Aqueous-Alcohol-Processable High-Mobility Semiconducting Copolymers with Engineered Oligo(ethylene glycol) Side Chains

Replacement of toxic chlorinated solvents with eco- and human-friendly solvents is an important task for the successful implemention of next-generation polymer electronics technology. Herein, we designed and synthesized five aqueous-alcohol-processable conjugated copolymers by incorporating linear or branched oligo­(ethylene glycol) side chains and systematically investigated their material and electronic properties. The resulting benzothiadiazole-based donor–acceptor alternating copolymers were well-soluble in both an ethanol/water mixed solvent and a chlorinated solvent, and their thin films showed distinct morphologies and crystalline characteristics that resulted from the self-assembling properties of the engineered side chains. Moreover, the copolymers showed excellent electrical characteristics with high hole mobilities of up to 0.1 cm2 V–1 s–1, which is among the highest values reported thus far for polymer field-effect transistors processed using truly eco- and human-friendly solvents without the use of any surfactants. These results clearly demonstrate the immense potential of branched oligo­(ethylene glycol) side chains for application in green electronics

Solid Lipid Nanoparticles of Curcumin Designed for Enhanced Bioavailability and Anticancer Efficiency

Curcumin (Cur) has anticancer properties but exhibits poor aqueous solubility, permeability, and photostability. In this study, we aimed to develop a solid lipid nanoparticle (SLN) system to enhance Cur bioavailability. The characteristics of Cur-loaded SLNs prepared by sonication were evaluated using UV–vis and Fourier transform infrared spectroscopy. The mean particle size of the stearic acid-based, lauric acid-based, and palmitic acid-based SLNs was 14.70–149.30, 502.83, and 469.53 nm, respectively. The chemical interactions between Cur and lipids involved hydrogen bonding and van der Waals forces. The formulations with high van der Waals forces might produce a neat arrangement between Cur and lipids, leading to a decrease in particle size. The Cur formulations showed enhanced cytotoxicity in HeLa, A549, and CT-26 cells compared with pure Cur. Additionally, the anticancer effect is dependent on particle size and the type of cell line. Therefore, Cur-loaded SLNs have the potential for use in anticancer therapy

Ladder-Type Silsesquioxane Copolymer Gate Dielectrics for High-Performance Organic Transistors and Inverters

A ladder-type poly­(phenyl-<i>co</i>-methacryl silsesquioxane) (PPMSQ) copolymer was developed for use as a gate dielectric in high-performance organic field-effect transistors (OFETs). The ladder-type PPMSQ copolymer was synthesized via the hydrolysis of two types of monomers, methacryloxypropyltrimethoxysilane and phenyltrimethoxysilane, followed by a condensation polymerization. The phenyl groups in one monomer were introduced to enhance the structural ordering of the overlying organic semiconductors, whereas the methacryloxypropyl groups in the other monomer were introduced to cross-link the polymer chains via thermal- or photocuring. The curing process enhanced the electrical strength of the gate dielectric layer due to the formation of a network structure with a reduced free volume. Thermal curing reduced the surface energy of the gate dielectrics, which improved the structural order of the overlying organic semiconductors and promoted the formation of large grains. The ladder-type PPMSQ was used as a gate dielectric to produce benchmark p- and n-channel OFETs based on pentacene and <i>N</i>,<i>N</i>′-dioctyl-3,4,9,10-perylenedicarboximide (PTCDI-C₈), respectively. The resulting OFETs exhibited excellent electrical performances, including a high carrier mobility (0.53 cm² V^–1s^–1 for the p-type pentacene OFET and 0.17 cm² V^–1s^–1 for the n-type PTCDI-C₈ OFET) and a high ON/OFF current ratio exceeding 10⁴. The photocured patterned PPMSQ film was successfully used to fabricate complementary OFET-based inverters that yielded high gains. The use of the ladder-type PPMSQ gate dielectrics provides a novel approach to realizing next-generation organic electronics

Defect-Free Copolymer Gate Dielectrics for Gating MoS₂ Transistors

In this study, the poly­(2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane-<i>co</i>-cyclohexyl methacrylate) [p­(V4D4-<i>co</i>-CHMA)] copolymer was developed for use as a gate dielectric in molybdenum disulfide (MoS₂) field-effect transistors (FETs). The p­(V4D4-<i>co</i>-CHMA) copolymer was synthesized via the initiated chemical vapor deposition (<i>i</i>CVD) of two types of monomers: 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane (V4D4) and cyclohexyl methacrylate (CHMA). Four vinyl groups of V4D4 monomers and cyclohexyl groups of CHMA monomers were introduced to enhance the electrical strength of gate dielectrics through the formation of a highly crosslinked network and to reduce the charge trap densities at the MoS₂–dielectric interface, respectively. The <i>i</i>CVD-grown p­(V4D4-<i>co</i>-CHMA) copolymer films yielded a dielectric constant of 2.3 and a leakage current of 3.8 × 10^–11 A/cm² at 1 MV/cm. The resulting MoS₂ FETs with p­(V4D4-<i>co</i>-CHMA) gate dielectrics exhibited excellent electrical properties, including an electron mobility of 35.1 cm²/V s, a subthreshold swing of 0.2 V/dec, and an on–off current ratio of 2.6 × 10⁶. In addition, the environmental and operational stabilities of MoS₂ FETs with p­(V4D4-<i>co</i>-CHMA) top-gate dielectrics were superior to those of devices with SiO₂ back-gate dielectrics. The use of <i>i</i>CVD-grown copolymer gate dielectrics as demonstrated in this study provides a novel approach to realizing next-generation two-dimensional electronics

Functionalized Organic Material Platform for Realization of Ternary Logic Circuit

Negative differential resistance/transconductance (NDR/NDT) has been attracting significant attention as a key functionality in the development of multivalued logic (MVL) systems that can overcome the limits of conventional binary logic devices. A high peak-to-valley current ratio (PVCR) and more than double-peak transfer characteristics are required to achieve a stable MVL operation. In this study, an organic NDR (ONDR) device with double-peak transfer characteristics and a high peak-to-valley current ratio (PVCR; >102) is fabricated by utilizing an organic material platform for the development of a key element device for MVL applications. The organic NDT (ONDT) device is fabricated using a series connection of electron-dominant (P­(NDI2OD-Se2)) and hole-dominant (P­(DPP2DT-T2)) channel ambipolar organic field-effect transistors (AOFETs), and the NDR feature is achieved via correlated biasing of the ONDT device. The PVCR of the ONDT device can reach up to 13,000 via carrier transfer modulation of the AOFETs by varying the PMMA:P­(VDF-TrFE) ratio of the mixed layer that is used as the top-gate dielectric of each AOFET. Further, ternary latch circuit operation is demonstrated using the developed ONDR device that stores three logic states with three distinct and controllable output states by adjusting the PMMA:P­(VDF-TrFE) ratio of the dielectric layer

Synthesis, Molecular Packing, and Electrical Properties of New Regioisomeric n‑type Semiconducting Molecules with Modification of Alkyl Substituents Position

We design and synthesize a series of regioisomeric n-type small molecules, which have an identical diketopyrrolopyrrole (DPP) core and 2-(2,3-dihydro-3-oxo-1H-inden-1-ylidene)­propanedinitrile (INCN) terminal groups with octyl substituents at different positions. The isomeric structures are confirmed by two-dimensional NMR spectroscopy based on the heteronuclear multiple-bond coupling method. Incorporation of the electron-deficient DPP and strongly electron-withdrawing INCN groups yields deep frontier molecular orbitals with n-type charge-transport properties in solution-processed organic field-effect transistors (OFETs). Interestingly, a minor change in the substitution position of the octyl side chains significantly influences the optoelectronic and morphological properties of the thin film. The polycrystalline morphology of the as-cast films is reorganized differently with thermal annealing depending on the octyl topology, significantly affecting the OFET performance. With thermal treatment at 200 °C, the kinked DPP­(EH)-INCNO1 (EH = 2-ethylhexyl) structures transform into single crystalline-like structures, exhibiting a remarkably improved electron mobility up to ∼0.6 cm2V−1 s−1 compared with DPP­(EH)-INCNO2 isomers. The more linear DPP­(EH or HD)-INCNO2 (HD = 2-hexyldecyl) molecules become more crystalline with thermal treatments, but their polycrystalline packing structures with large grain boundaries are the main reason for their lower electron mobility. When the solubilizing alkyl substituents are selected, careful molecular design is needed, with consideration of both the solubility and intermolecular packing, for optimizing the optoelectronic properties

Allrounder Strategy for Photopatterning Silver Nanowire Network Electrodes

Despite their high optical transparency and electrical conductivity, the commercialization of silver nanowire materials as transparent electrodes is challenging owing to the lack of a scalable micropatterning process. This paper proposes a versatile method for photopatterning silver nanowire networks, based on photoinduced nanowire–nanowire and nanowire–substrate cross-linking. Because the proposed method requires only a small loading of the photocross-linking agent, the intrinsic physical characteristics of the silver nanowire network can be preserved. Furthermore, through the roughness-assisted wetting phenomenon, the resulting patterns can be selectively hybridized to form bilayered nanowire/conducting polymer electrodes. The resulting hybrid transparent electrodes exhibit a low roughness, excellent tolerance to oxidation or electrochemical processes, and mechanical stability against bending without compromising the excellent optical/electrical characteristics achievable from the pristine silver nanowire network. These benefits are integrated to assemble an active-matrix-driven electrochromic display. The proposed method can thus facilitate the practical application of silver nanowire network based transparent electrodes