title: Morphology effectively controls singlet-triplet exciton relaxation and charge transport in organic semiconductors.
abstract: We present a comparative study of ultrafast photoconversion dynamics in tetracene (Tc) and pentacene (Pc) single crystals and Pc films using optical pump-probe spectroscopy. Photoinduced absorption in Tc and Pc crystals is activated and temperature-independent, respectively, demonstrating dominant singlet-triplet exciton fission. In Pc films (as well as C60-doped films) this decay channel is suppressed by electron trapping. These results demonstrate the central role of crystallinity and purity in photogeneration processes and will constrain the design of future photovoltaic devices.
authors.affiliation: Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
authors.forename: V K
authors.initials: VK
authors.lastname: Thorsmølle
authors.forename: R D
authors.initials: RD
authors.lastname: Averitt
authors.forename: J
authors.initials: J
authors.lastname: Demsar
authors.forename: D L
authors.initials: DL
authors.lastname: Smith
authors.forename: S
authors.initials: S
authors.lastname: Tretiak
authors.forename: R L
authors.initials: RL
authors.lastname: Martin
authors.forename: X
authors.initials: X
authors.lastname: Chi
authors.forename: B K
authors.initials: BK
authors.lastname: Crone
authors.forename: A P
authors.initials: AP
authors.lastname: Ramirez
authors.forename: A J
authors.initials: AJ
authors.lastname: Taylor