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.     

Calcium-free Solid Solutions in the System Ba<Subscript>7</Subscript>F<Subscript>12</Subscript>Cl<Subscript>2−x</Subscript>Br<Subscript>x</Subscript> (x < 1.5), a Single-component White Phosphor Host

We have recently prepared solid solutions of Ba_～6.3Ca_～0.7F₁₂Cl_2?xBr_x with x ranging from 0 to 2. In this work, the synthesis and single crystal X-ray structure of calcium-free crystals of Ba_～6.9Na_～0.2F₁₂Br_0.6Cl_1.4 (space group P6₃/m, a = 10.6024(10), c = 4.2034(4) Å), Ba_～6.9Na_～0.2F₁₂Br_1.4 Cl_0.6 (space group P6₃/m, a = 10.6155(9), c = 4.2355(4) Å) and Ba_～6.9Na_～0.2Br_1.32Cl_0.68F₁₂ (space group P6₃/m, a = 10.6218(9), c = 4.2284(4) Å) are reported.These crystals systematically present additional electron density at the 0 0 0.25 position which is associated with the presence of small, but significant amounts of Na⁺ ions in the crystal.     

Highly Luminescent Red Phosphorescent OLED with Interfacial Layers for Hole Transport and Electron Injection

Four kinds of red phosphorescent organic light-emitting devices were fabricated and compared to investigate the effect of interfacial layers for hole transport and electron injection. 1 nm-thick LiF in the device A and C and 1 nm-thick Cs₂CO₃ in the device B and D were deposited as an electron injection layer between the anode and the electron transport layer, and 5 nm-thick layer of dipyrazion[2,3-f:2′,2′-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile[HATCN] was inserted as a hole transport interfacial layer between the hole injection layer and the hole transport layer only in the device C and D. Under a luminance of 1000 cd/m², the power efficiencies were 7.6 lm/W and 8.5 lm/W in the device A and B, and 8.6 lm/W and 13.4 lm/W in the device C and D. The quantum efficiency of the device D was 15.8% under 1000 cd/m² which was somewhat lower than those of the device A and C, but a little higher than that of the device B. The luminance of the device D was much higher than those of the other devices at a given votage. The luminance of the device D at 7 V was 23,710 cd/m², which was 13.0, 3.4, and 4.0 times higher than those of the device A, B, and C at the same voltage, respectively.     

Study of the surface state density and potential in MIS diode Schottky using the surface photovoltage method

ABSTRACT

The effects of surface preparation and illumination on electric parameters of Au/GaN/GaAs Schottky diode were investigated. The thin GaN film is realized by nitridation of GaAs substrates with different thicknesses of GaN layers (0.7 – 2.2 nm). In order to study the electrical characteristics under illumination, we use an He-Ne laser of 632 nm wavelength. The I(V) current- voltage, the surface photovltage SPV measurement were plotted and analysed taking into consideration the influence of charge exchange between a continuum of the surface states and the semiconductor. The barrier height Ф_Bn, the serial resistance R_s and the ideality factor n are respectively equal to 0.66 eV, 1980 Ω, 2.75 under dark and to 0.65 eV, 1160 Ω, 2.74 under illumination for simple 1 (GaN theckness of 0.7 nm). The interface states density N_ss in the gap and the excess of concentration δn are determined by fitting the experimental curves of the surface photovltage SPV with the theoretical ones and are equal to 4.5×10¹² eV^?1 cm^?2, 5×10⁷ cm^?3, respectively, for sample 1 and 3.5×10¹² eV^?1 cm^?2, 7×10⁸ cm^?3 for sample 2 (GaN theckness of 2 nm). The results confirm that the surface photovoltage is an efficient method for optical and electrical characterizations.     

The field effect in amorphous chalcogenides: An investigation of localized states and electronic transport

The temperature dependence of the field effect response permits an unambiguous determination of the identity of those states responsible for electrostatic screening in the amorphous chalcogenides. We observe (1) in As₂Te₃, field effect screening by localized states at the Fermi level at low temperatures (～ 10¹⁹ cm^?3 eV^?1) and by mobile charge carriers (～ 10¹⁸ cm^?3 at 300 K) at high temperatures, and a transition from p-type to two-carrier (primarily n-type) conductivity as the temperature is raised above ～320 K; (2) in As₂SeTe₂, screening by mobile charge carriers (～ 10¹⁸ cm^?3 at 300 K) with strongly type conductivity; (3) in As₂Se₂Te, screening by localized states at the Fermi level (～ 10¹⁹ cm^?3 eV^?1) with strongly p-type conductivity; and (4) in Sb₂Te₃, a very high density of localized states at the Fermi level (～ 2 × 10²⁰ cm^?3 eV^?1) with both electron and hole contributions to the conductivity. Correlation with thermoelectric power results suggests that the p-type conductivity in As₂Te₃ is due to near-equal contributions from two processes: hopping in localized states plus extended state conduction. Aging and annealing behavior is described with the aid of a “chaotic potential model” that appears to be able to account for large changes in mobile carrier density that leave the conductivity unaltered.     

Enhancement of organic thin-film solar cells by incorporating hybrid Au nanospheres and Au nanorods on a metallic grating surface

Abstract

In this study, we demonstrate the fabrication of hybrid plasmonic solar cells using gold nanoparticles (AuNPs). Two types of AuNPs, gold nanospheres (AuNSs) and gold nanorods (AuNRs), were incorporated in a hole transport layer (HTL) (PEDOT:PSS) on a metallic grating electrode. The organic solar cells (OSCs) structure comprised an indium-tin-oxide (ITO)-coated glass substrate/PEDOT:PSS:AuNSs:AuNRs/P3HT:PCBM/Al grating electrode. Adding AuNPs induced localized surface plasmon resonance (LSPR), while grating structured Al at the interface with a photoactive layer excited the propagating surface plasmons. Compared with a flat reference device, the proposed OSCs exhibited improved photovoltaic properties by increasing both the short-circuit current density (J_SC) and the power conversion efficiency (PCE) with large enhancements of 16.23% and 14.06%, respectively. The efficiency improvement was attributed to increased broadband absorption and improved electrical properties inside the thin-film devices.     

Structural characterization and excited-state properties of luminescent <Emphasis Type="Italic">Tris</Emphasis>-(μ -3-methyl-5- trifluoromethylpyrazolato)trigold(I)

Tris-(-(3-methyl-5-trifluoromethylpyrazolato)-N:N)triangulo-trigold(I), (3,5-tfmpz)₃ Au₃, has been synthesized and exhibits a planar nine-member ring containing a central gold triangle with an average intramolecular Au–Au distance of 3.3455(8) Å. The complex crystallizes in the monoclinic space group Cc with a = 12.998(2) Å, b = 22.910 (3) Å, c = 7.217(1) Å, and = 104.781(1). The solid-state structure consists of sheets of (3,5-tfmpz)₃Au₃ units stacked in an offset fashion along the c axis such that one gold atom in each Au₃ unit (Au1) lies approximately over the midpoint of the Au1–Au3 edge of the triangle in the layer below it. The intermolecular Au–Au distances are between 3.880(1) and 4.023(1) Å, which are too long for there to be significant intertrimer bonding interaction suggesting that any supramolecular organization may be due to hydrogen-fluorine and fluorine-fluorine interactions between the molecules. The complex exhibits excitation-dependent emission at room temperature in the solid state. The structured higher energy emission (_em = 468, 517, and 556(sh) nm) is believed to be a ligand-centered ^* transition with a lower energy unstructured emission (_em = 658 nm) assigned to the classical Au–Au excited state transition.     

Electrical properties of semi-insulating CdTe0:9Se0:1:Cl crystal and its surface preparation

CdTe_0.9Se_0.1:Cl crystals doped with chlorine at 5×10¹⁷ cm^?3 level were grown by the vertical Bridgman method. The composition of Se throughout the ingot was nearly constant at x=0.110±0.016. The electrical resistivity of CdTeSe:Cl was 4.5×10⁹ Ω cm. Chemical etchants were employed to obtain stoichiometric and flat surfaces for electrode deposition, and the effects of the etchants on CdTeSe surfaces were analyzed by photoluminescence (PL) and AFM with different bromine concentrations and etching times. The mobility-lifetime products of electron and hole in CdTeSe:Cl crystals were of the order of ～10^?2 cm²/V and its values are greater than those for CdTe crystals. The energy resolution of a CdTeSe:Cl detector was tested using a ²⁴¹Am radioactive source.     

Crystal and molecular structure ofN-methylphenazinium bis(maleonitriledithiolato)gold(III), [NMP]+[Au(mnt)2]−

The crystal and molecular structure of the title compound, C₂₁H₁₁N₆S₄Au, is reported. The crystals are triclinic:P¯1,Z=2,a=7.739(1),b=8.415(1),c=17.815(1) Å,a=101.31(1),=86.20(1), =98.17(1)°. The structure was solved by the heavy-atom method, and refined by full-matrix least squares toR=0.046. Both the Au(mnt) ₂ ^– and NMP⁺ ions are planar, and form a kind of mixed stack alonga, with slightly alternating NMP⁺-Au(mnt) ₂ ^– distances of 3.46(8) and 3.59(5) Å.     

Crystal structure of a pentanuclear gold-silver cluster complex

The title compound, [C₁₆H₃₆N]⁺[C₄₈H₃₀Au₃Ag₂]^–, crystallizes in the triclinic space groupP1^–1, witha=18.199(12),b=19.210(8),c=19.270(9)Å,=71.34(3)°=76.43(4)° =72.95(5)° andZ=4, with two independent molecules in the asymmetric unit. The structure was solved by direct methods and refined by full-matrix least squares methods toR=0.072 for 3739 observed reflections. The metal atoms have a trigonal-bipyramidal arrangement with the three Au atoms forming an equilateral triangle and two Ag atoms occupying apical positions. Each Au atom is -bonded to phenylethynyl ligands in a linear coordination. Each Ag atom is asymmetrically pi-bonded to three alkyne groups. The Au-Au distances lie in the range of 3.934–4.010 A, indicating the lack of Au-Au bond.     

Synthesis and Characterization of the Osmium Compound <Emphasis Type="Italic">cis</Emphasis>(CO)<Emphasis Type="Italic">–</Emphasis>ClOs(CO)<Subscript>2</Subscript>(bpcd)[C(O)Et]

Photochemical activation of the triosmium cluster Os₃(CO)₁₂ in CH₂Cl₂ solvent and ethylene, followed by treatment with the diphosphine ligand 4,5-bis(diphenylphosphino)-4-cyclopenten-1,3-dione (bpcd), furnishes the new octahedral compound cis(CO)–ClOs(CO)₂(bpcd)[C(O)Et] in low yield. The title compound has been isolated and characterized in solution by IR and ¹H NMR spectroscopies, with the solid-state structure of cis(CO)–ClOs(CO)₂(bpcd)[C(O)Et] determined by X-ray diffraction analysis. cis(CO)–ClOs(CO)₂(bpcd)[C(O)Et] crystallizes in the triclinic space group P-1, a = 10.043(2), b = 11.455(2), c = 16.221(3) Å, α = 74.900(3)°, β = 76.150(3)°, γ = 76.221(2)°, V = 1718.2(5) ų, Z = 2, D _cacl = 1.717 Mg/m³; R = 0.0453, R _w = 0.0778 for 6703 observed reflections with I > 2σ(I). The presence of the chlorine and propanioyl groups in cis(CO)–ClOs(CO)₂(bpcd)[C(O)Et] is structurally confirmed, and the origin of the these groups from the reaction solvent and ethylene is discussed.     

Effects of tantalum doping on microstructure and ferroelectric properties of Bi4Ti3O12 thin films prepared by a sol–gel method

Tantalum-substituted Bi₄Ti₃O₁₂ (Bi₄Ti_3-x/5Ta_x/5O₁₂, BTTO) thin films were fabricated on Pt(111)/Ti/SiO₂/Si(100) substrates by sol–gel technology. The effects of various processing parameters, including Ta content (x=0～0.08) and annealing temperature (500～800 °C), on the growth and properties of thin films were investigated. X-ray diffraction analysis shows that the BTTO thin films have a bismuth-layered perovskite structure with preferred (117) orientation. With the increase of Ta content, the grain size of film decreased slightly, and highly (117)-oriented BTTO films were obtained in the composition of x=0.06. Ta doping on the B-site of Bi₄Ti₃O₁₂ could induce the distortion of oxygen octahedral and decrease the oxygen vacancy concentration by a compensating effect. The highly (117)-oriented BTTO thin films with x=0.06 exhibits the maximum remanent polarization (2P_r) of 50 μC/cm² and a low coercive field (2E_c) of 104 kV/cm, fatigue free characteristics up to ≧ 10⁸ switching cycles.     

Principal Electrical Conductivities in the Organic Conductors TEA.(TCNQ)2 and TTF.TCNQ: The Microwave Approach

Abstract

We describe a microwave technique to measure the directions and magnitude of the principal electrical conductivities and permittivities of organic conductors. The method is applied to single crystals of triethylammonium-bis 7,7,8,8-tetracyano-p-quinodimethane (TEA.(TCNQ)₂) and of tetrathiafulvalenium-7,7,8,8-tetracyano-p-quinodimethane (TTF.TCNQ). For the former, the apriori set of principal axes (a*, (a*∧c), c) is confirmed with principal conductivities of 430, 5.3 and 0.41–0.77 Ω^?1m^?1 respectively. The room temperature permittivities have been measured for the first time (ε*_α ～ 5.4–5.5, ε*_α∧c ～ 7.5). For the latter it is clearly shown that the principal electrical axes are (a, b, c*) and, in contrary to earlier d.c data, we observe σ_c· < σ<a which is more consistent with the anisotropy of interchain interactions in this compound. The observed transverse and longitudinal anisotropies (～3.3 10² and 2.8 10⁴ respectively) are larger than believed up to now.     

Crystal structure of the gold(I) complex [Au(tfp)Cl] with tfp = (C<Subscript>4</Subscript>H<Subscript>3</Subscript>O)<Subscript>3</Subscript>P

The Au(I) complex [Au(tfp)Cl] with tfp = (C₄H₃O)₃P has been prepared and characterised. It crystallises in the monoclinic P2₁/n space group with z = 4, a = 9.837(3), b = 12.684(4), c = 11.103(5)Å, = 91.58(2)° and V = 1384.8(2)ų. The structure of the complex consists of molecules connected in head-to-tail dimers by a metal-halogen contact as generally found in analogus complexes of lighter coinage metals. The typical feature of halogen gold compounds, the Au–Au interaction, seems prevented by the bulk of the tfp ligand.     

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).     

Charge transport in chlorine doped amorphous Se:Te xerographic photoreceptor films

Time-of-flight drift mobility experiments were carried out on a-Se_1?xTe_x (x = 0-0.1) with chlorine as an additive up to 70 atomic parts per million to investigate the charge transport mechanism in these xerographically important photoreceptor films. Hole drift mobility-temperature data indicate that hole transport in a-Se:Te alloys is controlled by a relatively discrete set of Te-introduced shallow traps (probably Te₁^? centres) at ～ 0.43 eV above E_v whose concentration increases nearly linearly with Te addition. Chlorine doping generates an additional set of traps (probably Cl₀^? centres) around the same energy as Te-induced traps in a similar fashion to the effect of Cl addition to a-Se. Electron drift mobility-temperature data for a-Se:Te alloys containing no Cl can also be interpreted by assuming Te-introduced electron traps at ～ 0.49 below E_c. There was no electron transport observable in Cl-doped a-Se:Te alloys.     

Synthesis and characterization of a layered chlorozincophosphate templated by protonated 4‐methylpiperidine

A chlorozincophosphate with the composition Zn(HPO₄)Cl·[C₆H₁₄N] has been synthesised under mild conditions in water medium in presence of 4‐methylpiperidine as organic template. The structure was determinated by single crystal X‐ray diffraction. The unit cell is orthorhombic (space group Pcab) with a = 8.743(9), b = 9.592(6), c = 26.573(6) Å, Z = 8 and V = 2228.91(12) ų. The structure involves a network of ZnO₃Cl and PO₃(OH) tetrahedra forming macroanionic inorganic layers with four and eight‐membered rings. Charge balance is achieved by the protonated amine which is trapped in the interlayers space and interacts with the organic framework through hydrogen bonding. Solid state ³¹P and ¹³C MAS‐NMR spectroscopies are in full agreement with the X‐ray structure. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

New data on the physical properties of Y3Al5O12-based nanocrystalline laser ceramics

Microhardness and fracture toughness of highly transparent Y₃Al₅O₁₂-and Y₃Al₅O₁₂: Nd³⁺-based nanocrystalline ceramics are measured for the first time. For the Y₃Al₅O₁₂: Nd³⁺ laser ceramics, the use of a longitudinal scheme with a diode-laser pumping at a wavelength of 1.3186 mm (⁴ F _3/2 → ⁴ I _13/2 channel) enabled one to attain an output power of continuous-wave lasing of ～3.7 W with 35% efficiency.     

Structural and optical spectroscopy of LiNbO3:Tm nanocrystals embedded in a SiO2 glass matrix

Transparent SiO₂:Li₂O:Nb₂O₅ glass doped with Tm³⁺ has been prepared by the sol–gel method, and heat-treated in air (HT) at temperatures between 500 and 800 °C. X-ray diffraction (XRD) patterns and Raman spectroscopy show SiO₂ and LiNbO₃ phases in samples HT above 650 °C, and a NbTmO₄ phase for T > 750 °C. The XRD SEM analysis show increasing particle size and number with the increase of HT temperature. Intra-4f¹² transitions due to Tm³⁺ ion dispersed in the matrix are observed in samples with T > 650 °C. The luminescence is dominated by the ¹G₄ → ³F₄ (～650 nm), ¹D₂ → ³F₃ (～780 nm), ³H₄ → ³H₆ (～800 nm), ³H₅ → ³H₆ (～1200 nm) and ³H₄ → ³F₄ (～1500 nm) transitions under resonant excitation to the ion levels.