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Jayabharathi J, Thanikachalam V. Robust luminogens as cutting-edge tools for efficient light emission in recent decades. Phys Chem Chem Phys 2024; 26:13561-13605. [PMID: 38655772 DOI: 10.1039/d4cp00737a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/26/2024]
Abstract
Blue luminogens play a vital role in white lighting and potential metal-free fluorescent materials and their high-lying excited states contribute to harvesting triplet excitons in devices. However, in TADF-OLEDs (ΔEST < 0.1 eV), although T1 excitons transfer to S1via RISC with 100% IQE, the longer lifetime of blue TADF suffers from efficiency roll-off (RO). In this case, hybridized local and charge transfer (HLCT) materials have attracted significant interest in lighting owing to their 100% hot exciton harvesting and enhanced efficiency. Both academics and industrialists widely use the HLCT strategy to improve the efficiency of fluorescent organic light-emitting diodes (FOLEDs) by harvesting dark triplet excitons through the RISC process. Aggregation-induced emissive materials (AIEgens) possess tight packing in the aggregation state, and twisted AIEgens with HLCT behaviour have a shortened conjugation length, inducing blue emission and making them suitable candidates for OLED applications. TTA-OLEDs are used in commercial BOLEDs because of their moderate efficiency and reasonable operation lifetime. In this review, we discuss the devices based on TTA fluorophores, TADF fluorophores, HLCT fluorophores, AIEgens and HLCT-sensitized fluorophores (HLCT-SF), which break through the statistical limitations.
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Affiliation(s)
- Jayaraman Jayabharathi
- Department of Chemistry, Annamalai University, Annamalainagar, Tamilnadu-608 002, India.
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Jayabharathi J, Thanikachalam V, Karunakaran U, Anudeebhana J, Thilagavathy S. Mechanoluminescence and Aggregation-Induced Emission in Bipolar Phenanthroimidazoles: Role of Positional Isomerization-Induced Switching Effect. Ind Eng Chem Res 2022. [DOI: 10.1021/acs.iecr.2c00892] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Jayaraman Jayabharathi
- Department of Chemistry, Annamalai University, Annamalai Nagar, Chidambaram 608002, Tamilnadu, India
| | - Venugopal Thanikachalam
- Department of Chemistry, Annamalai University, Annamalai Nagar, Chidambaram 608002, Tamilnadu, India
| | - Uthirapathy Karunakaran
- Department of Chemistry, Annamalai University, Annamalai Nagar, Chidambaram 608002, Tamilnadu, India
| | | | - Shanmugam Thilagavathy
- Department of Chemistry, Annamalai University, Annamalai Nagar, Chidambaram 608002, Tamilnadu, India
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Schleper AL, Goushi K, Bannwarth C, Haehnle B, Welscher PJ, Adachi C, Kuehne AJC. Hot exciplexes in U-shaped TADF molecules with emission from locally excited states. Nat Commun 2021; 12:6179. [PMID: 34702836 PMCID: PMC8548444 DOI: 10.1038/s41467-021-26439-w] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Accepted: 10/06/2021] [Indexed: 12/02/2022] Open
Abstract
Fast emission and high color purity are essential characteristics of modern opto-electronic devices, such as organic light emitting diodes (OLEDs). These properties are currently not met by the latest generation of thermally activated delayed fluorescence (TADF) emitters. Here, we present an approach, called "hot exciplexes" that enables access to both attributes at the same time. Hot exciplexes are produced by coupling facing donor and acceptor moieties to an anthracene bridge, yielding an exciplex with large T1 to T2 spacing. The hot exciplex model is investigated using optical spectroscopy and quantum chemical simulations. Reverse intersystem crossing is found to occur preferentially from the T3 to the S1 state within only a few nanoseconds. Application and practicality of the model are shown by fabrication of organic light-emitting diodes with up to 32 % hot exciplex contribution and low efficiency roll-off.
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Affiliation(s)
- A Lennart Schleper
- Institute of Organic and Macromolecular Chemistry, Ulm University, Albert-Einstein-Allee 11, 89081, Ulm, Germany
| | - Kenichi Goushi
- Department of Applied Chemistry and Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 744 Motooka, Nishi, Fukuoka, 819-0395, Japan.
- International Institute for Carbon Neutral Energy Research (WPI-I2CNER), Kyushu University, 744 Motooka, Nishiku, Fukuoka, 819-0395, Japan.
| | - Christoph Bannwarth
- Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52074, Aachen, Germany.
| | - Bastian Haehnle
- Institute of Organic and Macromolecular Chemistry, Ulm University, Albert-Einstein-Allee 11, 89081, Ulm, Germany
| | - Philipp J Welscher
- Institute of Organic and Macromolecular Chemistry, Ulm University, Albert-Einstein-Allee 11, 89081, Ulm, Germany
| | - Chihaya Adachi
- Department of Applied Chemistry and Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 744 Motooka, Nishi, Fukuoka, 819-0395, Japan.
- International Institute for Carbon Neutral Energy Research (WPI-I2CNER), Kyushu University, 744 Motooka, Nishiku, Fukuoka, 819-0395, Japan.
| | - Alexander J C Kuehne
- Institute of Organic and Macromolecular Chemistry, Ulm University, Albert-Einstein-Allee 11, 89081, Ulm, Germany.
- DWI - Leibniz-Institute for Interactive Materials, Forckenbeckstraße 50, 52074, Aachen, Germany.
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