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

Autor: Chen Sun, Xuelong Huang, Feng Liu, Yamin Liang, Cheng Zhou, Thomas P. Russell, Jean Roncali, Yong Cao, Fei Huang, Zengqi Xie
Přispěvatelé: MOLTECH-Anjou, Université d'Angers (UA)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)
Rok vydání: 2014
Předmět:
Zdroj: Advanced Functional Materials
Advanced Functional Materials, Wiley, 2014, 24 (47), pp.7538-7547. ⟨10.1002/adfm.201401945⟩
ISSN: 1616-301X
1616-3028
Popis: International audience; 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 ΔEand of the band gap of films (Eg) versus the reciprocal chain length show that ΔEandEgconverge towards a limit corresponding to an effective conjugation length (ECL) of 7–8S1units. 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.
Databáze: OpenAIRE
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