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.     

Synthesis and crystal structure of the iridium(I) carbene complex with a pair of hydrogen wing tips

The iridium(I) cyclooctadiene complex with two (3-tert-butylimidazol-2-ylidene) ligands [(H-Im^tBu)₂Ir(COD)]⁺PF₆^? (C₂₂H₃₂PF₆IrN₄) has been prepared, and its crystal structure is determined by X-ray diffraction. Complex exhibits slightly distorted square planar configurations around the metal atom, which is coordinated by two H-Im^tBu ligands and one cyclooctadiene group. The new iridium carbene complex has a pair of hydrogen wing tips. The Ir?C_carbene bond lengths are 2.066(5) and 2.052(5) Å, and the bond angle C?Ir?C between these bonds is 95.54(19)°. The dihedral angle between two imidazol-2-ylidene rings is 86.42°.     

Synthesis and Photophysical Properties of Cationic Iridium Complexes using Oxazoline based Ancillary Ligands for Lighting Applications

In this study, we report the design, synthesis and characterization of two new cationic iridium(III) complexes employing oxazole based ancillary ligand, namely, and [Ir(ppz)₂(mbdiho)]PF₆ (Complex 1) and [Ir(dfppy)₂(mbdiho)]PF₆ (Complex 2) and its use in light-emitting electrochemical cells (LECs). The design is based on 2-phenylpyrazole (ppz) and 2-(2,4-difluorophenyl)pyridine (dfppy) as cyclometalating ligands and 2,2-Methylenebis[3a,8a-dihydro-8H-indeno[1,2]oxazole] (mbdiho) as ancillary ligand. The effect of substituents in the cyclometalating ligands on the photophysical and electrochemical properties of the complexes has been investigated. The synthesized complexes were used for the fabrication of LEC devices and studied their electroluminescent properties. The complexes incorporated LECs resulted in a higher luminance of 2820 cd m^?2 and current efficiency of 1.04 cd A^?1 for Complex 2 than Complex 1. Our work suggests that the light emission of cationic iridium complexes can easily tuned by the substituents present on the cyclometalating ligands which resulted in yellow and green emission for LECs based on Complexes 1 and 2, respectively.     

Synthesis and Nonlinear Optical Properties of Novel Polyester Containing Nitrophenylazonitroresorcinoxy Group

A new X-type polyester (4) containing nitrophenylazonitroresorcinoxy groups as NLO chromophores, which are components of the polymer backbone was prepared. Polyester 4 is soluble in common organic solvents such as N,N-dimethylformamide and dimethylsulfoxide. It shows a thermal stability up to 280°C from thermogravimetric analysis with glass-transition temperature (T_g) obtained from differential scanning calorimetry near 120°C. The second harmonic generation (SHG) coefficient (d₃₃) of poled polymer films at the 1064 nm fundamental wavelength is around 5.08 × 10^?9 esu. The dipole alignment exhibits a thermal stability even at 5°C higher than T_g, and no SHG decay was observed below 125°C due to the partial main-chain character of polymer structure, which is acceptable for NLO device applications.     

Square-Planar trans-Bis-(1-p-n-octylphenylbutane-1,3-dionato) copper (II), a New Compound Exhibiting Three Kinds of ‘Double Melting’ Behaviour

The new compound, bis-(1-p-n-octylphenylbutane-1,3-dionato) copper(II) has four polymorphs, C¹ (m.p. 96°C), all having the same squareplanar trans structure. C¹, C^a, and C^m exhibit ‘double melting’ behaviour, i.e., they melt at their was observed only on very rapid heating, while that of C^a and C^m only on slow heating. Slow solid-solid phase transition from C¹ to C^h was observed at ca 50°C. Each polymorph could be obtained as a stable form at room temperature and gave a quite different X-ray diffraction powder pattern. The interrelationships of the four forms have been clarified by differential scanning calorimetric and micriscopic measurements. When the melt of the complex is rapidly cooled, it converts into a glassy state, which is stable at room temperature. The glass transition temperature T₈ and the crystallizing temperature T_e are very close to each other at 52.5°C and 58.0°C, respectively.     

Synthesis and Properties of Novel Nonlinear Optical Polyester Containing Cyanovinylnitroresorcinoxy Group

Novel X-type polyester 5 containing 4-(2’-carbomethoxy-2’-cyano)vinyl-6-nitroresorcinoxy group as nonlinear optical (NLO) chromophore, which constitutes parts of the polymer backbone, was prepared and characterized. Polyester 5 is soluble in common organic solvents such as N,N-dimethylformamide and acetone. Polyester 5 shows a thermal stability up to 280°C from thermogravimetric analysis with glass-transition temperature obtained from differential scanning calorimetry of near 116°C. The second harmonic generation (SHG) coefficient (d₃₃) of poled polymer film at the 1064 nm fundamental wavelength is 4.25 × 10^?9 esu. The dipole alignment exhibits a thermal stability even at 4°C higher than glass-transition temperature (T_g), and no significant SHG decay is observed below 120°C due to the partial main-chain character of polymer structure, which is acceptable for NLO device applications.     

Dinuclear Ir(III) Complex with an Unusual η<Superscript>1</Superscript>:η<Superscript>3</Superscript>-allylic Bridging Ligand from the Double C–H Activation of 2,5-Dimethylthiophene

Abstract  

The unique dinuclear Ir(III) complex (Cp*IrCl)(μ-H)[μ-(η¹:η³-C₆H₆S)](IrCp*) (1) has been synthesized and characterized by NMR spectroscopy (¹H and ¹³C), elemental analysis, and single crystal X-ray diffraction. It is the first structurally determined complex in which an activated thiophene ligand displays an η³-allylic interaction. 1 appears to form from successive C-H bond activations of 2,5-dimethylthiophene, resulting in its bridging the two iridium centers. The η³-allylic interaction occurs with one of the Ir centers and has Ir–C_thio bond lengths ranging from 2.133(5)-2.207(5) ?; the C–C double bond involved in the interaction has a bond length of 1.438(7) ? compared to 1.348(8) ? for the uncoordinated C–C double bond. The 3-carbon of the thiophene ring bridges both iridium centers with bond lengths of 2.036(5) ? and 2.208(5) ?. 1 crystallizes in space group P−1 with cell constants a = 8.6303(6) ?, b = 9.0153(6) ?, c = 18.1089(12) ?, α = 84.728(1)°, β = 87.534(1)°, γ = 64.373(1)°, and Z = 2. The structure was solved by direct methods and refined to R = 0.0363 (F ² > 2σ(F ²)) and wR = 0.0851 (F ²). The NMR data indicate the solution state structure is consistent with the solid state structure.     

Synthesis and Nonlinear Optical Properties of Novel Polyurethane Containing Cyanovinylnitroresorcinoxy Group

Novel X-type polyurethane 5 containing 4-(2′-carbomethoxy-2′-cyano)vinyl-6-nitroresorcinoxy groups as nonlinear optical (NLO) chromophores, which constitute part of the polymer backbone, was prepared and characterized. Polyurethane 5 is soluble in common organic solvents such as acetone and N,N-dimethylformamide. It shows thermal stabilities up to 260°C from thermogravimetric analysis with glass transition temperature obtained from differential scanning calorimetry near 108°C. The second harmonic generation (SHG) coefficient (d₃₃) of poled polymer film at 1064 nm fundamental wavelength is 9.83 × 10^?9 esu. Polymer 5 exhibits a high thermal stability even at 2°C higher than T_g, and no significant SHG decay is observed below 110°C, which is acceptable for nonlinear optical device applications.     

Effect of substrate temperature on the properties of vacuum evaporated indium selenide thin films

Thin films of InSe were obtained by thermal evaporation techniques on glass substrates maintained at various temperatures (T_sb = 30°, 400°C). X‐ray diffraction analysis showed the occurrence of amorphous to polycrystalline transformation in the films deposited at higher substrate temperature (400°C). The polycrystalline films were found to have a hexagonal lattice. Compositions of these films have been characterized by EDAX and the surface analysis by scanning electron microscopy. Optical properties of the films, investigated by using spectrophotometer transmittance spectra in the wavelength range (300 – 1100 nm), were explained in terms of substrate temperatures. Films formed at room temperature showed an optical band gap (E_g^opt) 1.56 eV; where as the films formed at 400°C were found to have a E_g^opt of 1.92 eV. The increase in the value of E_g^opt with T_sb treatment is interpreted in terms of the density of states model as proposed by Mott and Davis. The analysis of current ‐Voltage characteristics, based on space charge limited currents (SCLC) measurements, confirms the exponential decrease of density of states from the conduction band edge towards the Fermi level for both the amorphous and polycrystalline films. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis,Characterization and Crystal Structure of Iridium(III)bis(2-<Emphasis Type="Italic">p</Emphasis>-tolyl-benzothiazolato-N,C<Superscript>2</Superscript>)(acetylacetonate)

Abstract  A novel thiazole-based iridium (III) complex (iridium(III)bis(2-p-tolyl-benzothiazolato-N,C²)(acetylacetonate)) has been prepared and fully characterized by EA, IR, ¹H-NMR and MS. The molecular structure of the complex has been determined by single crystal X-ray diffraction analysis. The iridium (III) center adopts a distorted octahedral geometry with cis-O–O, cis-C–C, and trans-N–N chelate disposition. The complex crystallizes in the orthorhombic Pbca space group with cell parameters a = 10.1388(7) ?, b = 18.3565(12) ?, c = 31.021(2) ?, α = β = γ = 90 ° and Z = 8. The electronic absorption and emission spectra of this complex have been investigated. Index Abstract  A novel thiazole-based phosphorescent iridium (III) complex (iridium(III) bis (2-p-tolyl-benzothiazolato-N,C²)(acetylacetonate)) has been prepared and fully characterized by EA, IR, ¹H-NMR, MS and X-ray diffraction analysis.     

Electrical conductivity of pyrolyzed polyacrylonitrile

Abstract

Using ultrapure samples of polyacrylonitrile (PAN) of 485,000 or 150,000 average molecular weight solution cast in dimethylformamide, the dc conductivity ([sgrave]) of pyrolyzed PAN (PANP) films has been studied for pyrolysis temperatures (T_p) of 280-435°C. Conductivity measurements made during pyrolysis indicate the onset of a dramatic increase in [sgrave] for T_p of 390-435°C. Conductivities as high as 5 (ohm-cm)^?1 have been observed for T_p < 435°C. This situation contrasts sharply with previous literature which had indicated that a increased uniformly and monotonically with T_p for 200°C < T_p < 900°C and that values of [sgrave] > 1 (ohm-cm)^?1 were observed only for T_p > 600°C. Our results indicate that the maximum value of [sgrave] obtained is not a strong function of T_p (390°C < T_p < 435°C) or of molecular weight. However, the rate of increase of [sgrave](t) is strongly dependent on T_p in this range. After pyrolysis, repeated heating and cooling below T_p do not alter [sgrave](T). IR spectra show that the sudden increase in [sgrave] is correlated to the formation of conjugated C=C and C=N bonds. The shape of [sgrave](T) suggests that conduction is probably due to hopping.     

Synthesis and structure of iridium complex with thiocarbamide

A single crystal of the [Ir(Thio)₂Cl₄][Ir(Thio)₄Cl₂] compound synthesized by the reaction of K₃[IrCl₆] with thiocarbamide (Thio, SC(NH₂)₂) in a microwave field is investigated using X-ray diffraction. The compound crystallizes in the monoclinic crystal system with space group Cc(C _s ⁴ ). The unit cell parameters are as follows: a = 13.554(1) Å, b = 8.251(1) Å, c = 24.992(2) Å, β = 92.58(1)°, V = 2791.87(10) ų, and Z = 4. The compound has an island structure with two crystallographically independent iridium atoms. Thiocarbamide is coordinated to the central atom through the sulfur atom. The coordination sphere of the Ir(1) atom involves two Cl atoms and four S atoms, whereas the coordination sphere of the Ir(2) atom consists of four Cl atoms and two S atoms. The assignment of the bands in the IR absorption spectrum of the synthesized compound is presented. The thermal behavior of the compound in air is investigated.     

The effects of oxygen,hydrogen and fluorine on the conductivity of high purity evaporated amorphous silicon films

Electron bombardment evaporation was used to deposit amorphous silicon (α-Si) films in an evaporator with a base pressure of 2 × 10^?10 Torr. Rutherford backscattering analysis was used to establish the conditions necessary for deposition of pure films.The DC conductivity was measured as a function of temperature (? 150°C to + 140°C). Pure films, which were deposited between room temperature and 400°C, were found to have a room temperature conductivity (σ_RT) in the region of 10^?3μ^?1cm^?1 and a log $\text{σα}\text{T}{}^{\mathrm{<mtext>1</mtext><mtext>4</mtext>}}$ dependence. The value of σ_RT could be reduced by annealing reaching a minimum of 2 × 10^?7μ^?1 cm^?1 for an anneal temperature (T_A) of 520°C, but activated conduction was not observed.The implantation of hydrogen or fluorine (or contamination with oxygen) had the effect of reducing σ_RT, with a minimum value of less than 10^?8μ^?1cm^?1 (T_A = 400°C) for fluorine implantation to a dose of ≈ 10¹⁶ cm² (≈ 0.4 at% concentration). These films had high temperature (50°C) activation energies typical of activated conduction in extended states on the edge of the mobility gap. Implantation of fluorine to a dose of 1.5 × 10¹⁷ resulted in a rise of σ_RT (T_A = 400°C) to nearly 10⁴μ^?1 cm^?1 and log $\text{σα}\text{T}{}^{\mathrm{<mtext>?1</mtext><mtext>4</mtext>}}$ behaviour.X-ray analysis revealed that some crystallization occurred in films annealed at 600°C. This is correlated with a rise in σ_RT of the pure films and the disappearance of the effects of the introduced impurities.     

In‐Line Bulk Concentration Measurement by Method of Conductivity in Industrial KDP Crystal Growth from Aqueous Solution

The conductivity of KH₂PO₄ (KDP) aqueous solutions with varying saturation temperature from 28.5°C to 41.8°C was measured in the temperature range of 30°C to 40°C. It's proposed that the conductivity of KDP solutions can be expressed by L=L_o+b₁T+b₂T². This relation can be interpreted by Falkenhagen's (1971) conductivity model of high concentration electrolyte solution. The experimental data agrees well to the relation with an accuracy of super‐saturation within ±0.03g KDP/100g water (±0.10% relative super‐saturation).     

Synthesis and characteristics of multi-aryl substituted molecular glasses bearing biphenyl core

Two novel compounds based on biphenyl structure, 2,2′-di(3,5-di(tert-butylcarbonate)phenyl)-4,4′-di(tert-butylcarbonate)biphenyl (A) and 2,2′,4,4′-tetra(3,5-di(tert-butylcarbonate)phenyl)biphenyl (B) were synthesized by commercially available materials. The products were fully characterized by FTIR, NMR and elemental analysis. The thermal stability and the phase transition of these compounds had been studied by TGA and DSC techniques. For compound A, thermal decomposition temperature was of 176 °C and glass transition temperature (T_g) was of 105 °C. While for compound B, the thermal decomposition occurred at 186 °C and T_g was of 122 °C. The synthesized compounds were found to be amorphous materials by XRD analysis and good film-forming ability by AFM analysis. These results indicated that the synthetic molecular glasses would be suitable for low molecular weight photo resists in EUV lithography.     

Effect of Fluoride and Sodium Ions on Structural and Thermal Properties of γ-Al2O3

The structural properties of alumina as well as its fluoride and sodium modifications were characterized by X-ray diffraction, infrared spectroscopy and differential thermal analysis. We have shown, that fluoride ions interact with hydroxyls type Ia of γ-Al₂O₃ forming Al–F species, which then react at 400 °C forming β-Al₂O₃. Morever, F/Al₂O₃ sample heated up to 400 °C contain two acidic hydroxyls type IIa and III, which are also represented on a differential thermal curve as endoeffect with minima at 470 and 500 °C. For Na/Al₂O₃ sample the same types of hydroxyls interact with Na⁺ ions leading to substitution of their protons. After heating at 400 °C this sample contains also hydroxyls type IIa and III, which are represented by two endothermal effects with minima at 450 and 520 °C. Differential thermal analysis shown to be a powerful and simple technique to characterize surface hydroxyl types of Na and F samples supported on γ-alumina.     

Effect of OH-content on thermal and chemical properties of SnOP2O5 glasses

Glasses with 55–60 mol% SnO and 40–45 mol% P₂O₅ have shown extremely large differences in the chemical and thermal properties depending on the temperature at which they were melted. Glasses prepared at low melting temperature, 450–550 °C, had low T_g, 150–200 °C, and low chemical stability. Glasses prepared at high melting temperature, 800–1200 °C, had much higher T_g, 250–300 °C, and much higher chemical stability. No significant differences were found by ¹¹⁹Sn Mössbauer and ³¹P Nuclear Magnetic Resonance spectroscopy. Large differences in the OH-content could be detected as the reason by infrared absorption spectroscopy, thermal analyses, and ¹H Nuclear Magnetic Resonance spectroscopy. In samples with low T_g, a broad OH – vibration band around 3000 nm with an absorption intensity >20 cm^?1, bands at 2140 nm with intensity ～5 cm^?1, at 2038 nm with intensity ～2.7 cm^?1, and at 1564 nm with intensity ～0.4 cm^?1 were measured. These samples have shown a mass loss of 3–4 wt% by thermal gravimetric analyses under argon in the temperature range 400–1000 °C. No mass loss and only one broad OH-band with a maximum at 3150 nm and low absorption intensity <4 cm^?1 could be detected in samples melted at high temperature, 1000–1200 °C, which have much higher T_g, ～300 °C, and much higher chemical stability.     

Synthesis of stoichiometric LiNbO3 nanopowder through a wet chemical method

Stoichiometric lithium niobate powder which are used as feeding material in near stoichometric LiNbO₃ crystal growth have been successfully prepared from commercial niobium hydroxide [Nb(OH)₅] and nontoxic DL‐malic acid by a wet chemical method. The synthesis temperature was pre‐determined by the results from thermogravimetric and differential thermal analysis. The structure and morphology of the as‐prepared samples were observed by using the infrared spectroscopy and the scanning electron microscopy. The X‐ray diffraction experiment showed that lithium niobate powder had an ilmenite structure, and its unit cell parameters were calculated to be a = b = 0.5140 nm, c = 1.3738 nm, and V = 0.3144 nm³. The melting point of the synthesized powder is 1239 °C and Curie temperature T_c is 1122 °C. This synthesis method would be helpful to grow the near‐stoichiometric LiNbO₃ crystal with double crucible techniques. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Temperature Function of Birefringence and Structural Changes in Carbazole Crystal

With a modified quarter-wave Sénarmont compensator, exact measurements of the optical path difference have been carried out in (010) plates of carbazole, C₁₂H₉N, in the temperature range 20 < T < 190°C. At a temperature near 155°C distinct anomaly has been found corresponding to crystal-to-crystal phase transformation. The birefringence changes are discussed in terms of temperature dependence of density and orientation of molecules in the unit cell due to thermal expansion of the crystal.     

Thermal conductivity and refractive indices of Nd:GdVO4 crystals

The thermal conductivities of Nd:YAG, M(Y,Gd)VO₄ crystals were measured at 298 K. The value of Nd:GdVO₄ crystal along <001> direction was 11.4 W/mK, which was higher than that of YAG crystal measured to be 10.7 W/mK. The principal refractive indices of Nd:GdVO₄ crystal in the temperature range from 20 °C to 170 °C were determined by auto‐collimation method. Based on the measured values of refractive indices, the Sellmeier equation and expression of temperature dependence of refractive indices have been obtained. The measured results show that the birefringence Δn is 0.22007 at 20 °C and temperature coefficient of birefringence is 4.33 × 10⁻⁶/°C for 1.064 μm. These results prove that the GdVO₄ crystal is a laser crystal with excellent thermal and birefringence properties. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)