In order to estimate the deep-trapping mobility-lifetime (μτ) product for holes and electrons in poly(p-phenylene vinylene) (PPV), trap-free space-charge-limited current, and time-of-flight measurements were performed on bilayer devices comprising of a PPV layer and a trap-free molecularly doped polymer layer. μτ products of about 10−9 and 10−12 cm2/V were found for holes and electrons respectively, corresponding to an average range of 1 μm for holes and 10 Å for electrons under an electric field of 105 V/cm. The low μτ value for electrons is attributed to severe deep trapping of electrons in PPV, which effectively reduces their range. Implications on the efficiency of electroluminescence devices are discussed.

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