title: Side-chain tunability of furan-containing low-band-gap polymers provides control of structural order in efficient solar cells.
abstract: The solution-processability of conjugated polymers in organic solvents has classically been achieved by modulating the size and branching of alkyl substituents appended to the backbone. However, these substituents impact structural order and charge transport properties in thin-film devices. As a result, a trade-off must be found between material solubility and insulating alkyl content. It was recently shown that the substitution of furan for thiophene in the backbone of the polymer PDPP2FT significantly improves polymer solubility, allowing for the use of shorter branched side chains while maintaining high device efficiency. In this report, we use PDPP2FT to demonstrate that linear alkyl side chains can be used to promote thin-film nanostructural order. In particular, linear side chains are shown to shorten π-π stacking distances between backbones and increase the correlation lengths of both π-π stacking and lamellar spacing, leading to a substantial increase in the efficiency of bulk heterojunction solar cells.
authors.affiliation: Materials Sciences Division, Lawrence Berkeley National Laboratory Berkeley, California 94720, USA.
authors.forename: Alan T
authors.initials: AT
authors.lastname: Yiu
authors.forename: Pierre M
authors.initials: PM
authors.lastname: Beaujuge
authors.forename: Olivia P
authors.initials: OP
authors.lastname: Lee
authors.forename: Claire H
authors.initials: CH
authors.lastname: Woo
authors.forename: Michael F
authors.initials: MF
authors.lastname: Toney
authors.forename: Jean M J
authors.initials: JM
authors.lastname: Fréchet
mesh_terms: D005663:Furans / Q000737:chemistry*; D015394:Molecular Structure; D010316:Particle Size; D011108:Polymers / Q000138:chemical synthesis / Q000737:chemistry*; D012993:Solar Energy; D012995:Solubility; D013499:Surface Properties; D013876:Thiophenes / Q000737:chemistry
chemical_list: D005663:Furans; D011108:Polymers; D013876:Thiophenes; C039281:furan