Molecular Engineering of Coordination Ligand for Multifunctional Sol-Gel Oxides.

Here a ligand exchange strategy for synthesizing sol-gel oxides is demonstrated to achieve multifunctionality including direct photolithography, high dielectric strength, and high charge carrier mobility, which is challenging to obtain in such oxides. For this purpose, a series of bidentate ligands with azide termini and ethylene-glycol bridges is synthesized, and these ligands are universally applicable to the synthesis of a variety of dielectric and semiconductor oxides. Optimized photolithography conditions yield a high-quality ZrO dielectric film with a high dielectric constant and strength of ≈18 and ≈7 MV cm, respectively.

Hydrophilic Photocrosslinkers as a Universal Solution to Endow Water Affinity to a Polymer Photocatalyst for an Enhanced Hydrogen Evolution Rate.

A universal approach for enhancing water affinity in polymer photocatalysts by covalently attaching hydrophilic photocrosslinkers to polymer chains is presented. A series of bisdiazirine photocrosslinkers, each comprising bisdiazirine photophores linked by various aliphatic (CL-R) or ethylene glycol-based bridge chains (CL-TEG), is designed to prevent crosslinked polymer photocatalysts from degradation through a safe and efficient photocrosslinking reaction at a wavelength of 365 nm. When employing the hydrophilic CL-TEG as a photocrosslinker with polymer photocatalysts (F8BT), the hydrogen evolution reaction (HER) rate is considerably enhanced by 2.

Photophore-Anchored Molecular Switch for High-Performance Nonvolatile Organic Memory Transistor.

Over the past decade, molecular-switch-embedded memory devices, particularly field-effect transistors (FETs), have gained significant interest. Molecular switches are integrated to regulate the resistance or current levels in FETs. Despite substantial efforts, realizing large memory window with a long retention time, a critical factor in memory device functionality, remains a challenge.

Liquid-Film Rupture for Web-like Ag Nanowires toward High-Performance Organic Schottky Barrier Transistors.

Organic vertical transistors are promising device with benefits such as high operation speed, high saturation current density, and low-voltage operation owing to their short channel length. However, a short channel length leads to a high off-current, which is undesirable because it affects the on-off ratio and power consumption. This study presents a breakthrough in the development of high-performance organic Schottky barrier transistors (OSBTs) with a low off-current by utilizing a near-ideal source electrode with a web-like Ag nanowire (AgNW) morphology.

Visible-Light Communication with Lighting: RGB Wavelength Division Multiplexing OLEDs/OPDs Platform.

A multichannel/multicolor visible light communication (VLC) system using entirely organic components, including organic light emitting diodes (OLEDs) and organic photodiodes (OPDs), is developed to demonstrate indoor lighting applications where the integration of OLEDs and OPDs has significant potential. To achieve this, tricolor (Red/Green/Blue(R/G/B))-selective OPD arrays for the receiver and tricolor OLED arrays for the emitter are developed. For (R/G/B)-selective OPDs, a Fabry-Pérot electrode to enhance color selectivity and a thick junction structure to effectively accommodate a wide range of driving voltages are introduced.

Azide-functionalized ligand enabling organic-inorganic hybrid dielectric for high-performance solution-processed oxide transistors.

We propose a highly efficient crosslinking strategy for organic-inorganic hybrid dielectric layers using azide-functionalized acetylacetonate, which covalently connect inorganic particles to polymers, enabling highly efficient inter- and intra-crosslinking of organic and inorganic inclusions, resulting in a dense and defect-free thin-film morphology. From the optimized processing conditions, we obtained an excellent dielectric strength of over 4.0 MV cm, a high dielectric constant of ~14, and a low surface energy of 38 mN m.

Molecular-Switch-Embedded Solution-Processed Semiconductors.

Recent improvements in the performance of solution-processed semiconductor materials and optoelectronic devices have shifted research interest to the diversification/advancement of their functionality. Embedding a molecular switch capable of transition between two or more metastable isomers by light stimuli is one of the most straightforward and widely accepted methods to potentially realize the multifunctionality of optoelectronic devices. A molecular switch embedded in a semiconductor can effectively control various parameters such as trap-level, dielectric constant, electrical resistance, charge mobility, and charge polarity, which can be utilized in photoprogrammable devices including transistors, memory, and diodes.

Topochemical Postulates: Are They Relevant for Topochemical Reactions Occurring at Elevated Temperatures?

A rigid inositol-derived monomer functionalized with azide and alkyne as the complementary reactive groups (CRGs) crystallized as three distinct polymorphs I-III. Despite the unsuitable orientation of CRGs in the crystals for complete polymerization, all the three polymorphs underwent regiospecific and quantitative topochemical azide-alkyne cycloaddition (TAAC) polymerization upon heating to yield three different polymorphs of 1,2,3-triazol-1,4-diyl-linked-poly-neo-inositol. The molecules in these polymorphs exploit the weak intermolecular interactions, free space in the crystal lattice, and heat energy for their large and cooperative molecular motion to attain a transient reactive orientation, ultimately leading to the regiospecific TAAC reaction yielding distinct crystalline polymers.

Covalent Networking of a Conjugated-Polymer Photocatalyst to Promote Exciton Diffusion in the Aqueous Phase for Efficient Hydrogen Production.

A conjugated polymer particle in an aqueous phase is covalently networked in 3D by crosslinking with azide groups, leading to significantly enhanced activity-a high photocatalytic H evolution rate (11 024 µmol g h (λ > 420 nm)) and a high apparent quantum yield (up to 0.8%). The reaction between the photoactive azide and the alkyl chains of the conjugated polymer provides more intact intermolecular polymeric interactions in the colloidal state, thus preventing physical swelling and inhibiting the recombination of photoproduced carriers.

A Molecular-Switch-Embedded Organic Photodiode for Capturing Images against Strong Backlight.

When the intensity of the incident light increases, the photocurrents of organic photodiodes (OPDs) exhibit relatively early saturation, due to which OPDs cannot easily detect objects against strong backlights, such as sunlight. In this study, this problem is addressed by introducing a light-intensity-dependent transition of the operation mode, such that the operation mode of the OPD autonomously changes to overcome early photocurrent saturation as the incident light intensity passes the threshold intensity. The photoactive layer is doped with a strategically designed and synthesized molecular switch, 1,2-bis-(2-methyl-5-(4-cyanobiphenyl)-3-thienyl)tetrafluorobenzene (DAB).

Synergetic contribution of fluorinated azide for high EQE and operational stability of top-illuminated, semitransparent, photomultiplication-type organic photodiodes.

In this study, it is shown that fluorinated azide, employed as a functional additive to photomultiplication-type organic photodiodes (PM-OPDs), can not only enhance the operational stability by freezing the morphology consisting of matrix polymer/localized acceptor but also stabilize the trapped electron states such that the photomultiplication mechanism can be accelerated further, leading to exceptionally high external quantum efficiency (EQE). The consequent semitransparent OPD consisting of molybdenum oxide (MoO)/Au/MoO/photoactive layer/polyethyleneimine ethoxylated/indium tin oxide (ITO) rendered a maximum EQE of over 500 000% and 370 000% under bottom and top illumination, respectively. Owing to the remarkably high EQE, high specific detectivity of 5.

Sublimation-doping with super bases for high-performance solution-processed heterojunction oxide thin film transistors.

We elucidate how non-destructive sublimation-doping of InO/ZnO heterojunctions with various amidine-based organic dopants affects the degree of band bending of the heterojunction and thus the overall performance of solution-processed heterojunction oxide thin-film transistors (TFTs). Ultraviolet photoelectron spectroscopy and X-ray photoelectron spectroscopy analyses show that the stronger the basicity of the dopant, the smaller the - of ZnO that can be induced within a short doping time, resulting in a high electron mobility due to the increased electron density of the InO layer at the vicinity of the heterointerface. Mott-Schottky analysis combined with secondary ion mass spectroscopy shows the preferential modification of - selectively for the ZnO layer.

Surfactant-Induced Solubility Control To Realize Water-Processed High-Precision Patterning of Polymeric Semiconductors for Full Color Organic Image Sensor.

A fully water-based patterning method for polymer semiconductors was developed and utilized to realize high-precision lateral patterning of various polymers. Water-borne polymer colloids, wherein hydrophobic polymers are dispersed in water with the assistance of surfactant molecules, possess a hydrophilic surface when printed onto a substrate. When this surface is exposed to a washing molecule, the surface of the polymer film recovers its original hydrophobic nature.

Synthesis of a photo-responsive single-walled nanoscroll and its photo-reactivity in a nano-layered microenvironment.

A photo-responsive nanoscroll composed of niobate nanosheets and a polyfluoroalkyl azobenzene derivative (C3F-Azo-C6H) is one of the most interesting layered materials because the reversible winding and unwinding motion could be efficiently induced by photo-irradiations. Previously, we have studied a double-walled nanoscroll (DWNS) of niobate that could be synthesized by the intercalation of a cationic polyfluorinated surfactant only into the interlayer I of the layered niobate among the two interlayers, I and II. In this study, we have successfully synthesized another novel photo-responsive single-walled nanoscroll (SWNS) of niobate by a stepwise guest-guest ion-exchange method.

Molecular Engineering of a Donor-Acceptor Polymer To Realize Single Band Absorption toward a Red-Selective Thin-Film Organic Photodiode.

Herein, we explore the strategy of realizing a red-selective thin-film organic photodiode (OPD) by synthesizing a new copolymer with a highly selective red-absorption feature. PCZ-Th-DPP, with phenanthrocarbazole (PCZ) and diketopyrrolopyrrole (DPP) as donor and acceptor units, respectively, was strategically designed/synthesized based on a time-dependent density functional theory calculation, which predicted the significant suppression of the band II absorption of PCZ-Th-DPP due to the extremely efficient intramolecular charge transfer. We demonstrate that the synthesized PCZ-Th-DPP exhibits not only a high absorption coefficient within the red-selective band I region, as theoretically predicted, but also a preferential face-on intermolecular structure in the thin-film state, which is beneficial for vertical charge extraction as an outcome of a glancing incidence X-ray diffraction study.

Polyvinyl alcohol covalently grafted CNT for free-standing, flexible, and high-performance thermoelectric generator film.

We introduce a strategic approach to synthesize covalntly cross-linked carbon nanotube (CNT)-polymer nanocomposites, which can be applied as a free-standing and flexible organic thermoelectric generator film. Esterification of polyvinyl alcohol (PVA) to render PVA-COOH followed by an amide reaction with single-walled CNTs (SWCNTs) functionalized with amino groups (SWCNT-NH) yielded a covalently grafted PVA/SWCNT composite film with an excellent dispersion of SWCNTs within the polymer matrix as confirmed using Fourier-transform infrared spectroscopy and scanning electron microscopy. This amide reaction could be further optimized with the addition of a small amount of Triton™ X-100, which resulted in a better dispersion of SWCNT prior to the amide condensation reaction.

Regioselective S2 reactions for rapid syntheses of azido-inositols by one-pot sequence-specific nucleophilysis.

Triflates of myo-inositol undergo facile solvolysis in DMSO and DMF yielding S2 products substituted with O-nucleophiles; DMF showed slower kinetics. Axial O-triflate undergoes faster substitution than equatorial O-triflate. By exploiting this difference in kinetics, solvent-tuning and sequence-controlled nucleophilysis, rapid synthesis of three azido-inositols of myo-configuration from myo-inositol itself has been achieved.

Photo-induced morphological winding and unwinding motion of nanoscrolls composed of niobate nanosheets with a polyfluoroalkyl azobenzene derivative.

Photo-responsive nanoscrolls can be successfully fabricated by mixing a polyfluoroalkyl azobenzene derivative and a niobate nanosheet, which is exfoliated from potassium hexaniobate. In this study, we have found that the photo-responsive nanoscroll shows a morphological motion of winding and unwinding, which is basically due to the nanosheet sliding within the nanoscroll, by efficient photo-isomerization reactions of the intercalated azobenzene in addition to the interlayer distance change of the nanoscrolls. The relative nanosheet sliding of the nanoscroll is estimated to be ca.

Synthesis of double-wall nanoscrolls intercalated with polyfluorinated cationic surfactant into layered niobate and their magnetic alignment.

The orientation of nanomaterials with an anisotropic nature such as nanoscrolls is very important for realizing their efficient and sophisticated functions in devices, including nanostructured electrodes in artificial photosynthetic cells. In this study, we successfully synthesized a nanoscroll by intercalation of a cationic polyfluorinated surfactant into the interlayer spaces of layered niobate and successfully controlled its orientation by applying an external magnetic field in water. The exfoliated niobate nanosheets were efficiently rolled-up to form nanoscrolls, which have a fine layered structure (d020 = 3.