Phase separation and affinity between a fluorinated perylene diimide dye and an alkyl-substituted hexa-peri-hexabenzocoronene

Giovanna De Luca; Andrea Liscio; Manuela Melucci; Tobias Schnitzler; Wojciech Pisula; Christopher G. Clark; Luigi Monsù Scolaro; Vincenzo Palermo; Klaus Müllen; Paolo Samorì

doi:10.1039/B915484A

Phase separation and affinity between a fluorinated perylene diimide dye and an alkyl-substituted hexa-peri-hexabenzocoronene†

Giovanna De Luca,^ab Andrea Liscio,^a Manuela Melucci,^a Tobias Schnitzler,^c Wojciech Pisula,^c Christopher G. Clark, Jr,^c Luigi Monsù Scolaro,^b Vincenzo Palermo,*^a Klaus Müllen*^c and Paolo Samorì*^ad

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* Corresponding authors

^a Istituto per la Sintesi Organica e la Fotoreattività – Consiglio Nazionale delle Ricerche, via Gobetti 101, Bologna, Italy
E-mail: palermo@isof.cnr.it

^b Dipartimento di Chimica Inorganica, Chimica Analitica e Chimica Fisica – Università di Messina, Salita Sperone 31, Vill. S. Agata, Messina, Italy

^c Max Planck Institute for Polymer Research, Ackermannweg 10, Mainz, Germany
E-mail: muellen@mpip-mainz.mpg.de

^d Nanochemistry Laboratory, ISIS – CNRS 7006, Université de Strasbourg, 8 allée Gaspard Monge, Strasbourg, France
E-mail: samori@isis-ulp.org

Abstract

Fluorination of alkyl groups is a known strategy for hindering miscibility, thus promoting phase separation, when blends are prepared with a hydrocarbon compound. A new perylene bis(dicarboximide) derivative functionalized with branched N-perfluoroalkyl moieties (BPF-PDI) has been synthesized as electron acceptor to be potentially used in conjunction with the electron donor hexakis(dodecyl)hexabenzocoronene (HBC-C₁₂) in bulk heterojunction solar cells. Aiming at controlling self-assembly between the two components at the supramolecular level, stoichiometric blends in CHCl₃ have been prepared either by spin- or drop-casting onto silicon surfaces, and further subjected to solvent vapour annealing (SVA) treatment in a CHCl₃-saturated atmosphere. Spectroscopic investigation in solution shows the formation of supramolecular BPF-PDI–HBC-C₁₂ dimers, with an association constant K_ass = (2.1 ± 0.3) × 10⁴ M⁻¹, pointing to a strong and unexpected affinity between the two species within the mixture. Characterization through optical and atomic force microscopies of the deposited samples revealed that the self-assembly behaviour of the blends on SiO_x is remarkably different from mono-component films, thus confirming the absence of a macroscopic phase-separation between the two components featuring isolated domains of the neat acceptor or donor compound. In addition, X-ray studies provided evidence for the existence of a local-scale phase separation. These findings are of importance for organic photovoltaics, since they offer a new strategy to control the phase separation at different scales in electron acceptor–donor blends.

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Journal of Materials Chemistry

Phase separation and affinity between a fluorinated perylene diimide dye and an alkyl-substituted hexa-peri-hexabenzocoronene†

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Phase separation and affinity between a fluorinated perylene diimide dye and an alkyl-substituted hexa-peri-hexabenzocoronene

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