Contributions of Both the Eastman Entropy of Transfer and Electric Double Layer to the Electromotive Force of Ionic Thermoelectric Supercapacitors.

Recently, ionic thermoelectric supercapacitors have gained attention because of their high open circuit voltages, even for ions that are redox inactive. As a source of open circuit voltage (electromotive force), an asymmetry in electric double layers developed by the adsorption of ions at the electrode surfaces kept at different temperatures has previously been proposed. As another source, the Eastman entropy of transfer, which is related to the Soret coefficient, has been considered.

Interface Engineering for High-Performance Thermoelectric Carbon Nanotube Films.

Carbon nanotubes (CNTs) stand out for their exceptional electrical, thermal, and mechanical attributes, making them highly promising materials for cutting-edge, lightweight, and flexible thermoelectric applications. However, realizing the full potential of advanced thermoelectric CNTs requires precise management of their electrical and thermal characteristics. This study, through interface optimization, demonstrates the feasibility of reducing the thermal conductivity while preserving robust electrical conductivity in single-walled CNT films.

Transparent Patternable Large-Area Graphene p-n Junctions by Photoinduced Electron Doping.

We present a novel approach to achieve n-type doping in graphene and create graphene p-n junctions through a photoinduced electron doping method using photobase generators (PBGs). The unique properties of PBGs allow us to spatially and temporally control the doping process via light activation. The selective irradiation of specific regions on the graphene film enables switching their doping from p- to n-type, as confirmed by changes in the electromotive force and Seebeck and Hall coefficients.

High-Performance Isotropic Thermo-Electrochemical Cells Using Agar-Gelled Ferricyanide/Ferrocyanide/Guanidinium.

An isotropic thermo-electrochemical cell is introduced with a high Seebeck coefficient ( ) of 3.3 mV K that uses a ferricyanide/ferrocyanide/guanidinium-based agar-gelated electrolyte. A power density of about 20 µW cm is achieved at a temperature difference of about 10 K, regardless of whether the heat source is on the top or bottom section of the cell.

Chemical reactions of graphitic carbon nitride films with glass surfaces and their impact on photocatalytic activity.

Thin films of graphitic carbon nitride (g-CN), a visible-light-driven photocatalyst, have recently attracted interest for application in photoelectrochemical cells for water splitting and high-throughput photocatalysis. In typical syntheses, g-CN films are formed by heating the nitrogen-rich precursor and substrate to 500-600 °C. The heated substrate should affect the polycondensation of the precursor and thereby alter the properties of the g-CN film.

Bicyclic-ring base doping induces n-type conduction in carbon nanotubes with outstanding thermal stability in air.

The preparation of air and thermally stable n-type carbon nanotubes is desirable for their further implementation in electronic and energy devices that rely on both p- and n-type material. Here, a series of guanidine and amidine bases with bicyclic-ring structures are used as n-doping reagents. Aided by their rigid alkyl functionality and stable conjugate acid structure, these organic superbases can easily reduce carbon nanotubes.

Design and synthesis of proton-dopable organic semiconductors.

This paper shows how protonated 3,4-ethylene dioxythiophene moieties can be used as an end group to make organic conductors. An organic semiconductor 2,5-bis(5-(2,3-dihydrothieno[3,4-][1,4]dioxin-5-yl)-3-dodecylthiophen-2-yl)thieno[3,2-]thiophene is designed and synthesized. This molecule could be doped by protonic acid in both solution and solid-state, resulting in a broad absorption in the near-infrared range corresponding to polaron and bipolaron absorption.

Thermoelectrochemical Cells Based on Ferricyanide/Ferrocyanide/Guanidinium: Application and Challenges.

Ferricyanide/ferrocyanide/guanidinium-based thermoelectrochemical cells have been investigated under different loading conditions in this work. Compared with ferricyanide/ferrocyanide-based devices, the device with guanidinium-added electrolytes shows higher power and energy densities. We observed that the enhanced performance is not due to the ionic Seebeck effect of guanidinium but because of the configuration entropy change resulting from the selective binding of Gdm to Fe(CN).

Insight into the effect of the configuration entropy of additives on the Seebeck coefficient.

Thermogalvanic cells have attracted considerable attention because of their potential to directly convert waste heat into electricity by using redox reactions under continuous operation with a simple, cost-effective design. An increase in the Seebeck coefficient owing to the interactions between the redox ions and the additives has been reported in recent studies. The configuration entropy of the small additives coordinated to a large ion is calculated to analyze the Seebeck coefficient obtained from the entropy difference between the redox pairs.

Outstanding Electrode-Dependent Seebeck Coefficients in Ionic Hydrogels for Thermally Chargeable Supercapacitor near Room Temperature.

Thermoelectric power generation from waste heat is an important component of future sustainable development. Ion-conducting materials are promising candidates because of their high Seebeck coefficients. This study demonstrates that ionic hydrogels based on imidazolium chloride salts exhibit outstanding Seebeck coefficients of up to 10 mV K.

Reversible Protonic Doping in Poly(3,4-Ethylenedioxythiophene).

In this study, poly(3,4-ethylenedioxythiophene), a benchmark-conducting polymer, was doped by protons. The doping and de-doping processes, using protonic acid and a base, were fully reversible. We predicted possible doping sites along the polymer chain using density functional theory (DFT) calculations.

Moisture-responsive supramolecular nanotubes.

Living organisms have evolved functional structures for seeds dispersal in response to humidity changes. In this study, we construct moisture-responsive nanotubes by the supramolecular coordination of a peptide lipid with metal ions for potential applications in material delivery systems. These hydrophilic nanotubes can uptake atmospheric moisture and the water molecules are associated with unsaturated metal centers of the bis(lipid)-metal(ii) complex, thereby changing the molecular packing and inducing morphological transformation from nanotubes to sheets.

Humidity control in a closed system utilizing conducting polymers.

In this study, we demonstrate that conducting polymers could be ideal materials for continuously managing humidity in a wide range of enclosed spaces. We demonstrate a simple battery-driven humidity control unit to manage the humidity in a closed environment and studied humidity-responsive nanocapsules using Zn-coordinated lipid nanovesicles. This study not only promises new applications for conducting polymers but also provides an easy approach for fabricating chambers with a controlled environment, which are often used by physicists, chemists, and biologists.

Photoinduced Dedoping of Conducting Polymers: An Approach to Precise Control of the Carrier Concentration and Understanding Transport Properties.

Exploring the various applications of conjugated polymers requires systematic studies of their physical properties as a function of the doping density, which, consequently, calls for precise control of their doping density. In this study, we report a novel solid-state photoinduced charge-transfer reaction that dedopes highly conductive polyelectrolyte complexes such as poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate). Varying the UV-irradiation time of this material allows the carrier density inside the film to be precisely controlled over more than 3 orders of magnitude.

Recent Progress on PEDOT-Based Thermoelectric Materials.

The thermoelectric properties of poly(3,4-ethylenedioxythiophene) (PEDOT)-based materials have attracted attention recently because of their remarkable electrical conductivity, power factor, and figure of merit. In this review, we summarize recent efforts toward improving the thermoelectric properties of PEDOT-based materials. We also discuss thermoelectric measurement techniques and several unsolved problems with the PEDOT system such as the effect of water absorption from the air and the anisotropic thermoelectric properties.

Experimental Studies on the Anisotropic Thermoelectric Properties of Conducting Polymer Films.

We reported general methods for studying the thermoelectric properties of a polymer film in both the in-plane and through-plane directions. The bench-mark PEDOT/PSS films have highly anisotropic carrier transport properties and thermal conductivity. The anisotropic carrier transport properties can be explained by the lamellar structure of the PEDOT/PSS films where the PEDOT nanocrystals could be isolated by the insulating PSS in the through-plane direction.

Line patterns from cylinder-forming photocleavable block copolymers.

A robust route for the preparation of nanoscopic line patterns from polystyrene-block-poly(ethylene oxide) featuring a photocleavable o-nitrobenzyl ester junction is demonstrated. After mild UV (λ = 365 nm) exposure and selective removal of the PEO microdomains, the polymer trench patterns are used as scaffold to fabricate highly ordered arrays of silica or Au line patterns.

Morphological change and mobility enhancement in PEDOT:PSS by adding co-solvents.

Adding ethylene glycol (EG) to a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) solution improves the crystallinity of the PEDOT and the ordering of the PEDOT nanocrystals in solid films. The carrier-mobility enhancement is confirmed by using ion-gel transistors combined with in situ UV-vis-NIR spectroscopy.

Flexible low-voltage polymer thin-film transistors using supercritical CO2-deposited ZrO2 dielectrics.

The fabrication of low-voltage flexible organic thin film transistors using zirconia (ZrO(2)) dielectric layers prepared via supercritical fluid deposition was studied. Continuous, single-phase films of approximately 30 nm thick ZrO(2) were grown on polyimide (PI)/aluminum (Al) substrates at 250 °C via hydrolysis of tetrakis(2,2,6,6-tetramethyl-3,5-heptane-dionato) zirconium in supercritical carbon dioxide. This dielectric layer showed a high areal capacitance of 317 nF cm(-2) at 1 kHz and a low leakage current of 1.

Interfacial modification of organic photovoltaic devices by molecular self-organization.

This feature article focuses on the relationship between the interfacial structures constructed by molecular self-organization and the properties of organic photovoltaic devices. The use of self-assembled monolayers (SAMs) is reviewed for metal and metal oxide/organic interfaces, while surface-segregated monolayers (SSMs) are introduced as a new method for the modification of organic/organic interfaces. Research up to now has clearly demonstrated the effectiveness of the control of energy levels and other properties at the interfaces to enhance photovoltaic performance.

Effects of block length in copolymers based on regioregular oligothiophenes linked with electron-accepting units.

Copolymers with an alternating structure of regioregular oligo(3-hexylthiophene) (O3HT) with different lengths and 2,5-dibutyl-3,6-di(thiophen-2-yl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione (DPP) were synthesized through Stille coupling reaction. The light absorption of the copolymers can be rationally tuned to have a broad spectrum across the visible region by adjusting the length of O3HT. Organic solar cells fabricated with the copolymers and PCBM showed a broad photoresponse and a comparable efficiency to that of poly(3-hexylthiophene) (P3HT):PCBM cells.

Additive-driven assembly of block copolymer-nanoparticle hybrid materials for solution processable floating gate memory.

Floating gate memory devices were fabricated using well-ordered gold nanoparticle/block copolymer hybrid films as the charge trapping layers, SiO(2) as the dielectric layer, and poly(3-hexylthiophene) as the semiconductor layer. The charge trapping layer was prepared via self-assembly. The addition of Au nanoparticles that selectively hydrogen bond with pyridine in a poly(styrene-b-2-vinyl pyridine) block copolymer yields well-ordered hybrid materials at Au nanoparticle loadings up to 40 wt %.

Independent Tuning of the Band Gap and Redox Potential of Graphene Quantum Dots.

The band gap and redox potential of semiconductor nanocrystals are two quantities of primary importance for their applications in energy conversion devices. Herein, we report on covalent functionalization of colloidal graphene quantum dots through a solution-chemistry approach and studies of their band gaps and redox potentials. We show that their band gaps and redox potentials can be independently controlled, the former by size and the latter by functionalization.

Tailoring organic heterojunction interfaces in bilayer polymer photovoltaic devices.

In an ideal model, a p-n junction is formed by two stacked slabs of semiconductors. Although the construction of actual devices is generally more complex, we show that such a simple method can in fact be applied to the formation of organic heterojunctions. Two films of the organic semiconductors poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C(61)-butyric acid methyl ester (PCBM) can be connected by a simple film-transfer method without disturbing their flat surfaces.