TRAP DISTRIBUTION FOR CHARGE-CARRIERS IN POLY(PARA-PHENYLENE VINYLENE) (PPV) AND ITS SUBSTITUTED DERIVATIVE DPOP-PPV

In this paper, we present measurements of the charge-carrier transport in the conjugated polymer poly(paraphenylene vinylene) (PPV) and its substituted derivative poly(1,4-phenylene-1,2-diphenoxyphenyl vinylene) (DPOP-PPV) by using the time-of-flight technique. A method for evaluating the experiments, based on Fourier transform techniques, is presented to calculate the density of localized states from the measured photocurrent within a multiple trapping model. The transport properties of DPOP-PPV can be described by a conventional hopping mechanism, where nearly every monomer acts as a trap. At room temperature, the effective mobility for holes in DPOP-PPV is in the range of 10(-4) cm(2)/V s, whereas for PPV, a value of less than 10(-8) cm(2)/V a can be estimated.