title: Photoinduced charge separation and charge recombination in the [60]fullerene-diphenylbenzothiadiazole-triphenylamine triad: role of diphenylbenzothiadiazole as bridge.
abstract: Photoinduced electron-transfer processes of the newly synthesized [60]fullerene-diphenylbenzothiadiazole-triphenylamine (C60-PBTDP-TPA) triad in polar and nonpolar solvents have been studied by using time-resolved transient absorption and fluorescence measurements from picosecond to microsecond regions. By fluorescence lifetime measurements in picosecond time regions, excitation of the charge-transfer transition of the PBTDP-TPA moiety in C60-PBTDP-TPA induces energy transfer to the C60 moiety generating 1C60*-PBTDP-TPA, competitively with charge separation generating C60*--PBTDP-TPA*+. From 1C60*-PBTDP-TPA, which is generated directly and indirectly, charge separation occurs generating C60*--PBTDP-TPA*+ in polar solvents. The C60*--PBTDP-TPA*+ formed via the singlet excited states decayed within a few nanoseconds as revealed by the picosecond transient absorption spectra. In the nanosecond time region, C60*--PBTDP-TPA*+ is produced slowly, probably via 3C60*-PBTDP-TPA. Lifetimes of such slowly generated C60*--PBTDP-TPA*+ were longer than 1 micros, which are the longest values among the C60-bridge-TPA triad systems reported hitherto at room temperature. Roles of the PBTDP-TPA moiety with twisted intermolecular charge-transfer character playing as energy donor and electron donor in addition to the bridge have been disclosed.
authors.affiliation: Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-8577, Japan.
authors.forename: Atula S D
authors.initials: AS
authors.lastname: Sandanayaka
authors.forename: Yoshiki
authors.initials: Y
authors.lastname: Taguri
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Araki
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Ishi-I
authors.forename: Shuntaro
authors.initials: S
authors.lastname: Mataka
authors.forename: Osamu
authors.initials: O
authors.lastname: Ito