Ambipolar charge transport in bulk heterojunction of poly(2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene)∕C60 composite

Using the time-of-flight technique (TOF), the influence of C60 concentrations on ambipolar charge transport in poly(2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV)∕C60 composite has been investigated. Adding C60 to the blend increases both electron and hole mobilities, compared to the pristine polymer. In the pristine MEH-PPV, the mobility of electrons is below the measurable range. However, electron mobility (10−7 cm2 V−1 s−1) could be calculated when the weight ratio of C60: MEH-PPV increased to 1:18. The temperature and electric field dependence of mobility is analyzed in the disorder formalism. It is observed that above ∼290 K the slope of the electric field dependence of the electron mobility becomes negative. The occurrence of negative field dependence in composite samples is attributed to the large positional disorder (Σ=4).