In this paper, we present measurements of the charge-carrier transport in the conjugated polymer poly(paraphenylenevinylene) (PPV) and its substituted derivative poly(1,4-phenylene-1,2-diphen- oxyphenyl 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 ${10}^{\mathrm{-}4}$ ${\mathrm{cm}}^2$/V s, whereas for PPV, a value of less than ${10}^{\mathrm{-}8}$ ${\mathrm{cm}}^2$/V s can be estimated.

• Received 9 March 1995

DOI:https://doi.org/10.1103/PhysRevB.52.2587