High Charge Transport Research Articles

Large-fused-ring-based D-A type electrochromic polymer with magenta/yellowish green/cyan three-color transitions.

Large-fused-ring-based conjugated polymers possess wide application prospects in optoelectronic devices due to their high charge transport and wide optical absorption. In this paper, three low-bandgap donor-acceptor (D-A) type polymers PBIT-X (X = 1, 2, 3) based on alkylated benzodithiophene and tris(thienothiophene) as donors and thiadiazol-quinoxaline as an acceptor were synthesized via Stille coupling polymerization at different (donor/acceptor) D/A molar feed ratios. The band gaps of PBIT-1, PBIT-2, PBIT-3 were 1.10 eV, 1.04 eV and 1.02 eV, respectively. Spectroelectrochemistry studies showed that the three D-A type polymers have dual bands located in visible and near-infrared regions in the neutral state. The three D-A type polymers possess good electrochromic properties, such as an optical contrast of 56% and response time of 0.3 s. In particular, PBIT-3 could achieve three color changes from magenta to yellowish green to cyan during the oxidation process. The results indicate that these D-A type conjugated polymers based on large fused-ring units exhibit multiple color changes, endowing them with huge potential applications in visible and near-infrared electrochromic devices.

Cobalt sulfide nanosheets decorated on polypyrrole nanowires for improved charge storage in supercapacitors

Nanostructured cobalt sulfide-based electrode materials for supercapacitors (SCs) still suffer from easy aggregation, sluggish reaction kinetics, and poor structural stability. To resolve these issues, we adopt a two-step electrochemical deposition method to fabricate CoS nanosheets decorated on polypyrrole (PPy) nanowires that grow directly on Ni foam. The PPy nanowires serve as supports for growing CoS nanosheets, which not only make the CoS nanosheets well dispersed but also reduce their size and thickness. In addition, the intensive interaction between CoS and PPy endows the nanoarchitecture with high mechanical strength. Therefore, the constructed [email protected] nanocomposites feature abundant electroactive sites, high charge transport and transfer efficiencies, a short ion diffusion distance, and good structural stability. As a result, the optimized [email protected] nanocomposites as SC electrodes demonstrate specific capacities of 860C g−1 at 1 A g−1 and 595C g−1 at 20 A g−1, as well as a 92% initial capacity retention after 5000 cycles at 10 A g−1. Furthermore, a fabricated asymmetric supercapacitor (ASC) device with [email protected] nanocomposites as the positive electrode realizes a specific energy of 51.1 Wh kg−1 at 800 W kg−1, suggesting a promising potential for their practical application in SCs. This work may provide a feasible strategy for fabricating other metal sulfide/conducting polymer nanocomposites with enhanced charge storage capabilities as SC electrodes.

Photovoltaic effect in metal foils and crystals of topological insulators

Bi and Bi-based crystals of topological insulators demonstrate high surface charge transport and a change in polarity due to the photovoltaic effect.

Facilitated charge transfer in ZnIn2S4@CuInP2S6 heterojunctions towards efficient photocatalytic H2 generation

Accelerating charge separation and migration in semiconductor photocatalysts is the key for acquiring high performance in the photocatalytic hydrogen generation reaction. In this work, a new ZnIn2S4/CuInP2S6 hetero-structured system (ZIS/CIPS) is designed and constructed. Owing to the presence of face-to-face hetero-interface with high charge-transport capability, the photocatalytic hydrogen generation rate of ZIS/CIPS dramatically enhanced (76.2 μmol h−1) under the visible-light irradiation, which is up to 13 and 190 times compared to that of ZnIn2S4 and CuInP2S6 (CIPS), respectively.

In situ Self-Catalyzed Growth of Manganese-Embedded 3D Flakes-Coated Carbon Rod as an Efficient Oxygen-Reduction Reaction Catalyst of Zinc-Air Batteries.

The in situ self-catalyzed growth of manganese-embedded 3D flakes-coated carbon rods (GFC) as an efficient oxygen-reduction reaction (ORR) catalyst of Zinc-air batteries is described for the first time. By optimizing the amount of Mn in the precursor, a series of 3D graphene-like flakes-coated carbon rods were synthesized. GFC with a doping amount of Mn of 10 % (GFC-10) exhibits excellent ORR performance with an onset potential of 0.94 V (vs. reversible hydrogen electrode). The Zinc-air battery is constructed with GFC-10 as the cathode catalyst, and it exhibits a peak power density of 128.9 mW cm-2 and a cycling stability of 75 h at a current density of 10 mA cm-2 , which are superior to the commercial 20 wt% Pt/C-based Zinc-air battery. Interestingly, the introduction of Mn facilitates the self-catalyzed growth of carbon rods, and the change of Mn amount can effectively regulate the morphology of materials. The improved ORR performance of the catalyst is ascribed to the synergistic effect of unique hierarchical porous structure, high-charge transport capacity, abundant carbon defects/edges and Mn-Nx sites. This research provides a new avenue to fabricating highly active Mn-based electrocatalysts for renewable energy systems.

Quadratic nodal point with large surface arc states in half-Heusler material ScBiPt

Recently, the research focus of topological states in electronic systems has been shifted from the conventional linear type to high order dispersion, in which more exotic physical properties are exhibited, such as high topological charge, large magnetoresponse and unusual transport behavior. In this work, based on first principles calculations, we proposed a quadratic nodal point semimetal, the half-Heusler material ScBiPt. Detailed band structures reveal that an ideal nodal point is present exactly at the Fermi level and, more importantly, it exhibits quadratic dispersion along all directions, which has also been confirmed from the symmetry analyzation and effective model argument. Moreover, when the spin orbital coupling effect is considered, the nodal point changes from triple to quadruple degeneracy but the quadratic dispersion is still maintained. Two prominent arc surface states are emanated from the nodal point and they are well separated from the bulk bands, making the future experimental verification extremely beneficial. Overall, the current quadratic nodal point material with multiple advantages can serve as an ideal platform and the relative studies can be immediately inspired and advanced.

Regulating Crystal Packing by Terminal tert-Butylation for Enhanced Solid-State Emission and Efficacious Charge Transport in an Anthracene-Based Molecular Crystal.

Organic semiconductors with combinative high carrier mobility and efficient solid-state emission are full of challenges but urgently pursued for developing new emerging optoelectronics. Herein, by delicately regulating the crystal packing of an anthracene-based molecular crystal via terminal tert-butylation, we developed a superior high mobility emissive molecule, 2,6-di(6-tert-butylnaphthyl)anthracene (TBU-DNA). The unique "slipped herringbone" packing motif of TBU-DNA enables its appropriate exciton-exciton coupling and electron-phonon coupling, thus resulting in remarkably high solid-state emission (photoluminescence quantum yield, ΦF ≈74.9 %) and efficacious charge transport (carrier mobility, μ=5.0 cm2 V-1 s-1 ). Furthermore, OLETs based on TBU-DNA show an external quantum efficiency (EQE) of 1.8 %, which is among the highest EQE values for single component OLETs reported till now. This work presents a crystal engineering strategy via exquisite molecular design to realize high mobility emissive organic semiconductors.

Type-I SnSe2/ZnS heterostructure improving photoelectrochemical photodetection and water splitting

Two-dimensional van der Waals heterostructures have been widely designed and applied to numerous optoelectronic devices such as photoelectrochemical (PEC)-type photodetectors, water splitting, and solar cells. The understanding of the influence of band alignment in type-I heterostructures on the photoelectric response remains incomplete yet essential for designing new optoelectronic devices. Herein, two-step physical vapor deposition is used to construct a type-I SnSe2/ZnS heterostructure, which is confirmed by ultraviolet photoelectron spectroscopy and X-ray photoelectron spectroscopy. The type-I heterostructure-based PEC-type photodetector exhibits excellent photoresponse, high stability, and high sensitivity in the ultraviolet-visible range. Furthermore, the photoresponsivity of SnSe2/ZnS is up to 172.60 µA W−1, which is 7.4- and 2.0-fold larger than that of pure ZnS and SnSe2, respectively. Moreover, the SnSe2/ZnS heterostructure possesses high photoelectrocatalytic activity in water splitting, and the total hydrogen production within 2 h is up to 81.25 µmol cm−2. The high PEC-type photodetector and water splitting performances in SnSe2/ZnS are due to the synergistic effect of high light utilization and efficient charge transport. Our work provides a new method for improving photoelectric response by forming type-I heterostructures and for designing high-performance optoelectronic devices for photodetectors and water splitting.

Hydrophenazine-linked two-dimensional ladder-type crystalline fused aromatic network with high charge transport

•A ladder-type hydrophenazine-linked 2D fused aromatic network (HP-FAN) was realized •The HP-FAN has an inherent semiconducting band gap along with a parallel flat band •The HP-FAN has high intrinsic electrical conductivity without doping •The HP-FAN exhibits a remarkable performance in electronic devices with high mobility Since the advent of graphene, the development of crystalline two-dimensional (2D) organic materials with semiconducting features has been extensively explored for their potential optoelectronic applications. Despite extensive progress in this field, it is still challenging to realize laterally extended organic materials with high electrical transport properties. Here, we report a 2D ladder-type fused aromatic network (FAN) in which backbones are composed of hydrophenazine (HP) linkage (designated HP-FAN). Consequently, its 2D extended delocalization of π-molecular orbitals imparts a semiconducting band gap and facilitates fast intra-chain charge transport. The as-prepared HP-FAN exhibits semiconducting features with calculated and experimental band gaps of approximately 1.44 and 1.54 eV, respectively, with an unusual flat band. The HP-FAN thin flakes, isolated by polydimethylsiloxane stamping, exhibit remarkable performance in a p-type field-effect transistor (FET) and a Hall effect device. Given its laterally extended ladder-type π-conjugated structure, the HP-FAN has extensive potential for applications in thin-film optoelectronic devices. Since the advent of graphene, the development of crystalline two-dimensional (2D) organic materials with semiconducting features has been extensively explored for their potential optoelectronic applications. Despite extensive progress in this field, it is still challenging to realize laterally extended organic materials with high electrical transport properties. Here, we report a 2D ladder-type fused aromatic network (FAN) in which backbones are composed of hydrophenazine (HP) linkage (designated HP-FAN). Consequently, its 2D extended delocalization of π-molecular orbitals imparts a semiconducting band gap and facilitates fast intra-chain charge transport. The as-prepared HP-FAN exhibits semiconducting features with calculated and experimental band gaps of approximately 1.44 and 1.54 eV, respectively, with an unusual flat band. The HP-FAN thin flakes, isolated by polydimethylsiloxane stamping, exhibit remarkable performance in a p-type field-effect transistor (FET) and a Hall effect device. Given its laterally extended ladder-type π-conjugated structure, the HP-FAN has extensive potential for applications in thin-film optoelectronic devices.

New material for addressing charge transport issue in DSSCs: Composite WS2/MoS2 high porosity counter electrodes

Dye-sensitized solar cells (DSSCs) are among the third generation of solar cells which require further development to find practical applications. One reason that prevents the widespread use of DSSCs is the high cost of their counter electrode (CE). This study proposes a new CE based on WS2/MoS2 material, which demonstrates an excellent performance due to its high electrocatalytic performance and charge transport properties. These qualities are achieved due to the increased active surface area of the composite material. Our champion cell achieved an efficiency of 7.30%, which shows respective improvements of 25% and 18% from the DSSCs fabricated from WS2 and MoS2 CEs. It also displays an efficiency improvement of 3.5% in comparison with the expensive platinum CE. These efficiency enhancements correspond to the increased current densities of the DSSCs as a result of better CE properties.

Molecular doped, color-tunable, high-mobility, emissive, organic semiconductors for light-emitting transistors.

Developing high-mobility emissive organic semiconductors with tunable colors is crucial for organic light-emitting transistors (OLETs), a pivotal component of integrated optoelectronic devices, but remains a great challenge. Here, we demonstrate a series of color-tunable, high-mobility, emissive, organic semiconductors via molecular doping with a high-mobility organic semiconductor, 2,6-diphenylanthracene, as the host. The well-matched molecular structures and sizes with efficient energy transfer between the host and guest enable the intrinsically high charge transport with tunable colors. High mobility with the highest value >2 cm2 V−1 s−1 and strong emission with photoluminescence quantum yield >15.8% are obtained for these molecular-doped organic semiconductors. Last, a large color gamut for constructed OLETs is up to 59% National Television System Committee standard, meanwhile with an extremely high current density approaching 326.4 kA cm−2, showing great potential for full-color smart display, organic electrically pumped lasers and other related logic circuitries.

How Halogenation Impacts the Polymer Backbone Conformation: Learning from Combination of Solid‐State MAS NMR and X‐Ray Scattering

AbstractOver the past decade, halogenated semiconducting polymers have attracted considerable interest due to their outstanding optoelectronic properties. Thus, in most of today's organic photovoltaic devices benchmark organic semiconductors are halogenated materials, either electron donor polymers or non‐fullerene acceptor (NFA) small molecules. However, the nature and position of the substituted halogen atoms in halogenated semiconducting polymers impact, through self‐assembly modification, their optoelectronic properties in a way that is difficult to predict. Yet, the solid‐state self‐assembling of these materials has been shown to be a key parameter toward high charge transport properties and photovoltaic efficiencies. In this context, there is still a need to develop analytical methods that will enable an atomic‐scale structural characterization of these materials as a function of the halogenation. In this study, the solid‐state nuclear magnetic resonance (NMR) under magic angle spinning (MAS) is explored as a tool to investigate the local structure and supramolecular organization of a series of conjugated polymers, specially designed for this study. Through a comprehensive study using complementary techniques, including MAS–NMR, small and wide‐angle X‐ray scattering, and molecular modeling investigations, the molecular conformation of these polymers in relation to their chemical composition, is successfully determined.

Design of Ni(OH)2/M-MMT Nanocomposite With Higher Charge Transport as a High Capacity Supercapacitor.

Nano-petal nickel hydroxide was prepared on multilayered modified montmorillonite (M-MMT) using one-step hydrothermal method for the first time. This nano-petal multilayered nanostructure dominated the ion diffusion path to be shorted and the higher charge transport ability, which caused the higher specific capacitance. The results showed that in the three-electrode system, the specific capacitance of the nanocomposite with 4% M-MMT reached 1068 F/g at 1 A/g and the capacity retention rate was 70.2% after 1,000 cycles at 10 A/g, which was much higher than that of pure Ni(OH)2 (824 F/g at 1 A/g), indicating that the Ni(OH)2/M-MMT nanocomposite would be a new type of environmentally friendly energy storage supercapacitor.

Multi-layered shielding materials for high energy space radiation

One of the biggest challenges of the human spaceship in deep space is the harmful space radiation environment. In this paper, we present a multi-layered shielding approach, which reduces the radiation exposures from the trapped radiation, Solar Particle Events (SPE), and Galactic Cosmic Radiation (GCR). We have used shielding materials namely aluminum (Al), Polyethylene (PE), Hydrogen stored boron nitride, Water, Polybenzoxazine, Epoxy, Kevlar, Zylon, Polyetherimide, Polysulfone, Lithium Hydride (LiH), Liquid Methane, and Hydrogenated Graphite Nanofiber (HGNF) respectively. The dose equivalent (DE) for each shielding material is calculated using an On-line Tool for the Assessment of Radiation In Space (OLTARIS) and High Charge and Energy TRaNsport (HZETRN) for 2010 Solar minimum GCR. In addition, the dose equivalent for the first Al slab of 10 g/cm2 followed by a different combination of materials slabs of 90 g/cm2 is analyzed. In multi-layered analysis, we observed that Al + LiH is more effective than remaining shielding materials. In addition, combinations of hydrogen, boron, and nitrogen-rich materials slabs behind the Al slab are studied. In this analysis, the dose equivalent reduction per unit thickness is higher in the first hydrogen-rich material slab of a shield than over any of the other materials slabs. In Sandwich combinations, PE, LiH, Liquid Methane, and Hydrogen stored boron nitride sandwiched between Al. Al + LiH + Al showed better performance. In addition, the dose equivalent was compared between OLTARIS and HZETRN transport codes.

Assembling Hollow Cactus-Like ZnO Nanorods with Dipole-Modified Graphene Nanosheets for Practical Room-Temperature Formaldehyde Sensing

Formaldehyde (HCHO) sensing plays a critical role for indoor environment monitoring in smart home systems. Inspired by the unique hierarchical structure of cactus, we have prepared a ZnO/ANS-rGO composite for room-temperature (RT) HCHO sensing, through assembling hollow cactus-like ZnO nanorods with 5-aminonaphthalene-1-sulfonic acid (ANS)-modified graphene nanosheets in a facile and template-free manner. Interestingly, it was found that the ZnO morphology could be simply tuned from flower clusters to hollow cactus-like nanostructures, along with the increase of the reaction time during the assembly process. The ZnO/ANS-rGO-based sensors exhibited superior RT HCHO-sensing performance with an ultrahigh response (68%, 5 ppm), good repeatability, long-term stability, and an outstanding practical limit of detection (LOD: 0.25 ppm) toward HCHO, which is the lowest practical LOD reported so far. Furthermore, for the first time, a 30 m3 simulation test cabinet was adapted to evaluate the practical gas-sensing performance in an indoor environment. As a result, an instantaneous response of 5% to 0.4 ppm HCHO was successfully achieved in the simulation test. The corresponding sensing mechanism was interpreted from two aspects including high charge transport capability of ANS-rGO and the distinct gas adsorbability derived from nanostructures, respectively. The combination of a biomimetic hierarchical structure and supramolecular assembly provides a promising strategy to design HCHO-sensing materials with high practicability.

Evaluating Shielding Materials for High Energy Space Radiation

Space radiation is very hazardously harmful to human health and physically damaging to electronics equipment. The major radiation sources are Solar Particle Events (SPE) and Galactic Cosmic Rays/Radiation (GCR). GCR composed of high energy protons, alpha particles and electrons travelling from outside solar system are especially difficult to shield. Previous study has been shown that aluminum and higher atomic number structural alloys, provide fairly little shielding which may increase secondary radiation. In this work, we evaluate the range of materials for GCR shielding. Materials are aluminum, for its low atomic number, Liquid Hydrogen, Polyethylene,Water, Polybenzoxazine, Lithium hydride, Liquid Methane and Hydrogenated Graphite Nano fiber (HGNF) materials which containing high proportions of hydrogen which effectively slowing secondary neutrons and GCR radiation. Boron nitride storing hydrogen absorbs the secondary neutrons, GCR, and SPE effectively. Liquid Methane performance is also noticeable. The dose equivalent for each shielding materials are calculated using On-line Tool for the Assessment of Radiation In Space (OLTARIS) and High Charge and Energy TRaNsport (HZETRN) and compared for 2010 Solar minimum GCR. The results show that Liquid hydrogen is the good space radiation shielding material for a given thickness, followed by Lithium Hydride, Liquid Methane, Boron nitride storing hydrogen, Polyethylene, Polybenzoxazine, HGNF, and then aluminum. In addition, we plotted dose equivalent for Liquid hydrogen and Polyethylene at different densities.

Conductive 2D Conjugated Metal–Organic Framework Thin Films: Synthesis and Functions for (Opto‐)electronics

Two‐dimensional conjugated metal–organic frameworks (2D c‐MOFs), possessing extended π–d conjugated planar structure, are emerging as a unique class of electronic materials due to their intrinsic electrical conductivities. Taking advantage of the large‐area flat surface, 2D c‐MOF thin films allow facile device integration with sufficient electrode contact, high device stability, and high charge transport, thereby emerging as appealing active layers for a broad range of electronic applications. Synthesis and device investigation of thin films are of great importance for their further development, which are systematically summarized in the current review. Here, the authors firstly introduce the molecular structures of representative 2D c‐MOFs and present the fundamental understanding on structure–property relationships. After that, the state‐of‐art synthetic methodologies toward high‐quality 2D c‐MOF thin films are summarized, including exfoliation and reassembly (ERA), liquid‐interface‐assisted synthesis (LIAS), and chemical vapor deposition (CVD). By considering the advantages of 2D c‐MOF films in device integration, remarkable progress in (opto‐)electronic device applications are discussed, such as field‐effect transistors (FETs), chemiresistive sensors, photodetectors, superconductors, and thermoelectrics. In the end, the remained challenges about the development of 2D c‐MOF films for (opto‐)electronics are highlighted and possible future directions are proposed to address these challenges.

Thermally Stable Organic Field-Effect Transistors Based on Asymmetric BTBT Derivatives for High Performance Solar-Blind Photodetectors.

High‐performance solar‐blind photodetectors are widely studied due to their unique significance in military and industrial applications. Yet the rational molecular design for materials to possess strong absorption in solar‐blind region is rarely addressed. Here, an organic solar‐blind photodetector is reported by designing a novel asymmetric molecule integrated strong solar‐blind absorption with high charge transport property. Such alkyl substituted [1]benzothieno[3,2‐b][1]‐benzothiophene (BTBT) derivatives Cn‐BTBTN (n = 6, 8, and 10) can be easily assembled into 2D molecular crystals and perform high mobility up to 3.28 cm2 V−1s−1, which is two orders of magnitude higher than the non‐substituted core BTBTN. Cn‐BTBTNs also exhibit dramatically higher thermal stability than the symmetric alkyl substituted C8‐BTBT. Moreover, C10‐BTBTN films with the highest mobility and strongest solar‐blind absorption among the Cn‐BTBTNs are applied for solar‐blind photodetectors, which reveal record‐high photosensitivity and detectivity up to 1.60 × 107 and 7.70 × 1014 Jones. Photodetector arrays and flexible devices are also successfully fabricated. The design strategy can provide guidelines for developing materials featuring high thermal stability and stimulating such materials in solar‐blind photodetector application.

Achieving 12.6% Efficiency in Single‐Component Organic Solar Cells Processed from Nonhalogenated Solvents

Single‐component organic solar cells (SCOSCs), which contain only one photoactive material in their active layers, promise many advantages with respect to the excellent device and morphological stabilities and a simplified film fabrication process. However, most of the high‐efficiency SCOSCs are fabricated by halogenated solvents. Herein, the eco‐friendly and highly efficient SCOSCs based on a conjugated block copolymer PBDB‐T‐b‐PYT with power conversion efficiencies (PCEs) of over 12% are developed by utilizing a series of halogen‐free processing solvents (including tetrahydrofuran, toluene, o‐xylene), being higher than those of the devices cast from halogenated solvents (including chloroform, chlorobenzene, 1,2‐dichlorobenzene). Impressively, by using o‐xylene as processing solvent for the PBDB‐T‐b‐PYT active layer, high and balanced charge transport properties, and well‐developed morphological features are observed, leading to a high PCE of 12.60%, which is the highest value among SCOSCs to date. Importantly, the non‐halogenated solvents‐processed devices exhibited better storage and operational stabilities as compared to the chloroform (CF)‐processed SCOSCs. More importantly, higher photovoltaic performance (over 12% PCEs) of the green‐solvent‐processed devices as compared with the CF‐processed devices fabricated by blade coating in ambient conditions are achieved, suggesting the promising prospects of SCOSCs toward industrial production, particularly being relevant for environmentally benign solvents.

Microflowers of Sn-Co-S derived from ultra-thin nanosheets for supercapacitor applications

Herein, for the first time, we report 3D broccoli-like microflowers of Sn-Co-S directly grown on the Ni foam (Sn-Co-S/NiF) using an easy solvothermal method for the supercapacitor application. The as-fabricated Sn-Co-S/NiF electrode possesses an ultra-high specific capacitance of 2319.3 F g−1 (specific capacity of 418.7 mAh g−1) at 5 mA cm−2 and an outstanding rate capability of 70.3 %. The optimized Co doping, and unique architecture of the electrode may be responsible for the excellent performance of the electrode. Taking benefit from the high specific capacitance and fast charge transport properties of Sn-Co-S/NiF electrode, the fabricated asymmetric supercapacitor (ASC) exhibits a large potential window of 1.7 V and outstanding cycling stability of 95.8% after 10000 cycles. Moreover, the ASC device delivers an excellent energy density of 66.9 W h kg−1 at a power density of 560.1 W kg−1 which is substantially high as compared to recently reported ASC devices. These findings confirm the potential use of Sn-Co-S/NiF in new generation energy-storage devices.