Synthesis and Characteristic Valuation of a Thermoplastic Polyurethane Electrode Binder for In-Mold Coating.

A polyurethane series (PHEI-PU) was prepared via a one-shot bulk polymerization method using hexamethylene diisocyanate (HDI), polycarbonate diol (PCD), and isosorbide derivatives (ISBD) as chain extenders. The mechanical properties were evaluated using a universal testing machine (UTM), and the thermal properties were evaluated using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The PHEI-PU series exhibited excellent mechanical properties with an average tensile strength of 44.71 MPa and an elongation at break of 190%. To verify the applicability of different proportions of PU as an electrode binder, PU and Ag flakes were mixed (30/70 wt%) and coated on PCT substrates, the electrodes were evaluated by four-point probe before and after 50% elongation, and the dispersion was evaluated by scanning electron microscopy (SEM). The electrical resistance change rate of PHEI-PU series was less than 20%, and a coating layer with well-dispersed silver flakes was confirmed even after stretching. Therefore, it exhibited excellent physical properties, heat resistance, and electrical resistance change rate, confirming its applicability as an electrode binder for in-mold coating.

Synthesizing Polyurethane Using Isosorbide in Primary Alcohol Form, and Its Biocompatibility Properties.

Isosorbide is a bio-based renewable resource that has been utilized as a stiffness component in the synthesis of novel polymers. Modified isosorbide-based bis(2-hydroxyethyl)isosorbide (BHIS) has favorable structural features, such as fused bicyclic rings and a primary hydroxyl function with improved reactivity to polymerization when compared to isosorbide itself. Polyurethane series (PBH PU series) using polycarbonate diol (PCD) and bis(2-hydroxyethyl)isosorbide (BHIS) were polymerized through a simple, one-shot polymerization without a catalyst using various ratios of BHIS, PCD, and hexamethylene diisocyanate (HDI). The synthesized BHIS and PUs were characterized using proton nuclear magnetic resonance (1H-NMR), Fourier transform infrared (FT-IR), differential scanning calorimetry (DSC), and mechanical testing. To determine the feasibility of using these PUs as biomedical materials, we investigated the effects of their BHIS content on PBH PU series physical and mechanical properties. The PBH PU series has excellent elasticity, with a breaking strain ranging from 686.55 to 984.69% at a 33.26 to 63.87 MPa tensile stress. The material showed superb biocompatibility with its high adhesion and proliferation in the bone marrow cells. Given their outstanding mechanical properties and biocompatibility, the polymerized bio-based PUs can contribute toward various applications in the medical field.

Inkjet Printing of Mixed-Host Emitting Layer for Electrophosphorescent Organic Light-Emitting Diodes.

We have investigated the impact of the ink formulation on the properties of an inkjet-printed small molecular mixed host in a phosphorescent organic light-emitting diode (PhOLED). Host solubility, film roughness, and device efficiency improved by blending tris(4-carbazoyl-9-ylphenyl)amine (TCTA) with pyrido[3',2':4,5]furo[2,3- b]pyridine (3CzPFP). At a host ratio of 60:40 (TCTA/3CzPFP), the brightness increased by 33%, the efficiency roll-off at 1000 cd/m2 dropped to well below 10%, and the luminance half-lifetime (LT50) improved by 80% in comparison to the device with a single host (100% TCTA). When the optimized ink was deposited by inkjet printing, a maximum external quantum efficiency of 8.9% and a current efficiency of 28.8 cd/A were achieved at 1000 cd/m2 brightness. This amounted to around 84% of the efficiency of a spin-cast reference device. The obtained results provide a blueprint for designing enhanced PhOLEDs with inkjet-printed mixed hosts.

Unconventional Molecular Design Approach of High-Efficiency Deep Blue Thermally Activated Delayed Fluorescent Emitters Using Indolocarbazole as an Acceptor.

Unconventional blue thermally activated delayed fluorescent emitters having electron-donating type indolocarbazole as an acceptor were developed by attaching carbazolylcarbazole or acridine donors to the indolocarbazole acceptor. Three compounds were derived from the indolocarbazole acceptor. The indolocarbazole-acridine combined products showed efficient delayed fluorescent behavior and a high quantum efficiency of 19.5% with a color coordinate of (0.15, 0.16) when they were evaluated as thermally activated delayed fluorescent emitters in deep blue fluorescent devices. This is the first demonstration of the use of electron-donating carbazole-derived moieties as efficient acceptor units of blue thermally activated delayed fluorescent emitters.

Ideal Molecular Design of Blue Thermally Activated Delayed Fluorescent Emitter for High Efficiency, Small Singlet-Triplet Energy Splitting, Low Efficiency Roll-Off, and Long Lifetime.

Highly efficient thermally activated delayed fluorescent (TADF) emitters, 5-(2-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-5H-benzofuro[3,2-c]carbazole (oBFCzTrz), 5-(3-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-5H-benzofuro[3,2-c]carbazole (mBFCzTrz), and 5-(4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-5H-benzofuro[3,2-c]carbazole (pBFCzTrz), were synthesized to study the effects of ortho-, meta-, and para- linkages between donor and acceptor moieties. oBFCzTrz having ortho- linked donor and acceptor moieties showed smaller singlet-triplet energy gap, shorter excited state lifetime, and higher photoluminescence quantum yield than mBFCzTrz and pBFCzTrz which are interconnected by meta- and para- positions. The TADF device using oBFCzTrz as a blue emitter exhibited high external quantum efficiency over 20%, little efficiency roll-off, and long device lifetime.

Design strategy for 25% external quantum efficiency in green and blue thermally activated delayed fluorescent devices.

Carbazole- and triazine-derived thermally activated delayed fluorescent (TADF) emitters, with three donor units and an even distribution of the highest occupied molecular orbital, achieve high external quantum efficiencies of above 25% in blue and green TADF devices.

Benzofurocarbazole and benzothienocarbazole as donors for improved quantum efficiency in blue thermally activated delayed fluorescent devices.

Benzofurocarbazole and benzothienocarbazole were used as electron donors of thermally activated delayed fluorescence (TADF) emitters and the performances of the TADF devices were examined. The benzofurocarbazole and benzothienocarbazole donor moieties were better than carbazole as the electron donors of the TADF emitters.

Above 30% external quantum efficiency in green delayed fluorescent organic light-emitting diodes.

Highly efficient green thermally activated delayed fluorescent organic light-emitting diodes with an external quantum efficiency of 31.2% were investigated by using 3-(3-(carbazole-9-yl)phenyl) pyrido[3',2':4,5]furo[2,3-b]pyridine (3CzPFP) derived from carbazole and pyrido[3',2':4,5]furo[2,3-b]pyridine. The host material showed well-matched photoluminescence emission with absorption of the green dopant material, (4s,6s)-2,4,5,6-tetra(9H-carbazol-9-yl)isophthalonitrile (4CzIPN) and harvested all excitons of 4CzIPN. The 3CzPFP:4CzIPN film exhibited high photoluminescence quantum yield of 100%, and the green delayed fluorescence device employing the 3CzPFP host showed high maximum quantum efficiency of 31.2 ± 0.5% at 1% doping after optimization of the device structure.

Systematic control of photophysical properties of host materials for high quantum efficiency above 25% in green thermally activated delayed fluorescent devices.

Three donor-acceptor type host materials with different photophysical properties were developed by managing the interconnect position of the donor and acceptor moieties and molecular structure of the host materials was correlated with the electro-optical properties and device performances of the host materials. The linkage via the meta-position of aromatic units was better than the linkage via ortho- or para-positions and high quantum efficiency of 26.0% in the green thermally activated delayed fluorescent device was achieved using the host material with the meta-linkage.

New spiro[benzotetraphene-fluorene] derivatives: synthesis and application in sky-blue fluorescent host materials.

Blue light-emitting spiro[benzotetraphene-fluorene] (SBTF)-based host materials, 3-(1-naphthyl)-10-naphthylspiro[benzo[ij]tetraphene-7,9'-fluorene] (1), 3-(2-naphthyl)-10-naphthylspiro[benzo[ij]tetraphene-7,9'-fluorene] (2), and 3-[2-(6-phenyl)naphthyl]-10-naphthylspiro[benzo[ij]tetraphene-7,9'-fluorene] (3) were designed and prepared via multi-step Suzuki coupling reactions. Introducing various aromatic groups into SBTF core lead to a reduction in band gap and a determination of the color purity and luminescence efficiency. Typical sky-blue fluorescent organic light emitting diodes with the configuration of ITO/N,N'-di(1-naphthyl)-N,N'-bis[(4-diphenylamino)phenyl]-biphenyl-4,4'-diamie (60 nm)/N,N,N',N'-tetra(1-biphenyl)-biphenyl-4,4'-diamine (30 nm)/host: dopant (30 nm, 5%)/LG201 (electron transporting layer, 20 nm)/LiF/Al were developed using SBTF derivatives as a host material and p-bis(p-N,N-diphenyl-aminostyryl)benzene (DSA-Ph) as a sky-blue dopant material. A device obtained from three materials doped with DSA-Ph showed color purity of 0.148 and 0.239, a luminance efficiency of 7.91 cd/A, and an external quantum efficiency >4.75% at 5 V.

Carboline derivatives with an ortho-linked terphenyl core for high quantum efficiency in blue phosphorescent organic light-emitting diodes.

Two host materials, 9-(3''-(9H-carbazol-9-yl)-[1,1':2',1''-terphenyl]-3-yl)-α-carboline (CzOTCb) and 3,3''-bis(α-carbolin-9-yl)-1,1':2',1''-terphenyl (CbOTCb), derived from carboline and ortho-linked terphenyl were synthesized as high triplet energy materials and showed a high triplet energy of 2.90 eV. CzOTCb and CbOTCb were evaluated as the host materials for blue phosphorescent organic light-emitting diodes and high quantum efficiencies of 27.4% and 28.8% were obtained using the CzOTCb and CbOTCb hosts, respectively.

Above 30% external quantum efficiency in blue phosphorescent organic light-emitting diodes using pyrido[2,3-b]indole derivatives as host materials.

High quantum efficiencies of above 30% in blue phosphorescent organic light emitting diodes are achieved by using novel pyridoindole-based bipolar host materials. A high quantum efficiency of 30.0% is obtained at 100 cd/m(2) by using the new host materials.

Highly electron deficient pyrido[3',2':4,5]furo[2,3-b]pyridine as a core structure of a triplet host material for high efficiency green phosphorescent organic light-emitting diodes.

Highly electron deficient pyrido[3',2':4,5]furo[2,3-b]pyridine (PFP) was developed as a core structure of a triplet host material and a derivative of PFP, 3-(3-(carbazole-9-yl)phenyl) pyrido[3',2':4,5]furo[2,3-b]pyridine (CzPFP), was synthesized as a bipolar host material. The CzPFP host material showed similar hole and electron densities in single charge devices, and a high quantum efficiency of 27.7% and a high power efficiency of 86.8 lm W(-1) in green phosphorescent organic light-emitting diodes.

Simple heteroatom engineering for tuning the triplet energy of organometallic host materials for red, green and blue phosphorescent organic light-emitting diodes.

Triplet energy tuning from 2.48 eV to 2.94 eV by just a simple change of heteroatom in the ligand structure of Be complexes was studied using azole based triplet host materials. Three Be organometallic host materials with azole type ligands were synthesized and could be used as the host materials from red to deep blue phosphorescent organic light-emitting diodes. High quantum efficiency was obtained in red, green, blue and deep blue devices using the Be complexes. In particular, a high quantum efficiency of 26.1% was achieved in blue phosphorescent organic light-emitting diodes.

High quantum efficiency blue phosphorescent organic light-emitting diodes using 6-position-modified benzofuro[2,3-b]pyridine derivatives.

High quantum efficiency blue phosphorescent organic light-emitting diodes were developed using 6- position modified benzofuro[2,3-b]pyridine derivatives as host materials. Two high triplet energy host materials derived from benzofuro[2,3-b]pyridine modified with carbazole or 9-phenylcarbazole were synthesized and the device performances of the host materials were investigated. A high quantum efficiency of 24.3% was achieved using the benzofuro[2,3-b]pyridine host materials due to good charge balance and energy transfer.

Benzo[4,5]thieno[2,3-b]pyridine derivatives as host materials for high efficiency green and blue phosphorescent organic light-emitting diodes.

Benzo[4,5]thieno[2,3-b]pyridine (BTP) was newly developed as an electron deficient moiety for high triplet energy materials and two BTP derivatives with the BTP and carbazole groups were synthesized as high triplet energy bipolar host materials. The BTP derivatives were effective as the host materials for green and blue phosphorescent organic light-emitting diodes and a high quantum efficiency above 20% was achieved both in green and blue devices.

High quantum efficiency in solution and vacuum processed blue phosphorescent organic light emitting diodes using a novel benzofuropyridine-based bipolar host material.

High quantum efficiency in solution and vacuum processed blue phosphorescent organic light emitting diodes are achieved using a new benzofuropyridine based bipolar host material. High quantum efficiencies of 18.0% and 23.0% are obtained in soluble and vacuum evaporable blue devices.