title: Below-gap excitation of pi-conjugated polymer-Fullerene blends: implications for bulk organic heterojunction solar cells.
abstract: We used a variety of optoelectronic techniques such as broadband fs transient and cw photomodulation spectroscopies, electroabsorption, and short-circuit photocurrent in bulk heterojunctions organic solar cells for studying the photophysics in pi-conjugated polymer-fullerene blends with below-gap excitation. In contrast to the traditional view, we found that below-gap excitation, which is incapable of generating intrachain excitons, nevertheless efficiently generates polarons on the polymer chains and fullerene molecules. The polaron action spectrum extends deep inside the gap as a result of a charge-transfer complex state formed between the polymer chain and fullerene molecule. With appropriate design engineering the long-lived polarons might be harvested in solar cell devices.
authors.affiliation: Department of Physics, University of Utah, Salt Lake City, Utah 84112, USA.
authors.forename: T
authors.initials: T
authors.lastname: Drori
authors.forename: C-X
authors.initials: CX
authors.lastname: Sheng
authors.forename: A
authors.initials: A
authors.lastname: Ndobe
authors.forename: S
authors.initials: S
authors.lastname: Singh
authors.forename: J
authors.initials: J
authors.lastname: Holt
authors.forename: Z V
authors.initials: ZV
authors.lastname: Vardeny