ENHANCED PHOTOCONDUCTIVITY OF C-60 DOPED POLY(3-ALKYLTHIOPHENE)

Photoconductivity of poly(3-alkylthiophene) is found to be remarkably enhanced upon C60 doping. Excitation profile of photoconductivity shows two peaks in the spectral ranges around 650 nm and 350nm. The former peak is interpreted to be due to pi-pi* interband excitation of poly(3-alkylthiophene) followed by electron transfer to C60, while the latter is due to the optical excitation of C60 molecule, accompanied by hole transfer to poly(3-alkylthiophene). In both cases, positive polarons (P+) photogenerated with increased efficiency in poly(3-alkylthiophene) chains are considered to be responsible for enhanced photoconductivity, since geminate recombination of those positive charges (P+) in poly(3-alkylthiophene) with negative charges (P(c)-) in C60 is suppressed compared to intrachain P+-P- recombination in undoped poly(3-alkylthiophene). The decay time of photoconduction becomes shorter upon C60 doping.