Special Issue "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".

Deadline for manuscript submissions: closed (31 July 2018)

Special Issue Editors

Guest Editor
Mr. Geffroy Bernard

LICSEN, NIMBE, CEA, CNRS, Université Paris-Saclay, CEA Saclay 91191 Gif-sur-Yvette Cedex, France
Website 1 | Website 2 | E-Mail
Interests: organic electronics; OLEDs; OPVs
Co-Guest Editor
Dr. Denis Tondelier

Laboratoire de Physique des Interfaces et des Couches Minces (LPICM), CNRS, Ecole Polytechnique, Université Paris Saclay, CEA Saclay 91191 Gif-sur-Yvette Cedex, France
Website | E-Mail
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

Manuscript Submission Information

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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.

Published Papers (9 papers)

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Research

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Open AccessFeature PaperArticle Blue Electrofluorescence Properties of Furan–Silole Ladder Pi-Conjugated Systems
Appl. Sci. 2018, 8(5), 812; https://doi.org/10.3390/app8050812
Received: 14 April 2018 / Revised: 3 May 2018 / Accepted: 9 May 2018 / Published: 18 May 2018
Cited by 1 | PDF Full-text (1543 KB) | HTML Full-text | XML Full-text | Supplementary Files
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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Open AccessArticle Application of [Pt(II)(Tetra-Tert-Butylsalophen)] Complex within Organic Devices: Deep Red Emission, Bistable Light-Emitting Diodes and Operational Stability
Appl. Sci. 2018, 8(5), 762; https://doi.org/10.3390/app8050762
Received: 9 February 2018 / Revised: 27 April 2018 / Accepted: 30 April 2018 / Published: 11 May 2018
PDF Full-text (1956 KB) | HTML Full-text | XML Full-text | Supplementary Files
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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Open AccessFeature PaperArticle Organic Light-Emitting Diodes Based on Phthalimide Derivatives: Improvement of the Electroluminescence Properties
Appl. Sci. 2018, 8(4), 539; https://doi.org/10.3390/app8040539
Received: 4 March 2018 / Revised: 28 March 2018 / Accepted: 29 March 2018 / Published: 31 March 2018
Cited by 1 | PDF Full-text (22824 KB) | HTML Full-text | XML Full-text
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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Open AccessArticle Synthesis and Electroluminescence Properties of 3-(Trifluoromethyl)phenyl-Substituted 9,10-Diarylanthracene Derivatives for Blue Organic Light-Emitting Diodes
Appl. Sci. 2017, 7(11), 1109; https://doi.org/10.3390/app7111109
Received: 28 September 2017 / Revised: 12 October 2017 / Accepted: 23 October 2017 / Published: 26 October 2017
Cited by 4 | PDF Full-text (1681 KB) | HTML Full-text | XML Full-text | Supplementary Files
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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Open AccessArticle New Class of Wide Energy Gap Benzotriimidazole Optical Materials
Appl. Sci. 2017, 7(10), 1078; https://doi.org/10.3390/app7101078
Received: 28 September 2017 / Revised: 11 October 2017 / Accepted: 16 October 2017 / Published: 18 October 2017
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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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Open AccessArticle Enhanced Emission by Accumulated Charges at Organic/Metal Interfaces Generated during the Reverse Bias of Organic Light Emitting Diodes
Appl. Sci. 2017, 7(10), 1045; https://doi.org/10.3390/app7101045
Received: 13 September 2017 / Accepted: 9 October 2017 / Published: 12 October 2017
Cited by 5 | PDF Full-text (1148 KB) | HTML Full-text | XML Full-text
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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Open AccessReview Recent Advances of Exciplex-Based White Organic Light-Emitting Diodes
Appl. Sci. 2018, 8(9), 1449; https://doi.org/10.3390/app8091449
Received: 24 July 2018 / Revised: 11 August 2018 / Accepted: 20 August 2018 / Published: 24 August 2018
Cited by 2 | PDF Full-text (3270 KB) | HTML Full-text | XML Full-text
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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Open AccessFeature PaperReview Thermally Activated Delayed Fluorescence Emitters for Deep Blue Organic Light Emitting Diodes: A Review of Recent Advances
Appl. Sci. 2018, 8(4), 494; https://doi.org/10.3390/app8040494
Received: 4 March 2018 / Revised: 22 March 2018 / Accepted: 23 March 2018 / Published: 26 March 2018
Cited by 7 | PDF Full-text (9931 KB) | HTML Full-text | XML Full-text
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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Open AccessReview Emergence of White Organic Light-Emitting Diodes Based on Thermally Activated Delayed Fluorescence
Appl. Sci. 2018, 8(2), 299; https://doi.org/10.3390/app8020299
Received: 16 January 2018 / Revised: 16 January 2018 / Accepted: 13 February 2018 / Published: 19 February 2018
Cited by 7 | PDF Full-text (8530 KB) | HTML Full-text | XML Full-text
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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