Photoconductivity of acceptor substituted poly(3-butyl)thiophene: evidence for charge trapping

Summary form only given. We have studied acceptor substituted poly(3-butyl)thiophene (PBuT) in order to examine the usefulness of the acceptor as an intrinsic charge-trap under laser excitation. It has been anticipated that such an acceptor group will slow down the recombination, giving rise to considerably slower photoconductivity. The acceptor used is the chemically prepared high electron affinity monomer 3-(4-Nitrobenzene-1,2-ethen) Thiophene (NBET). We have measured the transient photoconductivity (PC) of these polymers employing the Auston switch transmission line configuration, with 5 nsec laser pulses at 0.35 /spl mu/m. For the homopolymer PBuT, the decay of the TPC is relatively fast with half amplitude decay time of /spl tilde/30 nsec. In the copolymers PBuT/NBET the PC becomes considerably longer with a power law decay. The longer lived PC in the copolymers is attributed to intrinsic charge trapping by the strong acceptor groups.