Solution processed n-channel organic field-effect transistors based on [6,6]-phenyl C61 butyric acid methyl ester with high mobility and low contact resistance are reported. Ca, Au, or Ca capped with Au (Ca/Au) was used as the top source/drain electrodes. The devices with Ca electrodes exhibit excellent n-channel behavior with electron mobility values of 0.12 cm2/V s, low threshold voltages (∼2.2 V), high current on/off ratios (105–106) and subthreshold slopes of 0.7 V/decade. By varying the channel lengths (25–200 μm) in devices with different metal/semiconductor interfaces, the effect of channel length scaling on mobility is studied and the contact resistance is extracted. The width-normalized contact resistance (RCW) for Au (12 kΩ cm) is high in comparison to Ca (7.2 kΩ cm) or Ca/Au (7.5 kΩ cm) electrodes at low gate voltage (VGS=10 V). However, in the strong accumulation regime at high gate voltage (VGS=30 V), its value is nearly independent of the choice of metal electrodes and in a range of 2.2–2.6 kΩ cm. These devices show stable electrical behavior under multiple scans and low threshold voltage instability under electrical bias stress (VDS=V<- roman>GS=30 V, 1 h) in N2 atmosphere.