Ultrafast Spectroscopic Study of Photoinduced Electron Transfer in an Oligo(thienylenevinylene):Fullerene Composite

• Published in: Advanced functional materials Vol. 17; no. 4; pp. 563 - 568
• Main Authors: Hwang, I.-W., Xu, Q.-H., Soci, C., Chen, B., Jen, A. K.-Y., Moses, D., Heeger, A. J.
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 05-03-2007; WILEY‐VCH Verlag
• Subjects: conjugated; Conjugated polymers; Electron transport; Fullerenes; Oligomers; Oligomers, conjugated; Polymeric materials
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.200600267

Photoinduced electron transfer and competing processes have been studied in composites of an oligo(thienylenevinylene) (OTV), comprised of ten dibuthoxyl‐thiophene units separated by vinylene units, and a C60 derivative, [6,6]‐phenyl‐C61 butyric acid methyl ester (PCBM), by using femtosecond transient absorption spectroscopy and sub‐nanosecond transient photoconductivity. We find that in OTV:PCBM the photoexcitations decay primarily via intrachain relaxation rather than photoinduced electron transfer from OTV to PCBM. The electron‐transfer process requires ca. 14 ps; larger by more than two orders of magnitude than the required time observed in conjugated‐polymer:C60 composites, and also larger than the 0.6 ps singlet‐state lifetime in OTV. These observations indicate that the quantum efficiency for photoinduced electron transfer in OTV:PCBM is less than 5 %.
Photoinduced electron transfer in an oligo(thienylenevinylene):fullerene composite (see figure) is studied by using ultrafast spectroscopic methods. In this composite, the photoexcitations decay primarily via intrachain relaxation rather than photoinduced electron transfer from the oligomer to the fullerene. These results differ strongly from photoexcitation dynamics typically found in conjugated polymers.