Ultrafast spectroscopic study of photoinduced electron transfer in an oligo(thienylenevinylene):Fullerene composite

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%. © 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim