Flexible 3D Porous MoS2/CNTs Architectures with ZT of 0.17 at Room Temperature for Wearable Thermoelectric Applications

Developing materials that possess high electrical conductivities (σ) and Seebeck coefficients (S), low thermal conductivities (κ), and excellent mechanical properties is important to realize practical thermoelectric (TE) devices. Here, 3D hierarchical architectures consisting of hybrid molybdenum disulfide (MoS₂)/carbon nanotubes (CNTs) films are fabricated with the goal of increasing σ and decreasing κ. In these films, perpendicularly orientated CNTs interpenetrate restacked MoS₂ layers to form a 3D architecture, which increases the specific surface area and charge concentration. The MoS₂/20 wt% CNTs film shows high σ (235 ± 5 S?cm^?1), high S (68 ± 2 µV?K^?1), and low κ (19 ± 2 mW?m^?1?K^?1). The corresponding figure of merit (ZT) reaches 0.17 at room temperature, which is 65 times higher than that of pure MoS₂ film. In addition, the MoS₂/20 wt% CNTs film shows a tensile stress of 38.9 MPa, which is an order of magnitude higher than that of a control MoS₂ film. Using the MoS₂/CNTs film as an active material and human body as a heat source, a flexible, wearable TE wristband is fabricated by weaving seven strips of the 3D porous MoS₂/CNTs film. The wristband achieves an output voltage of 2.9 mV and corresponding power output of 0.22 µW at a temperature gradient of about 5 K.     

Residual stress in silicon nitride films

The mechanical stress caused by Si₃N₄ films on (111) oriented Si wafers was studied as a function of the Si₃N₄ film thickness, deposition rate, deposition temperature and film composition. The Si₃N₄ films were prepared by the reaction of gaseous SiH₄ and NH₃ in the temperature range 700–1000°C. The curvature of the Si substrates caused by the Si₃N₄. films is related to the film stress; the substrate curvature was measured by an optical interference technique. The measured Si₃N₄. film stress was found to be highly tensile with a magnitude of about 10¹⁰ dynes/cm². For the thickness range of 2000–5000Å, there was no change in the measured stress. The total film stress was observed to decrease for decreasing deposition rate and increasing deposition temperature. A large change in film stress was observed for films containing excess Si; the stress decreased with increasing Si content. Based on published values for the thermal expansion coefficients for Si and Si₃N₄, a published value for Young’s Modulus for Si₃N₄, and the measured total stress values, a consistent argument is developed in which the total stress consists of a compressive component due to thermal expansion coefficient mismatch and a larger tensile intrinsic stress component. Both the thermal and intrinsic stress components vary with film deposition temperature in directions which decrease the total room temperature stress for higher deposition temperatures.     

Doping Indium Oxide Films with Amino-Polymers of Varying Nitrogen Content Markedly Affects Charge Transport and Mechanical Flexibility

Here, correlations between polymer structure and charge transport in solution-processed indium oxide, In₂O₃:polymer blend flexible thin film transistors (TFTs) are investigated using four polymers having electron-donating amine functionalities (polyethyleneimine (PEI), poly(allylamine), polyethyleneimine ethoxylated (PEIE), and PVP-NH₂ (PVP; poly(4-vinylphenol)), and two PEI-PEIE mixtures) with varied atomic amine nitrogen content (N%) of 12.6, 9.1, 6.9, 2.6, respectively. These amino-polymers influence the semiconducting oxide film TFT electron mobilities via a delicate interplay of electron transfer/doping, charge generation/trap-filling, film morphological/microstructural variations, which depend on the polymer structure, thermal stability, and N%, as well as the polymer content of the In₂O₃ precursor and the carbon residue content in In₂O₃. Thus, increasing the N% from 0.0% in the control PVP to 12.6% in PEI increases the electron doping capacity, the polymer content of the blend formulation, and the blend TFT field-effect mobility. Optimal polymer incorporation invariably enhances charge transport by as much as ≈2×, leading to a maximum carrier mobility of 8.47 ± 0.73 cm² V⁻¹ s⁻¹ on rigid Si/SiO_x substrates and a remarkable 31.24 ± 0.41 cm² V⁻¹ s⁻¹ on mechanically flexible polyimide/Au/F:AlO_x substrates with Al contacts. Furthermore, all of the polymers equally enhance the mechanical durability of the corresponding In₂O₃:polymer blend TFTs with respect to mechanical stress.     

Network Structure Modification‐Enabled Hybrid Polymer Dielectric Film with Zirconia for the Stretchable Transistor Applications

Stretchable electronic devices should be enabled by the smart design of materials and architectures because their commercialization is limited by the tradeoff between stretchability and electrical performance limits. In this study, thin‐film transistors are fabricated using strategies that combine the unit process of a novel hybrid gate insulator and low‐temperature indium gallium tin oxide (IGTO) channel layer and a stress‐relief substrate structure. Novel hybrid dielectric films are synthesized and their molecular structural configurations are analyzed. These films consist of a polymer [poly(4‐vinylphenol‐co‐methylmethacrylate)], cross‐linkers having different binding structures [1,6‐bis(trimethoxysilyl)hexane (BTMSH), dodecyltrimethoxysilane, and poly(melamine‐co‐formaldehyde)], and an inorganic zirconia component (ZrO_x). The hybrid film with BTMSH cross‐linker and 0.2 M ZrO_x exhibits excellent insulating properties as well as mechanical stretchability. IGTO transistors fabricated on polyimide‐coated glass substrates are transferred to the rubber substrate to offer stretchability of the transistor pixelated thin‐film transistors. IGTO transistors fabricated on stretchable substrates using these strategies show promising electrical performance and mechanical durability. After 200 stretchability test cycles under uniaxial elongation of approximately 300%, the IGTO transistor still retains a high carrier mobility of 21.7 cm² V^?1 s^?1, a low sub‐threshold gate swing of 0.68 V decade^?1 and a high I_ON/OFF ratio of 2.0 × 10⁷.     

A Scalable,Robust Polyvinyl-Butyral-Based Solid Polymer Electrolyte with Outstanding Ionic Conductivity for Laminated Large-Area WO3–NiO Electrochromic Devices

Polyvinyl butyral (PVB) is a well-established polymer interlayer material that has been used in laminated safety glass panels for over 80 years. However, its intrinsically poor ionic conductivity (σ) severely restricts its widespread application as a solid polymer electrolyte (SPE) for laminated WO₃–NiO electrochromic devices (ECDs). Here, a new strategy for significantly improving the σ of PVB via a cross-linking reaction with 3-glycidoxypropyltrimethoxysilane (KH560) is presented. The cross-linked PVB-SPE with 10 wt.% KH560 exhibits the highest room-temperature σ value among the investigated samples (1.51 × 10⁻⁴ S cm⁻¹), which is also higher than that of previously reported PVB-based SPEs (10⁻⁵–10⁻⁷ S cm⁻¹). Additionally, the prepared SPE exhibits comprehensive optical, mechanical, and thermal performances, including a high visible transmittance (>91%), relatively high adhesive strength (2.13 MPa), and superior thermal stability (up to 150 °C). Laminated WO₃–NiO ECDs with dimensions of 5 × 5 cm² and 20 × 20 cm², fabricated by leveraging the aforementioned properties of the electrolyte, operate stably at temperatures ranging from −20 to 80 °C, underscoring the potential of the PVB-SPE for realizing commercially viable large-area ECDs.     

SnS?Sno2 conversion of chemically deposited SnS thin films

The thermal decomposition of chemically deposited SnS thin films to SnO₂ films by air annealing at temperatures up to 400°C is discussed. The conversion of a 0.7 μm thick SnS thin film to an SnO₂ film involves the creation of non-stoichiometric SnS, SnS + SnS₂ mixed phase and non-stoichiometric SnO₂ (i.e. SnO_{2 ? x}), as concluded from X-ray diffraction patterns, optical transmission spectra and electrical characteristics. The SnO₂ thin films obtained in this manner are photoconductive, with a lowest sheet resistance (in the dark) of about 10⁵ Ω/□ and an activation energy (E_a) of 0.1 eV for the electrical conductivity observed for the SnS films annealed at 325°C. This was found as the onset temperature for conversion of the SnS + SnS₂ phase to the non-stoichiometric SnO_{2 – x} film. Elevation of the annealing temperature to 400°C results in an elevation of the sheet resistance to about 10⁹ Ω/□ with the value of E_a at 1.3 eV, indicating an improvement in the degree of stoichiometry.     

High-quality conformal silicon oxide films prepared by multi-step sputtering PECVD and chemical mechanical polishing

High-quality conformal oxide films were obtained by using multi-step sputtering (MSSP) plasma enhanced chemical vapor deposition (PECVD) process with argon ion sputtering and chemical mechanical polishing (CMP). The repeated deposition by plasma enhanced chemical vapor deposition (PECVD) and anisotropic etching of oxide films by multi-step sputtering PECVD improve the step coverage and gap filling capability significantly. The argon plasma treatment enhances the binding energy of Si-O in the SiO₂ network, and the temperature dependence of stress for MSSP oxide film showed no hysteresis after the heating cycle up to 440 °C. The stress-temperature slope of MSSP oxide film was found to be much less than that of conventional PECVD oxide film. The slope for 1.1 μm thick film is about 5.8×10⁵ dynes/cm²/°C which is smaller than that of thermally grown oxide film. It seems that MSSP oxide film reduces stress-temperature hysteresis and becomes more dense and void-free in the narrow gaps with inter-metal spacing of 0.5 μm. After filling of the narrow gap, we adopted the CMP process for global planarization and obtained good planarization performance. The uniformity of the film thickness was about 4% and the degree of the planarization was over 95% after CMP process.     

Modification of the structural lattice parameters and electron spectra of <Emphasis Type="Italic">n</Emphasis>-GaAs films on sapphire on irradiation with reactor neutrons

Changes in the structural parameters of epitaxial GaN films on sapphire (n-GaN/Al₂O₃(0001)) induced by irradiation with reactor neutrons with integrated fluences up to 7.25 × 10¹⁹ fn cm⁻² (φ_fn/φ_tn ≈ 1) and subsequent isochronal annealing at temperatures up to 1000°C are studied. Measurements of the lattice parameters a and c of the irradiated n-GaN films show that the parameter c increases by 0.38% and the parameter a remains almost unchanged. From theoretical estimations, it follows that, in the irradiated n-GaN film, the elastic tensile stress along the c axis is as high as ∼1.5 GPa, whereas the compression stress in the basal plane of the unit cell is about −0.5 GPa. The tension of the irradiated GaN film along the hexagonal axis induces a decrease in the band gap E _g by 37 meV and a lowering of the charge neutrality level by 22 meV with respect to the corresponding parameters in the initial GaN film on sapphire. The parameter c changed by irradiation with reactor neutrons by Δc can be recovered by annealing in the temperature range 100–1000°C, with the basic stage of annealing at about 400°C.     

Influence of Substrate Temperature on Structural and Thermoelectric Properties of Antimony Telluride Thin Films Fabricated by RF and DC Cosputtering

Antimony and tellurium were deposited on BK7 glass using direct-current magnetron and radiofrequency magnetron cosputtering. Antimony telluride thermoelectric thin films were synthesized with a heated substrate. The effects of substrate temperature on the structure, surface morphology, and thermoelectric properties of the thin films were investigated. X-ray diffraction patterns revealed that the thin films were well crystallized. c-Axis preferred orientation was observed in thin films deposited above 250°C. Scanning electron microscopy images showed hexagonal crystallites and crystal grains of around 500 nm in thin film fabricated at 250°C. Energy-dispersive spectroscopy indicated that a temperature of 250°C resulted in stoichiometric Sb₂Te₃. Sb₂Te₃ thin film deposited at room temperature exhibited the maximum Seebeck coefficient of 190 μV/K and the lowest power factor (PF), S ² σ, of 8.75 × 10⁻⁵ W/mK². When the substrate temperature was 250°C, the PF increased to its highest value of 3.26 × 10⁻³ W/mK². The electrical conductivity and Seebeck coefficient of the thin film were 2.66 × 10⁵ S/m and 113 μV/K, respectively.     

Nanostructured Vanadium Oxide Electrodes for Enhanced Lithium‐Ion Intercalation

This article summarizes our most recent studies on improved Li⁺‐intercalation properties in vanadium oxides by engineering the nanostructure and interlayer structure. The intercalation capacity and rate are enhanced by almost two orders of magnitude with appropriately fabricated nanostructures. Processing methods for single‐crystal V₂O₅ nanorod arrays, V₂O₅·n H₂O nanotube arrays, and Ni/V₂O₅·n H₂O core/shell nanocable arrays are presented; the morphologies, structures, and growth mechanisms of these nanostructures are discussed. Electrochemical analysis demonstrates that the intercalation properties of all three types of nanostructure exhibit significantly enhanced storage capacity and rate performance compared to the film electrode of vanadium pentoxide. Addition of TiO₂ to orthorhombic V₂O₅ is found to affect the crystallinity, microstructure, and possible interaction force between adjacent layers in V₂O₅, and subsequently leads to enhanced Li⁺‐intercalation properties in V₂O₅. The amount of water intercalated in V₂O₅ is found to have a significant influence on the interlayer spacing and electrochemical performance of V₂O₅·n H₂O. A systematic electrochemical study has demonstrated that the V₂O₅·0.3 H₂O film has the optimal water content and exhibits the best Li⁺‐intercalation performance.     

A Novel Cross‐linked Poly(vinyl alcohol) (PVA) for Vascular Grafts

Poly(vinyl alcohol) (PVA) is a water‐soluble synthetic polymer with excellent film‐forming, emulsifying, and adhesive properties. The aim of this study is to design a simple process for PVA cross‐linking with sodium trimetaphosphate to form membrane devices suitable for biomedical applications. This procedure requires no organic solvent, nor melting process to obtain films with high mechanical strength. Fabrication of a small diameter tube from a PVA film is easy with a single wrapping step around a Teflon rod. Dynamic mechanical analysis demonstrated that, upon removal of the applied stress, the PVA film with a Young's modulus of 2 × 10⁵ kPa returns to its original size and shape. The wall thickness of PVA tubes is 344 ± 13 µm (n = 12), which is close to the wall thickness of a human artery (350–710 µm). Suture retention of a PVA tube is excellent (140 ± 11 g), close to that of human vessels. The burst pressure of PVA tubes is found to be 507 ± 25 mm Hg, more than three times higher than the human healthy systolic arterial pressure. Under arterial pressure, there was no leakage even after needle puncture, contrary to clinical vascular expanded polytetrafluoroethylene prostheses. Finally, PVA tubes of 2 mm in diameter are used to replace a segment of an infrarenal aorta in rats. For at least one week, no mechanical nor thrombotic complications are noticed even in the absence of anticoagulant or antiplatelet treatment. Graft patency is also evidenced with non‐invasive imaging techniques. As a conclusion, this novel cross‐linking method confers to poly(vinyl alcohol) particular mechanical properties such as compliance, elasticity and resistance to mechanical stress, compatible with the circulatory blood flow.     

Design of the Magnetic Properties of Fe‐Rich,Glass‐Coated Microwires for Technical Applications

The magnetic anisotropy of Fe‐rich, thin, amorphous wires is tailored by stress annealing (SA). In particular, the effect of conventional annealing (CA) and SA on the magnetic properties of Fe₇₄B₁₃Si₁₁C₂ glass‐coated microwires is studied. CA treatment does not significantly change the character of the hysteresis loop. Under certain SA conditions (annealing temperature, T_ann > 300 °C; applied stress, σ > 400 MPa), a transverse magnetic anisotropy is induced: a rectangular hysteresis loop transforms into an inclined one at magnetic‐anisotropy fields above 1000 A m^–1. Under tensile stress, the rectangular hysteresis loop of microwires annealed using SA is recovered. Samples subjected to SA show noticeable magnetoimpedance and stress‐impedance effects, despite their large magnetostriction. The samples obtained exhibit a high stress sensitivity of their giant magnetoimpedance (GMI) effect and hysteretic properties, allowing the use of the obtained samples in magnetoelastic sensors, and for designing stress‐sensitive, tunable composite materials. By varying the time and temperature of such SA, we are able to tailor both the magnetic properties and the GMI of Fe‐rich microwires.     

3D Ion-Conducting,Scalable, and Mechanically Reinforced Ceramic Film for High Voltage Solid-State Batteries

Concerning the safety aspects of Li⁺ ion batteries, an epoxy-reinforced thin ceramic film (ERTCF) is prepared by firing and sintering a slurry-casted composite powder film. The ERTCF is composed of Li⁺ ion conduction channels and is made of high amounts of sintered ceramic Li_1+xTi_2-xAl_x(PO₄)₃ (LATP) and epoxy polymer with enhanced mechanical properties for solid-state batteries. The 2D and 3D characterizations are conducted not only for showing continuous Li⁺ ion channels thorough LATP ceramic channels with over 10⁻⁴ S cm⁻¹ of ionic conductivity but also to investigate small amounts of epoxy polymer with enhanced mechanical properties. Solid-state Li⁺ ion cells are fabricated using the ERTCF and they show initial charge–discharge capacities of 139/133 mAh g⁻¹. Furthermore, the scope of the ERTCF is expanded to high-voltage (>8 V) solid-state Li⁺ ion batteries through a bipolar stacked cell design. Hence, it is expected that the present investigation will significantly contribute in the preparation of the next generation reinforced thin ceramic film electrolytes for high-voltage solid-state batteries.     

Variable Temperature Mobility Analysis of n‐Channel,p‐Channel,and Ambipolar Organic Field‐Effect Transistors

The temperature dependence of field‐effect transistor (FET) mobility is analyzed for a series of n‐channel, p‐channel, and ambipolar organic semiconductor‐based FETs selected for varied semiconductor structural and device characteristics. The materials (and dominant carrier type) studied are 5,5′′′‐bis(perfluorophenacyl)‐2,2′:5′,2″:5″,2′′′‐quaterthiophene ( 1 , n‐channel), 5,5′′′‐bis(perfluorohexyl carbonyl)‐2,2′:5′,2″:5″,2′′′‐quaterthiophene ( 2 , n‐channel), pentacene ( 3 , p‐channel); 5,5′′′‐bis(hexylcarbonyl)‐2,2′:5′,2″:5″,2′′′‐quaterthiophene ( 4 , ambipolar), 5,5′′′‐bis‐(phenacyl)‐2,2′: 5′,2″:5″,2′′′‐quaterthiophene ( 5 , p‐channel), 2,7‐bis((5‐perfluorophenacyl)thiophen‐2‐yl)‐9,10‐phenanthrenequinone ( 6 , n‐channel), and poly(N‐(2‐octyldodecyl)‐2,2′‐bithiophene‐3,3′‐dicarboximide) ( 7 , n‐channel). Fits of the effective field‐effect mobility (µ_eff) data assuming a discrete trap energy within a multiple trapping and release (MTR) model reveal low activation energies (E_As) for high‐mobility semiconductors 1 – 3 of 21, 22, and 30 meV, respectively. Higher E_A values of 40–70 meV are exhibited by 4 – 7 ‐derived FETs having lower mobilities (µ_eff). Analysis of these data reveals little correlation between the conduction state energy level and E_A, while there is an inverse relationship between E_A and µ_eff. The first variable‐temperature study of an ambipolar organic FET reveals that although n‐channel behavior exhibits E_A = 27 meV, the p‐channel regime exhibits significantly more trapping with E_A = 250 meV. Interestingly, calculated free carrier mobilities (µ₀) are in the range of ～0.2–0.8 cm² V^?1 s^?1 in this materials set, largely independent of µ_eff. This indicates that in the absence of charge traps, the inherent magnitude of carrier mobility is comparable for each of these materials. Finally, the effect of temperature on threshold voltage (V_T) reveals two distinct trapping regimes, with the change in trapped charge exhibiting a striking correlation with room temperature µ_eff. The observation that E_A is independent of conduction state energy, and that changes in trapped charge with temperature correlate with room temperature µ_eff, support the applicability of trap‐limited mobility models such as a MTR mechanism to this materials set.     

High temperature annealing of mnos devices and its effect on si-nitride stress,interface charge density and memory properties

The effects of high temperature annealing in N₂ and H₂ ambients upon the following properties of MNOS devices have been investigated: Si-nitride stress, etch rate, index of refraction, fixed interface charge and fast surface state density, memory window and charge retention at elevated temperatures. The CVD Si-nitride and Si-oxynitride films were deposited at temperatures as low as 610°C with a NH₃/SiH₄ ratio of 1000:1, the heat treatments were performed in the temperature range from 640°C to 1130°C. A similar N₂-annealing behavior was found for film stress and flatband voltage. The film stress increased with increasing annealing time and temperature while the interface charge density changed from high positive values (Q_N/q = 4 × 10¹²cm⁻2) after nitride deposition at 610°C to high negative values (Q_N/q = -4 × 10¹²cm⁻2) after annealing at 930°C, The fast interface state density increased while the charge retention time was drastically reduced. The changes of the properties by N₂ annealing are mainly attributed to decomposition of SiH and NH bonds. Minor effects were obtained by annealing in H₂ and the drastic changes caused by N₂ annealing could be reversed to a great extent by subsequent H₂ annealing. Finally the different effects of deposition and annealing temperature on the propertiesare discussed .     

Structure and conductivity of liquid crystal channel-like linic complexes of taper-shaped compounds

Molecular packing and electrical conductivity were studied in complexes of alkali trifluoromethanesulphonates with low-molar or polymeric compounds containing both taper-shaped mesogens were esters of either 3,4,5-tris [p-(n-dodecan-l-yloxy) benzyloxy] benzoic acid (I) or 3, 4, 5-tris (n-dodecan-l-yloxy) benzoic acid (II). In the hexagonal columnar liquid crystal phase the tapered mesogens fan out from the centre of the column, with the ionic receptors forming the central channel and the aliphatic tails constituting the continuum matrix. In the case of side-chain polymethacrylates the column core also contains the backbone chain. The DC conductivity σ of unoriented samples increases greatly at the crystal-columnar transition, with only a minor further change upon columnar-isotropic transition. σ was in the range 10^?9 ? 10^?6 in the columnar phase 40–90 °C, whilst the activation energies for conduction were between 28 kcal mol^?1 for the crown ether and only 2 kcal mo^?1 for the complex of LiCf₃SO₃ with the non-polymeric ester of tri(ethylene oxide) with I.     

Photoluminescence of silicon after deposition of polycrystalline diamond films

Low-temperature (5K) photoluminescence of silicon substrates in the range 0.8–1.2 eV is studied before and after deposition of polycrystalline diamond films. The diamond films were deposited in the microwave plasma onto high-purity dislocation-free silicon (with the resitivity ρ ≈ 3 kΩ cm) subjected to mechanical polishing or more delicate chemical and mechanical polishing. The deposition temperature was 750–850°C. In the photoluminescence spectra of the samples with the substrates polished chemically and mechanically, two lines, D ₁ and D ₂, corresponding to the dislocation-related emission are recorded. Generation of dislocations in the substrates is caused by efficient adhesion of the diamond film and, as a result, by internal stresses that relax with the formation of dislocations. The experimental spectra are practically identical to the photoluminescence spectra observed in silicon (ρ ≈ 100 Ω cm) with the density of dislocations ∼10⁴ cm⁻².     

Research of SiO2/InP structure prepared by photo-CVD

The SiO₂ film as an insulator in InP MOS structure was grown by mercury-sensitized photo induced chemical-vapor deposition (photo-CVD) utilizing gaseous mixture of monosilane (SiH₄) and nitrous oxide (N₄O) under 253.7 nm ultraviolet light irradiation. The PHOTOX SiO₂ film (i.e., SiO₂ film prepared by photo-CVD system) deposited at 250° C has a refractive index of 1.46 and breakdown field strength of 7.0 MV/cm. The 1 MHz capacitance-voltage characteristics of the InP MOS diode was measured to study the interface state densities. The minimum value is 1.2 × 10¹¹ cm⁻²eV⁻¹ for the sample prepared at a substrate temperature of 250° C.     

SiO2/TiO2 Composite Film for High Capacity and Excellent Cycling Stability in Lithium‐Ion Battery Anodes

In this study, partially crystalline anodic TiO₂ with SiO₂ well‐distributed througout the entire oxide film is prepared using plasma electrolytic oxidation (PEO) to obtain a high‐capacity anode with an excellent cycling stability for Li‐ion batteries. The micropore sizes in the anodic film become inhomogeneous as the SiO₂ content is increased from 0% to 25%. The X‐ray diffraction peaks show that the formed oxide contains the anatase and rutile phases of TiO₂. In addition, X‐ray photoelectron spectroscopy and energy‐dispersive X‐ray analyses confirm that TiO₂ contains amorphous SiO₂. Anodic oxides of the SiO₂/TiO₂ composite prepared by PEO in 0.2 m H₂SO₄ and 0.4 m Na₂SiO₃ electrolyte deliver the best performance in Li‐ion batteries, exhibiting a capacity of 240 µAh cm^?2 at a fairly high current density of 500 µA cm^–2. The composite film shows the typical Li–TiO₂ and Li–SiO₂ redox peaks in the cyclic voltammogram and a corresponding plateau in the galvanostatic charge/discharge curves. The as‐prepared SiO₂/TiO₂ composite anode shows at least twice the capacity of other types of binder‐free TiO₂ and TiO₂ composites and very stable cycling stability for more than 250 cycles despite the severe mechanical stress.     

Layer‐by‐Layer Conjugated Extension of a Semiconducting Polymer for High‐Performance Organic Field‐Effect Transistor

A donor–acceptor (D–A) semiconducting copolymer, PDPP‐TVT‐29, comprising a diketopyrrolopyrrole (DPP) derivative with long, linear, space‐separated alkyl side‐chains and thiophene vinylene thiophene (TVT) for organic field‐effect transistors (OFETs) can form highly π‐conjugated structures with an edge‐on molecular orientation in an as‐spun film. In particular, the layer‐like conjugated film morphologies can be developed via short‐term thermal annealing above 150 °C for 10 min. The strong intermolecular interaction, originating from the fused DPP and D–A interaction, leads to the spontaneous self‐assembly of polymer chains within close proximity (with π‐overlap distance of 3.55 Å) and forms unexpectedly long‐range π‐conjugation, which is favorable for both intra‐ and intermolecular charge transport. Unlike intergranular nanorods in the as‐spun film, well‐conjugated layers in the 200 °C‐annealed film can yield more efficient charge‐transport pathways. The granular morphology of the as‐spun PDPP‐TVT‐29 film produces a field‐effect mobility (μ _FET) of 1.39 cm² V^?1 s^?1 in an OFET based on a polymer‐treated SiO₂ dielectric, while the 27‐Å‐step layered morphology in the 200 °C‐annealed films shows high μ _FET values of up to 3.7 cm² V^?1 s^?1.