Philippe Berrouard

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).

Synthesis and Characterization of 5-Octylthieno[3,4-c]pyrrole-4,6-dione Derivatives As New Monomers for Conjugated Copolymers

An efficient route for the synthesis of 1-iodo-5-octyl-4H-thieno[3,4-c]pyrrole-4,6(5H)-dione as a key intermediate to build new electron-deficient monomers and related conjugated polymers is reported. Along these lines, two new low bandgap copolymers were synthesized from Stille or Suzuki coupling. These polymers were characterized and their properties compared to those of analogous conjugated polymers.

[(IMes)2Pt(H)(ClBC5H4SiMe3)]: a Borabenzene–Platinum Adduct with an Unusual Pt-Cl-B Interaction†

Since the first report of a metallaboratrane by Hill et al. in 1999, there has been a quest for transition metal complexes containing a dative interaction with Group 13 Lewis acids. In a recent report, Braunschweig and co-workers demonstrated that [(PCy3)2Pt ] (Cy = cyclohexyl) interacts with alanes to form Lewis adducts [(PCy3)2Pt(AlX3)], [2] which are rare examples of well-characterized alane (M!AlR3) complexes. 4] However, the analogous reaction with haloboranes does not yield Lewis adducts, but instead forms platinum boryl complexes, a class of anionic boron-containing species of which numerous examples have been reported to date. The only compounds having an M!B dative interaction with boron are supported by ambiphilic ligands. The boron atom of bisor tris(methimazolyl)boranes coordinates selectively to the transition metal in metallaboratranes. In contrast, in addition to interacting with a transition metal, the Lewis acid moiety of phosphinoboranes prepared by Bourissou can interact with an anionic ligand within the coordination sphere, depending on the nature of the transition metal and the ambiphilic ligand. Such an interaction is seldom observed with Lewis acids, and is supported by ambiphilic ligands, with the exception of BF4 adducts and halocarboranes, in which the Lewis acidity of the boron atom can no longer be considered. Whereas borabenzene adducts are the subject of continuing interest, and in particular for their electronic properties, the coordination modes of these heterocyclic molecules with transition metals are quite limited. A common feature of borabenzenes and boratabenzenes, the analogue with anionic nucleophiles, is their h coordination by the aromatic ring in an analogous fashion to arene and cyclopentadienyl ligands. The exception is a phosphidoboratabenzene, which binds transition metals by the phosphine moiety. Using the efficient and general strategy of forming borabenzene organic adducts from boracyclohexadiene by the elimination of Me3SiCl, which was developed by Fu et al. (Scheme 1), [19]

Direct heteroarylation of β-protected dithienosilole and dithienogermole monomers with thieno[3,4-c]pyrrole-4,6-dione and furo[3,4-c]pyrrole-4,6-dione

Direct C–H bond arylation reactions between heteroarenes and aryl halides provide an atom-economical and “green” alternative to standard cross-coupling reactions (Stille, Suzuki, etc.). Unfortunately, this reaction is not selective and more than one type of C–H bond may react, which, during polymerization reactions, can lead to cross-linked materials. This paper reports the preparation of PDTSiTPD and PDTGeTPD, which have exhibited high efficiencies in organic solar cells, using direct (hetero)arylation polymerization methodologies. In order to circumvent side reactions leading to cross-linked polymers, a number of new dithieno[3,2-b:2′,3′-d]silole (DTSi) monomers were prepared where the β-positions were blocked with alkyl chains and the alkyl groups on the heteroatom were modified. Co-polymers were synthesized with N-alkylthieno[3,4-c]pyrrole-4,6-dione (TPD) and the oxygen congener, N-alkylfuro[3,4-c]pyrrole-4,6-dione (FPD). However, the resulting polymers were not planar, and conjugation of the backbone was disrupted. An efficiency of 1.7% was achieved in bulk heterojunction solar cells (BHJ-SCs).

Donor–acceptor alternating copolymers containing thienopyrroledione electron accepting units: preparation, redox behaviour, and application to photovoltaic cells

Four new donor–acceptor semiconducting alternating copolymers consisting of thienopyrroledione (TPD) electron-accepting sub-units and either 2,7-carbazole or dialkoxy substituted benzodithiophene electron-donating moieties were prepared either by Suzuki or Stille coupling. Analytical size exclusion chromatography (SEC) was used to fractionate the copolymer with 1:1 thienopyrroledione to carbazole ratio into 9 sharp fractions. The effective conjugation length (35 aromatic rings) was determined on the basis of the dependence of λmax of the π–π* band on the degree of polymerization, DPn. All four polymers showed similar supramolecular organization resembling that of poly(3-alkylthiophene)s since the mechanism of the self-assembly was the same in both cases: π-stacking of the π-conjugated polymer backbones and interdigitation of n-alkyl side chains. As shown by cyclic voltammetry studies, three copolymers showed band gaps inferior to 2 eV with HOMO and LUMO levels ranging between −5.62 eV to −5.08 eV and −3.53 eV to −3.13 eV, respectively. UV-vis-NIR spectroelectrochemical investigations confirmed the results obtained by cyclic voltammetry, enabling in addition more precise determination of the HOMO level. Raman spectroelectrochemical studies showed that the polymer with 1:1 thienopyrroledione to carbazole ratio is prone to oxidative degradation, consistent with cyclic voltammetry studies. A bulk-heterojunction solar cell was fabricated from the copolymer consisting of thienopyrroledione and dialkoxy substituted benzodithiophene. A power conversion efficiency of 1.63% was achieved for non-optimized devices.