Tuning and optimizing the intrinsic interactions between phthalocyanine-based PPV oligomers and single-wall carbon nanotubes toward n-type/p-type

• Published in: Chemical science (Cambridge) 2011-01, Vol.2 (4), p.652-660
• Main Authors: Bartelmess, Juergen, Ehli, Christian, Cid, Juan-José, García-Iglesias, Miguel, Vázquez, Purificación, Torres, Tomás, Guldi, Dirk M.
• Format: Article
• Language: English
• Subjects: Charge; Electronics; Nanomaterials; Nanostructure; Oligomers; Pictures; Single wall carbon nanotubes; Tuning
• ISSN: 2041-6520; 2041-6539
• DOI: 10.1039/C0SC00364F

In this work we have developed a strategy to immobilize functional groups such as ZnPc onto the surface of SWNT without, however, the needs of covalent functionalization, using substituted PPV-oligomers (1-4) with different electronic character. The complementary use of a series of microscopies and spectroscopies is central, especially to gather a comprehensive picture of the mutual interactions. Importantly, only 1, bearing electron-withdrawing CN substituents, interacts tightly with SWNT affording stable and finely dispersed SWNT suspensions. 2-4, on the other hand, fail to disperse SWNT in THF following our newly developed protocol. A likely rationale is the p-type character of PPV-oligomers 2-4, which imposes repelling forces relative to p-type SWNT, while placing CN groups yields p-type PPV-oligomer 1 and, in turn, strengthens the capital pi - capital pi interactions with SWNT. Photoexcitation of SWNT/1 hybrids generates a metastable radical ion pair state, namely oxidized ZnPc and reduced SWNT. Quite remarkable is the ratio of charge separation to charge recombination, namely nearly 3 orders of magnitude, which is encouraging to fabricate photovoltaic cells that are based, for example, on different nanocarbons.