Photoconductivity in fullerene-doped polysilane thin films

Flash photolysis time-resolved microwave conductivity (FP-TRMC) measurements have been performed to study the transport properties charge carriers in the polysilane films. The effect of C-60 concentrations on photoconductivity of poly(methylphenylsilane) (PMPS) and poly(n- which is the product of quantum hexylphenylsilane) (PHPS) films has been studied using a variety of excitation light sources. The value of phi Sigma mu, which is the product of quantum efficiency of photocarrier generation (phi) and sum of moibilities of the carriers (Sigma mu), depends strongly on C-60 concentration upon exposure 532 nm. The quantum efficiency reaches similar to 0.06 with C-60 concentration at 5.7 mol%, and saturates at the higher concentrations. The phi Sigma mu value increases considerably upon exposure of 193 nm up to 1.22 x 10(-3) cm(2)/Vs without significant dependence on C-60 concentration, suggesting direct formation of electron-hole pair by 6.39 eV photon absorption with the higher phi value at similar to 0.12. The present technique gave the estimates intra-chain mobility of charge carriers in PMPS and PHPS, and one-order magnitude higher intra-chain mobility was observed in PHPS than that PMPS. This is suggestive of a highly ordered Si backbone conformation in PHPS. The intra-chain mobility in PMPS, however, is at least two of magnitude higher than the mobility values estimated by conventional time-of-flight techniques. Thus we conclude that the higher mobility similar to 10(-3) cm(2)/Vs (E similar to 0) is realizable even with PMPS by precise synthesis and device fabrication free from disordering, defects, impurities, etc. 0 2005 Elsevier B.V. All rights reserved.