Nondispersive hole transport in a polyfluorene copolymer with a mobility of 0.01cm2V−1s−1

The hole mobility in the fluorene copolymer poly(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4′-(N-(4-sec-butylphenyl)) diphenylamine) (TFB) was measured using the time-of-flight technique. Transport was found to be nondispersive throughout the temperature range between 220 and 350K, indicating the absence of intrinsic traps in this material. At room temperature, TFB shows a hole mobility of 0.01cm2V−1s−1, with a weak field dependence. The hole mobility is independent of sample thickness in the range between 0.9 and 6.4μm. These results are in agreement with a narrow transport manifold, with a width of 65.9±0.5meV.