Mario Leclerc

Bulk heterojunction solar cells using thieno[3,4-c]pyrrole-4,6-dione and dithieno[3,2-b:2',3'-d]silole copolymer with a power conversion efficiency of 7.3%.

A new alternating copolymer of dithienosilole and thienopyrrole-4,6-dione (PDTSTPD) possesses both a low optical bandgap (1.73 eV) and a deep highest occupied molecular orbital energy level (5.57 eV). The introduction of branched alkyl chains to the dithienosilole unit was found to be critical for the improvement of the polymer solubility. When blended with PC(71)BM, PDTSTPD exhibited a power conversion efficiency of 7.3% on the photovoltaic devices with an active area of 1 cm(2).

A Thieno[3,4-c]pyrrole-4,6-dione-Based Copolymer for Efficient Solar Cells

A new low-band-gap thieno[3,4-c]pyrrole-4,6-dione-based copolymer, PBDTTPD, has been designed and synthesized. PBDTTPD is soluble in chloroform or o-dichlorobenzene upon heating and shows a broad absorption in the visible region. The HOMO and LUMO energy levels were estimated to be at -5.56 and -3.75 eV, respectively. These electrochemical measurements fit well with an optical bandgap of 1.8 eV. When blended with PC(71)BM, this polymer demonstrated a power conversion efficiency of 5.5% in a bulk-heterojunction photovoltaic device having an active area of 1.0 cm(2).

Optical Sensors Based on Hybrid Aptamer/Conjugated Polymer Complexes

Single-stranded DNA (aptamer) can specifically bind potassium ions or human alpha-thrombin. When binding takes place, the aptamer undergoes a conformational transition from an unfolded to a folded structure. This conformational change of the negatively charged oligonucleotide can be detected by adding a water-soluble, cationic polythiophene derivative, which transduces the new complex formation into an optical (colorimetric or fluorometric) signal without any labeling of the probe or of the target. This simple and rapid methodology has enabled the detection of human thrombin in the femtomole range. This new biophotonic tool can easily be applied to the detection of various other proteins as well as being useful in the high-throughput screening of new drugs.

Colorimetric and fluorometric detection of nucleic acids using cationic polythiophene derivatives.

Simple and reliable sequence-specific methods are needed for the rapid detection of oligonucleotides, to diagnose infections and various genetic diseases. In this regard, interesting optical and electrochemical DNA-hybridization sensors have been proposed.[1±5] The recognition capabilities of DNA are well established but, to transduce the recognition event into a physically measurable value, a fluorescent or electroactive tag is often bound to the analyte. Electrochemical and optical sensors based on conjugated polymers have also been reported[6±9] and some oligonucleotide-functionalized conjugated polymers can also transduce hybridization events into an electrical signal without labeling of the oligonucleotide target.[10±12] The detection relies on a modTo our knowledge this is the first report on the use of singlemolecule atomic-force spectroscopy to study the reduction pathway of multiple disulfide bonds in proteins and to evaluate the distributions of intermediates obtained under different reducing conditions without separating them and without any blocking and fractionation steps. The characterization of these intermediates has so far been accomplished by first blocking them with reagents such as alkylalkanethiosulfonates and then by fractionation by ion-exchange chromatography, 2D or capillary gel electrophoresis, or gel filtration.[11] The determination of thiol groups and disulfide bonds in a polythiol systems has always been a very challenging problem.[12] The single-molecule force-spectroscopy data presented here show: 1) how a redox environment can modulate the mechanical properties of angiostatin; 2) how this modulation relies, at the single-molecule level, on the extent of reduction of the disulfide bonds; and 3) how, at the level of a large sample of molecules, the distribution of the different thiol/ disulfide intermediates after reduction can be estimated by statistical analysis of the force curves.

Poly(2,7-carbazole)s: Structure−Property Relationships

Conjugated polymers combine the interesting optical and electrical properties of metals with the processing advantages and mechanical properties of traditional synthetic polymers. With clever use of a variety of synthetic tools, researchers have prepared highly pure polymers with optimized physical properties during the past 30 years. For example, the synthesis of well-defined polyacetylenes, polyphenylenes, polythiophenes, polyfluorenes, and other conjugated polymers have significantly improved the performance of these polymeric materials. However, one important class of conjugated polymers was missing from this chemical inventory: easy access to well-defined poly(2,7-carbazole)s and related polymers. This Account highlights advances in the synthesis of poly(2,7-carbazole) derivatives since they were first reported in 2001. Starting from 2-nitro-biphenyl derivatives, 2,7-functionalized carbazoles are typically obtained from Cadogan ring-closure reactions. In a second step, Yamamoto, Stille, Suzuki, or Horner-Emmons coupling polymerization leads to various poly(2,7-carbazole) derivatives. We discuss the characterization of their optical and electrical properties with a strong emphasis on the structure-property relationships. In addition, we carefully evaluate these polymers as active components in light-emitting diodes, transistors, and photovoltaic cells. In particular, several low band gap poly(2,7-carbazole) derivatives have revealed highly promising features for solar cell applications with hole mobilities of about 3 x 10(-3) cm2 V(-1) s(-1) and power conversion efficiencies up to 4.8%. Finally, we show how these new synthetic strategies have led to the preparation of novel poly(heterofluorene) derivatives and ladder-type conjugated polymers.

New conjugated polymers for plastic solar cells

The present review gives an overview of four of the most promising classes of conjugated polymers for plastic solar cells. The latest developments on poly(2,7-carbazole)s, poly(1,4-diketopyrrolopyrrole)s, poly(thieno[3,4-b]thiophene)s, and poly(thieno[3,4-c]pyrrole-4,6-dione)s are reported. More precisely, the synthesis and the physical and electronic properties of the polymers are discussed. Devices characteristics such as the open-circuit voltage, the fill factor, the short-circuit current density and the power conversion efficiency are also addressed. In summary, this review wants to give the reader a highlight of the very latest improvements in the organic photovoltaic field.

Bithiopheneimide-dithienosilole/dithienogermole copolymers for efficient solar cells: information from structure-property-device performance correlations and comparison to thieno[3,4-c]pyrrole-4,6-dione analogues.

Rational creation of polymeric semiconductors from novel building blocks is critical to polymer solar cell (PSC) development. We report a new series of bithiopheneimide-based donor-acceptor copolymers for bulk-heterojunction (BHJ) PSCs. The bithiopheneimide electron-deficiency compresses polymer bandgaps and lowers the HOMOs--essential to maximize power conversion efficiency (PCE). While the dithiophene bridge progression R(2)Si→R(2)Ge minimally impacts bandgaps, it substantially alters the HOMO energies. Furthermore, imide N-substituent variation has negligible impact on polymer opto-electrical properties, but greatly affects solubility and microstructure. Grazing incidence wide-angle X-ray scattering (GIWAXS) indicates that branched N-alkyl substituents increased polymer π-π spacings vs linear N-alkyl substituents, and the dithienosilole-based PBTISi series exhibits more ordered packing than the dithienogermole-based PBTIGe analogues. Further insights into structure-property-device performance correlations are provided by a thieno[3,4-c]pyrrole-4,6-dione (TPD)-dithienosilole copolymer PTPDSi. DFT computation and optical spectroscopy show that the TPD-based polymers achieve greater subunit-subunit coplanarity via intramolecular (thienyl)S···O(carbonyl) interactions, and GIWAXS indicates that PBTISi-C8 has lower lamellar ordering, but closer π-π spacing than does the TPD-based analogue. Inverted BHJ solar cells using bithiopheneimide-based polymer as donor and PC(71)BM as acceptor exhibit promising device performance with PCEs up to 6.41% and V(oc) > 0.80 V. In analogous cells, the TPD analogue exhibits 0.08 V higher V(oc) with an enhanced PCE of 6.83%, mainly attributable to the lower-lying HOMO induced by the higher imide group density. These results demonstrate the potential of BTI-based polymers for high-performance solar cells, and provide generalizable insights into structure-property relationships in TPD, BTI, and related polymer semiconductors.

Prion strain discrimination using luminescent conjugated polymers

The occurrence of multiple strains of prions may reflect conformational variability of PrPSc, a disease-associated, aggregated variant of the cellular prion protein, PrPC. Here we used luminescent conjugated polymers (LCPs), which emit conformation-dependent fluorescence spectra, for characterizing prion strains. LCP reactivity and emission spectra of brain sections discriminated among four immunohistochemically indistinguishable, serially mouse-passaged prion strains derived from sheep scrapie, chronic wasting disease (CWD), bovine spongiform encephalopathy (BSE), and mouse-adapted Rocky Mountain Laboratory scrapie prions. Furthermore, using LCPs we differentiated between field isolates of BSE and bovine amyloidotic spongiform encephalopathy, and identified noncongophilic deposits in prion-infected deer and sheep. We found that fibrils with distinct morphologies generated from chemically identical recombinant PrP yielded unique LCP spectra, suggesting that spectral characteristic differences resulted from distinct supramolecular PrP structures. LCPs may help to detect structural differences among discrete protein aggregates and to link protein conformational features with disease phenotypes.

Small‐Bandgap Polymer Solar Cells with Unprecedented Short‐Circuit Current Density and High Fill Factor

Small-bandgap polymer solar cells (PSCs) with a thick bulk heterojunction film of 340 nm exhibit high power conversion efficiencies of 9.40% resulting from high short-circuit current density (JSC ) of 20.07 mA cm(-2) and fill factor of 0.70. This remarkable efficiency is attributed to maximized light absorption by the thick active layer and minimized recombination by the optimized lateral and vertical morphology through the processing additive.

Solar‐Energy Production and Energy‐Efficient Lighting: Photovoltaic Devices and White‐Light‐Emitting Diodes Using Poly(2,7‐fluorene), Poly(2,7‐carbazole), and Poly(2,7‐dibenzosilole) Derivatives

World energy needs grow each year. To address global warming and climate changes the search for renewable energy sources with limited greenhouse gas emissions and the development of energy-efficient lighting devices are underway. This Review reports recent progress made in the synthesis and characterization of conjugated polymers based on bridged phenylenes, namely, poly(2,7-fluorene)s, poly(2,7-carbazole)s, and poly(2,7-dibenzosilole)s, for applications in solar cells and white-light-emitting diodes. The main strategies and remaining challenges in the development of reliable and low-cost renewable sources of energy and energy-saving lighting devices are discussed.