Controlled Migration of Lithium Cations by Diamine Bridges in Water-Processable Polymer-Based Solid-State Electrolyte Memory Layers for Organic Synaptic Transistors.

Synaptic transistors require sufficient retention (memory) performances of current signals to exactly mimic biological synapses. Ion migration has been proposed to achieve high retention characteristics but less attention has been paid to polymer-based solid-state electrolytes (SSEs) for organic synaptic transistors (OSTRs). Here, OSTRs with water-processable polymer-based SSEs, featuring ion migration-controllable molecular bridges, which are prepared by reactions of poly(4-styrenesulfonic acid) (PSSA), diethylenetriamine (DETA), and lithium hydroxide (LiOH) are demonstrated. The ion conductivity of PSSA:LiOH:DETA (1:0.4:X, PLiD) films is remarkably changed by the molar ratio (X) of DETA, which is attributed to the extended distances between the PSSA chains by the DETA bridges. The devices with the PLiD layers deliver noticeably changed hysteresis reaching an optimum at X = 0.2, leading to the longest retention of current signals upon single/double pulses. The long-term potentiation test confirms that the present OSTRs can gradually build up the postsynaptic current by gate pulses of -2 V, while the long-term depression can be adjusted by varying the depression gate pulses (≈0.2-1.2 V). The artificial neural network simulations disclose that the present OSTRs with the ion migration-controlled PLiD layers can perform synaptic processes with an accuracy of ≈96%.

Influence of Acid-Doped Poly(ethylene imine) Interlayers on the Performance of Polymer:Nonfullerene Solar Cells.

This work reports that ultrathin polymeric films doped with organic acid molecules can act as an electron-transporting interfacial layer in polymer:nonfullerene solar cells. The polymeric interfacial layers, which consist of poly(ethylene imine) (PEI) doped with 3-hydroxypropane-1-sulfonic acid (HPSA) at various HPSA molar ratios, are introduced between transparent indium-tin oxide (ITO) electrodes and polymer:nonfullerene bulk heterojunction layers. The HPSA-doped PEI (PEI:HPSA) films are optically translucent in the wavelength range of ≈300-800 nm, while the acidity of PEI solutions reached ≈pH = 7 at HPSA = 30 mol%. The power conversion efficiency of solar cells is improved by doping 20 mol% HPSA due to the increased short circuit current density without open circuit voltage reduction. The improvement in solar cell performances is attributed to an adequate control of HPSA doping ratios, which spares undoped amine units of PEI for making sufficient net dipole layers with ITO surfaces and makes permanent charges for high electrical conductivity in the layers. The surface morphology and doped states are characterized with atomic force microscopy and X-ray photoelectron spectroscopy.

Water-Soluble Reactive Polymer Blends for Stable Memory Layers in Low-Voltage Nonvolatile Organic Memory Transistors with High Mobility and Data-Retention Characteristics.

Here low-voltage nonvolatile organic memory transistors, featuring high charge-carrier mobility and outstanding data-retention characteristics, by employing water-soluble reactive polymer blends as a gate-insulating memory layer are demonstrated. Blend films of poly(vinyl alcohol) (PVA) and poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPSA) (PVA:PAMPSA) are prepared from their aqueous solutions with various molar ratios of PAMPSA (0-18 mol%) and thermally annealed at 70 and 110 °C. Organic field-effect transistors (OFETs) are fabricated by depositing poly(3-hexylthiophene) (P3HT) channel layers on the thermally treated PVA:PAMPSA films. Results show that the hole mobility of OFETs is remarkably increased (≈294 times at 70 °C and ≈42 times at 110 °C) by adding only 2 mol% PAMPSA to the PVA films and further improved at 10 mol% PAMPSA (>11.7 cm2  V-1 s-1 at 70 °C and >3.8 cm2  V-1  s-1 at 110 °C). The hysteresis characteristics are rather strengthened for the PVA:PAMPSA layers by annealing at 110 °C due to the formation of cross-linking sites, even though the OFETs with the pristine PVA layers do almost lose hysteresis characteristics at 110 °C. The optimized OFETs with the PVA:PAMPSA layers (10 mol%, 110 °C) deliver excellent data retention characteristics during >10 000 memory cycles at a voltage range of -5 to +5 V.

Performance and Stability of Polymer:Nonfullerene Solar Cells with 100 °C-Annealed Electron-Collecting Combination Layers.

Invited for this month's cover is the group of Youngkyoo Kim at the Kyungpook National University. The image shows the improved electron transfer by hybrid combination layers featuring peculiar morphology for better efficiency and stability in polymer solar cells. The Full Paper itself is available at 10.1002/cssc.202100841.

Performance and Stability of Polymer : Nonfullerene Solar Cells with 100 °C-Annealed Electron-Collecting Combination Layers.

Inverted-type organic solar cells, fabricated with low-temperature-processed combination layers of hybrid electron-collecting buffer layers (ECBLs) consisting of zinc oxide (ZnO) and poly(2-ethyl-2-oxazoline) (PEOz) and additional PEOz interlayers, showed improved performance and stability. The ZnO : PEOz precursor films with various PEOz compositions (0-12 wt %) were prepared and thermally treated at 100 °C, leading to the ECBLs on which the PEOz interlayers were subsequently deposited before coating of polymer : nonfullerene bulk heterojunction layers. Results showed that the power conversion efficiency of solar cells reached approximately 9.38 and 10.11 % (average) in case of the ZnO/PEOz and ZnO : PEOz(6 wt % PEOz)/PEOz combination layers, respectively, despite the low-temperature thermal annealing process. A continuous irradiation test for 12 h under one sun condition (air mass 1.5G, 100 mW cm-2 ) disclosed that the devices with the ZnO : PEOz(6 wt % PEOz)/PEOz combination layers were more stable than those with the ZnO/PEOz layers.

Acidity-Controlled Conducting Polymer Films for Organic Thermoelectric Devices with Horizontal and Vertical Architectures.

Organic thermoelectric devices (OTEDs) are recognized one of the next generation energy conversion platforms because of their huge potentials for securing electricity continuously from even tiny heat sources in our daily life. The advantage of OTEDs can be attributable to the design freedom in device shapes and the low-cost fabrication by employing solution coating processes at low temperatures. As one of the major OTE materials to date, poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) has been used, but no study has been yet carried out on its acidity control even though the acidic components in OTEDs can seriously affect the device performance upon operation. Here we demonstrate that the addition of aniline (a weak base) can control the acidity of PEDOT:PSS and enhance the performance of OTEDs. In particular, the vertical OTEDs with aniline-doped PEDOT:PSS films (active area = 1.0 cm2) could continuously generate electricity (0.06 nW) even at low temperatures (<38 °C) when they were mounted on a desk lamp (power = 24 W).

Short-term (-)-hydroxycitrate ingestion increases fat oxidation during exercise in athletes.

(-)-Hydroxycitrate (HCA) is known to inhibit increasing malonyl CoA concentration during endurance exercise. Furthermore, a short-term administration of HCA enhances endurance exercise performance in mice. Therefore we investigated the short-term administration of HCA on the exercise performance of athletes. Subjects were administered 250 mg of HCA or placebo as a control (CON) for 5 d, after each time performing cycle ergometer exercise at 60% VO2max for 60 min followed by 80% VO2max until exhaustion. Blood was collected and expired gas samples analyzed at rest and every 15 min. The respiratory exchange ratio was significantly lower in the HCA trial than in the CON trial (p < 0.05). Fat oxidation was significantly increased by short-term administration of HCA, and carbohydrate oxidation was significantly decreased (p < 0.05) during exercise, presumably resulting in increasing the cycle ergometer exercise time to exhaustion after 1 h of 60% VO2max exercise (p < 0.05). These results suggest that a short-term administration of HCA enhances endurance performance with increasing fat oxidation, which spares glycogen utilization during moderate intensity exercise in athletes.