title: Sub-Picosecond Singlet Exciton Fission in Cyano-Substituted Diaryltetracenes.
abstract: Thin films of 5,11-dicyano-6,12-diphenyltetracene (TcCN) have been studied for their ability to undergo singlet exciton fission (SF). Functionalization of tetracene with cyano substituents yields a more stable chromophore with favorable energetics for exoergic SF (2E(T1)-E(S1)=-0.17 eV), where S1 and T1 are singlet and triplet excitons, respectively. As a result of tuning the triplet-state energy, SF is faster in TcCN relative to the corresponding endoergic process in tetracene. SF proceeds with two time constants in the film samples (τ=0.8±0.2 ps and τ=23±3 ps), which is attributed to structural disorder within the film giving rise to one population with a favorable interchromophore geometry, which undergoes rapid SF, and a second population in which the initially formed singlet exciton must diffuse to a site at which this favorable geometry exists. A triplet yield analysis using transient absorption spectra indicates the formation of 1.6±0.3 triplets per initial excited state.
authors.affiliation: Department of Chemistry and Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208 (USA).
authors.forename: Eric A
authors.initials: EA
authors.lastname: Margulies
authors.affiliation: Department of Chemistry and Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208 (USA).
authors.forename: Yi-Lin
authors.initials: YL
authors.lastname: Wu
authors.affiliation: Laboratorium für Organische Chemie, ETH Zürich, Vladimir-Prelog-Weg 3, HCI, 8093 Zürich (Switzerland).
authors.forename: Przemyslaw
authors.initials: P
authors.lastname: Gawel
authors.affiliation: Department of Chemistry and Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208 (USA).
authors.forename: Stephen A
authors.initials: SA
authors.lastname: Miller
authors.affiliation: Department of Chemistry and Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208 (USA).
authors.forename: Leah E
authors.initials: LE
authors.lastname: Shoer
authors.affiliation: Department of Chemistry, Northwestern University and Center for Nanoscale Materials, Argonne National Laboratory, Argonne, IL 60439 (USA).
authors.forename: Richard D
authors.initials: RD
authors.lastname: Schaller
authors.affiliation: Laboratorium für Organische Chemie, ETH Zürich, Vladimir-Prelog-Weg 3, HCI, 8093 Zürich (Switzerland). diederich@org.chem.ethz.ch.
authors.forename: François
authors.initials: F
authors.lastname: Diederich
authors.affiliation: Department of Chemistry and Argonne-Northwestern Solar Energy Research (ANSER) Center, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208 (USA). m-wasielewski@northwestern.edu.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Wasielewski
keywords: chromophores; photophysics; singlet fission; tetracene derivatives; time-resolved spectroscopy