Role played by chain length and polarity of n-substitutents in electrochromic polymers from the tri-heterocyclic monomer pyrrole-thiophene-pyrrole

• Published in: Solar energy materials and solar cells 2012-04, Vol.99, p.101-108
• Main Authors: Salamone, Matteo M., Silvestri, Fabio, Sassi, Mauro, Mari, Claudio M., Ruffo, Riccardo, Beverina, Luca, Pagani, Giorgio A.
• Format: Article
• Language: English
• Subjects: Applied sciences; Charge trapping; Electrochromism; Electropolymerization; Energy; Exact sciences and technology; Miscellaneous; Natural energy; Photovoltaic conversion; Side chains; Solar cells. Photoelectrochemical cells; Solar energy
• ISSN: 0927-0248; 1879-3398
• DOI: 10.1016/j.solmat.2011.07.024

Conjugated polymers play an increasingly relevant role in a large number of technological applications (organic solar cells, electrochromic devices, OLEDs). Such preeminence is as much a consequence of their peculiar optoelectronic properties as it is of the possibility to be solution processed. In fact, although unfunctionalized conjugated polymers are almost insoluble, an extensive functionalization with suitable solubilizing chains conveys the required solution processability as well as good adhesion properties with respect to a number of different substrates. The chemical nature (polar, nonpolar) length and branching of the chains do not sizably influence the electronic properties of the polymer, but plays a major role in the solid-state morphology. We here present a systematic study on the role of the solubilizing chains in the overall performances of a series of electropolymerized 2,2′-{thiene-2,5-diylbis[(E)ethene-2,1-diyl]}bis(1H-pyrrole) derivatives. In particular, we show how the nature and length of the chain play a relevant role on the electrochemical behavior of the polymers. Our results can be rationalized in terms of lateral chain induced noncovalent interactions. Finally, the spectroelectrochemical properties of some of these polymers could be of interest for NIR-operating variable optical attenuators. [Display omitted] ► 2,2′-{thiene-2,5-diylbis[(E)ethene-2,1-diyl]}bis(1H-pyrrole) monomers were obtained. ► Monomers were electropolymerized to give the corresponding polymers. ► Solubilizing chains play a relevant role on the polymers behavior and morphology. ► Polar chains promote a charge trapping phenomenon at strongly negative potentials. ► The polymers could be used as active layer in variable optical attenuators.