Solution Processing Techniques Research Articles

Fabrication of a Hydrogen-Bonded Organic Framework Membrane through Solution Processing for Pressure-Regulated Gas Separation.

Ordered and flexible porous frameworks with solution processability are highly desirable to fabricate continuous and large-scale membranes for the efficient gas separation. Herein, the first microporous hydrogen-bonded organic framework (HOF) membrane has been fabricated by an optimized solution-processing technique. The framework exhibits the superior stability because of the abundant hydrogen bonds and strong π-π interactions. Thanks to the flexible HOF structure, the membrane possesses the unprecedented pressure-responsive H2 /N2 separation performance. Furthermore, the scratched membrane can be healed by the treatment of solvent vapor, achieving the recovery of separation performance.

Solution processed ZnInxOy sensing membranes on flexible PEN for extended-gate field-effect transistor pH sensors

This work describes the impact of indium content of the structural properties and sensing characteristics of ZnInxOy sensing films for extended-gate field-effect transistor (EGFET) sensors. The synthesis of the ZnInxOy sensing films was made by a solution processing technique directly deposited on flexible polyethylene naphthalate (PEN) through a simple spin-coating method. The synthesized ZnInxOy films at three different indium concentrations (10%, 20% and 30% moles) were characterized by X-ray photoelectron spectroscopy, X-ray diffraction, and atomic force microscopy to examine their chemical features, film structures and surface morphologies, respectively. Experiments were performed to explore the pH sensitivity, drift rate, and hysteresis voltage in the ZnInxOy EGFET sensors. Compare with these conditions, a higher pH sensitivity of 61.76 mV/pH, a lower drift rate of 1.08 mV/h, and a smaller hysteresis voltage of ∼1 mV were obtained in the ZnInxOy EGFET sensor fabricated at the 20% condition. Moreover, after 500 bending cycles, the ZnInxOy EGFET sensor fabricated at the 20% condition showed good mechanical flexibility. The ZnInxOy EGFET sensor also demonstrated a high selective response towards H+. This result indicates that the ZnInxOy sensing film with a rougher surface and a higher Zn–O–In content to generate lower crystal deformities, imperfections and oxygen vacancies.

Enhancement of mechanical properties of glass fiber reinforced vinyl ester composites by embedding multi-walled carbon nanotubes through solution processing technique

This experimental study emphasizes the effect of the incorporation of multi-walled carbon nanotubes (MWCNTs) in conventional fiber reinforced-polymer composites on mechanical and thermal performance. Hand layup method was adopted for fabricating glass fiber reinforced vinyl ester (GVE), and 0.1 wt% MWCNTs filled GVE (MWCNT-GVE) composites. Bidirectional woven glass fiber (GF) and vinyl ester (VE) resin were used as reinforcement and matrix, respectively. The MWCNTs-VE suspension was prepared by solution processing technique. Mechanical properties were found to be affected by embedding MWCNTs in the neat GVE composite. MWCNT-GVE composite showed about a 7.37% increment in flexural strength and about 11.64% increment in tensile strength over neat GVE composite. Through differential scanning calorimetry (DSC), glass transition temperature (Tg), and the effect of MWCNTs on thermal properties of experimental composites were analyzed. A decrease in Tg value was observed after incorporating MWCNTs in GVE composite. Post failure, analysis was done by scanning electron microscope (SEM).

Graphene-ferrites interaction for enhanced EMI shielding effectiveness of hybrid polymer composites

Hybrid polymer composites based on poly vinylidene fluoride (PVDF) matrix are fabricated by dispersion of few layered graphene (FLG) and nickel spinal ferrites (NSF) for improving EMI shielding effectiveness. The FLG loading is kept constant at 3 wt% while NSF content is varied from 15–30 wt% in PVDF using solution processing technique. The shielding effectiveness in the frequency domain of 1–12 GHz is enhanced ranging 25 dB–45 dB for PVDF/FLG composite as compared to ∼0 dB for neat PVDF. With addition of NSF up to 15 wt%, the attenuation is increased to 30 dB–53 dB, clearly indicating the effective interaction and network formation of FLG and NSF in PVDF matrix. Moreover, the shielding effectiveness trend is reduced to 12 dB–43 dB as the NSF loading is increased to 30 wt% owing to its agglomeration. Absorption is the dominant phenomena in obtaining the total shielding effectiveness of ∼53 dB for PVDF/FLG-3 wt%NSF-15 wt% hybrid polymer composites. Additionally, the I-V curves provide the electrical conductivity trend while scanning electron microscope (SEM) confirms the network formation in hybrid composite.

Microstructural and Nanostructural Evolution of Light Harvester Perovskite Thin Film under the Influence of Ultrasonic Vibrations.

A key step of inexpensive and scalable perovskite thin-film formation is defect-free fabrication through low-cost and facile post-treatment processes. Methods using high annealing temperatures are not favorable for the scale-up of solution-processed thin-film solar cells, particularly on plastic/flexible substrates. This contribution analyzes the effect of ultrasonic vibrations, a recently developed low-cost post-treatment process, on thin-film quality. Ultrasonic vibrations were applied to as-spun CH3NH3PbI3 perovskite thin films prepared with various solvents and antisolvents deposited on substrates with compact and mesoporous textures. Then, mechanisms of solvent evaporation, nucleation, and crystallization of perovskite grains were characterized during ultrasonic vibration. These studies demonstrate that ultrasonic vibration at low temperature facilitates heterogeneous crystallization of perovskite grains with a higher conversion of nuclei into crystal, compared with the conventional annealing process. Topographic scanning electron microscopy images confirm the dense and fully covered thin films after the evaporation of solvent. Furthermore, it is shown that crystal orientation does not change with the choice of solvent, eliminating the effect of solvent on the deposition of thin-film perovskites with this method. Therefore, this ultrasonic vibration post-treatment method is applicable to any solution-processed material and deposition technique, and it can be used to fabricate a range of thin-film devices and printed electronics.

Synthesis and Characterization of a Silver Nanoparticles-Reduced Graphene Oxide Nanohybrid by using ‘Zingiber Officinale’ Extract as a Reducing and Stabilizing Agent

An eco-friendly solution-based chemical approach has been used to prepare silver nanoparticles-reduced graphene oxide (AgNPs-rGO) nanohybrid using Zingiber officinale extract as a reducing and stabilizing agent. The products form a stable aqueous solution without any surfactant stabilizers and hence makes it possible to produce AgNPs-rGO nanohybrid on a large scale using low-cost solution processing technique. The nanohybrid was monitored at different concentration of GO solution (0.1 mg/ml, 0.5 mg/ml and 1.0 mg/ml) and characterized using UV- visible (UV-Vis) absorption spectrum, transmission electron microscopy (TEM), X-ray diffraction (XRD), and Raman spectroscopy analyses. From the UV-Vis analysis, the formation of silver nanoparticles (AgNPs) was confirmed and showed a surface plasmon resonance (SPR) absorption band at 420 nm for nanohybrids with GO concentration of 0.5 mg/ml. Raman spectra shows an increase in ID/IG ratio for rGO with values of 1.007 corresponding to the concentration of GO (0.5mg/ml) as compared to GO (0.88). Completely spherical Ag nanoparticles (NPs) were found at a nanohybrid with 0.5 mg/ml of GO with an average particle size of 20 nm. The AgNPs-rGO(0.5) nanohybrid exhibit fast electron-transfer kinetics for electrochemical reaction of Fe (CN)63-/4- redox couple, suggesting the potential applications for electrocatalysis and electrochemical sensor. Â

Facile Synthesis of Ti3C2Tx-Poly(vinylpyrrolidone) Nanocomposites for Nonvolatile Memory Devices with Low Switching Voltage.

MXenes, an emerging class of two-dimensional (2D) transition-metal carbide materials, have received increasing attention for their interesting physiochemical properties. For not only MXenes but also other 2D materials, delamination is a requisite step for the exploitation of their unique properties. In this work, a facile method for exfoliating Ti3C2Tx MXene to nanosheets of small size with the aid of poly(vinylpyrrolidone) (PVP) is designed, which has never been reported to our knowledge. Since both hydrophobic methylene groups and hydrophilic amide groups are provided with PVP, this method is applicable in a wide range of solvents, such as ethanol, water, and chloroform. Considering the charge detrapping and trapping behavior of 2D transition-metal materials in PVP dielectric, a memory device with the configuration of reduced graphene oxide (rGO)/Ti3C2Tx-PVP/Au is directly fabricated with these well-dispersed Ti3C2Tx-PVP composites by the solution process technique. Interestingly, the resultant device exhibits a typical bistable electrical switching, ultralow switching voltage (∼0.9 V), and a nonvolatile rewritable memory effect with the function of flash. This work might pave the way of using MXenes for future data storage, which is an indispensable field nowadays.

(Amazon Catalyst at ECS Grant Winner) Active Control of Heat Flow in Quantum Computing Applications through Piezoelectric Induced Mechanical Strain

Current technologies focused on manipulating heat flow primarily employ materials that exhibit metal-insulator transitions. However, for these materials to be efficient, the operating temperature of the device must be close to the transition temperature. Since the transition temperature is not easily tunable, the solution involves developing and studying new materials that have desirable transition temperatures which often is an inhibitor. Furthermore, as temperature and heat are strongly coupled, the ability to actively control heat flow can be limited. We propose a solution for active control of heat flow that involves altering the thermal conductivity of a material through mechanical strain. Stretching (compressing) a material leads to an increase (decrease) in the spacing between the atoms, results in a decrease (increase) in thermal conductivity of the material. Our approach involves achieving the required strain by applying an electrical voltage, referred to as the piezoelectric effect. In this study, the relationship between mechanical strain and thermal conductivity is experimentally studied on thin films. Both inorganic and organic films, fabricated using solution processing and sputtering techniques will be used to explore this effect. Thermal conductivity measurements will be carried out using 3-omega, which is a well-established electro-thermal technique. There will also be a thrust to quantify anisotropy in thermal conductivities of the piezoelectric films. In this talk, we report data from preliminary experiments that demonstrate the reversible and tunable thermal conductivity of piezoelectric thin films such as ZnO.

Fully Printed Organic Electrochemical Transistors from Green Solvents

AbstractTo achieve the full potential of scalable and cost‐effective organic electronic devices, developments are being made in both academic and industry environments to move toward continuous solution‐processing techniques that make use of safe and environmentally benign “green” solvents. In this work, the first example of a transistor device that is fully solution processed using only green solvents is demonstrated. This achievement is enabled through a novel multistage cleavable side chain process that provides aqueous solubility for semiconducting conjugated polymers, paired with aqueous inkjet printing of PEDOT:PSS electrodes, and a solution deposited ion gel electrolyte as the dielectric layer. The resulting organic electrochemical transistor devices operate in accumulation mode and reach maximum transconductance values of 1.1 mS at a gate voltage of − 1 V. Normalizing the transconductance value to the channel dimensions yields gm/W = 2200 S m−1 (µC* = 22 F cm−1 V−1 s−1), making these devices suitable for a range of applications requiring small signal amplification such as transistors, biosensors, and ion pumps. This new material design and device process paves the way toward scalable, safe, and efficient production of organic electronic devices.

Enhancement of spectral stability and outcoupling efficiency in organic light-emitting diodes with breath figure patterned microlens array films

We report outcoupling efficiency enhanced organic light-emitting diodes (OLEDs) using microlens array films prepared by a simple solution-processed imprinting technique with breath figure patterns. The films with breath figure micro-patterns (BFMP) effectively extract confined light in the glass substrate, which leads to the greatly improved outcoupling performance of OLEDs. We observe the enhancement of external quantum efficiency of the OLEDs employing the BFMP outcoupling film is about 1.51, corresponding to the enhancement of the power efficiency by a factor of 1.65. Moreover, the device with the outcoupling film shows the limited angle-dependency of emission spectrum over viewing angles. The BFMP films prepared with a low-cost, simple, and solution-processable fabrication process can pave the way to achieving high-performance OLEDs.

Controllable growth of LiMn2O4 by carbohydrate-assisted combustion synthesis for high performance Li-ion batteries

LiMn2O4 (LMO) spinels with diverse achievable morphologies are realized using solution processing techniques including sol-gel and cofuel-assisted combustion synthesis (CS). These LMOs are utilized as cathode materials in lithium ion batteries (LiBs), with LMO produced here by low-temperature, sorbitol-assisted combustion synthesis (SA-CS) yielding superior performance metrics. Morphological analysis by combined X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy demonstrates that these SA-CS LMO powders have optimum LiB grain (<500 nm) and crystallite (~30 nm) dimensions as well as spinel phase purity. Cathode mixtures having micron-scale, uniformly distributed LMO, conductive carbon, and a polymer binder provide effective electron and Li transport as assessed by electrochemical impedance spectroscopy and fabricated battery performance, showing high capacity (~120 mA h/g), good cycling stability (~95% capacity retention after 100 charge/discharge cycles), and high charge/discharge rates (up to 86 mA h/g at 10 C). SA-CS provides a simple, efficient, lower temperature, and scalable process for producing morphology-controlled high-performance LiB cathode oxides.

Stable Triple-Cation (Cs+-MA+-FA+) Perovskite Powder Formation under Ambient Conditions for Hysteresis-Free High-Efficiency Solar Cells.

Organometallic halide perovskite materials have promising photovoltaic properties and emerged as a cost-effective solar cell technology. However, a synthesis protocol to fabricate high-quality perovskite thin films under ambient conditions remains a critical issue and hinders commercialization of the technology. Therefore, this paper proposes efficient and stable fabrication of triple-cation perovskite photoactive solid-state thin film for solar cells using preformed perovskite powder under ambient conditions. Highly crystalline triple-cation perovskite powder was synthesized by a solution-processed antisolvent recrystallization technique, and films were prepared following a previously reported recipe for an efficient triple-cation perovskite. The synthesized perovskite powder was characterized using UV-visible absorption spectroscopy, X-ray diffraction, time-resolved photoluminescence, and field emission scanning electron microscopy. Fabricated solar cells were investigated for photovoltaic characteristics, including current density-voltage hysteresis, recombination losses, and thermal stability. The improved photovoltaic characteristics and thermal stability were attributed to the superior perovskite film quality and crystalline properties.

Graphene nanoparticles induces apoptosis in MCF-7 cells through mitochondrial damage and NF-KB pathway

In the present study, the synthesis of reduced graphene oxide (rGO) was performed via 20 kHz frequency ultrasonic solution processing technique. Synthesis of rGo was confirmed by various techniques including color changes, UV–vis spectra, x-ray analysis, infrared spectrophotometry, scanning electron microscopy, and dynamic light-scattering. The cytotoxicity of rGO was examined against human breast cancer MCF-7 cells by measuring different parameters including MTT, suppression of NF-κB translocation, mitochondrial membrane potential (MMP), reactive oxygen species (ROS) production, acridine orange-ethidium bromide staining, and single cell gel electrophoresis. Also, the gene expressions of Bax and Bcl-2 proteins were measured using quantitative PCR analysis as well as florescence microscopy and indicated that rGO induces cell death using apoptosis as an exclusive mechanism. Our results shows for the first time that the rGO inhibited the proliferation of MCF-7 cells, leading to programmed cell death through activation of the mitochondrial-mediated signaling pathway with the involvement of the NF-kB signalling pathway. Taken together the present data suggest that rGO can be possibly employed in the treatment of breast cancer with the function of a potent synergistic agent added to anticancer therapy protocols.

Polymer-Assisted Metal Deposition (PAMD) for Flexible and Wearable Electronics: Principle, Materials, Printing, and Devices.

The rapid development of flexible and wearable electronics favors low-cost, solution-processing, and high-throughput techniques for fabricating metal contacts, interconnects, and electrodes on flexible substrates of different natures. Conventional top-down printing strategies with metal-nanoparticle-formulated inks based on the thermal sintering mechanism often suffer from overheating, rough film surface, low adhesion, and poor metal quality, which are not desirable for most flexible electronic applications. In recent years, a bottom-up strategy termed as polymer-assisted metal deposition (PAMD) shows great promise in addressing the abovementioned challenges. Here, a detailed review of the development of PAMD in the past decade is provided, covering the fundamental chemical mechanism, the preparation of various soft and conductive metallic materials, the compatibility to different printing technologies, and the applications for a wide variety of flexible and wearable electronic devices. Finally, the attributes of PAMD in comparison with conventional nanoparticle strategies are summarized and future technological and application potentials are elaborated.

A Solid‐State Aqueous Electrolyte‐Gated Field‐Effect Transistor as a Low‐Voltage Operation Pressure‐Sensitive Platform

AbstractFlexible pressure sensors are increasingly impacting a wide variety of novel applications such as wearable health care sensors, in vivo monitoring, and even artificial skin. As a fundamental device component, organic field‐effect transistors (OFETs) are of great interest due to their inherent advantages related to low‐cost solution fabrication processes and compatibility with plastic substrates. During OFET fabrication, it is almost impossible to avoid the water traces in the organic semiconductor (OSC) active layer, especially when ambient solution processing techniques are employed. Water exhibits a strong influence on the electrical performance in OFETs, such as hysteresis and nonideal transfer characteristics. Here, it is shown that the presence of water in OSCs also results in pressure‐sensitive devices caused by the modification of the water dipole alignment. This exciting phenomenon is exploited in a novel OFET, namely, hydrogel‐based electrolyte‐gated organic field‐effect transistor (HYGOFET), where a soft water‐based hydrogel layer is employed as a dielectric layer. The hydrogel layer plays two major contributions: 1) providing a constant saturated humidity environment and 2) reducing the operation voltage. The HYGOFET exhibits a high electrical performance and relative long‐term stability. Importantly, this device also exhibits an excellent pressure response in the low‐pressure regime (&lt;10 kPa) working with a very low power consumption.

Carbon nanotubes embedded poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) hybrid hole collector for inverted planar perovskite solar cells

This study presents a hybrid hole collector that consists of metallic single-walled carbon nanotubes (CNTs) and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and is applicable in inverted planar perovskite solar cells. The drop-casted CNTs exhibit superior optical transmission and hole extraction properties compared to conventional PEDOT:PSS; however, the inherent random networks of CNTs result in many vacancies between nanotubes, causing recombination losses when employed solely as a hole transport layer in the planar architecture of solar cells. Thus, the proposed hybrid hole collector is designed by blending CNTs with various mixture ratios (10–50%) of PEDOT:PSS to enhance the electron-blocking properties. The preferred CNT (70%)/PEDOT:PSS (30%) composition shows a dense, pinhole-free surface and better photoluminescence quenching properties than pristine PEDOT:PSS. After device fabrication, we demonstrate that this hybrid hole collector impressively enhanced average power conversion efficiency from 13.2% to 15.6% (up to 16.0% for best-performing cell) with negligible hysteresis. Time-correlated single-photon counting and conductive atomic force microscopy analyses elucidate the performance progress for the CNT/PEDOT:PSS composite in terms of better hole collection and highly conductive characteristics. This approach supports simple solution-processing techniques at low temperatures, which can construct promising routes for the development of inverted planar perovskite-based photovoltaics with reduced hygroscopic and acidic PEDOT:PSS content.

A solution-processed binary composite as a cathode material in lithium–sulfur batteries

Poly (acrylonitrile) (PAN), acetylene black (AB) and graphene oxide (GO), as conductive constituents, were mixed with sulfur by solution-processing technique using dimethyl sulfoxide as a solvent. The physical properties of the as prepared composites were characterized by X-ray diffraction, Raman and scanning electron microscope analysis. The electrochemical property of S/GO composite material exhibits better cyclical stability. The first-cycle capacity obtained by S/GO composite was 937 mAh g−1 at 0.1 C with coulombic efficiency of 98% and good cycle ability around 813 mAh g−1 discharge capacity at the 50th cycle which is higher than of S/PAN and S/AB composite.

Electronic devices fabricated on mist-CVD-grown oxide semiconductors and their applications

This review summarizes progress in the fabrication of Schottky diodes (SDs), metal–semiconductor and metal–oxide–semiconductor FETs on mist-chemical vapor deposition-(CVD)-grown oxide semiconductor thin films for optical displays, high power devices, and gas sensing applications. These devices generally showed high on-currents, high rectification and on–off ratios. Mist-CVD-grown IGZO and ZTO MESFETs displayed an extreme stability against numerous standard stress conditions. Negative bias temperature stress produced a significant and permanent improvement in the performance of amorphous oxide SDs and MESFETs. Sub-kV breakdown voltage and low specific on-resistance of 0.4 mΩ cm2 were realized in vertical Sn-doped α-Ga2O3 Schottky barrier diodes by Oda et al. [Appl. Phys. Express 9, 021101 (2016)] but severe current collapse was observed in planar Sn-doped α-Ga2O3 MESFETs. Mist CVD has demonstrated its capacity for not only atomic layer-by-layer control but also the growth of active layers in high-performance electronic devices, even though it is a solution-processed atmospheric pressure technique.

Electrical transportation mechanisms of molybdenum disulfide flakes-graphene quantum dots heterostructure embedded in polyvinylidene fluoride polymer

In the interest of the trend towards miniaturization of electronic gadgets, this study demonstrates a high-density data storage device with a very simple three-stacking layer consisting of only one charge trapping layer. A simple solution-processed technique has been used to fabricate the tristable non-volatile memory. The three-stacking layer was constructed in between two metals to form a two-terminal metal-insulator-metal structure. The fabricated device showed a large multilevel memory hysteresis window with a measured ON/OFF current ratio of 107 that might be attributed to the high charge trapped in molybdenum disulphide (MoS2) flakes-graphene quantum dots (GQDs) heterostructure. Transmission electron microscopy was performed to examine the orientation of MoS2-GQD and mixture dispersion preparation method. The obtained electrical data was used further to speculate the possible transport mechanisms through the fabricated device by a curve fitting technique. Also, endurance cycle and retention tests were performed at room temperature to investigate the stability of the device.

Comprehensive study on photophysical properties of Eu(TTA)3bipy phosphor molecularly doped in PMMA and PS matrices

Abstract Successful synthesis of the most studied europium activated β-diketonate red light emitting complex Eu(TTA)3bipy in which 2,2′ bipyridine is used as a synergistic ligand has been demonstrated. This complex is incorporated into Polymethylmetha acrylate (PMMA) and Polysterene (PS) at 10 and 25 wt% to check its compatibility with polymers. The photophysical properties of molecularly doped blended thin films were characterized by UV–visible absorption spectra and photoluminescence (PL) spectra in the solid state as well as by dissolving them in different organic solvents such as chloroform, tetrahydrofuran (THF), toluene (basic) and acetic acid (acidic). From the results of UV–vis absorption spectra, probability transition parameters were calculated. Thin films illustrated red emission, always peaking at 614 nm when excited at 380 nm, irrespective of solid state or solvated state. Comparison of optical intensities of the doped thin films dissolved in chloroform for different wt % and the pure complex in the same solvent reveals enhancement in PL intensity in the doped thin films rather than in pure complex. Relative intensity ratio (R-values) for different wt% of doping in PMMA and PS matrix were found to be in the range of 13.0–14.3. CIE coordinates of Eu (TTA)3bipy in PMMA and PS for 10 and 25 wt% in solid state were found to be (0.66, 0.34) and (0.66, 0.33), whereas in solvated state the same was found to be (0.67, 0.32) and (0.66, 0.34), respectively, clearly indicating unique emission wavelength. These results dictates that the blended films are more economical as compared to the pure Eu(TTA)3bipy, proving its great potential as strong red light emitting phosphor for the fabrication of optoelectronic devices such as OLEDs, flat panel displays by solution processing techniques.