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Low band gap

Bahadur Singh, Barun Ghosh, Chenliang Su, Hsin Lin, Amit Agarwal, Arun Bansil
Materials with tunable charge and lattice degrees of freedom provide excellent platforms for investigating multiple phases that can be controlled via external stimuli. We show how the charge-ordered ferroelectric oxide Ag_{2}BiO_{3}, which has been realized experimentally, presents a unique exemplar of a metal-insulator transition under an external electric field. Our first-principles calculations, combined with a symmetry analysis, reveal the presence of a nearly ideal hourglass-Dirac-semimetal state in the nonpolar structure of Ag_{2}BiO_{3}...
November 30, 2018: Physical Review Letters
Samrat Ghosh, Reshma Raveendran, Akinori Saeki, Shu Seki, Manoj Ag Namboothiry, Ayyappanpillai Ajayaghosh
Organic semiconductors with variable charge carrier polarity are required for optoelectronic applications. Herein, we report the synthesis of three novel diketopyrrolopyrrole (DPP) based D-A molecules having three different terminal groups (amide, ester and dicyano) and studied their electronic properties. Increase in electron acceptor strength from amide to dicyano, leads to a bathochromic shift in absorption. Photoconductivity and field-effect transistor (FET) measurements confirmed that a small increase in acceptor strength can result in a large change in the charge transport properties from p-type to n-type...
December 13, 2018: ACS Applied Materials & Interfaces
Qichun Zhang, Xiaobing Fan, Jianhong Gao, Wei Wang, Shengqiang Xiao, Chun Zhan, Xinhui Lu
A ladder-type nonacyclic arene (bis(thieno[3,2-b]thieno)cyclopentafluorene (BTTF)) has been designed and synthesized through fusing thienothiophenes with the fluorene core from the synthon of dimethyl 9,9-dioctyl-2,7-bis(thieno[3,2-b]thiophen-2-yl)fluorene-3,6-dicarboxylate. With BTTF as the central donor unit, a novel acceptor-donor-acceptor (A-D-A) type non-fullerene small molecule acceptor (BTTFIC) was prepared with 1,1-dicyanomethylene-3-indanones (IC) as the peripheral acceptor units. The energy level of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of BTTFIC locate at -5...
December 10, 2018: Chemistry, An Asian Journal
Frederik Lohof, Alexander Steinhoff, Matthias Florian, Michael Lorke, Daniel Erben, Frank Jahnke, Christopher Gies
Nanolasers operate with a minimal amount of active material and low losses. In this regime, single layers of transition-metal dichalcogenides (TMDs) are being investigated as next generation gain materials due to their high quantum efficiency. We provide results from microscopic gain calculations of highly excited TMD monolayers and specify requirements to achieve lasing with four commonly used TMD semiconductors. Our approach includes band-structure renormalizations due to excited carriers that trigger a direct-to-indirect band-gap transition...
December 11, 2018: Nano Letters
Pierre Anthony Pantaleon Peralta, Ramon Carrillo-Bastos, Yang Xian
We examine the combined effects of a Kekulé coupling texture (KC) and a Dzyaloshinskii- Moriya interaction (DMI) in a two-dimensional ferromagnetic honeycomb lattice. By analyzing the gap closing conditions and the inversions of the bulk bands, we identify the parameter range in which the system behaves as a trivial or a nontrivial topological magnon insulator. We find four topological phases in terms of the KC parameter and the DMI strength. We present the bulk-edge correspondence for the magnons in a honeycomb lattice with an armchair or a zigzag boundary...
December 10, 2018: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Jun Hua Meng, Deng Gui Wang, Li Kun Cheng, Meng Lei Gao, Xing Wang Zhang
Featuring an absence of dangling bonds, large band gap, low dielectric constant, excellent chemical inertness, atomically thin hexagonal boron nitride (h-BN) is considered as an ideal candidate for the integration with graphene and other 2D materials. During the past years, great efforts have been devoted to the research area of h-BN based heterostructures from fundamental study to practical applications. In this review, we summarize the recent progress in the synthesis, novel properties and potential applications of h-BN based heterostructures, especially the synthesis technique...
November 22, 2018: Nanotechnology
Paul A Charpentier, Chao Chen, Koosha Azhie, Bernd Grohe, Md Abdul Mumin, Adria F Lotus, Patrick Therrien, Silvia Mittler
Visible region active photocatalytic coatings are of interest for antimicrobial activity in low light applications or those employing LED lights with limited UV content. This work examined Ag and Fe doped titania nanoparticles (nTiO2) with varying dopant ranges in polyaspartic polymer coatings for potential light and dark activity. First, the Ag and Fe doped nTiO2 were synthesized by sol-gel chemistry with varying dopant concentrations, then characterized with respect to their size and aggregate size distribution, crystallinity, and surface and band gap features...
November 30, 2018: Nanotechnology
Hamed Hedayati Kh, Edris Faizabadi
In this paper, transport properties, dwell time and electron conductance were theoretically investigated through a rectangular electrostatic potential barrier in bilayer phosphorene and compared the results with monolayer phosphorene and graphene. It has been shown that in bilayer phosphorene, in the presence of an interlayer induced bias, a four-band approximation describes transport process in the system. The results show that interlayer bias parameter drastically affect transport properties. These effects are including: (1) appearance of eight transmission and reflection coefficients from a band within the same band and between the two bands (2) appearing the anti-Klein tunnelling phenomenon and tuning the bias of system in such a way which is observed in specified biases and removed in other biases (3) tuning conductance of the system...
November 9, 2018: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Xin He, David J Singh, Patsorn Boon-On, Ming-Way Lee, Lijun Zhang
Dielectric screening plays an important role in reducing the strength of carrier scattering and trapping by point defects for many semiconductors such as the halide perovskite solar materials. However, it was rarely considered as a screen to find new electronic semiconductors. We performed a material search study using the dielectric properties as a screen to identify potential electronic materials in the class of metal-pnictide ternary sulfosalts, containing Bi or Sb. These salts are basically ionic due to the electronegativity difference between both the S and both the metal and pnictogen elements...
December 5, 2018: Journal of the American Chemical Society
Wei Jun Chen, Kai Bin Chu, Jun Ling Song
Organic-inorganic hybrid lead-based perovskite crystal materials have been widely studied due to their excellent optical-electronic properties. However, the toxicity of lead limits their widespread use. Here, a lead-free perovskite-type compound, tetrakis(1,2,3-trimethylimidazolium) di-μ3 -iodido-tetra-μ2 -iodido-decaiodidotetrabismuth(III), (C6 H11 N2 )4 [Bi4 I16 ], has been successfully synthesized by a simple solvothermal method. It exhibits a zero-dimensional (0D) tetrameric structure, including edge-sharing [Bi4 I16 ]4- distorted octahedra...
December 1, 2018: Acta Crystallographica. Section C, Structural Chemistry
Qadeer-Ul Hassan, Dou Yang, Jian-Ping Zhou, Yu-Xi Lei, Jing-Zhou Wang, Saif Ullah Awan
Novel multifeatured hollandite K1.46 Fe0.8 Ti7.2 O16 (KFTO) was synthesized by a simple hydrothermal method. Magnetic KFTO microrods were well controlled to long rectangular rods with pyramid-shaped tops. A KFTO growth mechanism was proposed on the basis of examining phase and morphology of the samples acquired at different reaction times. The KFTO morphology was confirmed by the calculated surface energies. The UV-vis diffuse reflectance spectra of KFTO microrods showed double absorption with band gaps of 2...
November 30, 2018: Inorganic Chemistry
Jyoti Shukla, M R Ajayakumar, Pritam Mukhopadhyay
The first successful Buchwald-Hartwig reaction at the naphthalenediimide core is reported, leading to the coupling of diverse secondary aromatic amines including dendritic donors. The G1-dendrimer-based donor exhibit blackish color, providing access to black absorbing systems. λonset values up to 1070 nm was achieved, which is the maximum from a single NDI scaffold. These dyes also manifest multielectron reservoir properties. A total of eight-redox states with a band gap of ∼0.95 eV was accomplished.
November 30, 2018: Organic Letters
Hyeong Jin Yun, Jaehoon Lim, Addis Fuhr, Nikolay S Makarov, Sam Keene, Matt Law, Jeffrey M Pietryga, Victor I Klimov
Colloidal quantum dots (QDs) have attracted considerable attention as promising materials for solution-processable electronic and optoelectronic devices. Copper indium selenium sulfide (CuInSexS2-x or CISeS) QDs are particularly attractive as an environmentally benign alternative to the much more extensively studied QDs containing toxic metals such as Cd and Pb. Carrier transport properties of CISeS-QD films, however, are still poorly understood. Here, we aim to elucidate the factors that control charge conductance in CISeS QD solids and, based on this knowledge, develop practical approaches for controlling the polarity of charge transport and carrier mobilities...
November 29, 2018: ACS Nano
Mehmet Akgul, Alper Ozgurluk, Clark T-C Nguyen
This part II of a two-paper sequence presents fabri-cation and measurement results for a micromechanical disk-based RF channel-select filter designed using the theory and procedure of Part I. Successful demonstration of an actual filter required sev-eral practical additions to an ideal design, including the introduc-tion of a 39nm-gap capacitive transducer, voltage-controlled fre-quency tuning electrodes, and a stress relieving coupled array de-sign, all of which combine to enable a 0.1%-bandwidth 223.4-MHz channel-select filter with only 2...
November 26, 2018: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
Nakul Jain, Urvashi Bothra, Dhanashree Moghe, Aditya Sadhanala, Richard Friend, Christopher R McNeill, Dinesh Kabra
By varying the concentration of a solvent additive, we demonstrate the modulation of intermolecular (donor:acceptor (D:A) interface) and intramolecular (bulk) disorder in blends of the low band gap polymer poly[2,6-(4,4-bis(2-ethylhexyl)-4H-cyclopental[2,1-b;3,4-b']-dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] (PCPDTBT) blended with [6,6]-Phenyl-C71-butyric acid methyl ester (PC71BM). Using the solvent additive concentration of 1,8-diiodooctane (DIO) in the host processing solvent, the disorder in the bulk and at the interface is studied in terms of Urbach energy, electroluminescence (EL) broadening and EL quantum efficiency (ELQE)...
November 29, 2018: ACS Applied Materials & Interfaces
Enrico Della Gaspera, Joseph Griggs, Taimur Ahmed, Sumeet Walia, Edwin L H Mayes, Arrigo Calzolari, Alessandra Catellani, Joel van Embden
Doping semiconductor nanocrystals is a powerful tool to impart new and beneficial optical and electrical properties to the host nanocrystals. Doping has been used to improve the performances of nanocrystal-based devices in applications as diverse as optics, magnetism, electronics, catalysis and sensing. In this work we present a low temperature colloidal synthesis of zinc sulfide (ZnS) nanocrystals doped with indium. Through optimization of the reaction parameters and the doping level, quantum confined (∼2 nm in size) crystalline colloids with highly tunable optical properties are achieved...
November 29, 2018: Nanoscale
Chien-Hung Wu, Kow-Ming Chang, Yi-Ming Chen, Yu-Xin Zhang, Yu-Hsuan Tan
In the past few years, thin film transistors have a wide range of applications on display technology, material selection and quality for its active layer is critical for device performance. Traditional amorphous silicon (a-Si) silicon has a lot of advantages such as good productivity, short process and low-cost. It also has a lot of shortcomings on these applications on TFTs such as photosensitivity, light degradation, and opacity, etc. The dispute of the material based on a-Si:H as an active layer in TFT is low field effect mobility (~1 cm²/V·S) (M...
April 1, 2019: Journal of Nanoscience and Nanotechnology
Chien-Hung Wu, Kow-Ming Chang, Yi-Ming Chen, Yu-Xin Zhang, Yu-Hsuan Tan
TFT panel production process can be divided into three kinds of technology. There have amorphous silicon (a-Si), low-temperature polysilicon (LTPS) and amorphous IGZO (a-IGZO) oxide. Traditional amorphous silicon (a-Si) silicon has a lot of advantages such as good productivity, short process and low-cost. It also has a lot of shortcomings on these applications on TFTs such as photosensitivity, light degradation, and opacity, etc. The dispute of the material based on a-Si:H as an active layer in TFT is low field effect mobility (~1 cm²/V·S) (M...
April 1, 2019: Journal of Nanoscience and Nanotechnology
Wageh Swelm, Ahmed Al-Ghamdi, Asim Jilani, Javed Iqbal
The synthesis of alloyed semiconductor quantum dots has produced structures that have distinct properties in comparison with both their bulk counterparts and their parent binary semiconductor quantum dots. In this work, the quantum confined structures of a ternary alloy of CdSe1- x S x were synthesized by one-pot synthesis method in an aqueous medium at a low temperature and capped with 3-mercaptopropoionic acid. Structures of the synthesized quantum dots were investigated by energy dispersive X-ray, X-ray diffraction, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy...
November 27, 2018: Nanomaterials
Jingjing Liu, Zhangbo Lu, Xianju Zhang, Yangyi Zhang, Haiguang Ma, Yang Ji, Xiangxing Xu, Linwei Yu, Jun Xu, Kunji Chen
Inorganic perovskites have emerged as a promising candidate for light-emitting devices due to their high stability and tunable band gap. However, the power consumption and brightness have always been an issue for perovskite light-emitting diodes (PeLEDs). Here, we improved the luminescence intensity and decreased the current density of the PeLEDs based on CsPbI₃ quantum dots (QDs) and p-type Si substrate through an alternating current (AC) driving mode. For the different driving voltage modes (under a sine pulsed bias or square pulsed bias), a frequency-dependent electroluminescent (EL) behavior was observed...
November 26, 2018: Nanomaterials
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