Negative Differential Resistance, Memory and Reconfigurable Logic Functions based on Monolayer Devices derived from Gold Nanoparticles Functionalized with Electro-polymerizable Thiophene-EDOT Units

We report on hybrid memristive devices made of a network of gold nanoparticles (10 nm diameter) functionalized by tailored 3,4(ethylenedioxy)thiophene (TEDOT) molecules, deposited between two planar electrodes with nanometer and micrometer gaps (100 nm to 10 um apart), and electropolymerized in situ to form a monolayer film of conjugated polymer with embedded gold nanoparticles (AuNPs). Electrical properties of these films exhibit two interesting behaviors: (i) a NDR (negative differential resistance) behavior with a peak/valley ratio up to 17, and (ii) a memory behavior with an ON/OFF current ratio of about 1E3 to 1E4. A careful study of the switching dynamics and programming voltage window is conducted demonstrating a non-volatile memory. The data retention of the ON and OFF states is stable (tested up to 24h), well controlled by the voltage and preserved when repeating the switching cycles (800 in this study). We demonstrate reconfigurable Boolean functions in multiterminal connected NP molecule devices.Comment: Full manuscript, figures and supporting information, J. Phys. Chem. C, on line, asap (2017

Structure-properties relationships in triarylamine-based donor-acceptor molecules containing naphtyl groups as donor material for organic solar cells

The effects of replacing the phenyl rings of triphenylamine (TPA) by naphtyl groups are analysed on a series of push-pull molecules containing a 2-thienyl-dicyanovinyl acceptor group. UV-Vis absorption spectroscopy and cyclic voltammetry show that the introduction of one or two naphtyl groups in the structure has limited effects on the optical properties and energy levels of the molecule. On the other hand, the evaluation of the compounds as donor material in bi-layer solar cells with C60 as acceptor shows that the number and mode of linkage of the naphtyl groups exert a marked influence on the power conversion efficiency (PCE) of the cell. Two naphtyl groups lead to a decrease of PCE with respect to TPA, while a single naphtyl group produces opposite effects depending on the linking mode. Compared to TPA, an alpha-naphtyl group leads to a small decrease of PCE while in contrast a beta-naphtyl leads to a ~35% increase of PCE due to improved short-circuit current density (Jsc) and fill-factor. The determination of the hole-mobility of these two donors by the space-charge-limited current method shows that these effects are correlated with the higher hole-mobility of the β-naphtyl compound

ADDA and ADADA systems based on triphenylamine as molecular donors for organic photovoltaics

Three molecular donor (D) acceptor (A) systems of structure A–D–A–D–A as well as an A–D–D–A compound have been synthesized by spatial extension of reference D–A system containing a triphenylamine donor block (5). UV–Vis absorption spectroscopy, cyclic voltammetry and theoretical calculations show that the presence of a median acceptor group has limited effect on the internal charge transfer while direct dimerization leads to an increase of the effective conjugation length. A cursory evaluation of the new compounds as donor material in bilayer solar cells using fullerene C60 as the acceptor material shows that the presence of a median acceptor has deleterious effect on conversion efficiency while the simple dimerization of the molecule leads to a substantial improvement of the short-circuit current density and efficiency

Oligothiophene-derivatized azobenzene as immobilized photoswitchable conjugated systems

Immobilization of an azobenzene-bithiophene compound on a gold surface leads to self-assembled monolayers with photoswitchable electrical properties

Functionalized Gold Nanoparticles with Electropolymerizable π-Conjugated Systems for a Neuro-inspired Memristive Nanoparticle Organic Synapse-Transistor

Nanoparticle Organic Memory Field-Effect Transistors (NOMFET) are molecule-based devices that exhibit the main behavior of a biological spiking synapse. This behavior is obtained by virtue of the combination of two properties of the NOMFET: the transconductance gain of the transistor and the memory effect due to the presence of nanoparticles (NPs) which are used as nanoscale capacitors to store the electrical charges, and which are embedded into an organic semiconducting layer [1]. Thus, the transconductance of the transistor can be dynamically tuned by the amount of charge in the NPs. In this context, we present here a novel method for the elaboration of NOMFET active materials based on the electrochemical deposition of gold NPs grafted with alkanethiol-terminated π-conjugated precursors combining low oxidation potential and high reactivity. The straightforward electropolymerization of these new precursors leads to the formation of a semiconducting network in which the electronic and transport properties and the charging/discharging speed of the gold NPs can be modulated. Such hybrid material could advantageously replace the pentacene layer generally used in NOMFETs. This novel approach is based on previously demonstrated enhancement of charge-tunneling across monolayers of SAMs of alkanethiol-bithiophenic systems on a planar gold surface after electrochemical conversion into more extended conjugated systems [2]. The synthesis of the precursors and nanoparticles will be described and the morphology and electronic properties of the hybrid electropolymerized films will be discussed with regard to the behavior of the resulting NOMFET-devices. [1] F. Alibart, S. Pleutin, D. Guerin, C. Novembre, S. Lenfant, K. Lmimouni, C. Gamrat, D. Vuillaume, Adv. Funct. Mater. 2010, 20, 330-337. [2] M. Oçafrain, T. K. Tran, P. Blanchard, S. Lenfant, S. Godey, D. Vuillaume, J. Roncali, Adv. Funct. Mater. 2008, 18, 2163-2171

3D-conjugated systems based on oligothiophenes and phosphorus nodes

3D-conjugated systems based on oligothiophene segments grafted on a phosphorus or on a phosphine oxide node have been synthesized. Under Stille coupling conditions, bromide terminated thienyl phosphine derivatives undergo a breaking of the phosphorus–carbon bond attributed to a ligand exchange with the Pd catalyst. The electronic properties of the new compounds have been analyzed by UV-vis and fluorescence spectroscopy and cyclic voltammetry