On the structure of linear codes with covering radius two and three

We obtain new bounds on l(m,r), the minimum length of a linear code with codimension m and covering radius r. All bounds are derived in a uniform way. We employ results from coding theory, some earlier results on covering codes, and combinatorial arguments. We prove the following bounds: l(6, 2)=13, l(7,2)=19, l(8,2)⩾25, l(9,2)⩾34, l(2m-l,2)⩾2^m+1 for m⩾3, l(14,2)⩾182, l(16,2)⩾363, l(18,2)⩾725, l(20,2)⩾1449, l(22,2)⩾2897, l(24,2)⩾5794, l(9,3)⩾17, l(10,3)⩾21, l(12,3)⩾31, l(13,3)⩾38     

Synthesis and characterization of blue-emitting Ir(III) complexes with multi-functional ancillary ligands for solution-processed phosphorescent organic light-emitting diodes

A series of Ir(III) complexes, (dfpmpy)₂Ir(pic), (dfpmpy)₂Ir(EO₂-pic), (dfpmpy)₂Ir(pic-N-O), and (dfpmpy)₂Ir(EO₂-pic-N-O), containing 2-(2,4-difluorophenyl)-4-methylpyridine (dfpmpy) based main ligand with varying ancillary ligands such as picolinic acid (pic), 4-(2-ethoxyethoxy)picolinic acid (EO₂-pic), picolinic acid N-oxide (pic-N-O), and 4-(2-ethoxyethoxy)picolinic acid N-oxide (EO₂-pic-N-O), respectively were successfully synthesized for highly efficient blue phosphorescent organic light-emitting diodes (PhOLEDs). The photophysical, electrochemical, and electroluminescent (EL) properties were systematically correlated. The solubilizing 2-ethoxyethanol (EO₂-) group was attached to the ancillary ligand through tandem reaction. All of the Ir(III) complexes show high thermal stability and good photoluminescence quantum yields (Ф_pl) in film state. Solution-processed PhOLEDs were fabricated using these Ir(III) complexes as dopants and achieved a maximum external quantum efficiency (EQE) of 10.9% and current efficiency of 21.15 cd/A for (dfpmpy)₂Ir(EO₂-pic). All the Ir(III) complexes emitted blue light with color purity at the Commission Internationale de L’Eclairage (CIE) coordinates of (0.15, 0.31).     

Fluorescence EXAFS analysis of ErP grown on InP by organometallic vapor phase epitaxy using a new organometal Er(EtCp)3

We have investigated local structures of ErP grown by organometallic vapor phase epitaxy Er source: tris(ethylcyclopentadienyl)erbium (Er(EtCp)₃ by extended X-ray absorption fine structure (EXAFS) measurement. The EXAFS analysis revealed that NaCl-type ErP and Er–O(–C) compounds coexisted in the case of ErP growth by using Er(EtCp)₃. The NaCl-type ErP was preferentially formed on InP(1 1 1)A compared with InP(0 0 1) and InP(1 1 1)B. It is considered that formation of unexpected Er–O(–C) compounds is due to low but significant concentration of residual O and/or C in Er(EtCp)₃.     

Synthesis and optoelectronic properties of novel fluorene-bridged dinuclear cyclometalated iridium (III) complex with A–D–A framework in the single-emissive-layer WOLEDs

To explore the influence of push–pull chromophores on properties of emitter in organic light-emitting devices (OLEDs), an acceptor–donor–acceptor (A–D–A)-based dinuclear iridium (III) complex of (dfppy)₄Ir₂(dipic-FL) was synthesized via Suzuki coupling reaction, in which dfppy is 2-(2,4-difluorophenyl)pyridine and dipic-FL is 2,7-di(5-pyridyl-2-carboxyl)-9,9-dioctyl-9H-fluorene. An intense emission peak at about 480 nm resulting from the (dfppy)₂Ir(pic) chromophore and a weak long-wavelength emission band at 580–660 nm attributed to intramolecular charge transfer transition were exhibited for (dfppy)₄Ir₂(dipic-FL) in dichloromethane solution. But a remarkably hypsochromic photoluminescence profile with an intense characteristical emission peak at 422 nm was observed, which is attributed to the intraligand (IL) π–π^∗ excited states in its thin film. White emission with a maximum luminance of 1040 cd/m² and current efficiency of 1.2 cd/A was obtained in its single-emissive-layer (SEL) OLEDs with a configuration of ITO/PEDOT:PSS/(dfppy)₄Ir₂(dipic-FL) (10 wt%):TCTA/TPBi/LiF/Al. To our knowledge, this is one of the best examples in term of dinuclear iridium complex as single dopant in the high-performance white-emitting SEL-OLEDs.     

Synthesis,characterization of the phenylquinoline-based on iridium(III) complexes for solution processable phosphorescent organic light-emitting diodes

A new series of highly efficient Ir(III) complexes, (DPQ)₂Ir(pic-N-O), (F₄PPQ)₂Ir(pic-N-O), (FPQ)₂Ir(pic-N-O), and (CPQ)₂Ir(pic-N-O) were synthesized for phosphorescent organic light-emitting diodes (PhOLEDs), and their photophysical, electrochemical, and electroluminescent (EL) properties were investigated. The Ir(III) complexes, including picolinic acid N-oxide (pic-N-O) ancillary ligand, are comprised with the various main ligands such as 2,4-diphenylquinoline (DPQ), 4-phenyl-2-(2,3,4,5-tetrafluorophenyl)quinoline (F₄PPQ), 2-(9,9-diethyl-9H-fluoren-2-yl)-4-phenylquinoline (FPQ) and 9-ethyl-3-(4-phenylquinolin-2-yl)-9H-carbazole. Remarkably, high performance PhOLEDs using a solution-processable (DPQ)₂Ir(pic-N-O) doped CBP host emission layer were fabricated to give a high luminance efficiency (LE) of 26.9 cd/A, equivalent to an external quantum efficiency (EQE) of 14.2%.The calculated HOMO–LUMO energy gaps for (DPQ)₂Ir(pic-N-O), (F₄PPQ)₂Ir(pic-N-O), (FPQ)₂Ir(pic-N-O) and (CPQ)₂Ir(pic-N-O) were in good agreement with the experimental results.     

Luminescent cationic/neutral Cu(I) complexes for use in light-emitting diodes: Synthesis,structural characterization,DFT studies and properties

Cationic and neutral mononuclear Cu(I) complexes, [Cu(PPh₃)₂(PmH)]BF₄ (1a), [Cu(DPEphos) (PmH)]BF₄ (2a), [Cu(Xantphos) (PmH)]BF₄ (3a), [Cu(PPh₃)₂(Pm)] (1b), [Cu(DPEphos) (Pm)] (2b) and [Cu(Xantphos) (Pm)] (3b) (PPh₃ = triphenylphosphine, DPEphos = bis(2-diphenylphosphinophenyl)ether, Xantphos = 9, 9-dimethyl-bis(diphenylphosphino)xanthenes, PmH = 2-(pyridin-2-yl)benzimidazole, Pm=(2-(Pyridin-2-yl)benzimidazolate), have been prepared and characterized by IR, ¹H NMR, ¹³C NMR, ³¹P NMR, XRD, elemental analysis and X-ray crystal structure analysis. The structural analysis shows that each of Cu(I) complexes includes a tetrahedral [Cu(NN) (PP)]⁺ moiety, and temperature variation from 99 K to 298 K leads to the change of bonds lengths, angles and weak interactions. Meanwhile, theoretical calculations indicate that the differences between cationic and neutral Cu(I) complexes affect the composition of HOMO and LUMO orbitals, and the effect of temperature on Mülliken atomic charges is limited. Furthermore, neutral Cu(I) complexes 1b–3b show better luminescence in comparison to cationic Cu(I) complexes 1a-3a at room temperature, and temperature variations from 99 K to 298 K result in changing photoluminescence to some extent, which partly agrees with the related calculation results. In these cationic and neutral Cu(I) complexes, the maximum phosphorescent lifetime and quantum yield reach respectively 137 μs and 42% at room temperature. Moreover, cationic and neutral Cu(I) complexes are utilized to fabricate the monochromatic LEDs, showing favorable electroluminescence with the maximum EQE of 7.10%.     

High Performance Polymer Electrophosphorescent Devices with tert‐Butyl Group Modified Iridium Complexes as Emitters

The synthesis and photophysical study of two novel tert‐butyl modified cyclometalated iridium(III) complexes, i.e., bis(4‐tert‐butyl‐2‐phenylbenzothiozolato‐N,C^2′) iridium(III)(acetylacetonate) [(tbt)₂Ir(acac)] and bis(4‐tert‐butyl‐1‐phenyl‐1H‐benzimidazolato‐N,C^2′) iridium(III)(acetylacetonate) [(tpbi)₂Ir(acac)], are reported, their molecular structures were characterized by ¹³C NMR, ¹H NMR, ESI‐MS, FT‐IR, and elementary analysis. Compared with their prototypes without tert‐butyl substituents [(bt)₂Ir(acac) and (pbi)₂Ir(acac)], (tbt)₂Ir(acac) and (tpbi)₂Ir(acac) both have shortened phosphorescent lifetimes[(tbt)₂Ir(acac) versus (bt)₂Ir(acac), 1.1 μs:1.8 μs; (pbi)₂Ir(acac) versus (tpbi)₂Ir(acac), 0.8 μs:1.82 μs]. Moreover, (tbt)₂Ir(acac) has much more improved phototoluminescence quantum efficiencies in CH₂Cl₂ solution, [(tbt)₂Ir(acac), 0.51; (bt)₂Ir(acac), 0.26]. Employing them as dopants, high performance double‐layer PLEDs were fabricated. The (tbt)₂Ir(acac)‐based and (tpbi)₂Ir(acac)‐based PLEDs have the maximum external quantum efficiencies of 8.71 % and 10.25 %, respectively, and high EL quantum efficiencies of 5.92 % and 7.21 % can be achieved under high driven current density of 100 mA cm^–2. PLEDs fabricated with both the two phosphors have much broadened EL spectra with FWHM of > 110 nm, which afford the feasibility to be used as dopants in white LEDs, and the best doping concentrations of the two complexes in fabrication of PLEDs were optimized.     

Tuning the Optoelectronic Properties of Carbazole/Oxadiazole Hybrids through Linkage Modes: Hosts for Highly Efficient Green Electrophosphorescence

A series of bipolar transport host materials: 2,5‐bis(2‐(9H‐carbazol‐9‐yl)phenyl)‐1,3,4‐oxadiazole (o‐CzOXD) ( 1 ), 2,5‐bis(4‐(9H‐carbazol‐9‐yl)phenyl)‐1,3,4‐oxadiazole (p‐CzOXD) ( 2 ), 2,5‐bis(3‐(9H‐carbazol‐9‐yl)phenyl)‐1,3,4‐oxadiazole (m‐CzOXD) ( 3 ) and 2‐(2‐(9H‐carbazol‐9‐yl)phenyl)‐5‐(4‐(9H‐carbazol‐9‐yl)phenyl)‐1,3,4‐oxadiazole (op‐CzOXD) ( 4 ) are synthesized through simple aromatic nucleophilic substitution reactions. The incorporation of the oxadiazole moiety greatly improves their morphological stability, with T_d and T_g in the range of 428–464 °C and 97–133 °C, respectively. The ortho and meta positions of the 2,5‐diphenyl‐1,3,4‐oxadiazole linked hybrids ( 1 and 3 ) show less intramolecular charge transfer and a higher triplet energy compared to the para‐position linked analogue ( 2 ). The four compounds exhibit similar LUMO levels (2.55–2.59 eV) to other oxadiazole derivatives, whereas the HOMO levels vary in a range from 5.55 eV to 5.69 eV, depending on the linkage modes. DFT‐calculation results indicate that 1 , 3 , and 4 have almost complete separation of their HOMO and LUMO levels at the hole‐ and electron‐transporting moieties, while 2 exhibits only partial separation of the HOMO and LUMO levels possibly due to intramolecular charge transfer. Phosphorescent organic light‐emitting devices fabricated using 1 – 4 as hosts and a green emitter, Ir(ppy)₃ or (ppy)₂Ir(acac), as the guest exhibit good to excellent performance. Devices hosted by o‐CzOXD ( 1 ) achieve maximum current efficiencies (η_c) as high as 77.9 cd A^?1 for Ir(ppy)₃ and 64.2 cd A^?1 for (ppy)₂Ir(acac). The excellent device performance may be attributed to the well‐matched energy levels between the host and hole‐transport layers, the high triplet energy of the host and the complete spatial separation of HOMO and LUMO energy levels.     

Green and blue-green phosphorescent heteroleptic iridium complexes containing carbazole-functionalized β-diketonate for non-doped organic light-emitting diodes

Two novel iridium complexes both containing carbazole-functionalized β-diketonate, Ir(ppy)₂(CBDK) [bis(2-phenylpyridinato-N,C²)iridium(1-(carbazol-9-yl)-5,5-dimethylhexane-2,4-diketonate)], Ir(dfppy)₂(CBDK) [bis(2-(2,4-difluorophenyl)pyridinato-N,C²)iridium(1-(carbazol-9-yl)-5,5-dimethylhexane-2,4-diketonate)] and two reported complexes, Ir(ppy)₂(acac) (acac = acetylacetonate), Ir(dfppy)₂(acac) were synthesized and characterized. The electrophosphorescent properties of non-doped device using the four complexes as emitter, respectively, with a configuration of ITO/N,N′-diphenyl-N,N′-bis(1-naphthyl)-1,1′-diphenyl-4,4′-diamine (NPB) (20 nm)/iridium complex (20 nm)/2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) (5 nm)/tris(8-hydroxyquinoline)aluminum (AlQ) (45 nm)/Mg_0.9Ag_0.1 (200 nm)/Ag (80 nm) were examined. In addition, a most simplest device, ITO/Ir(ppy)₂(CBDK) (80 nm)/Mg_0.9Ag_0.1 (200 nm)/Ag (80 nm), and two double-layer devices with configurations of ITO/NPB (30 nm)/Ir(ppy)₂(CBDK) (30 nm)/Mg_0.9Ag_0.1 (200 nm)/Ag (80 nm) and ITO/Ir(ppy)₂(CBDK) (30 nm)/AlQ (30 nm)/Mg_0.9Ag_0.1 (200 nm)/Ag (80 nm) were also fabricated and examined. The results show that the non-doped four-layer device for Ir(ppy)₂(CBDK) achieves maximum lumen efficiency of 4.54 lm/W and which is far higher than that of Ir(ppy)₂(acac), 0.53 lm/W, the device for Ir(dfppy)₂(CBDK) achieves maximum lumen efficiency of 0.51 lm/W and which is also far higher than that of Ir(dfppy)₂(acac), 0.06 lm/W. The results of simple devices involved Ir(ppy)₂(CBDK) show that the designed complex not only has a good hole transporting ability, but also has a good electron transporting ability. The improved performance of Ir(ppy)₂(CBDK) and Ir(dfppy)₂(CBDK) can be attributed to that the bulky carbazole-functionalized β-diketonate was introduced, therefore the carrier transporting property was improved and the triplet–triplet annihilation was reduced.     

Synthesis,photoluminescence and electroluminescence properties of iridium complexes with bulky carbazole dendrons

We synthesized solution-processable iridium complexes having bulky carbazole dendrons, fac-tris[2-{3-(3,5-bis(3,6-di-n-butylcarbazol-9-yl)phenyl)Phenyl)pyridine]iridium (III) (mCP)₃Ir and fac-bis[2-{3-(3,5-bis(3,6-di-n-butylcarbazol-9-yl)phenyl)phenyl}pyridine][2-{3-(3,5-di(4-pyridyl)phenyl)phenyl}pyridine]iridium (III) (mCP)₂(bpp)Ir. Photoluminescence quantum efficiencies (PLQEs) of (mCP)₃Ir and (mCP)₂(bpp)Ir in their diluted solutions were 91% and 84%, respectively. They showed high PLQEs of 49% for (mCP)₃Ir and 29% for (mCP)₂(bpp)Ir even in a neat film. The triplet exciton energy level of the dendronized ligand (2.8 eV), 2-[3-{3,5-bis(3,6-di-n-butylcarbazol-9-yl)phenyl}]pyridine 10, and the dendron (2.9 eV), 3,5-bis(3,6-di-n-butylcarbazol-9-yl)benzene 7, are enough higher than that of the core complex Ir(ppy)₃ (2.6 eV). External quantum efficiency (EQE) of single layer light-emitting device with (mCP)₂(bpp)Ir was much higher than that of (mCP)₃Ir because of better affinity of (mCP)₂(bpp)Ir to cathode metal. When an electron transporting and hole-blocking material was used, the EQEs of double layer devices were dramatically improved to 8.3% for (mCP)₃Ir and 5.4% for (mCP)₂(bpp)Ir at 100 cd/m².     

Characterization of Ni/Ho and Ni/Er fully silicided metal gates on SiO2 gate dielectric

This paper investigates the effects of Ho and Er on the sheet resistance and crystallinity of Ni(Ho) and Ni(Er) silicides, the work function (WF) modulation of Ni(Ho) and Ni(Er) fully silicided (FUSI) gate electrodes on SiO₂ dielectric, and the FUSI gated SiO₂/Si interface trap properties by using high-frequency capacitance-voltage (C-V) and photonic high-frequency C-V measurements. It was found that as the thickness percentage of rare earth (RE) metal in the Ni(Ho) or Ni(Er) increases, the sheet resistance of the silicide increases. The crystallinity decreases in the Ni(Ho) and Ni(Er) silicides, and the crystallinity decreases as the Ho thickness percentage increases. As the thickness percentage of Ho in the Ni(Ho) increases from 13% to 30%, the flatband voltage (V_FB) shift increases from −0.19 to −0.27 V. The V_FB shifts negatively 0.17 V due to 10% Er incorporation in the Ni(Er). The V_FB shift can be attributed to the effective WF decrease which may be due to the crystallinity decrease of Ni(Ho) and Ni(Er) FUSI. The interface trap density D_it calculated from the photonic high-frequency C-V curves is in good agreement with that calculated from the high-frequency and photonic high-frequency C-V curves. The Ho or Er addition does not increase the D_it.     

Alcohol soluble titanium(IV) oxide bis(2,4-pentanedionate) as electron collection layer for efficient inverted polymer solar cells

We demonstrate efficient inverted polymer solar cells (PSCs) based on poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C₆₁-butyric acid methyl ester (PCBM) by using solution-processed titanium(IV) oxide bis(2,4-pentanedionate) (TOPD) as electron collection layer (ECL) between the indium tin oxide (ITO) electrode and photoactive layer. The TOPD buffer layer was prepared by spin-coating isopropanol solution of TOPD on ITO and then baked at 140 °C for 5 min. The power conversion efficiency (PCE) of the inverted PSC with TOPD buffer layer reaches 4% under the illumination of AM1.5G, 100 mW/cm², which is increased by 76% in comparison with that (2.27%) of the inverted device without TOPD ECL. The results indicate that TOPD is a promising electron collection layer for inverted PSCs.     

Near‐Infrared Light‐Emitting Diodes (LEDs) Based on Poly(phenylene)/Yb‐tris(β‐Diketonate) Complexes

Near‐infrared‐emitting electroluminescent (EL) devices using blue‐light‐emitting polymers blended with the Yb complexes Yb(DBM)₃phen (DBM = dibenzoylmethane), Yb(DNM)₃phen (DNM = dinaphthoylmethane), and Yb(TPP)L(OEt) (L(OEt) = [(C₅H₅)Co{P(O)Et₂}₃]^–) have been studied. EL devices composed of Yb(DNM)₃phen blended with PPP‐OR11 showed enhanced near‐IR output at 977 nm when compared to those fabricated with Yb(DBM)₃phen/PPP‐OR11 blends. The maximum near‐IR external efficiencies of the devices with Yb(DBM)₃phen and Yb(DNM)₃phen are, respectively, 7 × 10^–5 (at 6 V and at 0.81 mA mm^–2) and 4 × 10^–4 (at 7 V, and 0.74 mA mm^–2). The optimal blend composition for EL device performance consisted of PPP‐OR11 blended with 10–20 mol‐% Yb(DNM)₃phen. A device fabricated using Yb‐(TPP)L(OEt)/PPP‐OR11 showed significantly enhanced near‐IR output efficiency, and future efforts will focus on devices fabricated using porphyrin‐based materials.     

Sensitized infrared electrophosphorescence based on divalent copper complex by an iridium(III) complex

We demonstrate enhanced near-infrared (NIR) electroluminescence (EL) of copper phthalocyanine (CuPc) phosphor doped organic light emitting diodes (OLED) by introducing a red phosphor, bis(1-phenylisoquinolinato) iridium(III) acetylacetonate (Ir(piq)₂acac). For the codoped device, due to presence of Ir(piq)₂acac, the NIR emission peaked at 1120 nm of CuPc was increased by 15 times comparing with the CuPc monodoped device. The enhancement of NIR emission of CuPc emitter was principally attributed to an energy transfer from Ir(piq)₂acac to CuPc, and the sensitized mechanism was also discussed in detail.     

High efficiency fluorescent white organic light-emitting diodes with red,green and blue separately monochromatic emission layers

Highly efficient fluorescent white organic light-emitting diodes (WOLEDs) have been fabricated by using three red, green and blue, separately monochromatic emission layers. The red and blue emissive layers are based on 4-(dicyanomethylene)-2-tert-butyl-6-(1,1,7,7-tetramethyljulolidin-4-yl-vinyl)-4H-pyran (DCJTB) doped N,N′-di(naphthalene-1-yl)-N,N′-diphenyl-benzidine (NPB) and p-bis(p-N,N-diphenyl-amino-styryl) benzene (DSA-ph) doped 2-methyl-9,10-di(2-naphthyl) anthracene (MADN), respectively; and the green emissive layer is based on tris(8-hydroxyquionline)aluminum(Alq₃) doped with 10-(2-benzothiazolyl)-2,3,6,7-tetrahydro-1,1,7,7-tetramethyl-1H,5H,1[H-(1)-benzopyropyrano(6,7-8-i,j)quinolizin-1]-one (C545T), which is sandwiched between the red and the blue emissive layers. It can be seen that the devices show stable white emission with Commission International de L’Eclairage coordinates of (0.41, 0.41) and color rendering index (CRI) of 84 in a wide range of bias voltages. The maximum power efficiency, current efficiency and quantum efficiency reach 15.9 lm/W, 20.8 cd/A and 8.4%, respectively. The power efficiency at brightness of 500 cd/m² still arrives at 7.9 lm/W, and the half-lifetime under the initial luminance of 500 cd/m² is over 3500 h.     

Thermoelectric Properties of Organic Charge-Transfer Compounds

We measured the thermoelectric (TE) properties of compressed pellets of various organic charge-transfer (CT) complexes, such as (TTF)(TCNQ), (BO)(TCNQ) and (ET)₂(HCNAL), where TTF, TCNQ, BO, ET, and HCNAL represent tetrathiafulvalene, tetracyanoquinodimethane, bis(ethylenedioxy)-tetrathiafulvalene, bis(ethylenedithio)tetrathiafulvalene, and 2,5-dicyano- 3,6-dihydroxy-p-benzoquinone, respectively. The metallic (TTF)(TCNQ) and semiconducting (BO)(TCNQ) complexes showed Seebeck coefficients (S) of −18 μV/K and −30 μV/K at 300 K, respectively. On the contrary, the Mott insulator (ET)₂(HCNAL) was found to show a rather high absolute S (−116 μV/K at 300 K), the magnitude of which is comparable to those of the conventional inorganic TE materials. With increasing temperature (170 K to 300 K), the electrical conductivity was increased about two orders of magnitude while the S value was nearly constant. These results suggest that S values could be determined mainly by spin entropy (configurations) of carriers in the Mott insulator (ET)₂(HCNAL). The magnitude of the observed S value was compared with that derived from a theoretical model (generalized Heikes formula).     

Orange and Red Organic Light‐Emitting Devices Employing Neutral Ru(II) Emitters: Rational Design and Prospects for Color Tuning

A new series of charge‐neutral Ru(II ) pyridyl and isoquinoline pyrazolate complexes, [Ru(bppz)₂(PPh₂Me)₂] (bbpz: 3‐tert‐butyl‐5‐pyridyl pyrazolate) ( 1 ), [Ru(fppz)₂(PPh₂Me)₂] (fppz: 3‐trifluoromethyl‐5‐pyridyl pyrazolate) ( 2 ), [Ru(ibpz)₂(PPhMe₂)₂] (ibpz: 3‐tert‐butyl‐5‐(1‐isoquinolyl) pyrazolate) ( 3 ), [Ru(ibpz)₂(PPh₂Me)₂] ( 4 ), [Ru(ifpz)₂(PPh₂Me)₂] (ifpz: 3‐trifluoromethyl‐5‐(1‐isoquinolyl) pyrazolate) ( 5 ), [Ru(ibpz)₂(dpp?)] (dpp? represents cis‐1,2‐bis‐(diphenylphosphino)ethene) ( 6 ), and [Ru(ifpz)₂(dpp?)] ( 7 ), have been synthesized, and their structural, electrochemical, and photophysical properties have been characterized. A comprehensive time‐dependant density functional theory (TDDFT) approach has been used to assign the observed electronic transitions to specific frontier orbital configurations. A multilayer organic light‐emitting device (OLED) using 24 wt % of 5 as the dopant emitter in a 4,4′‐N,N′‐dicarbazolyl‐1,1′‐biphenyl (CBP) host with 4,4′‐bis[N‐(1‐naphthyl)‐N‐phenylamino]biphenyl (NPB) as the hole‐transport layer exhibits saturated red emission with an external quantum efficiency (EQE) of 5.10 %, luminous efficiency of 5.74 cd A^–1, and power efficiency of 2.62 lm W^–1. The incorporation of a thin layer of poly(styrene sulfonate)‐doped poly(3,4‐ethylenedioxythiophene) (PEDOT) between indium tin oxide (ITO) and NPB gave anoptimized device with an EQE of 7.03 %, luminous efficiency of 8.02 cd A^–1, and power efficiency of 2.74 lm W^–1 at 20 mA cm^–2. These values represent a breakthrough in the field of OLEDs using less expensive Ru(II ) metal complexes. The nonionic nature of the complexes as well as their high emission quantum efficiencies and short radiative lifetimes are believed to be the key factors enabling this unprecedented achievement. The prospects for color tuning based on Ru(II ) complexes are also discussed in light of some theoretical calculations.     

Long‐Lived and Highly Efficient TADF‐PhOLED with “(A)n–D–(A)n” Structured Terpyridine Electron‐Transporting Material

The electron‐transporting material (ETM) is one of the key factors to determine the efficiency and stability of organic light‐emitting diodes (OLEDs). A novel ETM with a “(Acceptor)_n–Donor–(Acceptor)_n” (“(A)_n–D–(A)_n”) structure, 2,7‐di([2,2′:6′,2″‐terpyridin]‐4′‐yl)‐9,9′‐spirobifluorene (27‐TPSF), is synthesized by combining electron‐withdrawing terpyridine (TPY) moieties and rigid twisted spirobifluorene, in which the TPY moieties facilitate electron transport and injection while the spirobifluorene moiety ensures high triplet energy (T₁ = 2.5 eV) as well as enhances glass transition temperature (T_g = 195 °C) for better stability. By using tris[2‐(p‐tolyl)pyridine]iridium(III) (Ir(mppy)₃) as the emitter, the 27‐TPSF‐based device exhibits a maximum external quantum efficiency (η_{ext, max}) of 24.5%, and a half‐life (T₅₀) of 121, 6804, and 382 636 h at an initial luminance of 10 000, 1000, and 100 cd m^?2, respectively, which are much better than the commercialized ETM of 9,10‐bis(6‐phenylpyridin‐3‐yl)anthracene (DPPyA). Furthermore, a higher efficiency, a η_{ext, max} of 28.2% and a maximum power efficiency (η_PE, _max) of 129.3 lm W^?1, can be achieved by adopting bis(2‐phenylpyridine)iridium(III)(2,2,6,6‐tetramethylheptane‐3,5‐diketonate) (Ir(ppy)₂tmd) as the emitter and 27‐TPSF as the ETM. These results indicate that the derivative of TPY to form “(A)_n–D–(A)_n” structure is a promising way to design an ETM with good comprehensive properties for OLEDs.     

Surface active buffered hydrogen fluoride having excellentwettability for ULSI processing

By incorporating selected hydrocarbon surfactants, a surface-active BHF (buffered hydrogen fluoride) has been tailored to achieve the following requirements: (1) the same etch rate as that of conventional BHF; (2) low contact angle; (3) nonsegregation; (4) nonfoaming; (5) low particulate count; (6) few impurities (possibility of purification); (7) low particulate adhesion on the wafer surface; (8) no surface residues; (9) excellent surface smoothness; and (10) high SiO ₂/Si etching selectivity. In order to satisfy these requirements, surfactants must satisfy the following characteristics: (1) good solubility in BHF; (2) hydrophilic property at the wafer surface, (3) nondecomposition in BHF; (4) nonreaction with BHF; and (5) sufficient lowering of contact angle at the critical micelle concentration (CMC). Aliphatic amines satisfy these requirements but have foaming problems. The requirements have been achieved using a binary surfactant system consisting of a combination of aliphatic amine and aliphatic alcohol or aliphatic acid     

A high thermal stability terpyridine derivative as the electron transporter for long-lived green phosphorescent OLED

A new terpyridine-based compound of 2,2′,7,7′-tetra([2,2':6′,2″-terpyridin]-4′-yl)-9,9′-spirobi[fluorene] (4oTPSF) was designed and synthesized as the electron transporter in organic light-emitting diodes (OLEDs). 4oTPSF exhibited excellent thermal stability with high glass transition temperature (T_g) of 250 °C and melting temperature (T_m) of 460 °C during the thermal measurement. The excellent thermal stability is attributed to the molecular structure, that the steric effect of rigid twisted spirobiflourene and the connected terpyridine (TPY) resulted in a decrease of the intermolecular π-stacking interaction. The studies on electrical characteristics of electron-only devices revealed that 4oTPSF showed high electron-transporting capability, as good as the conventional electron-transporting material (ETM) 1,3,5-tris(N-phenylbenzimid-azol-2-yl-benzene (TPBi). A series of green phosphorescent OLEDs (PhOLEDs) based on bis(2-phenylpyridine)iridium(III)(2,2,6,6-tetramethylheptane-3,5-diketonate) (Ir(ppy)₂tmd) or tris[2-(p-tolyl)pyridine]iridium(III) (Ir(mppy)₃) as emitter and 4oTPSF as ETM displayed a turn-on voltage of 2.23 V and a maximum power efficiency of 97.8 l m/W and a half-life (T₅₀) of 101, 5680 and 319 390 h at an initial luminance of 10 000, 1000 and 100 cd/m², respectively. The lifetime of 4oTPSF-based device was twice more than the lifetime of TPBi-based device.