Blue Host Materials Research Articles

Deep Blue Fluorescent Host Materials Based on a Novel Spiro[benzo[c]fluorene-7,9'-fluorene] Core Structure with Side Aromatic Wings

E-mail: msgong@dankook.ac.krReceived March 24, 2012, Accepted April 9, 2012Deep blue fluorescent host materials based on a novel spiro[benzo[ c]fluorene-7,9'-fluorene] core structure withside aromatic wings in the 5- and 9-positions, namely, 5,9-di(naphthalen-2-yl)spiro[benzo[c]fluorene-7,9'-fluorene] (DN-SBFF), 5,9-bis(4-t-butylphenyl)spiro[benzo[ c]fluorene-7,9'-fluorene] (BP-SBFF), and 5,9-bis(4-fluorophenyl)spiro[benzo[ c]fluorene-7,9'-fluorene] (FP-SBFF), were designed and successfully pre-pared using the Suzuki reaction. The physical properties of these materials and their EL characteristics as bluehost materials doped with N,N,N',N'-tetraphenylspiro[benzo[c]fluorene-7,9'-fluorene]-5,9-diamine ( TPA-SBFF)were investigated. The device used comprised ITO/ N,N'-diphenyl-N,N'-bis[4-(phenyl-m-tolyl-amino)phenyl]-biphenyl-4,4'-diamine (DNTPD)/N,N'-di(1-naphthyl)-N,N'-diphenylbenzidine (NPB)/(FP-SBFF):dopant x%/tris(8-hydroxyquinoline)aluminum (Alq

Synthesis of Dibenzothiophene-Containing Ladder Polysilsesquioxane as a Blue Phosphorescent Host Material

A ladder polysilsesquioxanes with side chain of dibenzothiophene groups (BS-LPSQ) was successfully synthesized. The ladder structure of BS-LPSQ was characterized by MALDI-TOF MS, XRD, and (1)H NMR spectroscopy. Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), atomic force microscopy (AFM), and spectroscopic analyses revealed that the BS-LPSQ has good film-forming ability, high thermal and morphological stability, and good miscibility to the dopant iridium bis(4,6-difluorophenyl)pyridinato-N,C(2)-picolinate (FIrpic), high triplet energy, and a wide bandgap. In addition, compared with the ringed polysiloxane BS-PSQ phosphorescent host material reported previously, the ladder structure of BS-LPSQ has not only a higher thermal resistance, but also could prevent molecular aggregation and effectively avoid quenching of fluorescence. Thus, the BS-LPSQ may be used as a better host for the blue-light-emitting iridium complex FIrpic. The performance of the electrophosphorescent device, based on the ladder BS-LPSQ as the active layer, is superior to that of ringed BS-PSQ and any other polyhedral oligomeric silsesquioxane (POSS)-based or polymer host materials.

Efficient hybrid white polymer light-emitting devices with electroluminescence covered the entire visible range and reduced efficiency roll-off

We report efficient hybrid white polymer light emitting devices (WPLEDs) fabricated via simple solution-proceeded process from a newly synthesized wide band-gap fluorene-co-dibenzothiophene-S,S-dioxide copolymer, which dually function as fluorescent blue emitter and host material for electrophosphorescent sky-blue, yellow, and saturated-red dyes. The Commission Internationale d’Énclairage coordinates of the best devices are (0.356, 0.334), with electroluminescence covered the entire visible light spectrum from 400 to 780 nm, resulting in a high color rendering index of 90. Incorporation of a bilayer electrode consisting of water/alcohol-soluble conjugated polymer and Al as electron-injection cathode boosts an enhancement of 50% in device efficiency, leading to external quantum efficiency of 12.6%, and peak power efficiency of 21.4 l m W−1 as measured in an integrating sphere. Both the efficiency and the color quality of the obtained device are ranking among one of the highest values for WPLEDs reported to date. Furthermore, as compared with those all-phosphorescent WPLEDs, the hybrid WPLEDs studied here exhibit a significantly reduced efficiency roll-off due to the very low doping concentration.

Benzimidazole–carbazole-based bipolar hosts for high efficiency blue and white electrophosphorescence applications

A series of novel bipolar blue phosphorescent host materials mBICP, mBINCP and mBIPhCP have been designed and synthesized, which comprehensively outperform the widely used phosphorescent host, 1,3-di(9H-carbazol-9-yl)benzene (mCP). The thermal, photophysical and electrochemical properties of these host materials were finely tuned through linking different carbazole moieties to the benzimidazole. mBICP (Tg = 84 °C) and mBIPhCP (Tg = 103 °C) exhibit high morphological stabilities in comparison with mCP. Theoretical calculations show that the HOMO/LUMO orbitals of these materials are mainly dispersed on the electron donating and electron accepting groups, respectively. A blue PhOLED device fabricated using mBICP as the host exhibits a maximum external quantum efficiency (ηEQE,max) of 18.7% and a maximum power efficiency (ηP,max) of 33.6 lm W−1. Interestingly, the external quantum efficiencies (ηEQE) are still as high as 17.1% at a high luminance of 1000 cd m−2. Furthermore, the two-color, all-phosphor and single-emitting-layer white device hosted by mBICP achieved a maximum external quantum efficiency (ηEQE,max) of 20.5% corresponding to a maximum power efficiency (ηP,max) of 53.3 lm W−1.

Simple Structure and High Efficiency Phosphorescent OLEDs Using Narrow Band-gap Bipolar Host Material

ABSTRACTWe report high-efficiency phosphorescent blue OLEDs with an organic three stacked structure. Using a high-triplet-energy-hole transporting material of TAPC and a high-triplet-energy-electron transporting material of TmPyPB, the organic three stacked structure has been realized with three new narrow band-gap blue host materials. These host materials have bipolar characteristics and high triplet energy of >2.8 eV. Very low onset voltages of 2.8~3.0 V and driving voltages of 4.2~4.6 V to obtain a brightness of 1000 cd/m2 are achieved in this three stacked device configuration. Maximum external quantum efficiency above 20% is reported.

Novel heterofluorene-based hosts for highly efficient blue electrophosphorescence at low operating voltages

A novel concept for molecular design of blue host materials for phosphorescent OLEDs (PHOLEDs) by combining carbazole and heterofluorene via structurally mimicking 4,4′-N,N′-dicarbazole-biphenyl (CBP) was presented. The carbazole end-capped heterofluorenes (CzHFs) prepared accordingly in high yields, were found to be ideal hosts for blue PHOLEDs. At the brightness level of 1000 and 5000 cd m −2, the driving voltages are still lower than 4.5 V with the external quantum efficiencies retain as high as 18.1% and 16.8% respectively.

New Fluorescent Blue OLED Host and Dopant Materials Based on the Spirobenzofluorene

New spiro[benzo[c]fluorene-7,9'-fluorene] (SBFF)-based blue host materials, 9-phenyl-SBFF (BH-4P) and 5,9-diphenyl-SBFF (BH-6DP), were successfully prepared by spiro-formation of 9-phenyl-7H-benzo[c]fluoren-7-one with 2-bromobiphenyl via lithiation and reaction of 5,9-dibromo-SBFF with phenylboronic acid through the Suzuki reaction, respectively. Diphenyl-[4-(2-[1,1;4,1]terphenyl-4-yl-vinyl)-phenyl]-amine (BD-1) and N,N-diphenyl-N',N'-diphenyl-SBFF-5,9-diamine (BD-6DPA) were used as dopant materials. Blue OLEDs with the configuration ITO/N,N'-bis-[4-(di-m-tolylamino)phenyl]-N,N'-diphenylbiphenyl-4,4'-diamine (DNTPD)/bis[N-(1-naphthyl)-N-phenyl]benzidine (NPB)/host:5% dopant/SFC-137/Al-LiF were prepared from the two host materials doped with BD-1 and BD-6DPA dopants and the devices composed of BH-4P and BH-6DP doped with BD-6DPA showed blue EL spectra at 458 and 463 nm at 7 V and luminance efficiencies of 4.58 and 4.88 cd/A, respectively.

Fabrication and Characteristics of Vertical Type Organic Light Emitting Transistor Using Novel Blue Host Material

Vertical type organic light emitting transistor can perform as electroluminescence device as well as driving transistor. As the light emitting transistor containing vertical deposited configuration can control its own luminescence intensity, the device circuit can be simplified. In the present work, we have fabricated vertical type organic light emitting transistors consisting of Al(source)/C60/Al(gate)/C60/Bphen/TAT:FIrpic/CuPc/ITO(drain)/glass(substrate). TAT(9,10-bis(3",5"-diphenylbiphenyl-4'-yl)anthracene) and FIrpic were used as blue host material and phosphorescent dopant material, respectively. Relatively high radiance and on-off ratio were observed in the device using LiAl metal as source and gate electrodes.

High efficiency blue phosphorescent organic light-emitting diodes without electron transport layer

High efficiency blue phosphorescent organic light-emitting diodes were fabricated without an electron transport layer using a spirobifluorene based blue triplet host material. The simple blue PHOLEDs without the electron transport layer showed a high external quantum efficiency and current efficiency of 16.1% and 30.2 cd/A, respectively. The high device performances of the electron transport layer free blue PHOLEDs were comparable to those of blue PHOLEDs with the electron transport layer.

Blue organic light-emitting diodes with efficient host-dopant energy level alignment

The authors have demonstrated blue organic light-emitting diodes (OLED) with efficient host-dopant energy level alignment using a total of only two organic materials, 2-methyl-9,10-di(2-naphthyl)anthracene (MADN) and 4′-[2-(2-diphenylamino-9,9-diethyl-9H-fluoren-7-yl)vinyl]-p-terphenyl (PFVtPh). MADN, with ambipolar characteristics, has adequate band gap for junction of anode-cathode and multi-functional characteristics as hole-transporting, electron-transporting, and blue host material. PFVtPh doped in MADN had highest occupied molecular orbital and lowest unoccupied molecular orbital in comparison with 1,4-bis[2-(7-N-diphenyamino-2-(9,9-diethyl-9H-fluoren-2-yl))vinyl]benzene (DAF-ph). The optimized blue OLED fabricated in this study showed a maximum external quantum efficiency of 5.84%, a maximum power efficiency of 7.57 lm/W, and Commission Internationale de I’Eclairage coordinates of (0.15, 0.21). This result also showed 10 times higher power efficiency at 10 mA/cm 2 than blue device using DAF-ph dopant with mismatch of host-dopant energy level alignment.

New blue host materials based on anthracene-containing dibenzothiophene

A series of novel host blue-emitting materials based on anthracene have been synthesized and investigated in which, a π-electron-rich dibenzothiophene moiety was introduced as a side group to fine adjust the HOMO/LUMO levels of the anthracene and enhance the ability of hole-transport and electron-injection. These materials exhibit good film-forming capabilities, and display strong blue fluorescence in solution. To explore the electroluminescent properties of these materials, sky blue devices of 2-TNATA (60 nm)/NPB (10 nm)/Host: BUBD-1 (40 nm)/Alq 3 (15 nm)/LiF (1 nm)/Al (150 nm) were fabricated. For the device with 9, 10-bis(dibenzothiophen-4-yl)anthracene as the host, an electroluminescence efficiency of 13.14 cd/A and 6.76 lm/W at 20 mA/cm 2 and 6.09 V were achieved, with Commission Internationale d’Eclairage (CIE x , y ) color coordinates of ( x = 0.15, y = 0.30).

Asymmetric anthracene-based blue host materials: synthesis and electroluminescence properties of 9-(2-naphthyl)-10-arylanthracenes

A series of bulky aryl-substituted asymmetric anthracene blue host materials, 9-(2-naphthyl)-10-(3-(1-naphthyl)phenyl)anthracene, where phenyl was varied from H (5a), Me (5b), Ph (5e), and 1-Naph (5f) at the 6-position and Me (5c) at the 2-position, was synthesized by Suzuki coupling reaction between 10-(2-naphthyl)anthracene-9-boronic acid and 1-(3-iodophenyl)naphthalene derivatives. A less bulky aryl-substituted anthracene, 9-(2-naphthyl)-10-(2,5-diphenyl)phenyl)anthracene (5d), was also synthesized for comparison. All asymmetric anthracenes showed high glass transition temperatures in the range of 84–153 °C. The photophysical and electrochemical properties in solution showed that the substituent at the 10-positions of the anthracene unit did not influence the blue emission of 420 nm and HOMO–LUMO energy level (5.5–2.5 eV). However, a gradual decrease of bathochromic shift in solid state PL was observed from the increaseg of the substituent bulkiness, exhibiting 5e (18 nm) ≤ 5f (19 nm) < 5c (25 nm) ≤ 5b (26 nm) < 5a (30 nm) < 5d (41 nm), respectably. When 5a was used as a blue host material in the multilayered device structure of ITO/DNTPD/NPD/host:dopant (9%)/PyPySPyPy/LiF/Al, enhanced OLED device performance was observed, showing a luminous current efficiency of 9.9 cd A−1, power efficiency of 6.3 lm W−1 at 20 mA cm−2, deep blue color coordinates of (0.14, 0.18), and a 932 h device lifetime at L0 = 3000 cd m−2.

Multifunctional Materials in High-Performance OLEDs: Challenges for Solid-State Lighting

Recent advances in material chemistry have enabled white organic light-emitting device (OLED) efficacy beyond fluorescent tube efficacy up to 100 lm W−1. In this short review, we explore recent developments of small molecule-based multifunctional materials in high-performance OLEDs, especially blue phosphorescent emitters, host materials, and electron-transporting materials.

Highly Efficient Blue Light-Emitting Diodes Using New Fluorescent Host Materials Based on Naphthalenes

The naphthalene-based blue materials 4,4′-(Dinaphthalen-2-yl)-1,1′-binaphthyl (DNBN) and 1,4-(Dinaphthalen-2-yl)-naphthalene (DNN) were designed and synthesized for OLEDs. A device (non-doped) employing DNN as the emitter exhibited a maximum luminance, luminous efficiency, and external quantum efficiency of 1120 cd/m2, 1.40 cd/A, and 3.83%, respectively. Moreover, its CIE coordinates (0.152, 0.069) are very close to the NTSC blue standard of (0.14, 0.08). In order to improve EL efficiencies, these materials were used as the blue host materials for the blue dopants PFVtPh and PCVtPh. A device 1b (PFVtPh-doped) showed high EL efficiencies of 5.24 cd/A, 2.75 lm/W, and 3.82% at 20 mA/cm2.

Deep-blue OLEDs using novel efficient spiro-type dopant materials

The deep blue fluorescent spiro-type dopant materials N,N,N′ ,N′-tetraphenylspiro[fluorene-7,9′-benzofluorene] ( SFBF)-5,9-diamine (BD-6DPA), N,N′-di-(2-naphthyl)- N,N′-diphenyl- SFBF-5,9-diamine (BD-6NPA), N,N′-diphenyl- N,N′-di- m-tolyl- SFBF-5,9-diamine (BD-6MDPA) and N,N′-diphenyl- N,N′-bis(4-(trimethylsilyl)phenyl)- SFBF-5,9-diamine (BD-6TMSA) were designed and successfully prepared by amination reactions. The EL characteristics of MADN as the blue host material doped with the above blue dopant materials were evaluated. The electroluminescence spectra of ITO/ N,N′-diphenyl- N,N′-bis-[4-(phenyl- m-tolyl-amino)-phenyl]-biphenyl-4,4′-diamine (DNTPD/ N,N′-di(1-naphthyl)- N,N′-diphenylbenzidine (NPB)/2-methyl-9,10-di(2-naphthyl)anthracene (MADN):BD-6MDPA/tris(8-hydroxyquinoline)aluminum (Alq 3)/LiF/Al devices show a narrow emission band with a full width at half maximum of 48 nm and a λ max( ε) = 463 nm. The device obtained from MADN doped with BD-6MDPA showed a good color purity (0.135, 0.156), high luminance efficiency (9.11 cd/A at 6.5 V) and high external quantum efficiency (8.16%).

고효율 청색 유기발광다이오드의 DPVBi와 BCzVBi 사이에서 발생하는 흡열 페르스터 에너지전이

In this study, we demonstrated high-efficiency blue organic light-emitting diodes (OLEDs) employing BCzVBi as a blue fluorescent dye doped into blue host material, DPVBi with various concentration. The optimized blue OLED device having high-efficiency was constructed with structure of NPB (500 A) / DPVBi:BCzVBi-6% (150 A) / Alq3 (300 A) / Liq (20 A) / Al (1000 A). The maximum luminescence of blue OLED was 13200 cd/m at 13.8 V and current density and maximum efficiency were 26.4 mA/cm at 1000 cd/m and 4.24 cd/A at 3.9 V, respectively. Luminous efficiency shows two times higher than comparing with non-doped BCzVBi blue OLED whereas CIEx,y coordinate was similar with bare DPVBi blue OLED such as (0.16, 0.19). Electroluminescence of BCzVBi-6% doped blue OLED has two major peaks at 445 nm and 470 nm whereas pure DPVBi’s blue peak appears at 456 nm and it is happened through endothermic Forster energy transfer by molecule's vibration between LUMO of DPVBi as host material and LUMO of BCzVBi as dopant in device.

P‐188: Molecular Engineering of Host Materials for Blue Phosphorescent OLEDs: Past, Present and Future

AbstractWe report molecular design considerations for blue phosphorescent host materials, as well as propose design rules necessary to build ambipolar hosts and thus reach charge balance in a device. Our beginning developments are presented followed by the evolution of the original design to our state‐of‐the‐art, with the help of computational modeling

P‐154: High Efficiency White‐Phosphorescent OLED with Host‐Free Yellow Emitter

AbstractA white PHOLED with high power efficiency of 55 lm/W has been demonstrated by using a host‐free yellow phosphorescent emitter sandwiched by double blue phosphorescent emitters. The white PHOLED with host‐free yellow phosphorescent emitter achieved a comparable device performance to that of using complicated host‐guest doped system. Based on this device concept as well as the molecular engineering of blue host material, highly efficient white PHOLED can be achieved.

Study of Deep Blue Organic Light-Emitting Diodes Using Doped BCzVBi with Various Blue Host Materials

Deep blue organic light emitting diodes (OLEDs) were fabricated using 5 wt.% doped BCzVBi with various blue host materials such as NPB, DPVBi, MADN and TPBi. A blue OLED device, using DPVBi as host material, was constructed via NPB (<TEX>$500\;{\AA}$</TEX>) / DPVBi:BCzVBi (<TEX>$200\;{\AA}$</TEX>) / Bphen (<TEX>$300\;{\AA}$</TEX>) / LiF (<TEX>$20\;{\AA}$</TEX>) / Al (<TEX>$1,000\;{\AA}$</TEX>) and it shows a maximum luminescence of <TEX>$4,838\;cd/m^2$</TEX>, a current density of <TEX>$32.7\;mA/cm^2$</TEX>, a luminous efficiency of 3.3 cd/A and CIExy coordinates of (0.19, 0.15) at 4.5 V whereas the luminous efficiencies and CIExy coordinates of other blue OLEDs using NPB, MADN and TPBi as host materials have 1.1, 2.6 and 2.0 cd/A and (0.15, 0.11), (0.15, 0.10) and (0.15, 0.10), respectively. Energy transfer mechanisms between BCzVBi and its host materials were discussed with an energy band structure of host materials.

Highly efficient blue-emitting materials based on 10-naphthylanthracene derivatives for OLEDs

A series of new blue-emitting materials: 2-(10-(naphthalen-2-yl)anthracen-9-yl)pyridine ( 1 ); 1-(10-(naphthalen-2-yl)anthracen-9-yl)isoquinoline ( 2 ); 9-(3-(10-(naphthalen-2-yl)anthracen-9-yl)phenyl)-9H-carbazole ( 3 ); 9-(4-(10-(naphthalen-2-yl)anthracen-9-yl)phenyl)-9H-carbazole ( 4 ); 9-(4-(10-(naphthalen-1-yl)anthracen-9-yl)phenyl)-9H-carbazole ( 5 ); 9-(4′-(10-(naphthalen-2-yl)anthracen-9-yl)biphenyl-4-yl)-9H-carbazole ( 6 ); and 9-(4′-(10-(naphthalen-1-yl)anthracen-9-yl)biphenyl-4-yl)-9H-carbazole ( 7 ) were designed and synthesized via the Suzuki cross-coupling reaction. To explore the electroluminescent properties of these materials, multilayer OLEDs were fabricated in the following sequence: ITO/4,4′-bis( N -(1-naphthyl)-N-phenylamino)biphenyl (NPB) (50 nm)/blue-emitting materials ( 1–7 ) (30 nm) /4,7-diphenyl-1,10-phenanthroline (Bphen) (30 nm)/lithium quinolate (Liq) (2 nm)/Al (100 nm). Among those, a device using 6 as an emitter exhibited a high external quantum efficiency of 3.83% (3.20% at 20 mA/cm 2 ) with CIE coordinates of (0.152, 0.114). In order to improve EL efficiency, 1–7 were used as blue host materials for blue dopant materials 4′-[2-(2-diphenylamino-9,9-diethyl-9H-fluoren-7-yl)vinyl]- p -terphenyl ( PFVtPh ) and 3-( N -phenylcarbazol)vinyl- p -terphenyl ( PCVtPh ). Using 1 as a host material for blue dopant material PFVtPh , the resultant device showed high EL efficiencies with 10.35 cd/A, 8.77 lm/W, and 5.70% (10.24 cd/A, 6.06 lm/W, and 5.66% at 20 mA/cm 2 ). Furthermore, using 4 as a host for the PCVtPh blue dopant, device 4c exhibited efficient deep-blue emissions with a maximum external quantum efficiency of 2.96% and CIE coordinates of (0.154, 0.087), very close to the NTSC blue standard of (0.14, 0.08).