Molecular size dependence of field effect in organic single crystals

We explore the effect of molecular size on injected carrier transport. We have fabricated and characterized field effect transistors (FETs) on optically transparent single crystals of tetracene, the molecule of which is comprised of four benzene rings (BR). These FETs exhibit effective channel mobility µ eff up to 0.15 cm 2 /Vs, intrinsic free carrier mobility of µ ~ 75 cm 2 /Vs, and on/off ratios up to 2 × 10 7 . The present results show 1) the possibility of FET behavior in a transparent crystal with low intrinsic carrier density and 2) a weak dependence of performance on number of BRs, when compared to similar pentacene (5 BR) devices.