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Fluorescence and Phosphorescence in Organic Materials: from Fundamental to OLED Devices

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Materials Science and Engineering".

Deadline for manuscript submissions: closed (31 July 2018) | Viewed by 55206

Special Issue Editors


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Guest Editor
LICSEN, NIMBE, CEA, CNRS, Université Paris-Saclay, CEA Saclay, 91191 Gif-sur-Yvette, CEDEX, France
Interests: organic electronics; OLEDs; OPVs

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Co-Guest Editor
Laboratoire de Physique des Interfaces et des Couches Minces (LPICM), CNRS, Ecole Polytechnique, Université Paris Saclay, CEA Saclay, 91191 Gif-sur-Yvette, CEDEX, France
Interests: organic electronics

Special Issue Information

Dear Colleagues,

During the last few decades, organic light-emitting devices (OLEDs) have shown a strong utility as commercial products, such as in flat panel displays and lighting sources. Three different generations of organic materials have been used for the fabrication of OLEDs: 1) RGB fluorescent molecules (1987) with an internal quantum efficiency (IQE) up to 25%; 2) phosphorescent materials (1998) with an IQE reaching 100% by using both singlet and triplet states emission; and 3) Thermally Activated Delayed Fluorescent (TADF) materials (2012) with an IQE of nearly 100%. In this Special Issue devoted to fluorescence and phosphorescence in OLED devices, chemists, physicists, material scientists, and electronic and process engineers will find in-depth coverage on organic materials used in OLED technology, from basic concepts to technological and industrial aspects.

Mr. Geffroy Bernard
Dr. Denis Tondelier
Guest Editor

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Keywords

  • Singlet-triplet states

  • Fluorescence

  • Phosphorescence

  • Intersystem crossing

  • Thermally Activated Delayed Fluorescence

  • Organic light-emitting diode

  • PhOLEDs

  • White light

  • RGB Display

  • Lighting

  • Luminous efficiency.

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Published Papers (9 papers)

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Research

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10 pages, 1543 KiB  
Article
Blue Electrofluorescence Properties of Furan–Silole Ladder Pi-Conjugated Systems
by Hui Chen, Mathieu Denis, Pierre-Antoine Bouit, Yinlong Zhang, Xinda Wei, Denis Tondelier, Bernard Geffroy, Zheng Duan and Muriel Hissler
Appl. Sci. 2018, 8(5), 812; https://doi.org/10.3390/app8050812 - 18 May 2018
Cited by 6 | Viewed by 3955
Abstract
A synthetic route to novel benzofuran fused silole derivatives is described and the new compounds were fully characterized. These compounds showed optical and electrochemical properties that differ from their benzothiophene analog. Preliminary results show that these derivatives can be used as blue emitters [...] Read more.
A synthetic route to novel benzofuran fused silole derivatives is described and the new compounds were fully characterized. These compounds showed optical and electrochemical properties that differ from their benzothiophene analog. Preliminary results show that these derivatives can be used as blue emitters in organic light emitting devices (OLEDs) illustrating the potential of these new compounds for opto-electronic applications. Full article
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14 pages, 1956 KiB  
Article
Application of [Pt(II)(Tetra-Tert-Butylsalophen)] Complex within Organic Devices: Deep Red Emission, Bistable Light-Emitting Diodes and Operational Stability
by Benoît Blondel, Anaïs Colin, Manuel Lopes, Fabienne Alary, Georges Zissis, Isabelle Sasaki and Cédric Renaud
Appl. Sci. 2018, 8(5), 762; https://doi.org/10.3390/app8050762 - 11 May 2018
Cited by 4 | Viewed by 4029
Abstract
This paper focuses on the Negative Differential Resistance (NDR) we observed on organic light-emitting diodes (OLEDs) using [Pt(II)(tetra-tert-butylSalophen)] as host, since this Pt(II) complex displays a deep-red emission (λmax = 660 nm). Electrical characterizations of monolayer devices have shown that [...] Read more.
This paper focuses on the Negative Differential Resistance (NDR) we observed on organic light-emitting diodes (OLEDs) using [Pt(II)(tetra-tert-butylSalophen)] as host, since this Pt(II) complex displays a deep-red emission (λmax = 660 nm). Electrical characterizations of monolayer devices have shown that doping Tris-(8-hydroxyquinoline)aluminum (Alq3) as matrix emissive layer with this complex, leads to the modulation of the charge transport properties highlighted by Negative Differential Resistance (NDR). Upon electrical driving stresses, the conductivity of active layer can be switched between two electrical states (ON and OFF) with a figure of merit higher than 103. By adding an electron-blocking layer, we demonstrated that the NDR trend is closely related to negative charge accumulation within Alq3 leading to the modification of electronic properties in the vicinity of anode/active layer interface. The NDR phenomenon is interpreted in terms of space charge polarization (SCP) linked to charge trapping/untrapping mechanism as a consequence of the polarization/depolarization of the Pt(II) complex. Under electrical driving stresses, the performance of the devices which include the Pt(II) complex, are stabilized. A schematic model is proposed to depict the SCP responsible for NDR and decrease-resetting behaviors observed in these devices. Full article
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9 pages, 22824 KiB  
Article
Organic Light-Emitting Diodes Based on Phthalimide Derivatives: Improvement of the Electroluminescence Properties
by Frédéric Dumur, Malika Ibrahim-Ouali and Didier Gigmes
Appl. Sci. 2018, 8(4), 539; https://doi.org/10.3390/app8040539 - 31 Mar 2018
Cited by 5 | Viewed by 4555
Abstract
In this study, a phthalimide-based fluorescent material has been examined as a green emitter for multilayered organic light-emitting diodes (OLEDs). By optimizing the device stacking, a maximum brightness of 28,450 cd/m2 at 11.0 V and a maximum external quantum efficiency of 3.11% [...] Read more.
In this study, a phthalimide-based fluorescent material has been examined as a green emitter for multilayered organic light-emitting diodes (OLEDs). By optimizing the device stacking, a maximum brightness of 28,450 cd/m2 at 11.0 V and a maximum external quantum efficiency of 3.11% could be obtained. Interestingly, OLEDs fabricated with Fluo-2 presented a 20-fold current efficiency improvement compared to the previous results reported in the literature, evidencing the crucial role of the device stacking in the electroluminescence (EL) performance of a selected emitter. Device lifetime was also examined and an operational stability comparable to that reported for a standard triplet emitter i.e., bis(4-methyl-2,5-diphenyl-pyridine)iridium(III) acetylacetonate [(mdppy)2Iracac] was evidenced. Full article
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1681 KiB  
Article
Synthesis and Electroluminescence Properties of 3-(Trifluoromethyl)phenyl-Substituted 9,10-Diarylanthracene Derivatives for Blue Organic Light-Emitting Diodes
by Sang Woo Kwak, Kang Mun Lee, Ji-Eun Lee, Jisu Yoo, Yeonjin Yi, Hyoshik Kwon, Hyunbok Lee, Myung Hwan Park and Yongseog Chung
Appl. Sci. 2017, 7(11), 1109; https://doi.org/10.3390/app7111109 - 26 Oct 2017
Cited by 5 | Viewed by 4673
Abstract
Diaryl-substituted anthracene derivatives containing 3-(trifluoromethyl)phenyl) groups, 9,10-diphenyl-2-(3-(trifluoromethyl)phenyl)anthracene (1), 9,10-di([1,1′-biphenyl]-4-yl)-2-(3-(trifluoromethyl)phenyl)anthracene (2), and 9,10-di(naphthalen-2-yl)-2-(3-(trifluoromethyl)phenyl)anthracene (3) were synthesized and characterized. The compounds 13 possessed high thermal stability and proper frontier-energy levels, which make them suitable as host materials [...] Read more.
Diaryl-substituted anthracene derivatives containing 3-(trifluoromethyl)phenyl) groups, 9,10-diphenyl-2-(3-(trifluoromethyl)phenyl)anthracene (1), 9,10-di([1,1′-biphenyl]-4-yl)-2-(3-(trifluoromethyl)phenyl)anthracene (2), and 9,10-di(naphthalen-2-yl)-2-(3-(trifluoromethyl)phenyl)anthracene (3) were synthesized and characterized. The compounds 13 possessed high thermal stability and proper frontier-energy levels, which make them suitable as host materials for blue organic light-emitting diodes. The electroluminescent (EL) emission maximum of the three N,N-diphenylamino phenyl vinyl biphenyl (DPAVBi)-doped (8 wt %) devices for compounds 13 was exhibited at 488 nm (for 1) and 512 nm (for 2 and 3). Among them, the 1-based device displayed the highest device performances in terms of brightness (Lmax = 2153.5 cd·m−2), current efficiency (2.1 cd·A−1), and external quantum efficiency (0.8%), compared to the 2- and 3-based devices. Full article
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1069 KiB  
Article
New Class of Wide Energy Gap Benzotriimidazole Optical Materials
by Jianmin Shi, J. Matthew Chudomel and Richard Fu
Appl. Sci. 2017, 7(10), 1078; https://doi.org/10.3390/app7101078 - 18 Oct 2017
Viewed by 4238
Abstract
A new class of wide energy gap benzotriimidazole materials have been synthesized by a two-step condensation reaction. All of the benzotriimidazole compounds have π-π* absorption bands in the range of 250–400 nm. The photoluminescence (PL) quantum efficiency of each benzotriimidazole depends strongly on [...] Read more.
A new class of wide energy gap benzotriimidazole materials have been synthesized by a two-step condensation reaction. All of the benzotriimidazole compounds have π-π* absorption bands in the range of 250–400 nm. The photoluminescence (PL) quantum efficiency of each benzotriimidazole depends strongly on the presence of electron withdrawing groups. PL quantum efficiencies of benzotriimidazoles without electron withdrawing groups were less than desirable (40–43%), while molecules with electron withdrawing groups displayed much stronger PL with efficiencies in the range of 73–75%. The electron withdrawing groups shift the emission to a longer wavelength, towards a more “true blue” color. This new class of benzotriimidazole optical materials could be used as electron-injecting and electron-transporting blue luminescence materials for potential organic light-emitting diode (OLED) applications. Full article
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1148 KiB  
Article
Enhanced Emission by Accumulated Charges at Organic/Metal Interfaces Generated during the Reverse Bias of Organic Light Emitting Diodes
by Soichiro Nozoe and Masaki Matsuda
Appl. Sci. 2017, 7(10), 1045; https://doi.org/10.3390/app7101045 - 12 Oct 2017
Cited by 6 | Viewed by 3152
Abstract
A high frequency rectangular alternating voltage was applied to organic light emitting diodes (OLEDs) with the structure ITO/TPD/Alq3/Al and ITO/CoPc/Alq3/Al, where ITO is indium-tin-oxide, TPD is 4,4′-bis[N-phenyl-N-(m-tolyl)amino]biphenyl, CoPc is cobalt phthalocyanine, and Alq3 is [...] Read more.
A high frequency rectangular alternating voltage was applied to organic light emitting diodes (OLEDs) with the structure ITO/TPD/Alq3/Al and ITO/CoPc/Alq3/Al, where ITO is indium-tin-oxide, TPD is 4,4′-bis[N-phenyl-N-(m-tolyl)amino]biphenyl, CoPc is cobalt phthalocyanine, and Alq3 is Tris(8-quinolinolato)aluminum, and the effect on emission of the reverse bias was examined. The results reveal that the emission intensity under an alternating reverse-forward bias is greater than that under an alternating zero-forward bias. The difference in the emission intensity (∆I) increased both for decreasing frequency and increasing voltage level of the reverse bias. In particular, the change in emission intensity was proportional to the voltage level of the reverse bias given the same frequency. To understand ΔI, this paper proposes a model in which an OLED works as a capacitor under reverse bias, where positive and negative charges accumulate on the metal/organic interfaces. In this model, the emission enhancement that occurs during the alternating reverse-forward bias is rationalized as a result of the charge accumulation at the organic/metal interfaces during the reverse bias, which possibly modulates the vacuum level shifts at the organic/metal interfaces to reduce both the hole injection barrier at the organic/ITO interface and the electron injection barrier at the organic/Al interface under forward bias. Full article
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Review

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27 pages, 3270 KiB  
Review
Recent Advances of Exciplex-Based White Organic Light-Emitting Diodes
by Peng Xiao, Junhua Huang, Yicong Yu, Jian Yuan, Dongxiang Luo, Baiquan Liu and Dong Liang
Appl. Sci. 2018, 8(9), 1449; https://doi.org/10.3390/app8091449 - 24 Aug 2018
Cited by 43 | Viewed by 8777
Abstract
Recently, exciplexes have been actively investigated in white organic light-emitting diodes (WOLEDs), since they can be effectively functioned as (i) fluorescent or thermally activated delayed fluorescent (TADF) emitters; (ii) the hosts of fluorescent, phosphorescent and TADF dopants. By virtue of the unique advantages [...] Read more.
Recently, exciplexes have been actively investigated in white organic light-emitting diodes (WOLEDs), since they can be effectively functioned as (i) fluorescent or thermally activated delayed fluorescent (TADF) emitters; (ii) the hosts of fluorescent, phosphorescent and TADF dopants. By virtue of the unique advantages of exciplexes, high-performance exciplex-based WOLEDs can be achieved. In this invited review, we have firstly described fundamental concepts of exciplexes and their use in organic light-emitting diodes (OLEDs). Then, we have concluded the primary strategies to develop exciplex-based WOLEDs. Specifically, we have emphasized the representative WOLEDs using exciplex emitters or hosts. In the end, we have given an outlook for the future development of exciplex-based WOLEDs. Full article
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23 pages, 9931 KiB  
Review
Thermally Activated Delayed Fluorescence Emitters for Deep Blue Organic Light Emitting Diodes: A Review of Recent Advances
by Thanh-Tuân Bui, Fabrice Goubard, Malika Ibrahim-Ouali, Didier Gigmes and Frédéric Dumur
Appl. Sci. 2018, 8(4), 494; https://doi.org/10.3390/app8040494 - 26 Mar 2018
Cited by 50 | Viewed by 11974
Abstract
Organic light-emitting diodes offer attractive perspectives for the next generation display and lighting technologies. The potential is huge and the list of potential applications is almost endless. So far, blue emitters still suffer from noticeably inferior electroluminescence performances in terms of efficiency, lifespan, [...] Read more.
Organic light-emitting diodes offer attractive perspectives for the next generation display and lighting technologies. The potential is huge and the list of potential applications is almost endless. So far, blue emitters still suffer from noticeably inferior electroluminescence performances in terms of efficiency, lifespan, color quality, and charge injection/transport when compared to that of the other colors. Emitting materials matching the NTSC standard blue of coordinates (0.14, 0.08) are extremely rare and still constitutes the focus of numerous academic and industrial researches. In this context, we review herein the recent developments on highly emissive deep-blue thermally activated delayed fluorescence emitters that constitute the third-generation electroluminescent materials. Full article
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32 pages, 8530 KiB  
Review
Emergence of White Organic Light-Emitting Diodes Based on Thermally Activated Delayed Fluorescence
by Peng Xiao, Ting Dong, Jianing Xie, Dongxiang Luo, Jian Yuan and Baiquan Liu
Appl. Sci. 2018, 8(2), 299; https://doi.org/10.3390/app8020299 - 19 Feb 2018
Cited by 38 | Viewed by 8428
Abstract
Recently, thermally activated delayed fluorescence (TADF) organic light-emitting diodes (OLEDs) have attracted both academic and industrial interest due to their extraordinary characteristics, such as high efficiency, low driving voltage, bright luminance, lower power consumption and potentially long lifetime. In this invited review, the [...] Read more.
Recently, thermally activated delayed fluorescence (TADF) organic light-emitting diodes (OLEDs) have attracted both academic and industrial interest due to their extraordinary characteristics, such as high efficiency, low driving voltage, bright luminance, lower power consumption and potentially long lifetime. In this invited review, the fundamental concepts of TADF have been firstly introduced. Then, main approaches to realize WOLEDs based on TADF have been summarized. More specifically, the recent development of WOLEDs based on all TADF emitters, WOLEDs based on TADF and conventional fluorescence emitters, hybrid WOLEDs based on blue TADF and phosphorescence emitters and WOLEDs based on TADF exciplex host and phosphorescence dopants is highlighted. In particular, design strategies, device structures, working mechanisms and electroluminescent processes of the representative WOLEDs based on TADF are reviewed. Finally, challenges and opportunities for further enhancement of the performance of WOLEDs based on TADF are presented. Full article
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