Comprehensive Evaluation of Electron Mobility for a Trifluoroacetyl-Terminated Electronegative Conjugated Oligomer

We have synthesized the electronegative oligomer having trifluoroacetyl groups at the terminal positions as new organic semiconductors and revealed that the presence of trifluoroacetyl groups is effective in lowering the lowest unoccupied molecular orbital energy level and arranging the molecules in crystals. The oligomer exhibited good n-type characteristics on thin-film field-effect transistor (FET) devices with field-effect electron mobility of 0.08 cm2 V−1 s−1. Further evaluation of electron mobility for this compound by a single-crystal FET device and time-resolved microwave conductivity measurements has been accomplished, and the electron mobilities are calculated to be ∼0.2 and >2.4 cm2 V−1 s−1, respectively. Direct comparison of electron mobilities estimated from these methods shows the importance of not only the molecular properties and stacking structure but also the interface with gate dielectrics and metal electrodes.