Recent advances in organic light-emitting devices comprising copper complexes: A realistic approach for low-cost and highly emissive devices?

The past decades have driven a great deal of interest for developing low-cost electroluminescent devices. In this aim, highly emissive phosphors based on Earth-abundant metals and presenting the advantage of environment-benignancy are actively researched. Based on these requirements, copper(I) complexes have been identified as favorable candidates that could advantageously replace the well-established iridium(III) complexes.     

Two-dimensional π-conjugated molecules based-on 2,6,9,10-tetra(prop-1-yn-1-yl)anthracene and their application to solution-processed photovoltaic cells

Novel two-dimensional π-conjugated molecules, i.e., 5′,5″′-((9,10-bis((4-hexylphenyl)ethynyl)anthracene-2,6-diyl)bis(ethyne-2,1-diyl))bis(5-hexyl-2,2′-bithiophene) (2,6-HBT) and 5′,5″′-((2,6-bis((4-hexylphenyl)ethynyl)anthracene-9,10-diyl)bis(ethyne-2,1-diyl))bis(5-hexyl-2,2′-bithiophene) (9,10-THB) were successfully synthesized and utilized as highly soluble p-type organic semiconductors for organic thin film transistors (TFTs) and solar cells. From the TFTs, the high hole mobility of the pristine film of 9,10-THB was measured to be 0.07 cm² V⁻¹ s⁻¹ (I_on/off = 10⁶–10⁷), which is mainly attributed to slip-stacked charge-transport behavior in J-aggregation-induced crystallites. Further, a solution-processed solar cell made of 9,10-THB and PC₆₁BM exhibited very promising and reproducible power conversion efficiencies of 3.30% and 2.53% with composition 1:1 and 1:2 w/w ratio, respectively.     

Cooling rate controlled microstructure evolution and reduced coercivity in P(VDF–TrFE) devices for memory applications

We report on the tunability of ferroelectric properties of Poly(vinylidenedifluoride–trifluoroethylene) P(VDF–TrFE) thin films by controlling the cooling rate during transformation from high temperature paraelectric α-phase to low temperature ferroelectric β-phase. A faster cooling rate of P(VDF–TrFE) thin films leads to an increased polarization by 30% and much decreased coercivity by 60%. The origin of these improvements in the ferroelectric characteristics is attributed to evolution of a favorable microstructure and crystallographic alignment leading to (1 1 0) oriented films that are cooled faster. The microstructure of the films changes from a fine fibrous structure at fast cooling rate to a flatter ripple containing structure in the slow cooled samples. This dramatic change in the microstructure is attributed to the combination of incorporation of large stresses arising from almost 50% change in the molar volume of P(VDF–TrFE) upon α → β transformation and the cooling rate assisted stress relaxation, nucleation and growth. Infrared spectroscopy further showed that the substantial improvement in the device performance of the fast cooled samples arises from a favorable alignment of C–F dipoles due to short and ordered fibers lying on the substrate plane whose orientation becomes more random as the cooling rate is decreased.     

Ethylthio-substituted sandwich phthalocyaninato europium (III) semiconductors for sensing NO2 and NH3: Effect of the extended π-conjugate systems on tuning the conductivity and sensing behavior

By using the π-conjugated phthalocyanine macrocycle as the versatile building block, a series of five sandwich-type ethylthio substituted phthalocyaninato europium complexes, namely double-decker Eu[Pc(SC₂H₅)₈]₂ (Pc-1), triple-decker Eu₂[Pc(SC₂H₅)₈]₃ (Pc-2), and their corresponding dimers, [Pc(SC₂H₅)₈]₂Eu₂[BiPc(SC₂H₅)₁₂] (Pc-1@Pc-1), [Pc(SC₂H₅)₈]₃Eu₃[BiPc(SC₂H₅)₁₂] (Pc-1@Pc-2) and [Pc(SC₂H₅)₈]₄Eu₄[BiPc(SC₂H₅)₁₂] (Pc-2@Pc-2), are synthesized and prepared into the solution-processed films by a simple quasi-Langmuir-Shäfer (QLS) method. Combination between the extending π-conjugated system in the longitudinal and transverse directions of Pc macrocycles and/or radical nature of Pc-1 unit among different semiconducting molecules result in unusually small energy gaps (0.345–0.91 eV). Consequently, all of the semiconductors exhibit excellent conductivities. Among these materials, the conductivity for the radical species Pc-1@Pc-1, Pc-1@Pc-2 and Pc-1 is about 3–4 times larger than that for the non-radical compounds Pc-2@Pc-2 and Pc-2. Moreover, the QLS films of five semiconductors take excellent linear responses for both oxidizing NO₂ (100–300 ppb) and reducing NH₃ (4–8.6 ppm). Respectively, the sensitivity (in % ppm⁻¹) gets increased in the order of Pc-1 < Pc-2 < Pc-1@Pc-1 < Pc-1@Pc-2 < Pc-2@Pc-2 for NO₂, and Pc-1@Pc-2 < Pc-1 < Pc-1@Pc-1 < Pc-2@Pc-2 < Pc-2 for NH₃. Depending on the highly extended π-conjugated systems, Pc-2@Pc-2 and Pc-2 films achieve the highest sensitivity of 208.2% ppm⁻¹ and 0.97% ppm⁻¹ to NO₂ and NH₃, respectively. In addition, with a less than 2 min response time within a limit of detection at 10 ppb for NO₂ and 0.48 ppm for NH₃, good reproducibility and selectivity have been revealed for the Pc-2@Pc-2 and Pc-2 films among the best gas sensors obtained so far for all the solution-processed films based on organic semiconductors in dry air at room temperature. More importantly, it is firstly demonstrated that the high NO₂ sensing is resulted from low Oxd₁, and high NH₃ sensing is resulted from high Red₁ among the sandwich Pc-based semiconductors.     

Opportunities and challenges for Ge CMOS – Control of interfacing field on Ge is a key (Invited Paper)

Ge CMOS is very attractive for the post size-scaled Si-CMOS. However, we have to tackle a number of challenges with regard to materials and their interface control. In this paper, we discuss gate stack formation and source/drain engineering, as well as their implications for the performance of n- and p-MOSFETs. Because the Ge interface is significantly degraded by the GeO desorption occurring at a relatively low temperature (～500 °C), it is very hard to control Ge gate stack formation by a simple thermal budget control. In addition, strong Fermi-level pinning at the Ge/metal interface is a big problem in source/drain engineering. After discussing ways to control this desorption and Fermi-level pinning at the interface in both p-FETs and n-FETs, we discuss our current status of both electron and hole mobilities.     

Organic light-emitting devices based on new rare earth complex Tb(p-ClBA)_3phen

Since Tang and Vanslyke[1]reportedtheir doublelay-er device in 1987 ,the organic light emitting devices(OLEDs) have attracted more and more attention all o-ver the world because of their potential applications infull color flat panel displays .However ,th…     

Evanescent field absorption sensor for detection of copper(Ⅱ) in water using multimode optical fiber

The evanescent field absorption sensor for the detection of trace amount of copper (Ⅱ) in water is experimentally analyzed with the etched step index multimode plastic clad silica (PCS) fiber. The designed sensor is sensitive to copper (Ⅱ) content in water with a range up to 250 ppm.     

Reliability impact due to high current,lattice and hot carriers temperatures on β(2×2) matrix ESD power devices for advanced CMOS technologies

The main purpose of this paper is to present the behavior of a β^(2×2) matrix ESD power device with the effects of high ESD current, lattice and hot carriers temperatures. The beta matrix is a candidate for ESD device network for advanced CMOS technologies. This demonstrator is done in C45 & C32 nm CMOS technologies. The high ESD current, lattice temperature and hot carriers temperature are study thanks to 3D TCAD simulations in ACS stimulus. Thus, it is possible to identify the potential weakness point and optimize the topology of this kind of power device. Moreover, the IV curves are measured in TLP condition to determine the ESD response.     

An Improved Method of Synthesis for N-(3-acetyphenyl)Acetamide

3-acetaminoacephenone is synthesized from acetophenone by nitrating,reducing andacetylating through an improved method.The designed route is reasonable and the new procedure issimple.The overall yield is 43.1%,which is about 15% higher than literature reported,and the structureof the product is identified by IR,1~HNMR,MS and elemental analysis.     

Nanostructuring and Thermoelectric Characterization of (GaSb)3(1−x)(Ga2Te3) x

GaSb is a promising thermoelectric material that exhibits good electrical properties. However, it has a high lattice thermal conductivity (κ _lat). Nanostructured bulk materials have been attracting interest because they effectively scatter phonons, significantly reducing κ _lat. AgPb _m SbTe _m+2 (LAST-m) compounds have recently been reported to have low κ _lat. These compounds have a NaCl structure, similar to that of binary PbTe, where Ag and Sb occupy the Pb site. In these compounds, two divalent Pb atoms are replaced with a monovalent Ag atom and a trivalent Sb atom to maintain charge compensation. In the present study, we reduced κ _lat of GaSb by applying the same principle as in LAST-m. Specifically, we substituted Te for Sb and generated vacancies at the Ga site to maintain charge compensation. This produced compounds with chemical compositions of (GaSb)_3(1?x)(Ga₂Te₃) _x (x = 0, 0.05, 0.10, and 0.25), where GaSb and Ga₂Te₃ both have the zincblende crystal structure. We employed two different annealing conditions: annealing at 833 K followed by quenching, and annealing at 833 K followed by cooling to room temperature over 3 days. The former annealed samples with compositions of x = 0.05 and 0.10 had nanoscale Ga-rich precipitates and exhibited a large reduction in κ _lat.     

Growth and Characterization of TCNQ-Doped Ni(II)TAAB Thin Film As a New π-Conjugated Organic Semiconductor

Semiconductors - The aim of this work was to obtain a π-conjugated organic semiconductor with the macrocycle Ni(II)(TAAB) ([tetrabenzo (b, f, j, n) [1,5,9,13]tetraazacyclohexadecine]Ni(II) and...     

Thermal stability of lead-free CH3NH3SnxI3 systems (0.9 ≤ x ≤ 1.1) for photovoltaics

Methylammonium-tin-iodide (MASn_xI₃, 0.9 ≤ x ≤ 1.1) systems were prepared by precipitation process in aqueous solutions. The “as prepared” MASn_xI₃ systems exhibited a tetragonal crystalline phase (space group I4cm) with polyhedral crystallites (length 50–400 µm). The as prepared samples were annealed at T = 150 °C for t = 8 h under nitrogen and synthetic air. Under nitrogen, the CH₃NH₃Sn_xI₃ systems adopt nearly-cubic tetragonal structure (space group P4mm) with crystallites of 2–4 µm length whereas a degradation process with formation of non-crystalline phases occurred in air. The differential thermal analysis (DTA) profile in nitrogen revealed events at T = 247 °C, T = 297 °C (decomposition of CH₃NH₃Sn_xI₃ systems into methylamine (CH₃NH₂), hydroiodic acid (HI) and SnI₂), and in the range T = 342–373 °C (melting of SnI₂) respectively. The thermal profile in air showed endothermic events at T = 139 °C and T = 259 °C with additional events at onset temperatures of T = 337 °C and T = 423 °C respectively which correspond to the formation of Sn(IV)-O binds and to the decomposition of methylamine. Static thermogravimetry analysis (TG), performed at T = 85 °C and T = 150 °C for t = 2 h, revealed a linear weight loss as a function of the time. The optical absorption spectra displayed absorbance edges in near infrared range, at 1107.0 nm (x = 0.9), 1098.6 nm (x = 1.0) and 1073.2 nm (x = 1.1) respectively.     

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.     

Optical Waveguide Property of Nd-doped Laser Materials Nd_xY_(1-x)Al_3(BO_3) _4 and Nd∶MgO∶LiNbO_3

Lanthanide has attracted much attention in the field of optical communications in recent years. Some property analyses on optical waveguide of Nd doped crystal Nd x Y 1-x A1 3(BO 3) 4 and Nd∶MgO∶LiNbO 3 are made in this paper, followed by introduction of the methods of experimentation and theoretical calculation for the planar optical waveguides. The refractive index profiles of the optical waveguides are analyzed. The above work offers useful information for study on new type materials for optical communications.     

Performance Comparison of M-QAM Communications for (S + N) and (S/N) Channel State Estimation Schemes

Channel estimation at the receiver side is essential for adaptive modulation schemes, prohibiting low complexity systems from using variable rate (VR) and/or variable power transmissions. This problem can be solved using variable-rate M-QAM modulation scheme for communications over fading channels in the absence of channel gain estimation at the receiver. It is shown that signal plus noise (S + N) sampling value can serve as a much better criterion compared to signal-to-noise ratio (S/N) for determining modulation order in VR systems. In this way, low complexity transceivers use VR transmissions to improve spectrum efficiency under an error performance constraint. Two kinds of fading channels: Weibull fading and α–μ fading are considered. Spectrum efficiency of (S + N) based systems are compared to that of S/N systems and the advantage of (S + N) scheme over (S/N) scheme is shown. The symbol error rates of two schemes are also studied. As an application, the proposed VR modulation scheme is shown to work with a maximum ratio combining diversity receiver.     

Thermal expansion and thermal conductivity of In2S3 and CuIn5S8 compounds and (CuIn5S8)1 − x (In2S3) x alloys

Thermal expansion and thermal conductivity are studied in the respective temperature ranges 80–600 and 300–600 K for In₂S₃ and CuIn₅S₈ single-crystal compounds and (CuIn₅S₈)_{1 ? x} (In₂S₃) _x alloys grown by planar crystallization of the melt (the vertical Bridgman method). From the data, the thermal-expansion coefficient α _L is calculated. The dependences of the thermal-expansion coefficient α _L and the thermal conductivity χ on the composition parameter x are constructed. It is established that α _L linearly varies with x, whereas χ has a minimum at intermediate values of x.     

Short Range Magnetic Order From Spin-Polarized Photoelectron Diffraction and Holography: Experiment and Theory for MnO(001)

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