Chain Length Dependence of the Photovoltaic Properties of Monodisperse Donor-Acceptor Oligomers as Model Compounds of Polydisperse Low Band Gap Polymers

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TitreChain Length Dependence of the Photovoltaic Properties of Monodisperse Donor-Acceptor Oligomers as Model Compounds of Polydisperse Low Band Gap Polymers
Type de publicationArticle de revue
AuteurZhou, Cheng, Liang, Yamin, Liu, Feng, Sun, Chen, Huang, Xuelong, Xie, Zengqi, Huang, Fei, Roncali, Jean , Russell, Thomas P., Cao, Yong
EditeurWiley-VCH Verlag
TypeArticle scientifique dans une revue à comité de lecture
Année2014
DateJan-09-2014
Numéro47
Pagination7538-7547
Volume24
Titre de la revueAdvanced Functional Materials
ISSN1616-301X
Mots-clésconjugated oligomers, D-A structure, Morphology, Organic photovoltaics, repeat units
Résumé en anglais

Well-defined conjugated oligomers (Sn) containing from 1 to 8 units of a tricyclic building block involving a dioctyloxybenzothiadiazole unit with two thienyl side rings (S1) are synthesized by a bottom-up approach. UV–Vis absorption data of solutions show that chain extension produces a narrowing of the HOMO–LUMO gap (ΔE) to values slightly smaller than that of the parent polymer (P1). Plots of ΔE and of the band gap of films (E g) versus the reciprocal chain length show that ΔE and E g converge towards a limit corresponding to an effective conjugation length (ECL) of 7–8 S1 units. UV–Vis absorption and photoluminescence data of solutions and solid films show that chain extension enhances the propensity to inter-chain aggregation. This conclusion is confirmed by GIXD analyses which reveal that the edge-on orientation of short-chain systems evolves toward a face-on orientation as chain length increases while the π-stacking distance decreases beyond 7 units. The results obtained on solution-processed BHJ solar cells show a progressive improvement of power conversion efficiency (PCE) with chain extension; however, the convergence limit of PCE remains inferior to that obtained with the polymer. These results are discussed with regard to the role of mono/polydispersity and chain aggregation.

URL de la noticehttp://okina.univ-angers.fr/publications/ua5473
DOI10.1002/adfm.201401945
Titre abrégéAdv. Funct. Mater.