Nouveaux dérivés de fullerènes (C60 et C70) et de nanotubes de carbone, et étude de leur contribution dans les domaines du photovoltaïque et des biomatériaux

De nouveaux dérivés de C60 et C70 ont été obtenus via le dianion C602- et la réaction de Bingel, en vue d'examiner leur contribution en tant que composés accepteurs dans des cellules photovoltaïques du type réseau interpénétré, où P3HT est le partenaire donneur. L'objectif était de chercher à évaluer si les résultats photovoltaïques ainsi obtenus permettent de définir de nouveaux repères en ce qui concerne l'influence de la structure moléculaire de ces composés, comparée à celle de PCBM. D'autre part, à partir de nanotubes de carbone mono-paroi issus de plusieurs sources (HiPco, Nanoledge, CarboLex, Carbon Solutions), divers dérivés fonctionnalisés notamment par des groupements esters ont été préparés, selon plusieurs méthodologies (via la polyréduction des nanotubes et via la carboxylation des nanotubes). La caractérisation physico-chimique des nanotubes de carbone fonctionnalisés a été faite par plusieurs techniques complémentaires (ATG, IR,Raman, XPS). Puis la contribution des nanotubes de carbone carboxylés et estérifiés a été étudiés dans deux domaines : les dérivés estérifiés ont été intégrés comme composants complémentaires dans un mélange P3HT/PCBM (collab : équipe physique-Angers). Une optimisation spectaculaire des paramètres photovoltaïques a été mise en évidence lorsqu'un dérivé ester, en série HiPco, est ajouté au mélange P3HT/PCBM ; les dérivés carboxylés ont été testés comme constituants de biomatériaux dans un milieu aqueux dont la composition est celle de la lymphe (collab : équipe INSERM-Angers). La minéralisation d'hydroxyapatite a été ainsi observée sur les nanotubes de carbone de ce milieu, correspondant à la génération de tissu osseux artificiel.New C60 and C70 derivatives have been obtained via the C602 anion and the Bingel reaction, in order to test their abilities as acceptor components mixed with P3HT in bulk heterojunction organic sola cells. This work aimed to study to what extent the molecular structure of such fullerene derivatives may influence the performances of organic solar cells, compared to PCBM. In a second part, various carbon nanotubes derivatives have been prepared from the polyreduction and the carboxylation of starting nanotubes. The obtained nanotubes derivatives have been characterized by physico-chemical methods (TGA, IR, Raman and XPS), and their contribution was studied in two fields : the esterified derivatives have been used as complementary components in P3HT/PCBM mixtures, in order to study their impact on the photovoltaic properties of solar cells composed of such blends ; the carboxylated derivatives have been tested as partners of biomaterials in aqueous medium, in order to initiate the formation of ydroxyapatitte, thus leading to the generation of artificial bone tissue.ANGERS-BU Lettres et Sciences (490072106) / SudocSudocFranceF

Functionalization of [60]fullerene through the anionic route

The reactivity of C602– anion, easily generated upon chemical reduction of the C60 core by sodium methanethiolate, has been systematically investigated versus a great number of saturated halogenated compounds RX or X–CH2–R′–CH2–X (X = I or Br), while these halo-compounds are unreactive with C60 itself. Various C60-derivatives in the series of bis-adducts R2C60 and fused cycloadducts R′(CH2)2C60 are thus obtained in fair to good yields, the R or R′ groups bearing functionalities such as ethylenic double bond, halogen, ketone, alcohol, or ester moieties. On the other hand a judicious utilization of the overall mechanism of the reaction between C602– anion and well chosen different RX and R′X compounds allow to extend this methodology to the preparation of mixed adducts RR′C60. Functional adducts in the series R2C60 and R′(CH2)2C60 are new attractive building blocks in C60 chemistry, and can lead to novel highly functionalized C60-based molecules. Some examples of such covalent ensembles are presented, the specific physical properties of which are typical of organic materials

Chimie du dianion C60 2- (accès à de nouveaux dérivés fonctionnels du fullerène C60)

De nouveaux dérivés fonctionnels du fullerène C60 ont été synthétisés à partir du dianion C60 2- selon la méthodologie mise au point au Laboratoire : - des dihydrofullerènes C60(CH2CO2R)2 (R = Me, Et). Des cellules photovoltaïques à base de ces dérivés et de MEH-PPV en réseaux interpénétrés montrent de bonnes performances, assez proches de celles obtenues lorsque l'accepteur est le PCBM ; - des dihydrofullerènes fonctionnels dissymétriques C60RR'. Les synthèses correspondantes reposent sur l'exploitation, jusqu'alors non réalisée dans ce but, du mécanisme réactionnel (Kadish-Fukuzumi) de la réaction entre C60 2- et divers dérivés halogénés ; - un fullerène diol, issu de dérivés du pentaérythritol. Les bons rendements obtenus pour cette synthèse font de ce fullerène diol un nouveau synthon de choix en chimie du fullerène C60. A partir de ce fullerène diol, de nouvelles dyades et triades ont été obtenues, l'entité électro-donneur étant le motif tétrathiafulvalène ou l'anion perchlorotriphénylméthyle. Les propriétés physico-chimiques de ces assemblages covalents donneur-accepteur ont été étudiées (spectroscopies UV-Vis, fluorescence, RPE ; électrochimie ; photophysique).New functionalized [60]fullerene derivatives have been synthesized starting from C60 2- anion, following the procedure previously developed in our Laboratory : - dihydrofullerenes C60(CH2CO2R)2 (R = Me, Et). Solar cells have been built using a mixture of these compounds and MEH-PPV in interpenetrating network and they exhibit good photovoltaic characteristics, which are close to those obtained when the acceptor is PCBM ; - functionalized dissymmetric dihydrofullerenes C60RR'. The corresponding syntheses lie upon a new interpretation of the Kadish-Fukuzumi mechanism, so far unexplored in this way, associated with the reaction between C60 2- and various halogeno derivatives ; - a fullerene diol, issued from pentaerythritol derivatives. Thanks to good yields observed in this synthesis, this fullerene diol appears to be a new promising building block in fullerene chemistry. Starting from the latter diol, new C60-based dyads and triads have been obtained, the electron donor moiety being the tetrathiafulvalene core or the perchlorotriphenylmethyl anion. The physico-chemical properties of these donor-acceptor covalent assemblies have been studied (UV-Vis, fluorescence, ESR spectroscopic methods ; electrochemistry ; photophysics).ANGERS-BU Lettres et Sciences (490072106) / SudocSudocFranceF

Through-space communication in a TTF–C60–TTF triad

7 pages, 7 figures, 2 charts, 2 tables, 2 schemes.-- et al.A 2-pyrazolino[60]fullerene-based triad, possessing two TTF units connected with flexible long linkages, has been prepared. Fluorescence quenching was observed in polar and non-polar solvents, suggesting the existence of a through-space photoinduced charge separation process with rates faster than 3.8 × 109 s–1 and with high efficiency (>0.85). The charge separated states were confirmed by transient absorption spectra in the visible and near-IR regions. The longest lifetime of the charge separated state was found to be 230 ns in CH2Cl2 solvent.Financial support for this work was provided by the MEC of Spain and FEDER funds (projects CTQ2004-00364/BQU, BQU2002-00219), the Junta de Comunidades de Castilla-La Mancha (project PAI-05-068). F. O. gives thanks for a grant from the EU (RTN contract ‘‘FAMOUS’’, HPRN-CT-2002- 00171). The CNRS is also gratefully acknowledged for financial support, as well as Ministère de la Recherche (France) for a PhD grant to S. C.Peer reviewe

Improving the photovoltaic properties of organic solar cells by structuring the P3HT:PCBM photoactive layer with functionalized SWCNTs

International audienceThe optical and electrical properties of bulk polymer RR-P3HT (Regio-Regular Poly(3-hexylthiophene-2,5-diyl):PCBM (Methanofullerene Phenyl-C61-Butyric-Acid-Methyl-Ester) heterojunction incorporating single wall carbon nanotubes (SWCNTs) have been already reported by a number of research groups. We investigated a new approach to functionalize CarboLex single wall carbon nanotubes (SWCNTs-e) for increasing their dispersion in various solvents. The addition of SWCNTs-e in the matrix of P3HT:PCBM improves the photovoltaic (PV) characteristics. Results show that the photovoltaic parameters depend on the concentration of SWCNTs-e. The incorporation of low concentrations of SWCNTs-e in the photoactive layer increases the current density Jscbefore annealing. We attribute the improved performance to partial crystallisation of the RR-P3HT. As revealed by XRD studies and confirmed by the absorbance spectra which exhibit the characteristic 600 nm shoulder. Interestingly, we observed also that doping the P3HT:PCBM system with the functionalized SWCNTs increases Voc from 0.583 to 0.744 V.</p

Functionalized single wall carbon nanotubes improve the properties of polymer solar cells

International audienceThe optical and electrical properties of bulk polymer RR-P3HT (Regio-Regular Poly(3-hexylthiophène-2,5- diyl):PCBM (Methanofullerene Phenyl-C61-Butyric-Acid-Methyl-Ester) heterojunction incorporating single wall carbon nanotubes (SWCNTs) have been already reported by a number of research groups. We investigated a new approach to functionalize CarboLex single wall carbon nanotubes (SWCNTs-e) for increasing their dispersion in various solvents. The addition of SWCNTs-e in the matrix of P3HT:PCBM improves the photovoltaic (PV) characteristics. Results show that the photovoltaic parameters depend on the concentration of SWCNTs-e. The incorporation of low concentrations of SWCNTs-e in the photoactive layer increases the current density Jsc before annealing. We attribute the improved performance to partial crystallisation of the RR-P3HT. As revealed by XRD studies and confirmed by the absorbance spectra which exhibit the characteristic 600 nm shoulder. Interestingly, we observed also that doping the P3HT:PCBM system with the functionalized SWCNTs increases Voc from 0.583 to 0.744 V.</p