Low operating voltage n-channel organic field effect transistors using lithium fluoride/PMMA bilayer gate dielectric

We report low temperature processed, low voltage operable n-channel organic field effect transistors (OFETs) using N,N′-Dioctyl-3,4,9,10-perylenedicarboximide (PTCDI-C₈) organic semiconductor and poly(methylmethacrylate) (PMMA)/lithium fluoride (LiF) bilayer gate dielectric. We have studied the role of LiF buffer dielectric in effectively reducing the gate leakage through the device and thus obtaining superior performance in contrast to the single layer PMMA dielectric devices. The bilayer OFET devices had a low threshold voltage (V_t) of the order of 5.3 V. The typical values of saturation electron mobility (μ_s), on/off ratio and inverse sub-threshold slope (S) for the range of devices made were estimated to be 2.8 × 10^-3 cm²/V s, 385, and 3.8 V/decade respectively. Our work thus provides a potential substitution for much complicated process of chemically crosslinking PMMA to achieve low leakage, high capacitance, and thus low operating voltage OFETs.