Photoinduced Charge Separation and Charge Recombination in the [60]Fullerene−Diphenylbenzothiadiazole−Triphenylamine Triad:  Role of Diphenylbenzothiadiazole as Bridge

• Published in: The journal of physical chemistry. B Vol. 109; no. 47; pp. 22502 - 22512
• Main Authors: Sandanayaka, Atula S. D, Taguri, Yoshiki, Araki, Yasuyuki, Ishi-i, Tsutomu, Mataka, Shuntaro, Ito, Osamu
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 01.12.2005
• ISSN: 1520-6106; 1520-5207
• DOI: 10.1021/jp053809c

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 μs, 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.