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Mechanisms for Enhanced State Retention and Stability in Redox-Gated Organic Neuromorphic Devices
摘要： Recent breakthroughs in artificial neural networks (ANNs) have spurred interest in efficient computational paradigms where the energy and time costs for training and inference are reduced. One promising contender for efficient ANN implementation is crossbar arrays of resistive memory elements that emulate the synaptic strength between neurons within the ANN. Organic nonvolatile redox memory has recently been demonstrated as a promising device for neuromorphic computing, offering a continuous range of linearly programmable resistance states and tunable electronic and electrochemical properties, opening a path toward massively parallel and energy efficient ANN implementation. However, one of the key issues with implementations relying on electrochemical gating of organic materials is the state-retention time and device stability. Here, revealed are the mechanisms leading to state loss and cycling instability in redox-gated neuromorphic devices: parasitic redox reactions and out-diffusion of reducing additives. The results of this study are used to design an encapsulation structure which shows an order of magnitude improvement in state retention and cycling stability for poly(3,4-ethylenedioxythio phene)/polyethyleneimine:poly(styrene sulfonate) devices by tuning the concentration of additives, implementing a solid-state electrolyte, and encapsulating devices in an inert environment. Finally, a comparison is made between programming range and state retention to optimize device operation.
关键词： resistive memory,PEDOT:PSS,polymer semiconductor,artificial synapse,neural network
更新于2025-09-23 15:21:01
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Luminescent switch of polysaccharide-peptide-quantum dot nanostructures for targeted-intracellular imaging of glioblastoma cells
摘要： Glioblastoma multiforme (or GBM) remains one of the deadliest types of brain cancers. Nanomedicine can offer new strategies for fighting against GBM by combining the earliest possible diagnosis with multiple options of therapy. Hence, in this work, cysteine (Cys) and Poly-L-Arginine (PA) moieties were grafted to carboxymethyl cellulose (CMC) to produce biofunctional hybridized macromolecules (CMC_Cys and CMC_PA). These polymer-peptide conjugates were used simultaneously as surface capping ligands and biofunctional modifiers for the synthesis of ternary Ag-In-S (AIS) quantum dots (AIS QDs) via a green chemical process in aqueous medium and room temperature. These core-shell supramolecular nanostructures (AIS@CMC, AIS@CMC_Cys, and AIS@CMC_PA) were tested as fluorescent nanoprobes (“OFF-ON”) for targeted bioimaging and in vitro intracellular tracking of glioblastoma cells (GBM, U-87 MG). The nanosystems were characterized for physicochemical, structural, and morphological properties by NMR, UV–Vis, PL, FTIR, TEM/EDX/SAED, zeta potential, and DLS. Cytocompatibility was evaluated by mitochondrial activity assay, and confocal laser scanning microscopy was performed for investigating the kinetics of cellular uptake. The grafting caused a noticeable reduction of surface charges, associated with a drastic photoluminescence quenching (i.e., “OFF-state”) of AIS@CMC_Cys and AIS@CMC_PA compared to unmodified AIS@CMC. This effect was smartly applied for bioimaging GBM cells and for monitoring the internalization process by intracellular tracking, which underwent strong “de-quenching” at very early incubation times (~5 min). Thus, these novel hybrid nanocolloids produced via eco-friendly scalable aqueous process show potential as responsive fluorescent bioprobes for bioimaging and tracking intracellular pathways and mechanisms as a powerful weapon for fighting against brain cancer cells.
关键词： nanoconjugates,nanomaterials,colloids,polymer-semiconductor nanoprobes,supramolecular nanoparticles,fluorescent nanoparticles
更新于2025-09-23 15:19:57
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Polarization Properties and Polarization Depth Profiles of (Cd:Zn)S/P(VDF-TrFE) Composite Films in Dependence of Optical Excitation
摘要： The influence of optical excitation intensity on the electrical, ferroelectric and pyroelectric properties of ferroelectric-semiconductor-composites was investigated. For this purpose, composite thin films consisting of poly(vinylidene fluoride-co-trifluoroethylene) and 10 vol % (Cd:Zn)S particles with a thickness of 34 μm were fabricated. The samples were used to measure the absolute pyrocoefficient and to determine the relative pyroelectric depth profile using Laser Intensity Modulated Method. It was shown that a polarization of the samples without an optical excitation at the utilized relatively small peak-to-peak voltages could not be verified by the Sawyer–Tower circuit and the measurement setup of the pyroelectric coefficient, respectively. Both remanent polarization and pyroelectric coefficients increased with increasing optical excitation intensity during poling as well as increasing peak-to-peak voltage. The pyrocoefficient shows a temporal decay in the first hours after poling. The specific heat and thermal conductivity or the thermal diffusivity are required for the calibration of the pyroelectric depth profile. Rule of mixture and photo-acoustic investigations proved that the thermal properties of the utilized composites do not differ significantly from those of the pristine polymer. Based on the pyroelectric depth profile which is proportional to the polarization profile, the existing “three phase model” has been extended to generate a replacement circuit diagram, explaining the local polarization due to the optical excitation dependency for both local resistivity and local field strength.
关键词： composite,optical excitation,ferroelectric polymer,semiconductor
更新于2025-09-19 17:15:36
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Facile synthesis of a semiconducting bithiophene-azine polymer and its application for organic thin film transistors and organic photovoltaics
摘要： A new azine polymer poly(4,40-didodecyl-2,20-bithiophene-azine) (PDDBTA) was synthesized in only three steps. PDDBTA showed hole mobilities of up to 4.1 (cid:2) 10(cid:3)2 cm2 V(cid:3)1 s(cid:3)1 in organic thin ?lm transistors (OTFTs) as a p-channel material. As a donor in organic photovoltaics (OPVs), power conversion e?ciencies (PCEs) of up to 2.18% were achieved, which is the ?rst example of using an azine-based polymer for OPVs. These preliminary results demonstrate the potential of bithiophene-azine polymers as a new type of low-cost semiconductor material for OPVs and other organic electronics.
关键词： azine polymer,semiconductor material,organic photovoltaics,organic thin film transistors
更新于2025-09-19 17:13:59
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Influences of Energetically Controlled Dielectric Functionality on Polymer Field-Effect Transistor Performance
摘要： We systematically demonstrated the effects of surface modification of gate dielectrics and the thermal annealing of an ad-deposited polymer semiconducting film on the electrical performance of organic field-effect transistors (OFETs) in which they were incorporated. Chemically or energetically engineered dielectrics were designed by introducing various end-functional groups (CF3, CH3, NH2, Cl, and SH). Poly(dioctyl-quaterthiophene-dioctyl-bithiazole) (PDQDB), consisting of 5,5 ′ -bithiazole and oligothiophene rings, was employed as the polymer semiconductor. We analyzed the PDQDB semiconducting films’ crystalline character, which has an important effect on the FET performance, and confirmed that the crystallinity of the PDQDB semiconducting films was higher in the cases (CF3 and CH3) of low surface energy than in the cases (NH2, SH, and Cl) of high surface energy, yielding μFET values as high as 0.13 and 0.12 cm2 V?1 s?1 for the CF3 and CH3 cases, respectively. Another important observation was the tendency of the μFET value to change depending on the thermal annealing temperature—increasing and decreasing in the cases of surface functionalities with low and high surface energies, respectively. These results could be interpreted on the basis of the differently competitive molecule–molecule and molecule–dielectric surface interactions, where the π–π stacking configuration of the conjugated molecular structures was enhanced on lower-energy surfaces. We also discussed the effect of permanent dipoles for the engineered self-assembled monolayer dielectrics on the threshold and turn-on voltages in the PDQDB FET devices.
关键词： thermal annealing,surface modification,polymer semiconductor,organic field-effect transistors,dielectric functionality
更新于2025-09-12 10:27:22
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Self-assembled monolayer for polymer-semiconductor interface with improved interfacial thermal management
摘要： Reliability and lifespan of highly miniaturized and integrated devices will be effectively improved if excessive accumulated heat can be quickly transported to heat sinks. In this study, both molecular dynamics (MD) simulations and experiments were performed to demonstrate that self-assembled monolayers (SAMs) have high potential in interfacial thermal management and can enhance thermal transport across polystyrene (PS) / silicon (Si) interface, modelling the common polymer/semiconductor interfaces in actual devices. The influence of packing density and alkyl-chain length of SAMs are investigated. Firstly, MD simulations show that the interfacial thermal transport efficiency of SAM is higher with high packing density. The interfacial thermal conductance (ITC) between PS and Si can be improved up to 127 ± 9 MW m-2 K-1, close to the ITC across metal and semiconductor interface. At moderate packing density, the SAMs with less than 8 carbon atoms in alkyl-chain show superior improvements over those with more carbons due to the assembled structure variation. Secondly, time-domain thermoreflectance technique was employed to characterize the ITCs of a bunch of Al/PS/SAM/Si samples. C6-SAM enhances the ITC by 5 folds, from 11 ± 1 MW m-2 K-1 to 56 ± 17 MW m-2 K-1. The interfacial thermal management efficiency will weaken when alkyl-chain exceeds 8 carbon atoms, which agrees with the ITC trend from MD simulations at moderate packing density. The relationship between SAM morphology and interfacial thermal management efficiency is also discussed in detail. This study demonstrates the feasibility of molecular level design for interfacial thermal management from both theoretical calculation and experiment, and may provide a new idea for improving the heat dissipation efficiency of micro devices.
关键词： polymer/semiconductor interface,time-domain thermoreflectance,molecular dynamics simulation,self-assembled monolayer,interfacial thermal management
更新于2025-09-11 14:15:04
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Uniform Insulating Properties of Low-Temperature Curable Gate Dielectric for Organic Thin-Film Transistor Arrays on Plastic Substrate
摘要： Achieving a high-resolution display on a plastic substrate requires a to ensure dimensional stability during fabrication process, including the deposition of gate dielectrics. Evaluation platform to confirm the uniform insulating properties of organic dielectric material prior to actual application to organic thin-film transistor (OTFT) arrays was proposed. This test method enabled verification of the suitability of the low-temperature curable dielectric and chemical resistance during fabrication process. A cross-linked poly(hydroxy imide) (PHI) that can be cured at a low temperature of 130°C exhibited stable insulating properties in a large area that sudden breakdown was not observed in an electric field up to 4 MV/cm. Thiophene-thiazole-based copolymer semiconductor was used as an active layer and inkjet-printed. In all the processes, the temperature of the substrate was kept below 130°C, and 4.8-inch electrophoretic display panels on a polyethylene naphthalate (PEN) substrate with a resolution of 98 dpi was demonstrated.
关键词： Organic thin-film transistors,Organic gate dielectric,Plastic substrates,Low-temperature process,Polymer semiconductor,Flexible displays,Inkjet printing
更新于2025-09-10 09:29:36