Influences of oligomer length on carrier-transport properties of oligofluorenes

In this letter, carrier-transport properties of a homologous series of oligofluorenes with C9 diaryl substitution have been examined. These substituted oligofluorenes possess stable amorphous states, ambipolar carrier-transport properties, and processability to thin films for a range of oligomer lengths, rendering feasible investigating dependence of carrier transport on oligomer length in disordered systems. It is found that carrier mobilities of these oligofluorenes show a clear decreasing trend with the oligomer length. Such findings are in contrast with previous observations for crystalline oligomers and impose certain implications in carrier transport of conjugated polymers and oligomers.