Comparison Study of Phenylquinoline-based Iridium(III) Complexes for Solution Processable Phosphorescent Organic Light-Emitting Diodes by PEDOT:PSS and Graphene Oxide as a Hole Transport Layer

Electroluminescent (EL) properties of Ir(III) complex, [(2,4-diphenylquinoli-ne)]₂Iridium picolinic acid N-oxide [(DPQ)₂Ir(pic-N-O)] were investigated using PEDOT:PSS and reduced graphene oxide (rGO) as a hole transport layer for solution processable phosphorescent organic light-emitting diodes (PhOLEDs). High performance solution-processable PhOLED with PEDOT:PSS and (DPQ)₂Ir(pic-N-O) (8 wt%) doped CBP:TPD:PBD (8:56:12) host emission layer were fabricated to give a high luminance efficiency (LE) of 26.9 cd/A, equivelent to an external quantum efficiency (EQE) of 14.2%. The corresponding PhOLED with rGO as a hole transport layer exhibited the maximum brightness and LE of 13540 cd/m² and 16.8 cd/A, respectively. The utilization of the solution processable rGO thin films as the hole transport layer offered the great potential to the fabrication of solution processable PhOLEDs.     

New Blue-Light Emitting Materials in White OLED Based on Solution and Vacuum Methods

New host material of 2-tert-butyl-9,10-bis(3′′,5′′-diphenylbiphenyl-4′-yl)anthracene [T-TAT] substituted t-butyl group was investigated in solution process WOLED device compared with 9,10-bis (3′′,5′′-diphenylbiphenyl-4’-yl) anthracene [TAT]. A two-color WOLED of a co-host system using solution process method was demonstrated. The device configuration was ITO / PEDOT:PSS (40 nm) / emitting layer (50 nm) / TPBi (20 nm) / LiF (1 nm) / Al. The emitting layer consisted of TAT or T-TAT, NPB, DPAVBi (blue dopant), and rubrene (yellow dopant). NPB was used to help hole carrier transport as well as blue host role. The device using the T-TAT compound as a co-host showed a luminance efficiency of 2.73 cd/A, which is 77% higher than TAT device of 1.54 cd/A at 20 mA/cm².     

New Emitting Materials Based on HTL Moiety with High Hole Mobility for OLEDs

New green emitting compounds based on tris(N-methylindolo)benzene (NMT), anthracene and pyrene were synthesized. NMT-An and NMT-Py were used as an emitting layer in OLED device to examine emitting property. OLED device containing NMT-An emitting layer and conventional hole transporting layer (HTL) of NPB was found to exhibit better characteristics compared to NMT-Py. And that device showed maximum EL emission at 502 nm and 550 nm, CIE coordinates (0.38, 0.48), and a luminance efficiency of 2.06 cd/A. Also when NMT and NMT-An were used as a HTL instead of NPB, the device including NMT-An emitter showed 2.67 cd/A and 2.29 cd/A in luminance efficiency.     

Organic Light-Emitting Diodes based on Benzo[q]quinoline Derivatives

Abstract

In this study, we synthesized two emitting materials based on benzo[q]quinoline derivatives. OLED devices using these materials were facricated in the following sequence;ITO(180nm)/4,4',4''-Tris[2-naphthyl(phenyl)amino]triphenylamine(2-TNATA)(30nm)/N,N'-di(1-naphthyl)-N,N'-diphenyl-(1,1'-biphenyl)-4,4'-diamine(NPB)(20nm)/Emitting materials(30nm)/4,7-diphenyl-1,10-phenanthroline (Bphen)(30nm)/Liq(2nm)/Al(100nm). Particularly, a device using 2,4-di(naphtalene-1-yl)benzo[q]quinoline as an emitter exhibited the efficient emission with a luminous efficiency, a power efficiency, and exteranl quantum efficiency of, and the CIE coordinates of 2.91cd/A, 0.99lm/W, 0.90% at 20mA/cm², and (0.33, 0.55) at 1000cd/m², respectively. Interestingly, emissions from electromers and electroplexes were shown to be crucial role in electroluminescences from benzo[q]quinoline derivatives     

Fabrication of Al2O3 Coatings on Metal Substrates by Electrophoretic Deposition by the Addition of Polydimethylsiloxane-Based Organic-Inorganic Hybrid Materials as Binders

Polydimethylsiloxane (PDMS)-based organic-inorganic hybrids have been studied because of their high dielectric strength, heat resistivity, and flexibility. In this study, we fabricated Al₂O₃ coatings on metal substrates with sufficient electrical insulation, heat conductivity, and thermal stability by electrophoretic deposition (EPD) using PDMS-based hybrid binders. The scratch hardness, thermal conductivity, and electrical breakdown strength of the Al₂O₃ coating before and after heat treatment at 300 °C for 500 h were 2.0 N, 3.1 W/mK, and 60 kV/mm, respectively. These results demonstrate the usefulness of EPD using PDMS-based hybrid binders for fabricating flexible heat dissipative substrates used in high-temperature environments.     

Bulk Heterojunction Solar Cells with Ternary Mixed PTB7:PCDTBT:PC71BM Active Layers

We report on bulk-heterojunction solar cells fabricated based on ternary mixed solutions of two donors of poly[[4,8-bis[(2-ethylhexyl)oxy]benzo [1,2-b:4,5-b’] dithiophene-2, 6-diyl] [3-fluoro-2- [(2-ethylhexyl) carbonyl]thieno[3,4-b]-thiophenediyl] (PTB7) and [N-9’-heptadecanyl-2,7-carbazole-alt-5,5-(4’,7’-di-2-thienyl-2’,1’,3’-benzothiadiazole)] (PCDTBT), and an accepter of [6,6]-phenyl C₇₁ butyric acid methyl ester (PC₇₁BM). The solar cells had a glass/ITO/NiO/PTB7:PCDTBT:PC₇₁BM/LiF/Al structure. Solar cells containing a 1-2% PCDTBT weight fraction showed a noticeable improvement in short circuit current density (J_sc), fill factor (FF), and power conversion efficiency (PCE). Solar cells with a 2% PCDTBT weight fraction exhibited an open circuit voltage (V_oc) of 0.77 V, J_sc of 13 mA/cm², FF of 0.42, and PCE of 4.23%. Possible mechanisms for the solar cell performance improvement by the introduction of the small amount of PCDTBT in the PTB7:PC₇₁BM active layer was discussed based on the active layer morphology changes and carrier transport mechanisms.     

Synthesis and Characterization of New Phosphorescent Heteroleptic Iridium (III) Complex by Using Tetrazole as an Ancillary Ligand for Organic Light-Emitting Diodes

The yellow emitting tetrazole based heteroleptic iridium(III) complex, bis(diphenylquinoline)iridium(pyridyltetrazole) [(DPQ)₂Ir(PyTz)], was synthesized and conformed by ¹H-,¹³C NMR spectral techniques. The purity was also confirmed by HPLC. The thermal, electrochemical, photophysical and electroluminescent properties were intrinsically investigated. The Ir(III) complex is thermally more stable having thermal decomposition temperature (T_d, 5% weight loss) more than 350°C and it shows very high glass transition temperature T_g-233°C. We have followed the easy and cost effective solution process for (DPQ)₂Ir(PyTz) device fabrication and achieved better performance yellow phosphorescent organic light-emitting diodes (PhOLEDs), maximum external quantum efficiency (EQE) of 5.68%, luminance efficiency 12.63 cd/A, and CIE coordinate of (0.56, 0.43).     

Synthesis of Hydrotalcite using Magnesium from Seawater and Dolomite

Abstract

Three methods of synthesizing hydrotalcite(HT) have been developed using magnesium from seawater and dolomite(MgCa(CO₃)₂). In the first process, 1.0M Na₂CO₃solution was added to calcium ion free artificial seawater containing AlCl₃ with an initial Mg/Al molar ratio of 2.0～3.7 until a pH of 10 was obtained. The solution was then continuously stirred for Ih at 60°C. CO₃ ^2--HT was precipitated as a single phase, and the initial Mg/Al molar ratio, which each recovery of Mg²⁺and Al³⁺ from the solution was above 98%, was 2.0–2.3. In the second process, a Ca(OH)₂ slurry was added to artificial seawater containing AlCl₃ with an initial Mg/Al molar ratio of 1.0～5.0 until a pH of 10.5 was obtained, and then was stirred for Ih at 60°C. HT was also precipitated as a single phase with initial Mg/Al molar ratio 2.0～4.0. The initial Mg/Al molar ratio, which each recovery of Mg²⁺ and Al³⁺ from the solution was above 98%, was 2.2～3.3, but SO₄ ^2- and Cl^? were contained in the precipitated HT. When HT was produced using initial Mg/Al molar ratio of 3.0 at 25°C, SO₄ ^2- and Cl^?in the HT were ion-exchanged with CO₃ ^2- in a 0.05M Na₂CO₃solution for 24h at 25°C, and SO₄ ^2- and Cl^? content of the HT were decreased to 0.5 and 0.05wt%, respectively. In the third process, dolomite calcined at 1000°C was added to an AlCl₃ solution with an initial Mg/Al molar ratio of 1.0～2.0, and the solution was stirred for 1～4h at 25～90°C. HT was precipitated with the smallest amount of MgO and Mg(OH)₂ when the initial Mg/Al molar ratio was 1.5 and the solution was stirred for 4h at 90°C.     

Synthesis and Characterization of Violet Light Emitting Polymer based on Fluorene and Dimethylsilane

New fluorene based light emitting polymer, poly[(4-(9,9-didecyl-9H-fluoren-2-yl) phenyl)dimethyl(phenyl)silane] (PFDPS), was synthesized by palladium-catalzed Suzuki coupling reaction. The obtained copolymer was characterized by ¹H-NMR, and IR-spectroscopy. The polymer showed good solubility in common organic solvents and weight average molecular weight of 16,300 with polydispersity index of 1.4. The maximum photoluminescence of the solution and film of the polymer was observed at 392 nm and 410 nm, respectively.

The double-layered device with the configuration, ITO/PEDOT/PFDPS/LiF/Al structure has a turn-on voltage at about 5.5 V and maximum brightness of 9.40 cd/m², and emitted violet light at 414 nm.     

Identification of a new family of diphosphate compounds, AI2BII3(P2O7)2: Structures of Ag2Co3(P2O7)2, Ag2Mn3(P2O7)2, and Na2Cd3(P2O7)2

Syntheses and single-crystal X-ray structural results are reported for three new mixed diphosphates of the family A^I ₂B^II ₃(P₂O₇)₂; Ag₂Co₃(P₂O₇)₂ (I), Ag₂Mn₃(P₂O₇)₂ (II), and Na₂Cd₃(P₂O₇)₂ (III). All crystallize in the triclinic system, space group P1 bar: (I) a = 5.351(4), b = 6.375(4), c = 16.532(4) Å, = 80.83(6) = 81.45(4), = 72.87(5)°, V = 528.9(6) ų, Z = 2, D _calc = 4.649 mg/m³, R/Rw = 0.0428/0.0548 for 3949 obs. reflns; (II) a = 5.432(7), b = 6.619(6), c = 16.51(3) Å, = 80.78(8) = 82.43(9), = 72.82(7)°, V = 557.7(13) ų, Z = 2, D _calc = 4.338 mg/m³, R/Rw = 0.0679/0.1303 for 2100 obs. reflns and (III) a = 5.67(3), b = 7.08(4), c = 7.90(4) Å, = 77.0(2), = 82.5(2), = 67.8(2)°, V = 286(3) ų, Z = 2, D _calc = 4.249 mg/m³, R/Rw = 0.0307/0.0342 for 1945 obs. reflns. (I) and (II) are isostructural but (III) is of a different type. All three structures are characterized by layers of P₂O₇ groups alternating with layers of mixed metal atoms. Differences are seen in the conglomerate bonding patterns of B atoms and in the irregular geometry of Ag in (I) and (II) compared to the octahedral bonding seen for Na in (III). The differences in structure may be understood in terms of the ratios of the ionic radii of A and B atoms.     

Enhanced persistent photoconduction in CuInS2–ZnIn2S4 alloys single crystals and processes of its relaxation

ABSTRACT

Photoelectrical response in CuInS₂–ZnIn₂S₄ alloys single crystals was analysed in the low temperature region from 30 K up to 100 K. The molar ratio of ZnIn₂S₄ in the alloys was varied in the range 0 mol%?16 mol%. The crystals with up to 12 mol% were the single-crystalline, meanwhile those with 16 mol% were the two phase ones. We have analysed spectral distribution of their photocurrent at different temperatures and the following relaxation towards the stationary values. The photo-induced photoconductivity phenomena were identified. Moreover the long-lasting relaxations with characteristic times exceeding 1.5×10³ sec were observed at lowest temperatures. They used to shorten exponentially with increasing temperature showing thermally activated behaviour. The main parameters of the photoconductivity kinetics and their temperature dependencies were determined. The observed behaviour was explained by the slow multicenter recombination due to the combined effect of different trapping and recombination centers. The effects of both – “fast” and “slow” recombination centers were taken into account.     

Fabrication of two-dimensional MoS2 thin-film transistors using a reactive thermal evaporation method combined with an annealing step

ABSTRACT

Two-dimensional (2-D) MoS₂ films were fabricated by reactive thermal evaporation combined with thermal annealing. The 2-D nature of the MoS₂ films is demonstrated by observation of direct transition and a Van Hove singularity in the absorbance curve. The 1T phase MoS₂ is confirmed by X-ray photoelectron spectroscopy. MoS₂ thin-film transistors (TFTs) are fabricated using the MoS₂ active layer transferred onto an oxidized Si wafer from a sapphire wafer. The MoS₂ TFT demonstrates a threshold voltage of 37.6 V, a field-effect mobility of 6.94 cm²V^?1s^?1 a sub-threshold swing of 29.2 V/dec and a switching ratio of 10³.     

Crystal structure, vibrational spectra, and thermal decomposition and nitrogen adsorption behaviour of a new tetramanganese(II) dipyrophosphate decahydrate, Mn4(P2O7)2·10H2O

A new manganese(II) pyrophosphate, Mn₄(P₂O₇)₂·10H₂O, has been synthesized and characterized by single-crystal X-ray diffraction [orthorhombic space group Pnma, with unit cell parameters of a=9.3288(3) ?, b=25.9532(9) ?, c=8.4783(3) ?; Z=4]. All the pyrophosphate anions show non-linear P–O–P bonds with an average angle of 128.60°. The framework of this new pyrophosphate is made up of packed layers of MnO₆ octahedra connected by double-tetrahedra P₂O₇ groups and a layer of Mn(H₂O)₆ units. The [P₂O₇]⁴⁻ anions adopt a bent, near-staggered conformation. The absence of coincidences for the majority of the IR and Raman bands is in accord with the centrosymmetric structure of the material. The vibrational spectra have been interpreted in part on the basis of factor group effects. The structural changes occurring during heating have been investigated by TG-ATD. When Mn₄(P₂O₇)₂ ^.10H₂O is gradually heated, it decomposes into an intermediate hydrated salt at 96°C and then to anhydrous Mn₂P₂O₇ at 325°C. This thermal behaviour is different from that of Zn₄(P₂O₇)₂·10H₂O. The crystal structure of the new managenese(II) pyrophosphate is compared with the known structures of Zn₄(P₂O₇)₂·10H₂O, Mn₂P₂O₇·2H₂O and anhydrous Mn₂P₂O₇. The adsorption and desorption isotherms of Mn₄(P₂O₇)₂·10H₂O, Zn₄(P₂O₇)₂·10H₂O and MnKHP₂O₇·2H₂O have been investigated by BET measurements and the results show that the capacity for N₂ sorption of the Mn(II) salt is two times lower than is that of the Zn(II) isotype and two or three times higher than is that of MnKHP₂O₇·2H₂O.     

Blue electroluminescent materials based on indeno[1,2-a]arene derivatives for Organic Light-Emitting Diodes

Abstract

In this study, as a continuous effort for searching efficient blue-emitting materials, we designed and synthesized materials based on indeno[1,2-a]arene. OLED devices using these materials were fabricated in the following sequence; ITO (180?nm)/N,N'-diphenyl-N,N'-(2-napthyl)-(1,1'-phenyl)-4,4'-diamine (NPB) (50?nm)/emitting materials (30?nm)/4,7-diphenyl-1,10-phenanthroline (Bphen) (30?nm)/Liq/Al (2/100?nm). Particularly, a device using 7,7-dimethyl-7H-indeno[1,2-a]pyrene as emitter showed maximum values of luminous efficiency, power efficiency, and external quantum efficiency of 1.10?cd/A, 0.49?lm/W, 1.47% at 20?mA/cm², respectively with CIE (x,y) coordinates of (0.15, 0.08) at 6.0V.     

Organic light-emitting transistors with a thin metal layer covering a diffraction grating

We fabricated organic light-emitting transistors (OLETs) characterized by an Ag layer deposited on a one-dimensional (1D) or two-dimensional (2D) diffraction grating that acts as a combined gate insulator with SiO₂. The Ag layer was entirely covered with an organic crystal. Upon photoexcitation that crystal showed narrow linewidth emissions (NLEs) parallel to the substrate plane. The narrowed lines were either redshifted or blueshifted with rotation of the crystal around a normal to its surface with respect to the grating wave vector. Strong emissions (～10⁴–10⁶ cd m^?2) accompanied by current-injected NLEs were observed from the 1D and 2D grating OLETs.     

Liquid crystal properties of dimers having two identical terminal units and a central oxyethylene spacers

ABSTRACT

In 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.     

Synthesis and crystal structure of anhydrous copper suberate: [Cu<Subscript>2</Subscript>(OOC-(CH<Subscript>2</Subscript>)<Subscript>6</Subscript> -COO)<Subscript>2</Subscript>]

The title compound [Cu₂(OOC-(CH₂)₆-COO)₂] was synthesized and its crystal structure has been determined by single crystal X-ray diffraction methods. The complex crystallizes in the triclinic space group P-1 with a=5.1077(5) ?, b=8.362(2) ?, c=11.378(2) ?, α=93.773(6)°, β=97.587(9)°, γ=90.493(’9)° and D _cal=1.629 mg/m³ for Z=1.  The structure is polymeric and consists of discrete anhydrous centrosymmetric binuclear units [Cu₂(OOC-(CH₂)₆-COO)₂]. The two copper(II) centres bridged by the suberate groups in a syn-syn conformation, are in pentacoordinated distorted square-pyramidal coordination environment, with an intramolecular Cu–Cu distance of 2.5793(10) ?. Each binuclear unit, related to the next through μ_oxo bridges with a Cuμ_oxo–Cuμ_oxo separation of 3.2326(10)?, defines infinite chains of one-edge sharing CuO₅ square pyramid.     

Structural and electrical properties of lead-free perovskite ceramic: Ba(In1/2Nb1/2)O3

Lead-free perovskite Ba(In_1/2Nb_1/2)O₃ was prepared by conventional ceramic fabrication technique at 1350 °C/5 h in air atmosphere. The crystal symmetry, space group and unit cell dimensions were determined from Rietveld analysis using FullProf software whereas crystallite size and lattice strain were estimated from Williamson-Hall approach. XRD analysis of the compound indicated the formation of a single-phase cubic structure with the space group Pm3m. EDAX and SEM studies were carried out in order to evaluate the quality and purity of the compound. Complex impedance as well as electric modulus analyses suggested the dielectric relaxation to be of non-Debye type. The correlated barrier hopping (CBH) model was employed to successfully explain the mechanism of charge transport in Ba(In_1/2Nb_1/2)O₃.     

Stereoselective Synthesis and X-Ray Structure Determination of Labeled [1, 2, 3-<Superscript>13</Superscript>C<Subscript>3</Subscript>]-1-(Phenylsulfinyl)-3-Benzyloxyacetone

[1,2,3-¹³C₃]-1-(Phenylsulfinyl)-3-benzyloxyacetone, C₁₆H₁₆O₃S, (3) has been synthesized and its crystal structure has been determined by a single-crystal X-ray diffraction analysis. The X-ray diffraction study revealed that compound 3 crystallizes in the monoclinic crystal system in the acentric space group Pc, with cell constants at T = 100 K: a = 16.073(5), b = 5.5079(16), c = 7.949(2) Å, β = 100.221(4)^°, V = 692.6(3) ų, Z = 2, d _calc = 1.383 g/cm³. Compound 3 contains the chiral tetravalent three-coordinated sulfur atom, which has a distorted tetrahedral configuration with a lone electron pair occupying one of the tetrahedron vertices. In the crystal, the molecules are packed in stacks along the b axis; the stacks consist of the molecules of the same chirality. Furthermore, the stacks of the molecules of the opposite chirality alternate along the c axis. The molecules in neighboring stacks are arranged by head-to-tail orientations. There are no short intermolecular contacts in the crystal of 3.     

Advanced nanostructure Ti0.7In0.3O2 support enhances electron transfer to Pt: Used as high performance catalyst for oxygen reduction reaction

ABSTRACT

The slow rate of the oxygen reduction reaction (ORR) and the instability of Pt based catalysts are two of the most important issues which must be solved in order to make proton exchange membrane fuel cells (PEMFCs) a reality. Here, we present a new approach by exploring robust non-carbon Ti_0.7In_0.3O₂ used as a novel functionalised co-catalytic support for Pt. This approach is based on the novel nanostructure Ti_0.7In_0.3O₂ support with “electronic transfer mechanism” from Ti_0.7In_0.3O₂ to Pt that can modify surface electronic structure of Pt, owing to a shift in the d-band centre of the surface Pt atoms. The 20 wt% Pt/Ti_0.7In_0.3O₂ catalyst shows high activity than that of that of the commercial 20 wt% Pt/C (E-TEK). Our data suggest this enhancement is a result of both the electronic structure change of Pt upon its synergistic interaction with Ti_0.7In_0.3O₂ and the inherent structural and chemical stability and the corrosion-resistance of the Ti_0.7In_0.3O₂ in acidic and oxidative environments.