Conjugated polymer blends for faster organic mixed conductors.

A model mixed-conducting polymer, blended with an amphiphilic block-copolymer, is shown to yield systems with drastically enhanced electro-chemical doping kinetics, leading to faster electrochemical transistors with a high transduction. Importantly, this approach is robust and reproducible, and should be readily adaptable to other mixed conductors without the need for exhaustive chemical modification.

Temperature-Dependent Structural Phase Transition in Rubrene Single Crystals: The Missing Piece from the Charge Mobility Puzzle?

Accurate structural models for rubrene, the benchmark organic semiconductor, derived from synchrotron X-ray data in the temperature range of 100-300 K, show that its cofacially stacked tetracene backbone units remain blocked with respect to each other upon cooling to 200 K and start to slip below that temperature. The release of the blocked slippage occurs at approximately the same temperature as the hole mobility crossover. The blocking between 200 and 300 K is caused by a negative correlation between the relatively small thermal expansion along the crystallographic -axis and the relatively large widening of the angle between herringbone-stacked tetracene units.

A positive to negative uniaxial thermal expansion crossover in an organic benzothienobenzothiophene structure.

Compound 6,6'-([1]benzothieno[3,2-b][1]benzothiophene-2,7-diyl)bis(butan-1-ol) (BTBT-C4OH) displays a continuous type 0 first-order isosymmetric phase transition at 200 K which is accompanied by a continuous change of the thermal expansion along the b axis from positive to negative. The equivalent isotropic atomic displacement parameters for all non-hydrogen atoms as well as all the eigenvalues of the anisotropic atomic displacement tensor show discontinuous behavior at the phase transition. The eigenvalues of the translational tensor in a rigid-body description of the molecule are all discontinuous at the phase transition, but the librational eigenvalues are discontinuous only in their temperature derivative.

Experimental and theoretical evidence of a supercritical-like transition in an organic semiconductor presenting colossal uniaxial negative thermal expansion.

Thermal expansion coefficients of most materials are usually small, typically up to 50 parts per million per kelvin, and positive, materials expand when heated. Some materials show an atypical shrinking behavior in one or more crystallographic directions when heated. Here we show that a high mobility thiophene-based organic semiconductor, , has an exceptionally large negative expansion between 95 and 295 K (-216 < = < -333 MK), being compensated by an even larger positive expansion in the perpendicular direction (287 < < 634 MK).

Bis-Azide Low-Band Gap Cross-Linkable Molecule N-[CPDT(FBTTh)] to Fully Thermally Stabilize Organic Solar Cells Based on P3HT:PCBM.

We synthesized a novel bis-azide low-band gap cross-linkable molecule N-[CPDT(FBTTh)] with wide absorption. This compound is of interest as an additive in polymer/fullerene bulk heterojunction solar cells. In addition to providing efficient thermal stabilization of the morphology, the additive can harvest additional solar light compared with pristine poly(3-hexyl thiophene) to improve the power-conversion efficiency (PCE).

The Importance of Materials Design to Make Ions Flow: Toward Novel Materials Platforms for Bioelectronics Applications.

Chemical design criteria for materials for bioelectronics applications using a series of copolymer derivatives based on poly(3-hexylthiophene) are established. Directed chemical design via side-chain functionalization with polar groups allows manipulation of ion transport and ion-to-electron transduction. Insights gained will permit increased use of the plethora of materials employed in the organic electronics area for application in the bioelectronics field.

Thermal stabilisation of polymer-fullerene bulk heterojunction morphology for efficient photovoltaic solar cells.

A novel stable bisazide molecule that can freeze the bulk heterojunction morphology at its optimized layout by specifically bonding to fullerenes is reported. The concept is demonstrated with various polymers: fullerene derivatives systems enable highly thermally stable polymer solar cells.

Electroactive nanorods and nanorings designed by supramolecular association of pi-conjugated oligomers.

In investigations into the design and isolation of semiconducting nano-objects, the synthesis of a new bisureido pi-conjugated organogelator has been achieved. This oligo(phenylenethienylene) derivative was found to be capable of forming one-dimensional supramolecular assemblies, leading to the gelation of several solvents. Its self-assembling properties have been studied with different techniques (AFM, EFM, etc.

Self-organized ureido substituted diacetylenic organogel. Photopolymerization of one-dimensional supramolecular assemblies to give conjugated nanofibers.

The introduction of the urea function as structure directing agent of diacetylene organogels (DA-OGs) has been achieved. Despite the urea function being one of the most frequently used structure directing agents for the formation of organogels, it has never been exploited in the fabrication and photopolymerization of DA-OGs. The self-association of ureas involving two hydrogen bonds is much stronger than that of urethanes or amides, and the resulting supramolecular assemblies are completely insoluble.

Nanostructuration of phenylenevinylenediimide-bridged silsesquioxane: from electroluminescent molecular J-aggregates to photoresponsive polymeric H-aggregates.

A new approach to control molecular aggregation of pi-conjugated chromophores in the solid state has been investigated. Our strategy was to use a modifiable bulky fragment which should induce a J-aggregation and offer the possibility to reach an H-aggregation upon its chemical modification by lateral slip of pi-conjugated molecules. The chosen fragment for that purpose was the hydrolyzable triethoxysilane function (Si(OEt)3).

Synthesis and properties of highly fluorescent indolizino[3,4,5-ab]isoindoles.

We report here the synthesis, X-ray structures, optical and electrochemical properties, fabrication of light-emitting devices, and density functional calculations for indolizino[3,4,5-ab]isoindole (INI) derivatives. Strongly luminescent heterocycles based on the INI unit were synthesized by 1,3-dipolar cycloaddition reactions between pyrido[2,1-a]isoindole (PIS) and acetylene or ethylene derivatives. They are indolizino[3,4,5-ab]isoindoles 2-9 and 14-15, benzo[1',2'-1,2]indolizino[3,4,5-ab]isoindoles 10, pyridazino[4',5':1,2]indolizino[3,4,5-ab]isoindoles 12-13, and 2,3-hydropyridazino[4',5':1,2]indolizino[3,4,5-ab]isoindole-1,4-dione 11.

Vapour diffusion hydrolysis of a self-assembled silylated organogel, the OG-HG transcription process: a new way to cast and handle fluorescent silsesquioxane.

A new method of hydrolysis-polycondensation of silsesquioxanes, the OG-HG (Organo Gel-Hybrid Gel or Organised Gel-Hydrolysed Gel) process allows the transcription of the supramolecular architecture of organogels to corresponding hybrid silsesquioxanes.