title: Nonlinear optical pulse suppression via ultrafast photoinduced electron transfer in an aggregated perylene diimide/oligothiophene molecular triad.
abstract: A donor-acceptor-donor triad material in which two quinquethiophene moieties are attached via nonconjugated, flexible bridges to the 1,7-positions (80% isomer) and 1,6-positions (20% isomer) of a perylene diimide (PDI-5T) has been synthesized, and its nonlinear suppression of nanosecond laser pulses in the 680-750 nm range has been studied. The kinetics of the photoinduced charge separation processes have been characterized using femtosecond transient pump-probe spectroscopy. Excitation of either the quinquethiophene donor or perylene diimide acceptor leads to ultrafast (<700 fs) photoinduced charge separation, yielding quinquethiophene and perylene diimide radical ions that are strongly absorbing in the red-near-IR region. Despite the short lifetime (52 ps) of the charge-separated state, reasonably strong nonlinear suppression of nanosecond pulses, with figures-of-merit up to 14, has been realized with 4 mM solutions of PDI-5T. Although the radical ion absorption (RIA) is much stronger at 750 nm than that at 680 or 700 nm, the best optical suppression figures-of-merit were observed at 680 and 700 nm. Comparison of the optical parameters at these wavelengths suggests that the stronger ground-state absorption, due to aggregates of PDI-5T, is responsible for the enhanced figure-of-merit at the shorter wavelength.
authors.affiliation: School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology , Atlanta, Georgia 30332-0400, United States.
authors.forename: Matthew M
authors.initials: MM
authors.lastname: Sartin
authors.forename: Chun
authors.initials: C
authors.lastname: Huang
authors.forename: Ariel S
authors.initials: AS
authors.lastname: Marshall
authors.forename: Nikolay
authors.initials: N
authors.lastname: Makarov
authors.forename: Stephen
authors.initials: S
authors.lastname: Barlow
authors.forename: Seth R
authors.initials: SR
authors.lastname: Marder
authors.forename: Joseph W
authors.initials: JW
authors.lastname: Perry