Next to the molecular structure, homo-coupling of the central donor moiety has a profound influence on organic solar cell efficiency.

Three distinct low bandgap copolymers are synthesized by the combination of N-(2′-propylpentanoyl)dithieno[3,2-b:2′,3′-d]pyrrole (DTP) and (fluorinated) 2,3-bis[5′-(2”-ethylhexyl)thiophen-2′-yl]quinoxaline (Qx) and these PDTPQx derivatives are investigated as electron donor materials in bulk heterojunction polymer solar cells. Due to the DTP N-acylation and the introduction of the Qx units, both the open-circuit voltage (Voc) and the short-circuit current density (Jsc) increase compared to previous devices based on DTP-type donor polymers. Organic solar cells with an average Voc of 0.67V, a Jsc of 12.57mA/cm² and a fill factor of 0.54 are obtained, affording a power conversion efficiency of 4.53% (4.81% for the top-performing device), a record value for (N-acyl-)DTP-based polymer solar cells devoid of special interlayer materials. Despite further enhancement of the Voc, the solar cell efficiency declines for the fluorinated PDTPQx copolymers because of the inability to achieve a finely intermixed bulk heterojunction blend nanomorphology.

Organic photovoltaics represent a promising thin-film solar cell technology with appealing mechanical, aesthetical, and cost features. In recent years, a strong growth in power conversion efficiency (to over 10%) has been realized for organic solar cells through extensive material and device research. To be competitive in the renewable energy market, further improvements are mandatory though, both with respect to efficiency and lifetime. High intrinsic stability of the photoactive layer is obviously a crucial requirement for long lifetimes, but the generally applied bulk heterojunction blends and their components are prone to light-induced and thermal degradation processes. In the present contribution, the high-T-g polymer strategy is combined with specific side chain functionalization to address the thermal stability of polymer solar cells. These two design concepts are applied to a prototype low bandgap copolymer, PCPDTBT. Accelerated aging tests (at 85 degrees C) indicate an improved thermal durability of the PCPDTBT:PC71BM blends and the resulting devices by the insertion of ester or alcohol moieties on the polymer side chains. The different stages in the efficiency decay profiles are addressed by dedicated experiments to elucidate the (simultaneously occurring) degradation mechanisms.

N-Acylation of dithieno[3,2-b:2′,3′-d]pyrrole (DTP) leads to enhanced open-circuit voltages and hence higher power conversion efficiencies in polymer solar cells.

Disubstituted poly(phenanthrene), a conjugated polymer, unexpectedly shows a record-high second-order nonlinear optical response, in absence of donor–acceptor substitution.

•Diblock copolythiophenes are synthesized by Grignard metathesis polymerization.•Straightforward post-polymerization conversion to amphiphilic block copolymers.•Solution behavior and thermal properties are analyzed for different block lengths.•Potential active layer and/or interlayer materials for organic photovoltaics.

Quinoxaline fluorination leads to enhanced properties and efficiencies in PCPDTQx-based polymer solar cells.

A two-step synthetic protocol involving (i) a Wittig-type carbonyl olefination, and (ii) regioselective alkylation of the exocyclic double bond with LiAlH4 and an alkyl bromide, was developed as an alternative to the recently reported three-step synthetic approach toward asymmetrically substituted/functionalized 4H-cyclopenta[2,1-b:3,4-b′]dithiophenes. The two routes are rather complementary, with specific advantages depending on the desired substitution pattern, and are of particular appeal for the construction of semiconducting materials to be applied in organic photovoltaics.

In this Proceedings paper, we report on the synthesis of a family of polythiophene-based conjugated polyelectrolytes, both homopolymers and random copolymers varying in the building block ratio and counter ions, toward a better fundamental understanding of the structure-property relations of these ionic derivatives in organic photovoltaics. One of the ionic homopolymers was successfully implemented as a donor material in fully solution-processed efficient bi-layer solar cells (up to 1.6% PCE in combination with PC71BM) prepared by the low impact meniscus coating technique. On the other hand, these imidazolium-substituted polythiophenes were also applied as materials for electron transport layers (ETLs), boosting the I-V properties of PCDTBT:PC71BM solar cell devices up to average PCE values of 6.2% (~20% increase), which is notably higher than for previously reported ETL materials. Advanced scanning probe microscopy techniques were used to elucidate the efficiency enhancing mechanism.

This manuscript discusses the conformation and chiroptical properties of poly(dithienopyrrole)s (PDTPs), Substituted with oligo(phenylenevinylene) (OPV) side chains and the influence of the substitution of the OPV moiety on these features. The OPV side chains were equipped with gallic acid moieties in order to promote the formation of a helical conformation in poor solvents. The polymers were prepared by Stille-couplings and characterized by GPC and NMR, UV-vis, CID, and emission spectroscopy. It was found that OPV-PDTPs, solely equipped with (chiral) alkyl groups at the terminal gallic acid group, show a very strong tendency to adopt a helical conformation, but no resolution or the mixture of helices and therefore no chiral expression. Additional substitution of the allows for a discrimination of the mixture of lielical senses. In this way, the OPV side chains can bechirally organized by the helical PDTP backbone. Substitution of the OPV in a-position, however, sterically excludes the possibility to adopt a helical conformation, but results in a lamellar supramolecular Structure in poor solvents. The macromolecular behavior is explained in terms of space confinement and sieric hindrance in the respective Structures.

The synthesis of a chiral, 9, 10-dialkoxy-functionalized poly(3,6-phenanthrene) and the study of its chiroptical properties in different solvents is reported. The polymer was prepared by a Suzuki cross-coupling reaction. UV-vis, circular dichroism, and fluorescence spectroscopy and hyper-Rayleigh scattering were used to demonstrate that this polymer adopts a random coil conformation in a good solvent and folds into a one-handed helical conformation in poor solvents rather than stacking in a chiral way. Hyper-Rayleigh scattering proved to be a powerful tool for the investigation of the conformation of conjugated polymers because its response strongly depends on the conformation of the polymer.

An achiral and chiral poly(dithieno[3,2-b:2',3'-d]pyrrole) (PDTP), substituted with a gallic acid-derived moiety, was prepared by a Stille coupling, and the supramolecular behavior in solution was studied. In a good solvent (THE), the polymers are present as unordered, highly conjugated, rigid-rod-like strands. Upon addition of a nonsolvent (hexane) or in toluene, the polymer strands adopt a helical conformation in contrast to previously reported alkyl-substituted PDTPs, which aggregate by decreasing the solvent quality. The folding and unfolding process was investigated by probing the UV-vis and CD intensifies at different wavelengths and temperatures. On the basis of these experiments, it could be concluded that the helical folding and unfolding is a single-step process. The PDTP could also be oxidized and rereduced, and thus, in principle, a molecular solenoid can be obtained.

ADVERTISEMENT RETURN TO ISSUECommunication to the...Communication to the EditorNEXTSynthesis and Properties of Polydithieno[3,2-b:2',3'-d]pyrroles: A Class of Soluble (Chiral) Conjugated Polymers with a Stable Oxidized StateGuy Koeckelberghs, Lieven De Cremer, Wouter Vanormelingen, Thierry Verbiest, André Persoons, and Celest SamynView Author Information Laboratory of Macromolecular and Physical Organic Chemistry, Katholieke Universiteit Leuven, Celestijnenlaan 200 F, B-3001 Leuven, Belgium, and Laboratory of Chemical and Biological Dynamics, Katholieke Universiteit Leuven, Celestijnenlaan 200 D, B-3001, Belgium Cite this: Macromolecules 2005, 38, 11, 4545–4547Publication Date (Web):May 4, 2005Publication History Received7 December 2004Revised30 March 2005Published online4 May 2005Published inissue 1 May 2005https://pubs.acs.org/doi/10.1021/ma047481hhttps://doi.org/10.1021/ma047481hrapid-communicationACS PublicationsCopyright © 2005 American Chemical SocietyRequest reuse permissionsArticle Views537Altmetric-Citations29LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-AlertscloseSupporting Info (1)»Supporting Information Supporting Information SUBJECTS:Conjugated polymers,Oxidation,Polymer solutions,Polymers,Thin films Get e-Alerts

A new, convergent and improved synthetic method to prepare N-alkyl substituted dithienopyrroles is described. The procedure consists of a Pd-catalyzed amination of 3,3′-dibromo-2,2′-bithiophene. The reaction conditions were optimized, which makes this method applicable to prepare these molecules easily in high yields and on a large scale.