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Using Si as anode materials for Li-ion batteries remain challenging due to its morphological evolution and SEI modification upon cycling. The present work aims at developing a composite consisting of carbon-coated Si nanoparticles (Si@C NPs) intimately embedded in a three-dimensional (3D) graphene hydrogel (GHG) architecture to stabilize Si inside LiB electrodes. Instead of simply mixing both components, the novelty of the synthesis procedure lies in the in situ hydrothermal process, which was shown to successfully yield graphene oxide reduction, 3D graphene assembly production, and homogeneous distribution of Si@C NPs in the GHG matrix. Electrochemical characterizations in half-cells, on electrodes not containing additional conductive additive, revealed the importance of the protective C shell to achieve high specific capacity (up to 2200 mAh.g−1), along with good stability (200 cycles with an average Ceff > 99%). These performances are far superior to that of electrodes made with non-C-coated Si NPs or prepared by mixing both components. These observations highlight the synergetic effects of C shell on Si NPs, and of the single-step in situ preparation that enables the yield of a Si@C-GHG hybrid composite with physicochemical, structural, and morphological properties promoting sample conductivity and Li-ion diffusion pathways. [ABSTRACT FROM AUTHOR]

Organic electrochemical transistors (OECT) are gaining momentum in future applications of biosensors and bioelectronics. Nonetheless, contact (or series) resistances (RS/D) remain underexplored, even though physical processes between the source/drain electrodes and organic mixed ionic‐electron conductors (OMIECs) drive a substantial part of their performances. To address this shortcoming, in this study, low‐dimension OECTs featuring 2 µm‐long poly(3,4‐ethylenedioxythiophene) and polystyrene sulfonate acid (PEDOT:PSS) channel are explored. Normalized contact resistances (RS/D⋅W) values as low as 1.4 W cm are obtained. It is observed that channel PEDOT:PSS thickness is not detrimental to RS/D but is impacting the cut‐off frequency. A figure‐of‐merit (h) expressing the charge‐carrier injection (or extraction, respectively) efficiency shows that planar depletion‐mode OECTs are not contact‐limited up to L = 30 µm channel length. Finally, an unprecedented approach that highlight the importance of optimizing the micro‐fabrication technologies is shown, by decreasing the contact overlap length, according to OMIECs physicochemical contact properties. Indeed, a transfer‐length method coupled to a current‐crowding model allow to fully understand the behavior of low‐dimension PEDOT:PSS OECTs and next, to optimize its circuits design. This is paving the way toward the development of OECTs‐based integrated circuits with faster switching speed, broadening further their scopes and future use as advanced bioelectronics platforms. [ABSTRACT FROM AUTHOR]

This work deals with electroactive conducting polymers (ECPs) used as a complementary component on purely capacitive silicon nanowires protected by a 3 nm alumina layer. Accordingly, in this work, we use a fast and simple deposition method to create a pseudocapacitive material based on the electropolymerization in aqueous micellar media (SDS and SDBS 0.01 M) of hydroxymethyl-EDOT (EDOT-OH) onto 3 nm alumina-coated silicon nanowires (Al3@SiNWs). The composite material displays remarkable capacitive behavior with a specific capacitance of 4.75 mF·cm−2 at a current density of 19 µA·cm−2 in aqueous Na2SO4 electrolyte. [ABSTRACT FROM AUTHOR]

Adv. Electronic Mater. 2023, 9, 2201067DOI: 10.1002/aelm.202201067In the abstract of the originally published manuscript, the sentence "Normalized contact resistances (RS/D⋅W) values as low as 1.4 W cm are obtained." is incorrect.The correct sentence is: "Normalized contact resistances (RS/D⋅W) values as low as 1.4 Ohm.cm are obtained."This error does not alter the conclusions of the report. The authors apologize for any inconvenience caused.By Galyna Sych; Patrice Rannou; Maxime Jullien‐Palletier; Saïd Sadki; Yvan Bonnassieux and Sébastien SanaurReported by Author; Author; Author; Author; Author; Author [Extracted from the article]

All-solid-state devices and thermal resistance to solder reflow are crucial issues with respect to micro-supercapacitors. While the latter issue can be addressed by using ionic liquids, the former shows promising results by employing the ionogel approach. The present study focuses on a novel formulation of ionogels―for use as solid state electrolytes in micro-supercapacitors with silicon nanowire electrodes―which promotes the crack-free formation of an efficient solid electrolyte onto silicon nanostructures in a single-step sol–gel process. The capacitance obtained was the same as that for a device using a non-confined ionic liquid, showing a good wetting of the 3D nanostructured silicon electrodes by the sol precursor of the solid ionogel. The assembled symmetric micro-supercapacitor exhibits very high cycling stability and can sustain the reflow soldering process used in the fabrication of microelectronic devices without compromising their electrochemical performance, and even improving their frequency response. [ABSTRACT FROM AUTHOR]

Vertically oriented graphene nanosheets were synthesized by an alternative and simple approach based on electron cyclotron resonance-plasma enhanced chemical vapor deposition (ECR-CVD) onto highly doped silicon substrates. The as-grown graphene electrodes were employed in a symmetric micro-supercapacitor using an aprotic ionic liquid [N-methyl-N-propylpyrrolidinium bis(trifluoromethylsulfonylimide); PYR13TFSI] as electrolyte. The device was able to deliver an outstanding specific capacitance value of 2 mF cm−2, a power density value of 4 mW cm−2 and an energy density value of 4 μW h cm−2 operating at a large and stable cell voltage of 4 V with a quasi-ideal capacitive behaviour. Moreover, the lifetime of the device exhibited a remarkable electrochemical stability retaining 80% of the initial capacitance after 150 000 galvanostatic charge–discharge cycles at a high current density of 1 mA cm−2. This excellent electrochemical performance results from the obtained channel-based 3-D graphene network promoting rapid electrolyte ion-transport and short diffusion paths. [ABSTRACT FROM AUTHOR]

In this work, an innovative 3-D symmetric micro-supercapacitor based on polypyrrole (PPy) coated silicon nanotree (SiNTr) hybrid electrodes has been fabricated. First, SiNTrs were grown on silicon substrates by chemical vapor deposition (CVD) and then via an electrochemical method, the conducting polymer coating was deposited onto the surface of SiNTr electrodes. This study illustrates the excellent electrochemical performance of a hybrid micro-supercapacitor device using the synergistic combination of both PPy as the electroactive pseudo-capacitive material and branched SiNWs as the electric double layer capacitive material in the presence of an aprotic ionic liquid (N-methyl-N-propylpyrrolidinium bis(trifluoromethylsulfonyl)imide; PYR13TFSI) as the electrolyte. The hybrid device exhibited a specific capacitance as high as ∼14 mF cm−2 and an energy density value of ∼15 mJ cm−2 at a wide cell voltage of 1.5 V using a high current density of 1 mA cm−2. Furthermore, a remarkable cycling stability after thousands of galvanostatic charge–discharge cycles with a loss of approximately 30% was obtained. The results reported in this investigation demonstrated that PPy coated SiNTr-based micro-supercapacitors exhibit the best performances among hybrid micro-supercapacitors made of silicon nanowire electrodes grown by CVD in terms of specific capacitance and energy density. [ABSTRACT FROM AUTHOR]

Building of hierarchical core-shell hetero-structures is currently the subject of intensive research in the electrochemical field owing to its potential for making improved electrodes for high-performance micro-supercapacitors. Here we report a novel architecture design of hierarchical MnO2@silicon nanowires (MnO2@SiNWs) hetero-structures directly supported onto silicon wafer coupled with Li-ion doped 1-Methyl-1-propylpyrrolidinium bis(trifluromethylsulfonyl)imide (PMPyrrBTA) ionic liquids as electrolyte for micro-supercapacitors. A unique 3D mesoporous MnO2@SiNWs in Li-ion doped IL electrolyte can be cycled reversibly across a voltage of 2.2 V and exhibits a high areal capacitance of 13 mFcm−2. The high conductivity of the SiNWs arrays combined with the large surface area of ultrathin MnO2 nanoflakes are responsible for the remarkable performance of these MnO2@SiNWs hetero-structures which exhibit high energy density and excellent cycling stability. This combination of hybrid electrode and hybrid electrolyte opens up a novel avenue to design electrode materials for high-performance micro-supercapacitors. [ABSTRACT FROM AUTHOR]

Geminate recombination of bound polaron pairs at the donor/acceptor interface is one of the major loss mechanisms in organic bulk heterojunction solar cells. One way to overcome Coulomb attraction between opposite charge carriers and to achieve their full dissociation is the introduction of high dielectric permittivity materials such as nanoparticles of narrow band gap semiconductors. We selected CuInS2 nanocrystals of 7.4 nm size, which present intermediate energy levels with respect to poly(3-hexylthiophene) (P3HT) and Phenyl-C61-butyric acid methyl ester (PCBM). Efficient charge transfer from P3HT to nanocrystals takes place as evidenced by light-induced electron spin resonance. Charge transfer between nanocrystals and PCBM only occurs after replacing bulky dodecanethiol (DDT) surface ligands with shorter 1,2-ethylhexanethiol (EHT) ligands. Solar cells containing in the active layer a ternary blend of P3HT:PCBM:CuInS2-EHT nanocrystals in 1:1:0.5 mass ratio show strongly improved short circuit current density and a higher fill factor with respect to the P3HT:PCBM reference device. Complementary measurements of the absorption properties, external quantum efficiency and charge carrier mobility indicate that enhanced charge separation in the ternary blend is at the origin of the observed behavior. The same trend is observed for blends using the glassy polymer poly(triarylamine) (PTAA). [ABSTRACT FROM AUTHOR]

Silicon nanotrees (SiNTrs) have been grown by Chemical Vapor Deposition (CVD) via gold catalysis and a three steps process: trunks and branches growth are separated by a new gold catalyst deposition. The influence of growth conditions and the second gold catalyst deposition method on SiNTrs morphology are investigated. SiNTrs based electrodes show a capacitive behavior and better capacitance than the corresponding silicon nanowires (SiNWs) electrode. Electrode capacitance is increased up to 900 µF cm-2, i.e. 150 fold higher than for bulk silicon. Micro-supercapacitors with SiNTrs electrodes have a remarkable stability (only 1.2% loses of their initial capacitance after more than one million cycles). The use of an ionic liquid based electrolyte leads to a high maximum power density (around 225 mW cm-2) which is competitive with Onion Like Carbon based micro-supercapacitors. [ABSTRACT FROM AUTHOR]

Abstract: A conjugated oligomer containing central bi-ethylenedioxythiophene (BEDOT) unit and two terminal anil-substituted carbazole units has been characterized by cyclic voltammetry and spectroelectrochemical methods (UV–vis–NIR and Raman). It shows two oxidation waves at −0.01V and +0.24V (versus Fc/Fc+), which can be ascribed to two successive oxidative dopings of the molecule. The molecule is transmissive sharp yellow when fully reduced, transmissive green upon oxidation up to the end of the first oxidative process, and dark blue upon full oxidation. UV–vis–NIR and Raman spectroelectrochemical investigations show that the colour changes within the potential of the first oxidation wave are associated with the oxidation of both carbazole and ethylenedioxythiophene subunits whereas the electrochromic effect in the potential range of the second oxidation wave involves predominantly the oxidation of the ethylenedioxythiophene subunits. [Copyright &y& Elsevier]

Building of hierarchical core-shell hetero-structures is currently the subject of intensive research in the electrochemical field owing to its potential for making improved electrodes for high-performance micro-supercapacitors. Here we report a novel architecture design of hierarchical MnO2@silicon nanowires (MnO2@SiNWs) hetero-structures directly supported onto silicon wafer coupled with Li-ion doped 1-Methyl-1-propylpyrrolidinium bis(trifluromethylsulfonyl)imide (PMPyrrBTA) ionic liquids as electrolyte for micro-supercapacitors. A unique 3D mesoporous MnO2@SiNWs in Li-ion doped IL electrolyte can be cycled reversibly across a voltage of 2.2 V and exhibits a high areal capacitance of 13 mFcm(-2). The high conductivity of the SiNWs arrays combined with the large surface area of ultrathin MnO2 nanoflakes are responsible for the remarkable performance of these MnO2@SiNWs hetero-structures which exhibit high energy density and excellent cycling stability. This combination of hybrid electrode and hybrid electrolyte opens up a novel avenue to design electrode materials for high-performance micro-supercapacitors.

Geminate recombination of bound polaron pairs at the donor/acceptor interface is one of the major loss mechanisms in organic bulk heterojunction solar cells. One way to overcome Coulomb attraction between opposite charge carriers and to achieve their full dissociation is the introduction of high dielectric permittivity materials such as nanoparticles of narrow band gap semiconductors. We selected CuInS2 nanocrystals of 7.4 nm size, which present intermediate energy levels with respect to poly(3-hexylthiophene) (P3HT) and Phenyl-C61-butyric acid methyl ester (PCBM). Efficient charge transfer from P3HT to nanocrystals takes place as evidenced by light-induced electron spin resonance. Charge transfer between nanocrystals and PCBM only occurs after replacing bulky dodecanethiol (DDT) surface ligands with shorter 1,2-ethylhexanethiol (EHT) ligands. Solar cells containing in the active layer a ternary blend of P3HT:PCBM:CuInS2-EHT nanocrystals in 1:1:0.5 mass ratio show strongly improved short circuit current density and a higher fill factor with respect to the P3HT:PCBM reference device. Complementary measurements of the absorption properties, external quantum efficiency and charge carrier mobility indicate that enhanced charge separation in the ternary blend is at the origin of the observed behavior. The same trend is observed for blends using the glassy polymer poly(triarylamine) (PTAA).

The simple and elegant Buchwald-Hartwig cross-coupling reaction has been used to synthesise a designed range of new aniline-based tetramers in one step, and without the need for protecting groups. Variation of the central aromatic ring has provided the opportunity to carefully tune the optoelectronic properties in this series, thus enabling a structure-activity relationship study by using a range of photophysical and electrochemical techniques. As a result, the long-proposed sequences of electron-electron (EE) and electron-chemical (EC) processes that support the complex redox and proton-transfer reactions involved in the well-known switching of redox states of poly- and oligo(aniline)s are revealed here for the first time. We also present the initial results from time-dependent DFT calculations to clarify the optoelectronic behaviour of these oligomers. The dc-conductivity measurements of conducting thin films of this series, doped with the prototypical poly(aniline) protonating agent D,L-camphor-10-sulfonic acid (CSA), externally plasticised with triphenyl phosphate (TPP), and processed from m-cresol (MC) solutions, are also presented., (Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A new donor-acceptor dyad, namely, a 3,6-bis(thiophen-2-yl)carbazole derivative bearing a C(60) fullerene as a side group (BTC-F), was prepared and characterized. Electropolymerization of BTC-F leads to the formation of a donor-acceptor double-cable polymer (PBTC-F) with high fullerene content (63 wt %) corresponding to one C(60) per polymer repeat unit. The electronic properties of BTC-F and PBTC-F were studied by electrochemical and spectroscopic techniques. Photoluminescence quenching is observed in diluted solutions of BTC-F compared to the nongrafted monomer BTC indicating that an intramolecular charge transfer takes place between the two components of the dyad. The positions of the HOMO and LUMO levels of the monomer and the polymer were accurately determined by differential pulse voltammetry (DPV). The LUMO energy level of the fullerene moiety in BTC-F lies at 3.7 eV below the vacuum level, i.e., slightly higher than corresponding levels of C(60) and PCBM. DPV characterization of PBTC-F indicates little ground state interaction between the pi-conjugated main chain and the C(60) side groups and a high donor HOMO-acceptor LUMO gap of 1.47 eV.