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Organic Light-Emitting Materials: Current Status, Challenges, and Future Outlook

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Colorants".

Deadline for manuscript submissions: closed (15 November 2023) | Viewed by 7733

Special Issue Editors

College of Chemical Engineering, Zhejiang University of Technology, Hangzhou, China
Interests: phosphorescence material; delayed fluorescence; organic synthesis; OLED

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Guest Editor
Polymers and Functional Materials Division, Indian Institute of Chemical Technology, Hyderabad, India
Interests: organic functional materials: self-assembly and optoelectronic characterization; polymer chemistry

Special Issue Information

Dear Colleagues,

Organic light-emitting diodes (OLEDs) are reputed for their diverse use in the lighting and display industry. The main aim of this Special Issue is to unify the current status and to find out the future priority and route map in research and applications of light-emitting materials, their emission mechanism, such as fluorescence (F), phosphorescence (Ph), thermally delayed fluorescence (TADF), excimer, exciplex, and hybridized local and charge transfer (HLCT). This Special Issue will also cover the import parameters for OLEDs, such as efficiency, lifetime, power consumption, flexibility of the device, and material strategy for developing efficient models for OLED application. This Special Issue will provide a stage and opportunity to spread the information about white light, yellow light, blue light, green light, red light, green-blue light and yellow-blue light OLEDs. We invite researchers, scientists and technocrats who are working on design strategies for material, flexible device fabrications, and the manufacturing of OLEDs for various applications to contribute their original research, reviews, and theoretical studies on “Organic Light-Emitting Materials: Current Status, Challenges, and Future Outlook”.

All the manuscripts received for this Special Issue will undergo a rigorous peer-review process, and the decisions of acceptance or rejection will be based on the recommendations of independent reviewers. 

Dr. Guijie Li
Dr. Sidhanath V. Bhosale
Guest Editors

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Keywords

  • organic light-emitting diodes (OLED)
  • white
  • yellow
  • blue
  • green
  • colors
  • thermally delayed fluorescence (TADF)
  • excimer
  • exciplex
  • phosphorescent metal complexes
  • hybridized local and charge transfer (HLCT) materials
  • hyperfluorescence

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Published Papers (4 papers)

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Research

12 pages, 2374 KiB  
Article
A High-Efficiency Deep Blue Emitter for OLEDs with a New Dual-Core Structure Incorporating ETL Characteristics
by Yeongjae Heo, Hyukmin Kwon, Sangwook Park, Sunwoo Dae, Hayoon Lee, Kiho Lee and Jongwook Park
Molecules 2023, 28(22), 7485; https://doi.org/10.3390/molecules28227485 - 8 Nov 2023
Viewed by 1227
Abstract
In this study, we introduced the weak electron-accepting oxazole derivative 4,5-diphenyl-2-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)oxazole (TPO) into both anthracene and pyrene moieties of a dual core structure. Ultimately, we developed 2-(4-(6-(anthracen-9-yl)pyren-1-yl)phenyl)-4,5-diphenyloxazole (AP-TPO) as the substitution on the second core, pyrene, and 4,5-diphenyl-2-(4-(10-(pyren-1-yl)anthracen-9-yl)phenyl)oxazole (TPO-AP) as the substitution on [...] Read more.
In this study, we introduced the weak electron-accepting oxazole derivative 4,5-diphenyl-2-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)oxazole (TPO) into both anthracene and pyrene moieties of a dual core structure. Ultimately, we developed 2-(4-(6-(anthracen-9-yl)pyren-1-yl)phenyl)-4,5-diphenyloxazole (AP-TPO) as the substitution on the second core, pyrene, and 4,5-diphenyl-2-(4-(10-(pyren-1-yl)anthracen-9-yl)phenyl)oxazole (TPO-AP) as the substitution on the first core, anthracene. Both materials exhibited maximum photoluminescence wavelengths at 433 and 443 nm in solution and emitted deep blue light with high photoluminescence quantum yields of 82% and 88%, respectively. When used as the emitting layer in non-doped devices, TPO-AP outperformed AP-TPO, achieving a current efficiency of 5.49 cd/A and an external quantum efficiency of 4.26% in electroluminescence. These materials introduce a new category of deep blue emitters in the organic light-emitting diodes field, combining characteristics related to the electron transport layer. Full article
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14 pages, 4418 KiB  
Article
A Comparison between Triphenylmethyl and Triphenylsilyl Spirobifluorenyl Hosts: Synthesis, Photophysics and Performance in Phosphorescent Organic Light-Emitting Diodes
by Wei Wei, Jie Ma, Jonas Schaab, Jason Brooks, Seogshin Kang, Matthew T. Whited, Peter I. Djurovich and Mark E. Thompson
Molecules 2023, 28(13), 5241; https://doi.org/10.3390/molecules28135241 - 6 Jul 2023
Cited by 1 | Viewed by 1632
Abstract
This study presents the synthesis and characterization of two spirobifluorenyl derivatives substituted with either triphenylmethyl (SB-C) or triphenylsilyl (SB-Si) moieties for use as host materials in phosphorescent organic light-emitting diodes (PHOLED). Both molecules have similar high triplet energies and [...] Read more.
This study presents the synthesis and characterization of two spirobifluorenyl derivatives substituted with either triphenylmethyl (SB-C) or triphenylsilyl (SB-Si) moieties for use as host materials in phosphorescent organic light-emitting diodes (PHOLED). Both molecules have similar high triplet energies and large energy gaps. Blue Ir(tpz)3 and green Ir(ppy)3 phosphorescent devices were fabricated using these materials as hosts. Surprisingly, SB-Si demonstrated superior charge-transporting ability compared to SB-C, despite having similar energies for their valence orbitals. In particular, SB-Si proved to be a highly effective host for both blue and green devices, resulting in maximum efficiencies of 12.6% for the Ir(tpz)3 device and 9.6% for the Ir(ppy)3 device. These results highlight the benefits of appending the triphenylsilyl moiety onto host materials and underscore the importance of considering the morphology of hosts in the design of efficient PHOLEDs. Full article
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12 pages, 2980 KiB  
Article
Multi-Resonant Indolo[3,2,1-jk]carbazole-Based Host for Blue Phosphorescent Organic Light-Emitting Diodes
by Xiang Li, Peng Yuan, Jinyu Song, Yu Chang, Xueting Jiao, Jianfeng Zhao, Cong Zhang, Wenjuan Li and Xiao-Chun Hang
Molecules 2023, 28(13), 5118; https://doi.org/10.3390/molecules28135118 - 29 Jun 2023
Cited by 3 | Viewed by 1874
Abstract
In organic light-emitting diodes, positive and negative charge carriers mostly migrate at different rates. This could result in excitons formed in the EML often migrating to the vicinity of the hole transport layer and the electron transport layer. To address this, it is [...] Read more.
In organic light-emitting diodes, positive and negative charge carriers mostly migrate at different rates. This could result in excitons formed in the EML often migrating to the vicinity of the hole transport layer and the electron transport layer. To address this, it is important to design high-quality multi-resonance hosts that can balance the migration rate of carriers. Here, we report two newly developed multi-resonance hosts, m-ICzPBI and o-ICzPBI. The hosts contain an indolo[3,2,1-jk]carbazole (ICz) motif, which functionalized as either a donor or an acceptor unit. The hosts exhibit extremely high molecular rigidity and thermal stability. Devices A and B were constructed using FIrpic as a phosphorescent emitter with m-ICzPBI or o-ICzPBI as a host. Device A achieved high maximum values of EQE, PE and CE of 13.4%, 24.8 lm W−1 and 31.6 cd A−1, respectively, and low efficiency roll-off at 5000 cd m−2 of 8.6%, 10.6 lm W−1 and 20.3 cd A−1, respectively. Full article
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16 pages, 3896 KiB  
Article
Tailoring Carbene–Metal–Amides for Thermally Activated Delayed Fluorescence: A Computationally Guided Study on the Effect of Cyclic (Alkyl)(amino)carbenes
by Nguyen Le Phuoc, Alexander C. Brannan, Alexander S. Romanov and Mikko Linnolahti
Molecules 2023, 28(11), 4398; https://doi.org/10.3390/molecules28114398 - 28 May 2023
Cited by 4 | Viewed by 2248
Abstract
Gold-centered carbene–metal–amides (CMAs) containing cyclic (alkyl)(amino)carbenes (CAACs) are promising emitters for thermally activated delayed fluorescence (TADF). Aiming at the design and optimization of new TADF emitters, we report a density functional theory study of over 60 CMAs with various CAAC ligands, systematically evaluating [...] Read more.
Gold-centered carbene–metal–amides (CMAs) containing cyclic (alkyl)(amino)carbenes (CAACs) are promising emitters for thermally activated delayed fluorescence (TADF). Aiming at the design and optimization of new TADF emitters, we report a density functional theory study of over 60 CMAs with various CAAC ligands, systematically evaluating computed parameters in relation to photoluminescence properties. The CMA structures were primarily selected based on experimental synthesis prospects. We demonstrate that TADF efficiency of the CMA materials originates from a compromise between oscillator strength coefficients and exchange energy (ΔEST). The latter is governed by the overlap of HOMO and LUMO orbitals, where HOMO is localized on the amide and LUMO over the Au–carbene bond. The S0 ground and excited T1 states of the CMAs adopt approximately coplanar geometry of carbene and amide ligands, but rotate perpendicular in the excited S1 states, resulting in degeneracy or near-degeneracy of S1 and T1, accompanied by a decrease in the S1-S0 oscillator strength from its maximum at coplanar geometries to near zero at rotated geometries. Based on the computations, promising new TADF emitters are proposed and synthesized. Bright CMA complex (Et2CAAC)Au(carbazolide) is obtained and fully characterized in order to demonstrate that excellent stability and high radiative rates up to 106 s−1 can be obtained for the gold–CMA complexes with small CAAC–carbene ligands. Full article
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