title: Charge carrier dynamics of vapor-deposited small-molecule/fullerene organic solar cells.
abstract: Although small-molecule organic solar cells (SMOSCs) have shown increasingly promising prospects as a source of solar power, there have been few studies concerning the photophysics of these systems. Here, we report the time scale and efficiency of charge separation and recombination in a vapor-deposited SMOSC material that produces 5.81% power conversion efficiency. Transient absorption and time-resolved photoluminescence (trPL) studies of thin film blends comprising DTDCTB, a narrow-band gap electron donor, and either C60 or C70 as an electron acceptor show that charge separation occurs in ~100 fs, while charge recombination takes place over sub-ns and ns time scales. trPL indicates a donor electron-hole pair lifetime of ~33 ps in the neat film and reveals that ~20% of donors fail to charge separate in donor-acceptor mixed films, likely owing to some spatially extended donor-rich regions that interact poorly with acceptors. Our results suggest that morphological manipulations of this material could further improve device efficiency.
authors.affiliation: Department of Chemistry, Northwestern University, Evanston, Illinois 60208, USA.
authors.forename: Angela Y
authors.initials: AY
authors.lastname: Chang
authors.forename: Yi-Hong
authors.initials: YH
authors.lastname: Chen
authors.forename: Hao-Wu
authors.initials: HW
authors.lastname: Lin
authors.forename: Li-Yen
authors.initials: LY
authors.lastname: Lin
authors.forename: Ken-Tsung
authors.initials: KT
authors.lastname: Wong
authors.forename: Richard D
authors.initials: RD
authors.lastname: Schaller