, A-1060 Vienna, Austria
| | - Johannes Fröhlich
- Institute of Applied Synthetic Chemistry, TU Wien, Getreidemarkt 9/163, A-1060 Vienna, Austria.
| | - Daniel Lumpi
- Institute of Applied Synthetic Chemistry, TU Wien, Getreidemarkt 9/163, A-1060 Vienna, Austria.
| | - Felix Plasser
- Institute of Theoretical Chemistry, Faculty of Chemistry, University of Vienna, Währinger Str. 17, A-1090 Vienna, Austria.
| |
Collapse
|
25
|
Etherington MK, Franchello F, Gibson J, Northey T, Santos J, Ward JS, Higginbotham HF, Data P, Kurowska A, Dos Santos PL, Graves DR, Batsanov AS, Dias FB, Bryce MR, Penfold TJ, Monkman AP. Regio- and conformational isomerization critical to design of efficient thermally-activated delayed fluorescence emitters. Nat Commun 2017; 8:14987. [PMID: 28406153 PMCID: PMC5399286 DOI: 10.1038/ncomms14987] [Citation(s) in RCA: 126] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2016] [Accepted: 02/19/2017] [Indexed: 11/12/2022] Open
Abstract
Regio- and conformational isomerization are fundamental in chemistry, with profound effects upon physical properties, however their role in excited state properties is less developed. Here two regioisomers of bis(10H-phenothiazin-10-yl)dibenzo[b,d]thiophene-S,S-dioxide, a donor–acceptor–donor (D–A–D) thermally-activated delayed fluorescence (TADF) emitter, are studied. 2,8-bis(10H-phenothiazin-10-yl)dibenzo[b,d]thiophene-S,S-dioxide exhibits only one quasi-equatorial conformer on both donor sites, with charge-transfer (CT) emission close to the local triplet state leading to efficient TADF via spin-vibronic coupling. However, 3,7-bis(10H-phenothiazin-10-yl)dibenzo[b,d]thiophene-S,S-dioxide displays both a quasi-equatorial CT state and a higher-energy quasi-axial CT state. No TADF is observed in the quasi-axial CT emission. These two CT states link directly to the two folded conformers of phenothiazine. The presence of the low-lying local triplet state of the axial conformer also means that this quasi-axial CT is an effective loss pathway both photophysically and in devices. Importantly, donors or acceptors with more than one conformer have negative repercussions for TADF in organic light-emitting diodes. The search for brighter emitting materials is essential to the development of OLED devices. Etherington et al. show how the presence of two regioisomers of a donor-acceptor-donor thermally-activated delayed fluorescence molecule affects the device efficiency, with one acting as a triplet quencher.
Collapse
Affiliation(s)
- Marc K Etherington
- Department of Physics, Durham University, South Road, Durham DH1 3LE, UK
| | - Flavio Franchello
- Department of Physics, Durham University, South Road, Durham DH1 3LE, UK
| | - Jamie Gibson
- School of Chemistry, Newcastle University, Newcastle upon Tyne NE1 7RU, UK
| | - Thomas Northey
- School of Chemistry, Newcastle University, Newcastle upon Tyne NE1 7RU, UK
| | - Jose Santos
- Department of Chemistry, Durham University, South Road, Durham DH1 3LE, UK
| | - Jonathan S Ward
- Department of Chemistry, Durham University, South Road, Durham DH1 3LE, UK
| | | | - Przemyslaw Data
- Department of Physics, Durham University, South Road, Durham DH1 3LE, UK.,Faculty of Chemistry, Silesian University of Technology, Marcina Strzody 9, 44-100 Gliwice, Poland
| | - Aleksandra Kurowska
- Faculty of Chemistry, Silesian University of Technology, Marcina Strzody 9, 44-100 Gliwice, Poland
| | | | - David R Graves
- Department of Physics, Durham University, South Road, Durham DH1 3LE, UK
| | - Andrei S Batsanov
- Department of Chemistry, Durham University, South Road, Durham DH1 3LE, UK
| | - Fernando B Dias
- Department of Physics, Durham University, South Road, Durham DH1 3LE, UK
| | - Martin R Bryce
- Department of Chemistry, Durham University, South Road, Durham DH1 3LE, UK
| | - Thomas J Penfold
- School of Chemistry, Newcastle University, Newcastle upon Tyne NE1 7RU, UK
| | - Andrew P Monkman
- Department of Physics, Durham University, South Road, Durham DH1 3LE, UK
| |
Collapse
|
26
|
Dias FB, Penfold TJ, Monkman AP. Photophysics of thermally activated delayed fluorescence molecules. Methods Appl Fluoresc 2017; 5:012001. [DOI: 10.1088/2050-6120/aa537e] [Citation(s) in RCA: 287] [Impact Index Per Article: 41.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
|
27
|
Jing YM, Zheng YX, Zuo JL. Efficient green electroluminescence based on an iridium(iii) complex with different device structures. RSC Adv 2017. [DOI: 10.1039/c6ra27068a] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Organic light-emitting diodes based on an iridium complex using different device structure show high performances with a maximum current efficiency of 86.5 cd A−1and a maximum power efficiency of 52.2 lm W−1, respectively.
Collapse
Affiliation(s)
- Yi-Ming Jing
- State Key Laboratory of Coordination Chemistry
- Collaborative Innovation Center of Advanced Microstructures
- School of Chemistry and Chemical Engineering
- Nanjing University
- Nanjing 210093
| | - You-Xuan Zheng
- State Key Laboratory of Coordination Chemistry
- Collaborative Innovation Center of Advanced Microstructures
- School of Chemistry and Chemical Engineering
- Nanjing University
- Nanjing 210093
| | - Jing-Lin Zuo
- State Key Laboratory of Coordination Chemistry
- Collaborative Innovation Center of Advanced Microstructures
- School of Chemistry and Chemical Engineering
- Nanjing University
- Nanjing 210093
| |
Collapse
|
28
|
Jing YM, Zheng YX. Photoluminescence and electroluminescence of an iridium(iii) complex with 2′,6′-bis(trifluoromethyl)-2,4′-bipyridine and 2-(5-phenyl-1,3,4-thiadiazol-2-yl)phenol ligands. NEW J CHEM 2017. [DOI: 10.1039/c7nj00163k] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Efficient greenish yellow OLEDs based on an iridium(iii) complex containing electron transport ligands of 2′,6′-bis(trifluoromethyl)-2,4′-bipyridine and 2-(5-phenyl-1,3,4-thiadiazol-2-yl)phenol show a maximum current efficiency of 54.5 cd A−1and a maximum external quantum efficiency of 16.1%.
Collapse
Affiliation(s)
- Yi-Ming Jing
- State Key Laboratory of Coordination Chemistry
- Jiangsu Key Laboratory of Advanced Organic Materials
- Collaborative Innovation Center of Advanced Microstructures
- School of Chemistry and Chemical Engineering
- Nanjing University
| | - You-Xuan Zheng
- State Key Laboratory of Coordination Chemistry
- Jiangsu Key Laboratory of Advanced Organic Materials
- Collaborative Innovation Center of Advanced Microstructures
- School of Chemistry and Chemical Engineering
- Nanjing University
| |
Collapse
|