Dissolution Behavior of Fluoroalkylated Diazonaphthoquinone and Its Blends with Fluorinated Copolymers under UV Irradiation.

This article reports on the synthesis of materials containing both a fluoroalkyl group and a diazonaphthoquinone (DNQ) moiety as well as the fabrication of negative- and positive-tone stencil patterns. Additionally, the photoreaction mechanism that contributes to the pattern formation process is discussed, and the application of these materials is explored in the pixel-formation process in organic light-emitting diode (OLED) displays. Fluoroalkylated diazonaphthoquinone (RF2D1) was synthesized using chemically binding a DNQ unit, which can be converted into carboxylic acid derivatives having stronger polarity, with two fluorinated alkyl chains. The purified compound is found to be soluble in a nonpolar fluorous solvent and can be uniformly coated as a thin film. When the thin film of RF2D1 is exposed to 365 nm UV light, its solubility in a fluorous solvent decreases due to the Wolff rearrangement and subsequent hydrolysis of a ketene moiety. In contrast, when a mixture of RF2D1 and a hydrophobic, fluorinated copolymer is tested for the patterning process, the copolymer delays the conversion of the ketene intermediate to carboxylic acid, resulting in the dissolution of the exposed areas in the fluorous solvent. Finally, the applicability of these materials in micropatterning is demonstrated by adopting them in the orthogonal photolithography process to create pixels of OLEDs.

High Performance Transparent Silver Grid Electrodes for Organic Photovoltaics Fabricated by Selective Metal Condensation.

Silver grid electrodes on glass and flexible plastic substrates with performance that exceeds that of commercial indium-tin oxide (ITO) coated glass are reported and show their suitability as a drop-in replacement for ITO glass in solution-processed organic photovoltaics (OPVs). When supported on flexible plastic substrates these electrodes are stable toward repeated bending through a small radius of curvature over tens of thousands of cycles. The grid electrodes are fabricated by the unconventional approach of condensation coefficient modulation using a perfluorinated polymer shown to be far superior to the other compounds used for this purpose to date. The very narrow line width and small grid pitch that can be achieved also open the door to the possibility of using grid electrodes in OPVs without a conducting poly(3,4-ethylenedioxythiophene-poly(styrenesulfonate) (PEDOT: PSS) layer to span the gaps between grid lines.

Extreme UV Resist Exhibiting Synergism between Chemical and Physical Crosslinking Mechanisms.

Carbon-fluorine bonds in fluorinated molecules can undergo homolytic cleavage reactions when electrons are injected, and the resulting radicals combine to form network structures characterized by reduced solubility. This crosslinking chemistry suggests a new category of patterning materials that function under electron beam (e-beam) and extreme ultraviolet (EUV) lithographic conditions. Although this chemistry enables the production of 50 nm or smaller-sized features of simple fluoroalkylated polymers, it is limited by the need for relatively large amounts of irradiation energy to achieve required solubility changes. Therefore, this study was undertaken to devise a sensitivity-enhancing strategy based on a synergistic combination of radical crosslinking and hydrogen-bonding interactions between highly fluoroalkylated copolymers. An alternating copolymer was synthesized using tert-butoxystyrene and a fluoroalkylated maleimide, the former of which produces active hydrogens through catalytic acidolysis reactions. When the polymer was blended with a catalytic amount of a photoacid generator and subjected to lithographic patterning tests under e-beam and EUV irradiation, the deprotection reactions of tert-butoxy moieties proceeded at room temperature and led to a solubility decrease. We presume the small number of hydroxyl moieties produced formed an intermolecular hydrogen-bonding network, which acted synergistically with the covalent crosslinks generated by C-F bonds. When 30 nm features of copolymer thin films were fabricated by EUV lithography, sensitivity was improved by 25-34% without significant deterioration of pattern quality, especially line-edge roughness. These results demonstrate that EUV resists with improved patterning capabilities can be achieved by combining catalytic acidolysis reactions and noncatalytic crosslinking chemistry.

Triggering ZT to 0.40 by Engineering Orientation in One Polymeric Semiconductor.

Breaking the thermoelectric (TE) trade-off relationship is an important task for maximizing the TE performance of polymeric semiconductors. Existing efforts have focused on designing high-mobility semiconductors and achieving ordered molecular doping, ignoring the critical role of the molecular orientation during TE conversion. Herein, the achievement of ZT to 0.40 is reported by fine-tuning the molecular orientation of one diketopyrrolopyrrole (DPP)-based polymer (DPP-BTz). Films with bimodal molecular orientation yield superior doping efficiency by increasing the lamellar spacing and achieve increased splitting between the Fermi energy and the transport energy to enhance the thermopower. These factors contribute to the simultaneous improvement in the Seebeck coefficient and electrical conductivity in an unexpected manner. Importantly, the bimodal film exhibits a maximum power factor of up to 346 µW m-1 K-2 , >400% higher than that of unimodal films. These results demonstrate the great potential of molecular orientation engineering in polymeric semiconductors for developing state-of-the-art organic TE (OTE) materials.

Single-Component Hydrophilic Terpolymer Thin Film Systems for Imparting Surface Chemical Versatility on Various Substrates.

We demonstrate a single-component hydrophilic photocrosslinkable copolymer system that incorporates all critical functionalities into one chain. This design allows for the creation of uniform functional organic coatings on a variety of substrates. The copolymers were composed of a poly(ethylene oxide)-containing monomer, a monomer that can release a primary amine upon UV light, and a monomer with reactive epoxide or cyclic dithiocarbonate with a primary amine. These copolymers are easily incorporated into the solution-casting process using polar solvents. Furthermore, the resulting coating can be readily stabilized through UV light-induced crosslinking, providing an advantage for controlling the surface properties of various substrates. The photocrosslinking capability further enables us to photolithographically define stable polymer domains in a desirable region. The resulting copolymer coatings were chemically versatile in immobilizing complex molecules by (i) post-crosslinking functionalization with the reactive groups on the surface and (ii) the formation of a composite coating by mixing varying amounts of a protein of interest, i.e., fish skin gelatin, which can form a uniform dual crosslinked network. The number of functionalization sites in a thin film could be controlled by tuning the composition of the copolymers. In photocrosslinking and subsequent functionalizations, we assessed the reactivity of the epoxide and cyclic dithiocarbonate with the generated primary amine. Moreover, the orthogonality of the possible reactions of the presented reactive functionalities in the crosslinked thin films with complex molecules is assessed. The resulting copolymer coatings were further utilized to define a hydrophobic surface or an active surface for the adhesion of biological objects.

Near-field infrared nanoscopic study of EUV- and e-beam-exposed hydrogen silsesquioxane photoresist.

This article presents a technique of scattering-type scanning near-field optical microscopy (s-SNOM) based on scanning probe microscopy as a nanoscale-resolution chemical visualization technique of the structural changes in photoresist thin films. Chemical investigations were conducted in the nanometer regime by highly concentrated near-field infrared on the sharp apex of the metal-coated atomic force microscopy (AFM) tip. When s-SNOM was applied along with Fourier transform infrared spectroscopy to characterize the extreme UV- and electron-beam (e-beam)-exposed hydrogen silsesquioxane films, line and space patterns of half-pitch 100, 200, 300, and 500 nm could be successfully visualized prior to pattern development in the chemical solutions. The linewidth and line edge roughness values of the exposed domains obtained by s-SNOM were comparable to those extracted from the AFM and scanning electron microscopy images after development. The chemical analysis capabilities provided by s-SNOM provide new analytical opportunities that are not possible with traditional e-beam-based photoresist measurement, thus allowing information to be obtained without interference from non-photoreaction processes such as wet development.

The roles of individual differences in time perspective, promotion focus, and innovativeness: Testing technology acceptance model.

The goal of this study is to examine the roles of Zimbardo's time perspective along with other individual differences such as promotion focus and innovativeness in perceived ease of use, perceived usefulness, and attitude toward SNSs (social networking sites) in the technology acceptance model (TAM). A total of 234 participants joined this online study in South Korea. As predicted, past positive time perspective (TP) positively affected promotion focus and innovativeness, whereas past negative TP negatively affected them. Present hedonic TP positively affected innovativeness, and present fatalistic TP negatively affected promotion focus each. Future TP also positively related to promotion focus and innovativeness. In addition, simple and serial mediation effects of perceived ease of use and perceived usefulness independently and sequentially mediated the impact of TP on attitude toward SNSs. By considering TP along with promotion focus and innovativeness in conjunction with beliefs in the TAM, this study identifies psychological underpinnings of how individual differences affect technology adoption attitude and behavior. Research implications and future research suggestions will be discussed in detail.

Investigation of correlative parameters to evaluate EUV lithographic performance of PMMA.

Investigations to evaluate the extreme ultraviolet (EUV) lithographic performance of 160 nm thick poly(methyl methacrylate) with 13.5 nm wavelength EUV light were performed using a synchrotron radiation source at Pohang Light Source-II (PLS-II). The single system enabled the determination of the sensitivity, contrast, linear absorption coefficient, critical dimension, and line edge roughness of polymer thin films through tests and measurements. The experimental findings were also compared to theoretical results and those of previously reported studies. According to the results of the dose-to-clear test and transmission measurements, the critical dimension of a line and space pattern (>50 nm) via interference lithography with 250 nm pitch grating agreed well with the results calculated using the lumped parameter model. The experimental results demonstrated that the equipment and test protocol can be used for EUV material infrastructure evaluation in academia and in industry.

Structural and Dynamic Disorder, Not Ionic Trapping, Controls Charge Transport in Highly Doped Conducting Polymers.

Doped organic semiconductors are critical to emerging device applications, including thermoelectrics, bioelectronics, and neuromorphic computing devices. It is commonly assumed that low conductivities in these materials result primarily from charge trapping by the Coulomb potentials of the dopant counterions. Here, we present a combined experimental and theoretical study rebutting this belief. Using a newly developed doping technique based on ion exchange, we prepare highly doped films with several counterions of varying size and shape and characterize their carrier density, electrical conductivity, and paracrystalline disorder. In this uniquely large data set composed of several classes of high-mobility conjugated polymers, each doped with at least five different ions, we find electrical conductivity to be strongly correlated with paracrystalline disorder but poorly correlated with ionic size, suggesting that Coulomb traps do not limit transport. A general model for interacting electrons in highly doped polymers is proposed and carefully parametrized against atomistic calculations, enabling the calculation of electrical conductivity within the framework of transient localization theory. Theoretical calculations are in excellent agreement with experimental data, providing insights into the disorder-limited nature of charge transport and suggesting new strategies to further improve conductivities.

The effects of social comparison orientation on psychological well-being in social networking sites: Serial mediation of perceived social support and self-esteem.

This study investigates the effects of the social comparison orientation in social networking sites on psychological well-being. In particular, it examines the mediation effect of perceived social support and self-esteem in the relationship between social comparison orientation and psychological well-being. Data were collected through an online survey with 236 participants in South Korea. The results showed that social comparison orientation negatively influenced psychological well-being. In the relationship between social comparison orientation and psychological well-being, perceived social support had no mediation effect, self-esteem had a significant negative mediation effect, and perceived social support and self-esteem had a negative serial mediation effect. The social comparison orientation in social networking sites could elicit negative emotions, which decrease perceived social support, self-esteem, and psychological well-being. Theoretical and practical implications as well as suggestions for future studies are discussed in detail.

Highly Sensitive Electrochemical Sensor for Diagnosis of Diabetic Ketoacidosis (DKA) by Measuring Ketone Bodies in Urine.

In this report, we present an enzyme deposited Au electrode for an electrochemical measurement of acetylacetic acid (AcAc) in urine. The electrode has an immobilized layer of a mixture of D-ß-hydroxybutyrate dehydrogenase (HBDH) and nicotinamide adenine dinucleotide (NADH) as sensing material to investigate its electroanalytical properties by means of cyclic voltammetry (CV). The modified electrodes are used for the detection of AcAc and present a linear current increase when the AcAc concentration increases. The electrode presents a limit of detection (LOD) of 6.25 mg/dL in the range of 6.25-100 mg/dL for investigation of clinical relevance. Finally, the electrode was evaluated using 20 patient samples. The measured results of urine ketone by the developed electrode were compared with the clinical results from a commercial kit, and the analysis showed good agreement. The proposed electrode was demonstrated to be a very promising platform as a miniaturized electrochemical analyzer for point-of-care monitoring of the critical biochemical parameters such as urine ketone.

Perfluoroalkylated alternating copolymer possessing solubility in fluorous liquids and imaging capabilities under high energy radiation.

A highly fluorinated alternating polymer, P(RFMi-St), possessing improved thermal properties and patterning capabilities over perfluoroalkyl polymethacrylates under high energy radiation was achieved with semi-perfluorododecyl maleimide (RFMi) and styrene (St). RFMi could be synthesised efficiently via a Mitsunobu reaction condition and copolymerised with St by free radical and reversible-deactivation radical polymerisation protocols. P(RFMi-St) showed a satisfactory glass-transition temperature (108 °C) and intermolecular cross-linking behaviour under electron-beam and commercially more important extreme UV (λ = 13.5 nm) irradiation. The exposed regions lost their solubility, resulting in the successful formation of mechanically non-deteriorated negative-tone images down to 50 nm. In addition, P(RFMi-St) could be solution-processed with chemically non-damaging fluorous liquids, which enabled the polymer to be applied effectively on top of an organic semiconductor layer as a dielectric material (dielectric constant 2.7) for the organic field-effect transistor fabrication.

Two-Color Pixel Patterning for High-Resolution Organic Light-Emitting Displays Using Photolithography.

Nowadays, the display industry is endeavoring to develop technology to provide large-area organic light-emitting diode (OLED) display panels with 8K or higher resolution. Although the selective deposition of organic molecules through shadow masks has proven to be the method of choice for mobile panels, it may not be so when independently defined high-resolution pixels are to be manufactured on a large substrate. This technical challenge motivated us to adopt the well-established photolithographic protocol to the OLED pixel patterning. In this study, we demonstrate the two-color OLED pixels integrated on a single substrate using a negative-tone highly fluorinated photoresist (PR) and fluorous solvents. Preliminary experiments were performed to examine the probable damaging effects of the developing and stripping processes upon a hole-transporting layer (HTL). No significant deterioration in the efficiency of the develop-processed device was observed. Efficiency of the device after lift-off was up to 72% relative to that of the reference device with no significant change in operating voltage. The procedure was repeated to successfully obtain two-color pixel arrays. Furthermore, the patterning of 15 µm green pixels was accomplished. It is expected that photolithography can provide a useful tool for the production of high-resolution large OLED displays in the near future.

New Surface Modification Method To Develop a PET-Based Membrane with Enhanced Ion Permeability and Organic Fouling Resistance for Efficient Production of Marine Microalgae.

This paper presents a new surface modification strategy to develop a poly(ethylene terephthalate) (PET)-based membrane having a hydrophilic surface, high nutrient ion permeability, sufficient mechanical strength, and organic fouling resistance, using an anthracene (ANT)-attached polyethylene glycol (PEG) surface modification agent (SMA) synthesized in this work. During the modification process, the ANT parts of the SMAs poke through and anchor to the surface of a commercial PET woven fabric via physical interactions and mechanical locking. The PEG chain parts coat the surface in the brush and arch forms, which generates a hydration layer on the fabric surface. The consequently obtained surface property and unique structure of the modified PET-based membrane result in higher nitrate ion permeability, organic fouling resistance, and microalgae production compared to those of the unmodified one. These are also affected by the molecular weight of the PEG and the number density of the anchored SMAs. The study demonstrates that this new surface modification method has the potential to allow the development of a desirable PET-based membrane for the efficient massive production of marine microalgae.

Role of Multivalent Interactions in Dynamic-Template-Directed Assembly of Conjugated Polymers.

Dynamic-template-directed assembly is a promising method to enhance molecular ordering and electronic properties of solution-coated polymer semiconductor thin films over a large area. In this work, we establish that multicomponent dynamic templates of complementary chemistries can promote polymer crystallization through cooperative multivalent interactions. We investigate this phenomenon using a combination of templating substrates including a fluoropolymer, a hydrogen-bonded liquid, and an ionic liquid (IL). Template-dependent multiscale morphology is studied by a comprehensive set of characterization techniques to understand how introducing diverse chemical moieties modulates polymer assembly. Our results clearly confirm synergistic effects between components of complementary chemistries constituting the dynamic template. The relative degree of crystallinity is improved by 50-150% for films deposited on multicomponent dynamic templates compared to their neat constituents. In addition, macroscopic alignment is increased significantly (2-5 times) compared to single-component templates. As a result, highly anisotropic charge transport is observed with apparent hole mobilities up to 3.6 cm2 V-1 s-1. In contrast, such a synergistic effect is not observed when using a multicomponent dynamic template of comparable chemistries (i.e., IL and polymerized IL). We elucidate the origin of this synergistic effect by using attenuated total reflectance Fourier transform infrared spectroscopy and isothermal titration calorimetry. When the dynamic template comprises two or more components interacting with complementary binding sites on the conjugated polymer (CP) (esp. backbone vs side chain), the template-polymer interactions is significantly enhanced compared to the sum of single component contributions. These results provide valuable insights into surface-directed CP crystallization during large-area solution coating. Template dynamics is rarely studied and represents a new opportunity for guiding assembly of soft functional matter.

Highly Fluorinated Barium Titanate Nanoparticle Dispersion for Fabrication of Lithographically Patterned Thin Films.

We report the synthesis, characterization, and photopatterning of high-k inorganic nanoparticles that are covered with highly fluorinated carboxylic acid and, as a result, are solution-processable in fluorous liquids. Barium titanate (BTO) nanoparticles, 7-8 nm in diameter, were prepared under solvothermal conditions and were surface-modified with perfluoroalkyl ether-type carboxylic acid molecules via ligand-exchange reactions. Thin films with a high dielectric constant (9.27 at 1 kHz) were achieved by spin-coating homogeneous solutions of BTO nanoparticles in a fluorous solvent (HFE-7500). Additionally, electron-beam lithography and photolithography were applied to the thin films of BTO nanoparticles, yielding BTO patterns with scales of 300 nm and 5 µm, respectively. Thus, an approach for a chemically non-damaging solution process of inorganic materials for device implementation was successfully demonstrated.

Tuning conformation, assembly, and charge transport properties of conjugated polymers by printing flow.

Intrachain charge transport is unique to conjugated polymers distinct from inorganic and small molecular semiconductors and is key to achieving high-performance organic electronics. Polymer backbone planarity and thin film morphology sensitively modulate intrachain charge transport. However, simple, generic nonsynthetic approaches for tuning backbone planarity and the ensuing multiscale assembly process do not exist. We first demonstrate that printing flow is capable of planarizing the originally twisted polymer backbone to substantially increase the conjugation length. This conformation change leads to a marked morphological transition from chiral, twinned domains to achiral, highly aligned morphology, hence a fourfold increase in charge carrier mobilities. We found a surprising mechanism that flow extinguishes a lyotropic twist-bend mesophase upon backbone planarization, leading to the observed morphology and electronic structure transitions.

Ion Gel Dynamic Templates for Large Modulation of Morphology and Charge Transport Properties of Solution-Coated Conjugated Polymer Thin Films.

Dynamic surfaces play a critical role in templating highly ordered complex structures in living systems but are rarely employed for directing assembly of synthetic functional materials. We design ion gel templates with widely tunable dynamics ( Tg) to template solution-coated conjugated polymers. We hypothesize that the ion gel expedites polymer nucleation by reconfiguring its surface to facilitate cooperative multivalent interactions with the conjugated polymer, validated using both experimental and computational approaches. Varying ion gel dynamics enables large modulation of alignment, molecular orientation, and crystallinity in templated polymer thin films. At the optimal conditions, ion-gel-templated films exhibit 55 times higher dichroic ratio (grazing incidence X-ray diffraction) and 49% increase in the relative degree of crystallinity compared to those templated by the neat polymer matrix. As a result, the maximum hole mobilities increase by factors of 4 and 11 along the π-π stacking and the backbone directions. Intriguingly, we observe a synergistic effect between the gel matrix and the ionic liquid that produces markedly enhanced templating effect than either component alone. Molecular dynamics simulations suggest that complementary multivalent interactions facilitated by template reconfigurability underlie the observed synergy. We further demonstrate field-effect transistors both templated and gated by ion gels with average mobility exceeding 7 cm2 V-1 s-1.

High-mobility, trap-free charge transport in conjugated polymer diodes.

Charge transport in conjugated polymer semiconductors has traditionally been thought to be limited to a low-mobility regime by pronounced energetic disorder. Much progress has recently been made in advancing carrier mobilities in field-effect transistors through developing low-disorder conjugated polymers. However, in diodes these polymers have to date not shown much improved mobilities, presumably reflecting the fact that in diodes lower carrier concentrations are available to fill up residual tail states in the density of states. Here, we show that the bulk charge transport in low-disorder polymers is limited by water-induced trap states and that their concentration can be dramatically reduced through incorporating small molecular additives into the polymer film. Upon incorporation of the additives we achieve space-charge limited current characteristics that resemble molecular single crystals such as rubrene with high, trap-free SCLC mobilities up to 0.2 cm2/Vs and a width of the residual tail state distribution comparable to kBT.

Bio-orthogonal fluorinated resist for biomolecules patterning applications.

The patterning of organic materials on solid substrate surfaces has been demonstrated by several methods, such as photolithography, soft lithography, imprint lithography and ink-jet printing. Fluorinated polymers and solvents provide attractive material systems to develop new patterning approaches, as they are chemically orthogonal to non-fluorinated organic molecules, allowing their efficient incorporation in different devices and systems. Moreover, fluorinated polymers are soluble in hydrofluoroether solvents, benign to biomolecules, and can be properly engineered to enable efficient photolithographic patterning. In this work, we report the development of a new photolithographic process for patterning biomolecules on any kind of surfaces either by physical adsorption or covalent bonding. The photoresist is based on a fluorinated material and hydrofluoroether solvents that have minimum interactions with biomolecules and thus they can be characterized as orthogonal to the biomolecules (bio-orthogonal). In both cases, the creation of patterns with dimensions down to 2 µm was achieved. The implementation of the developed photolithographic procedure for the creation of a multi-protein microarray is demonstrated.