Commission Internationale d'Énclairage Research Articles

Biindenophenanthrene derivatives as non-doped blue fluorescent materials for organic light-emitting diodes

We designed and synthesized biindenophenanthrene derivatives for blue fluorescent organic light-emitting diodes (OLEDs) materials to overcome the disadvantages of blue emitter caused by the wide band gap. To demonstrate the electroluminescence (EL) properties, the OLEDs devices were fabricated in the following sequence: indium-tin-oxide (180 nm)/4,4’,4’’-tris[2-naphthyl(phenyl)amino (30 nm)/4,4’-bis(N-(1-naphthyl)-N-phenylamino) biphenyl (20 nm)/Blue emitting materials (20 nm)/Bathophenanthroline (30 nm)/lithium quinolate (2 nm)/Al (100 nm). Device A that using 13,13,13',13'-tetramethyl-13H,13'H-11,11'-biindeno[1,2-l]phenanthrene in emitting layer showed luminous efficiency, power efficiency, and external quantum efficiency of 1.72 cd/A, 0.58 lm/W, 1.03% at 20 mA/cm2 with Commission Internationale d’Énclairage (CIE) coordinates of (0.15, 0.23) at 8.0 V.

Blue Fluorescent Organic Light-Emitting Diodes Using 11,11-Dimethyl-3-(10-phenylanthracen-9-yl)-11H-Indeno[1,2-b]Quinoline Derivatives.

In this study, we designed and synthesized two blue fluorescence materials using phenylanthracenesubstituted-indenoquinoline derivatives by Suzuki coupling reaction for organic light-emitting diodes (OLEDs). In order to study their electroluminescent properties, we fabricated the OLED devices using these two materials as emissive layer (EML) with the following sequence: indium-tin-oxide (ITO, 180 nm)/4,4',4″-tris[2-naphthyl(phenyl)-amino]triphenylamine (2-TNATA, 30 nm)/N,N'-diphenyl-N,N'-(2-napthyl)-(1,1'-phenyl)-4,4'-diamine (NPB, 20 nm)/Blue emitting materials (20 nm)/4,7-Diphenyl-1,10-phenanthroline (Bphen, 30 nm)/lithium quinolate (Liq, 2 nm)/Al (100 nm). In particular, a device using 11,11-dimethyl-3-(10-phenylanthracen-9-yl)-11H-Indeno[1,2-b]quinoline in emitting layer showed luminous efficiency, power efficiency, and external quantum efficiency of 2.18 cd/A, 1.10 lm/W, 2.20% at 20 mA/cm², respectively, with Commission Internationale d'Énclairage (CIE) coordinates of (0.15, 0.11) at 8.0 V.

Efficient Organic Light-Emitting Diodes Based on Indeno-Type Polyaromatic Hydrocarbons.

To develop the efficient emitters for organic light-emitting diode (OLED), three indeno-type polyaromatic hydrocarbons materials were designed and synthesized through Buchwald-Hartwig amination. OLED devices using these materials were fabricated in the following sequence: indium-tin-oxide (ITO) (180 nm)/N,N'-diphenyl-N,N'-(2-napthyl)-(1,1'-phenyl)-4,4'-diamine (NPB) (50 nm)/Emitting materials (1-3) (30 nm)/4,7-diphenyl-1,10-phenanthroline (BPhen) (30 nm)/lithium quinolate (Liq) (2 nm)/Al (100 nm). All devices showed the efficient emissions. In particular, a device using 8,8-dimethyl-N,N-diphenyl-8H-indeno[2,1-b]fluoranthen-6-amine (2) as efficient emitter showed luminous efficiency, power efficiency, and external quantum efficiency of 8.35 cd/A, 5.70 lm/W, 2.37% at 20 mA/cm², respectively, with Commission Internationale d'Énclairage (CIE) coordinates of (0.37, 0.59) at 6.0 V.

Studies on Organic Light Emitting Diodes Using Phenanthroline Derivatives as Emitters.

In this study, we designed and synthesized blue emitting materials based on 1, 10-phenanthroline derivatives. OLED devices using these materials were fabricated in the following sequence; indium-tin-oxide (ITO) (180 nm)/N,N'-diphenyl-N,N'-(2-napthyl)-(1,1'-phenyl)-4,4'-diamine (NPB) (50 nm)/Tris(4-carbazoyl-9-ylphenyl)amine (TCTA) (10 nm)/Blue materials (20 nm)/2,2',2″-(1,3, 5-Benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi) (30 nm)/lithium quinolate (Liq) (2 nm)/Al (100 nm). Particularly, a device using 2-(4-(9,9-dimethylacridin-10(9H)-yl)phenyl)-1-phenyl-1Himidazo[ 4,5-f][1,10] phenanthroline as a blue emitter showed the maximum values of luminous efficiency, power efficiency, and external quantum efficiency of 1.45 cd/A, 1.52 lm/W, 0.99%, respectively with the Commission Internationale d'Énclairage (CIE) (x,y) coordinates of (0.16, 0.14) at 8.0 V.

Fabrication of Blue Organic Light-Emitting Diodes Based on Indeno-Phenanthrene/Triphenylene Amine Derivatives.

Among the three primary colors, blue-emitting materials are limited by the wide energy band gap. In this study, we designed and synthesized emitting materials based on indeno-phenanthrene/ triphenylene derivatives. Organic light emitting-diodes (OLEDs) using these materials were fabricated in the following sequence; ITO/N,N'-diphenyl-N,N'-(2-napthyl)-(1,1'-phenyl)-4,4'-diamine (NPB) (500 Å)/Blue materials (30 nm)/4,7-diphenyl-1,10-phenanthroline (BPhen) (30 nm)/lithium quinolate (Liq) (20 Å)/Al (1000 Å). All the devices showed efficient blue emission. Particularly, a device using 10,10-dimethyl-N,N-diphenyl-10H-indeno[1,2-b]triphenylen-12-amine as an emitter exhibited luminous efficiency, power efficiency, and external quantum efficiency of 3.62 cd/A, 1.83 lm/W, 2.82% at 20 mA/cm², respectively, with Commission Internationale d'Énclairage (CIE) coordinates of (0.16, 0.15) at 6.0 V.

Highly Efficient Organic Light-Emitting Diodes Based on Naphthoanthracene Derivatives Containing Different Arylamines.

Herein, we designed and synthesized emitting materials based on naphthoanthracene with the different arylamino-substituents. Organic Light Emitting-Diodes (OLEDs) devices using these materials were fabricated in the following sequence; ITO/N,N'-diphenyl-N,N'-(2-napthyl)-(1,1'-phenyl)-4,4'- diamine (NPB) (500 Å)/Emitters (400 Å)/Alumium quinolate (Alq₃) (150 Å)/lithium quinolate (Liq) (20 Å)/Al (1000 Å). All devices showed efficient emissions. In particular, a device using 4-((5,5-dimethyl-9-phenyl-5H-naphtho[3,2,1-de]anthracen-3-yl)(phenyl)amino)benzonitrile as an emitter exhibited the luminous efficiency, power efficiency, and external quantum efficiency of 9.15 cd/A, 6.36 lm/W, 2.72% at 20 mA/cm², respectively, with the Commission Internationale d'Énclairage (CIE) coordinates of (0.30, 0.62) at 6.0 V.

Efficient blue fluorescent emitters based on imidazole-pyridine derivatives for organic light-emitting diodes

Imidazole-pyridine derivatives such as 2-(1-phenyl-5-(pyridin-2-yl)-1H-imidazol-4-yl)pyridine were synthesized for the efficient blue light-emitting materials. OLED devices using these materials were fabricated in the following sequence; Indium tin oxide (ITO) (150 nm)/N,N'-diphenyl-N,N'-(2-napthyl)-(1,1'-phenyl)-4,4'-diamine (NPB) (50 nm)/Tris(4-carbazoyl-9-ylphenyl)amine (TCTA) (10 nm)/Blue materials (20 nm)/2,2′,2"-(1,3,5-Benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi) (30 nm)/Lithium quinolate (Liq)/Aluminum (Al) (2/100 nm). Particularly, a device using 9,10-dihydro-9,9-dimethyl-10-(4-(1-phenyl-4,5-di(pyridin-2-yl)-1H-imidazol-2-yl)phenyl)acridine as a blue emitter showed maximum values of luminous efficiency, power efficiency, and external quantum efficiency of 0.21 cd/A, 0.10 lm/W, 0.26% at 20 mA/cm2, respectively with the Commission Internationale d’Énclairage (CIE) (x,y) coordinates of (0.19, 0.11) at 6.0 V.

Efficient Organic Light-Emitting Diodes Based on Naphthoanthracene Derivatives.

In this study, we designed and synthesized emitting materials based on naphthoanthracene derivatives. Organic Light Emitting-Diodes (OLEDs) devices using each four materials were fabricated. All devices showed efficient emissions. In particular, a device using 1-(5,5-Dimethyl-9-phenyl-[5H-naphth[3,2,1-de]anthracen-3-yl])-1H-indole as an emitter at 20 mA/cm2 exhibited luminous efficiency, power efficiency, and external quantum efficiency of 6.51 cd/A, 4.19 lm/W, and 2.48%, respectively, with Commission Internationale d'Énclairage (CIE) coordinates of (0.19, 0.49) at 7.0 V.

Aminofluorene-substituted pyrene derivatives for efficient blue organic light-emitting diodes

ABSTRACTIn this research, we designed and synthesized blue emitting materials based on aminofluorene-substituted pyrene derivatives. Organic light-emitting diodes (OLEDs) devices using these materials were fabricated in the following sequence; ITO/N,N′-diphenyl-N,N′-(2-napthyl)-(1,1′-phenyl)-4,4′-diamine (NPB) (500 Å)/Blue emitters 1 or 2 (300 Å)/4,7-diphenyl-1,10-phenanthroline (BPhen) (300 Å)/lithium quinolate (Liq) (20 Å)/Al (1000 Å). These devices showed efficient blue emissions. Particularly, a device A using 7-(1-(2-(diphenylamino)-9,9-diethyl-9H-fluoren-7-yl)pyren-6-yl)-9,9-diethyl-N,N-diphenyl-9H-fluoren-2-amine (1) as blue emitter exhibited luminous efficiency, power efficiency, and external quantum efficiency of 2.20 cd/A, 0.80 lm/W, 1.62% at 100 mA/cm2, respectively, with Commission Internationale d’Énclairage (CIE) coordinates of (0.17, 0.24) at 8.0 V.

Diarylaminophenyl-substituted bianthracene derivatives for blue organic light-emitting diodes

ABSTRACTIn this study, we designed and synthesized blue emitting materials based on diarylaminophenyl-substituted bianthracene derivatives. Organic Light Emitting-Diodes (OLEDs) devices using these materials were fabricated in the following sequence; indium-tin-oxide (ITO) / N,N'-diphenyl-N,N'-(2-napthyl)-(1,1′-phenyl)-4,4′-diamine (NPB) (50 nm) / Blue materials 1 and 2 (30 nm) / 4,7-diphenyl-1,10-phenanthroline (BPhen) (30 nm) / lithium quinolate (Liq) (2 nm) / Al (100 nm). These devices showed efficient blue emissions. In particular, a device using compound 2 as blue emitter showed luminous efficiency, power efficiency, and external quantum efficiency of 2.47 cd/A, 1.16 lm/W, 2.45% at 20 mA/cm2, respectively, with Commission Internationale d’Énclairage (CIE) coordinates of (0.18, 0.25) at 8.0 V.

Blue emitting materials based on diphenylamine-substituted diphenylvinylarenes for OLEDs

ABSTRACTTo develop the efficient blue emitters for Organic light-emitting diodes (OLEDs), this paper reports the synthesis and electroluminescent properties of diphenylvinylarenes end-capped with diphenylamine groups. Two OLEDs were fabricated in the following sequence: indium-tin-oxide (ITO) / N,N′-di(1-naphthyl)-N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diam-ine (NPB) (50 nm) / Blue emitters (30 nm) / bathophenanthroline (Bphen) (30 nm) / lithium quinolate (Liq) (2 nm) /Al (100 nm). Two devices exhi-bited blue electroluminescence. In particular, a device using 9,9-diethyl-N,N-diphenyl-7-(2,2-diphenylvinyl)-9H-fluoren-2-amine exhibited blue emission with a luminance efficiency, a power efficiency, an external quantum efficiency and Commission Internationale d’Énclairage (CIE) coordinates of 5.48 cd/A, 2.45 lm/W, 2.85% at 20 mA/cm² and (x = 0.17, y = 0.25) at 8.0 V, respectively.

Highly efficient blue and deep-blue emitting zwitterionic iridium(iii) complexes: synthesis, photophysics and electroluminescence

We report on a series of blue and deep-blue emitting zwitterionic iridium(III) complexes, consisting formally of a cationic Ir centre and a N,N′-heteroaromatic (N^N) ligand bearing negatively charged side groups, i.e. sulfonate and borate. The synthesis, photophysical and electrochemical properties of this series are described in detail together with their X-ray crystal structure determination. The reported complexes exhibit intense blue (λmax at 450 nm) and deep blue (λmax at 435 nm) emission in deaerated solution, similar to the related cationic complexes. The strategy employed, namely the internal salt formation, allows high solubility in many organic solvents as well as for some of the complexes a low sublimation temperature. For this reason, one of the complexes was further tested as an emitter in phosphorescent organic light emitting diodes (PhOLEDs). Despite the zwitterionic nature of the triplet emitter employed, the devices were fabricated by means of sublimation process. The devices showed a peak external quantum efficiency (EQE) as high as 11.0% and Commission Internationale d'Enclairage (CIE) coordinates x = 0.21 and y = 0.33.

Fluorescent deep-blue and hybrid white emitting devices based on a naphthalene–benzofuran compound

We report the synthesis, photophysics and electrochemical properties of naphthalene–benzofuran compound 1 and its application in organic light emitting devices. Fluorescent deep-blue emitting devices employing 1 as the emitting dopant embedded in 4-4′-bis(9-carbazolyl)-2,2′-biphenyl (CBP) host show the peak external quantum efficiency of 4.5% and Commission Internationale d’Énclairage (CIE) coordinates of (0.15, 0.07). Hybrid white devices using fluorescent blue emitting layer with 1 and a phosphorescent orange emitting layer based on an iridium-complex show the peak external quantum efficiency above 10% and CIE coordinates of (0.31, 0.37).

Efficient white emitting copolymers based on bipolar fluorene-co-dibenzothiophene-S,S-dioxide-co-carbazole backbone

Efficient white light emitting polymers were synthesized based on poly(9,9-dioctylfluorene-co-dibenzothiophene-S,S-dioxide) as blue emitter and a bisphenylamine functionalized 2,1,3-benzothiadiazole (DPABT) as red emitter. It was found that the incorporation of hole-transporting carbazole moiety into polymer main chain could effectively reduce the hole injection barriers, which can lead to distinctly improved charge balance in the emissive layer. Additionally, the holetransporting carbazole units may form efficient bipolar host with electron-transporting dibenzothiophene-S,S-dioxide units. The white light emitting diodes based on single polymer PFSOCzDPABT showed the maximum luminous efficiency of 3.3 cd/A with the maximum luminance of 10282 cd/m2, and the luminous efficiency showed only 24% roll off at current density of 400 mA/cm2. These Commission Internationale d’Enclairage (CIE) coordinates of the devices changed slightly with the driving voltages increasing from 8 V to 12 V, and were very close to National Television System Committee (NTSC) standard white light emission of (0.33, 0.33). The results indicated that the incorporating bipolar host and low band gap DPABT unit was a promising way to achieve efficient single white light emitting copolymers.

Indenofluorene‐Based Blue Fluorescent Compounds and Their Application in Highly Efficient Organic Light‐Emitting Diodes

AbstractBlue fluorescent compounds based on indenofluorene derivatives incorporating the (diphenylamino)arylvinyl group and di‐tert‐butylphenyl blocking units have been synthesized by Suzuki coupling and the Horner–Wadsworth–Emmons reaction. Their electroluminescence in multilayered OLEDs was examined; the devices have the structures ITO/DNTPD/NPB/MADN:blue dopant/Alq3/LiF/Al. A device with 7 % 2‐(3,5‐di‐tert‐butylphenyl)‐8‐(9,9‐diethyl‐2‐(diphenylamino)fluoren‐7‐ylethenyl)‐6,6,12,12‐tetraethylindeno[1,2‐b]fluorene (3) as blue dopant showed a luminous efficiency of 12.2 cd A–1, a power efficiency of 6.08 lm W–1, and an external quantum efficiency of 7.84 % at 20 mA cm–1 with CIE (Commission Internationale d'Énclairage) (x, y) coordinates of (0.148, 0.241) at 8.5 V. A deep‐blue OLED with CIE (x, y) coordinates of (0.153, 0.128) doped with 2‐(3,5‐di‐tert‐butylphenyl)‐8‐[9‐(3,5‐di‐tert‐butylphenyl)carbazol‐3‐ylethenyl]‐6,6,12,12‐tetraethylindeno[1,2‐b]fluorene (4) exhibited a luminous efficiency of 3.25 cd A–1, a power efficiency of 1.74 lm W–1, and an external quantum efficiency of 2.93 % at 20 mA cm–1.

On the Improvement of Blue Emission for All sp2-Hybridized Bistriphenylenyls: Incorporating Phenylenyl Moieties To Enhance Film Amorphism

The film amorphism of 2,2′-bistriphenylenyl (BTP), a blue-light emitter with all sp2-hybridized polyaromatic, is enhanced by incorporating phenyl groups between the two triphenylene (TP) planes. This series of compounds are BTP, 1,4-di(triphenylen-2-yl)benzene (T1), and 4,4′-di(triphenylen-2-yl)biphenyl (T2), where the latter preserve the characteristics of all sp2 hydrocarbons and improve the optimized electroluminescence (EL) performance. Specifically, the most efficient T2-based device can reach a maximum external quantum efficiency of 5.2% and a very high luminescence of 47776 cd/m2 in the deep-blue region with Commission Internationale d’Enclairage (CIE) coordinates of (0.15, 0.12). The efficiency approaches the upper theoretical limit of 5−5.5%, estimated for a singlet emitter with a refractive index of 1.7−1.5. For comparison, the optimized BTP-based devices confer the corresponding values of 4.2%, 21 204 cd/m2, and (0.14, 0.11). Such an improvement is ascribed to the effect of introducing the phen...

Highly efficient excimer-based white phosphorescent devices with improved power efficiency and color rendering index

Power efficiency, Commission Internationale d’Énclairage (CIE) coordinates, and color rendering index (CRI) of white phosphorescent excimer devices were improved by utilizing two platinum complexes as emissive dopants and exploring different device structures. Compared with devices containing two emissive layers each having a different dopant, devices having two dopants incorporated in a single host layer showed better color stability with the change in operating voltage. White phosphorescent excimer devices having the double-doped emissive layer showed an external quantum efficiency and a power efficiency of 14.5% and 17 lm/W, respectively, at 500 cd/m2. The CIE coordinates and CRI of the devices were (0.382, 0.401) and 81, which were almost independent of the drive voltage.

The Photophysical Properties of Dipyrenylbenzenes and Their Application as Exceedingly Efficient Blue Emitters for Electroluminescent Devices

AbstractThree blue‐light emitting dipyrenylbenzene derivatives, 1‐(4‐(1‐pyrenyl)phenyl)pyrene (PPP), 1‐(2,5‐dimethoxy‐4‐(1‐pyrenyl)phenyl)pyrene (DOPPP), and 1‐(2,5‐dimethyl‐4‐(1‐pyrenyl)phenyl)pyrene (DMPPP), have been prepared by the Suzuki coupling reaction of aryl dibromides with pyreneboronic acid in high yields. These compounds exhibit high glass‐transition temperatures of 97–137 °C and good film‐forming ability. As revealed from single‐crystal X‐ray analysis, these dipyrenylbenzenes adopt a twisted conformation with inter‐ring torsion angles of 44.5°–63.2° in the solid state. The twisted structure is responsible for the low degree of aggregation in the thin films that leads to fluorescence emission of the neat films at 446–463 nm, which is shorter than that of the typical pyrene excimer emission. The low degree of aggregation is also conducive for the observed high fluorescence quantum yields of 63–75%. In organic light‐emitting diode (OLED) applications, these dipyrenylbenzenes can be used as either the charge transporter or host emitter. The non‐doped blue OLEDs that employ these compounds as the emissive layer can achieve a very high external quantum efficiency (ηext) of 4.3–5.2%. In particular, the most efficient DMPPP‐based device can reach a maximum ηext of 5.2% and a very high luminescence of 40 400 cd m–2 in the deep‐blue region with Commission Internationale d'Énclairage (CIE) coordinates of (0.15, 0.11).

Highly efficient white-electrophosphorescent devices based on polyfluorene copolymers containing charge-transporting pendent units

We have developed an efficient green-emitting polymer (FTO-BT5) through the incorporation of low-bandgap 2,1,3-benzothiadiazole (BT) moieties into the backbone of a blue-light-emitting polyfluorene copolymer (PF-TPA-OXD), which contains hole-transporting triphenylamine (TPA) and electron-transporting oxadiazole (OXD) pendent groups. A polymer light-emitting device based on this BT-containing copolymer exhibited very bright green emission having Commission Internationale d'Énclairage (CIE) chromaticity coordinates (0.32, 0.61); the maximum brightness was 10232 cd m−2 and the maximum luminance efficiency was 8.9 cd A−1. In addition, a highly efficient three-band white-light-emitting diode was prepared using PF-TPA-OXD as a blue-light-emitting host doped with this green-light-emitting FTO-BT5 copolymer and a red-light-emitting Os phosphor Os(fppz). Without co-doping any other electron- and/or hole-transporting molecules, this white-light-emitting device reached a maximum external quantum efficiency of 4.1% (8.3 cd A−1) at a luminance of 402 cd m−2 and a current density of 4.8 mA cm−2. When the luminance increased from 26 cd m−2 (0.36, 0.32) to 5258 cd m−2 (0.33, 0.31), the corresponding CIE chromaticity coordinates remain almost unaltered and very close to the emission of pure white light; the value of ηext remained above 3% in this high-luminance region.