Ambiently and Mechanically Stable Ionogels for Soft Ionotronics

Stretchable ionic conductors such as hydrogels and ionic-liquid-based gels (aka ionogels) have garnered great attention as they enable the development of soft ionotronics. Notably, soft ionotronic devices inevitably operate in humid environments or under mechanical loads. However, many previously reported hydrogels and ionogels, however, are unstable in environments with varying humidity levels owing to hydrophilicity, and their liquid components (i.e., ionic liquid, water) may leak easily from polymer matrices under mechanical loads, causing deterioration of device performance. This work presents novel hydrophobic ionogels with strong ionic liquid retention capability. The ionogels are ambiently and mechanically stable, capable of not absorbing moisture in environments with high relative humidity and almost not losing liquid components during long periods of mechanical loading. Moreover, the ionogels exhibit desirable conductivity (10⁻⁴–10⁻⁵ S cm⁻¹), large rupturing strain (>2000%), moderate fractocohesive length (0.51–1.03 mm), and wide working temperature range (−60 to 200 °C). An ionic skin is further designed by integrating the concept of sensory artificial skins and triboelectric nanogenerators, which can convert multiple stimuli into various types of signals, including resistance, capacitance, short-circuit current, and open-circuit voltage. This work may open new avenues for the development of soft ionotronics with stable performance.     

Universal Bottom Contact Modification with Diverse 2D Spacers for High-Performance Inverted Perovskite Solar Cells

Although the 2D spacer modification is widely studied in perovskite solar cells (PVSCs), the energy level alignment between the 2D/3D interfaces makes it unfavorable for top surface passivation in the inverted p-i-n device structure. To address this issue, the effect of bottom interface modification is studied with three representative 2D spacers, i.e., the Ruddlesden-Popper 2D spacer, Dion-Jacobson 2D spacer, and strong passivation 2D spacer, in inverted p-i-n PVSCs. After optimization, the PVSCs with these 2D spacer modifications universally exhibit the best efficiencies of ≈21.6%, which constitutes dramatic improvement compared to the control device (20.7%). By lifting off the perovskite layer, the optoelectronic properties of the bottom surface are studied, and the mechanism underlying the improved device performance is unveiled to be uniformly originated from the formation of 2D/3D heterojunction, where the cascade valence band facilitates the hole collection and electron back scattering field suppresses the charge recombination at the anode interface. Besides, the unencapsulated device retains 90% of initial efficiency after 30 days of storage in ambient air with a relative humidity of 30 ± 5%, indicating excellent stability against moisture and oxygen. This study provides insight into the bottom interface modification with diverse 2D spacers for high-performance p-i-n structured PVSC devices.     

Concurrent topology optimization design of structures and non-uniform parameterized lattice microstructures

This paper presents a novel concurrent topology optimization approach for finding the optimum topologies of macrostructures and their corresponding parameterized lattice microstructures in an integrated manner. Considering the manufacturability of the structure designs and computational efficiency, additional parameters are introduced to define the microstructure unit cell patterns and their non-uniform distribution, which avoids expensive iterative numerical homogenization calculations during topology optimization and results in an easier modelling of structure designs as well. It is worth mentioning that the equivalent properties of material microstructures serve as a link between the macro and the micro scale with the help of homogenization theory and the Porous Anisotropic Material with Penalization (PAMP) model. Besides, sensitivities of global structure compliance with respect to the pseudo-density variables and the microstructure parameter variables are derived, respectively. Moreover, several numerical examples are presented and reasonable solutions have been obtained to demonstrate the efficiency of the proposed method. Finally, mechanical testing is conducted to investigate the better performance of the optimized structure which is fabricated by 3D printing.     

Synthesis,structure and properties of a novel quinoid compound

A novel quinoid compound α,α,α′,α′-tetra(4-tert-butylphenyl)-1,3,4-oxadiazole-quinodimethane (TPOQ) was synthesized through oxidative dehydrogenation in basic condition. The structure was characterized by elemental analysis, ¹H NMR, and mass spectrum. UV–vis spectra, photoluminescence (PL) spectra, and electron spin resonance (ESR) measurements showed that the compound had a small bandgap and π–π^* transition process produced an increase of polarity. Pure red emission at near 670 nm was observed from a single layer electroluminescence (EL) device, the emission color was unchanged with increase of applied voltage, which showed that TPOQ could be used as red emission material.     

Effects of composition and stacking sequence on dielectric properties of the multilayered (Pb,Sr)TiO3 thin films for tunable device application

Multilayered (Pb_1−xSr_x)TiO₃ (PST(x)) thin films consisted of uniform, PST(x) and heterostructure, PST(x)–PST80 were synthesized by coating the solutions with different Sr contents (50 ≤ x, Sr(mol%) ≤80), respectively. Their structural and dielectric properties were investigated in terms of composition and stacking sequence of each film. Among uniform PST(x) thin films, the PST60 films showed the highest dielectric constant and tunability, while so lower figure of merit which is an important parameter for microwave tunable device application was obtained due to relatively higher dielectric loss. In an effort to bring down the dielectric loss, the PST(x) thin films were alternately coated with PST80 thin layer. Dielectric properties of the heterostructured PST(x)–PST80 films were found to be dependent on the intrinsic dielectric values of each film composition and corresponding phase transition temperature shift effect. Furthermore, surface roughness became smoother by inserting PST80 thin layer, resulting in decrease in dielectric loss. In case of the PST60–PST80 heterostructured film, despite of slight decrease in tunability, the figure of merit on account of lowered dielectric loss was effectively improved (>40%), compared to that of the uniform PST60 film.     

Fabrication of Ag/polypyrrole coaxial nanocables through common ions adsorption effect

According to the common ions adsorption effect, Ag⁺ ions will be adsorbed onto the closest surface of silver nanowires after being immersed in AgNO₃ solution. This makes the surface of silver nanowires become the active sites to oxidize pyrrole monomer to form PPy sheath without adding other oxidizing agent. The results of FT-IR and UV–vis spectra show the formation of PPy chain when pyrrole monomer was added to the reaction mixture containing the disposed silver nanowires. TEM images further prove that the Ag/polypyrrole (PPy) coaxial nanocables have been fabricated. The thickness of PPy sheath can be controlled by adjusting the concentration of AgNO₃ aqueous solution, which used to dispose silver nanowires. To some extent, the thickness of PPy layer would increase with the increasing of the concentration of AgNO₃ solution. After the adsorbed Ag⁺ ions on the surface of silver nanowires reach to the saturation, the thickness of PPy layer would not change greatly with continuously increasing of AgNO₃ concentration.     

Conducting polymer micro-tubules hosting electroactive species without guest modification

A hollow micro-tubule structure comprised of the conducting polymer, PEDOT, was manufactured by the electrochemical polymerization of EDOT into a template membrane containing 1.2 μm pores. The tubules formed were then capped with a conducting PEDOT/PSS aqueous dispersion. In order to assist in effective capping, a piece of a PC membrane containing 0.05 μm pores was attached to the capping film of the aqueous dispersion. The cap was then reinforced with PEDOT via the electrochemical polymerization of EDOT in order to make it insoluble in aqueous solutions. The cavity of this micro-cylinder structure worked as a container retaining water-soluble electroactive materials and played the role as a current collector for the electrochemical reaction of the species retained inside. In this study, K₃Fe(CN)₆ was used as the probe material stored in the cylinders. The current collector exhibited a fine current response due to the redox reaction of the interior species. These results show that guest materials can be stored in this capped cylinder structure without the problems associated with the use of organic solvents during the manufacturing processes. Moreover, the most important part of the whole process can be monitored using simple electrochemical methods.     

New catalytic systems for coupling of dihalogenopyridines and 5,5″-dibromo-2,2′:6′,2″-terpyridine with 5-bromo-2-trialkylstannylpyridines and 2-trialkylstannylthiophenes

Catalytic activity of a number of systems consisting of a stable palladium precursor ([Pd(acac)₂], [PdCl₂(1,5-COD)], …) and a ligand (phosphines, AsPh₃, SbPh₃, P(OPh)₃, …) in Stille coupling reactions of 2,6-dihalogenopirydines with 5-bromo-2-trialkylstannylpyridines, forming 5,5″-dibromo-2,2′:6′,2″-terpyridine. A new, active, selective and convenient catalytic system for this reaction, consisting of [Pd(acac)₂] and triphenyl phosphite was found. A new, four membered library of thienyl-substituted pyridine and terpyridine ligands has been synthesized at the same conditions, by coupling of 2-tributylstannyl-3,4-ethylenedioxythiophene or 5-tributylstannyl-2,2′-bithiophene with 5,5″-dibromo-2,2′:6′,2″-terpyridine or 3,5-dibromopyridine.     

Preparation and characterization of (K0.5Na0.5)NbO3 ceramics

In this paper the preparation and characterization of the ceramic material (K_0.5Na_0.5)NbO₃ (KNN) has been studied. Although conventional processing of KNN is often reported to result in sintered bodies lacking sufficient density, samples produced in this work exhibit theoretical density over 95% and yield superior piezoelectric properties than those obtained by the same method and reported previously. The electromechanical coupling coefficient in the thickness direction, k_t, is found to reach 45%. Apart from k_t, the piezoelectric coefficients in longitudinal and planar directions (d₃₃ of 100pC/N and d₃₁ of 43pC/N), hysteresis loop, pyroelectric coefficient measurements and dielectric properties are presented.     

Streaming flows in differentially heated square porous cavity under sinusoidal g-jitter

Transient transport phenomenon in a square porous cavity under sinusoidal g-jitter has been solved numerically. Sinusoidal g-jitter introduces a true periodic behavior to the average Nusselt number. Pulsating wave from hot and cold side travels to-wards the center and almost in the center of the cavity the two waves engage in constructive/destructive interference leading to the formation of stationary wave. Sinusoidal g-jitter creates the streaming flows inside the porous cavity and time-dependent rolls have been observed inside the cavity due to differences in thermal diffusivities among solid matrix, wall and the fluid.