Research

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10 pages, 1543 KiB

Open AccessFeature PaperArticle

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 3672

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

(This article belongs to the Special Issue Fluorescence and Phosphorescence in Organic Materials: from Fundamental to OLED Devices)

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14 pages, 1956 KiB

Open AccessArticle

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 3671

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 (λ_max = 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 (λ_max = 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

(This article belongs to the Special Issue Fluorescence and Phosphorescence in Organic Materials: from Fundamental to OLED Devices)

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9 pages, 22824 KiB

Open AccessFeature PaperArticle

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 4227

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

(This article belongs to the Special Issue Fluorescence and Phosphorescence in Organic Materials: from Fundamental to OLED Devices)

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1681 KiB

Open AccessArticle

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 4417

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 1–3 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 1–3 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 1–3 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 (L_max = 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

(This article belongs to the Special Issue Fluorescence and Phosphorescence in Organic Materials: from Fundamental to OLED Devices)

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1069 KiB

Open AccessArticle

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 4087

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

(This article belongs to the Special Issue Fluorescence and Phosphorescence in Organic Materials: from Fundamental to OLED Devices)

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1148 KiB

Open AccessArticle

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 2948

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

(This article belongs to the Special Issue Fluorescence and Phosphorescence in Organic Materials: from Fundamental to OLED Devices)

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Review

Jump to: Research

27 pages, 3270 KiB

Open AccessReview

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 41 | Viewed by 8255

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

(This article belongs to the Special Issue Fluorescence and Phosphorescence in Organic Materials: from Fundamental to OLED Devices)

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23 pages, 9931 KiB

Open AccessFeature PaperReview

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 47 | Viewed by 11395

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

(This article belongs to the Special Issue Fluorescence and Phosphorescence in Organic Materials: from Fundamental to OLED Devices)

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32 pages, 8530 KiB

Open AccessReview

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 36 | Viewed by 8001

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

(This article belongs to the Special Issue Fluorescence and Phosphorescence in Organic Materials: from Fundamental to OLED Devices)

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