Dual Threshold Voltage Organic Thin-Film Transistor Technology

A fully photolithographic dual threshold voltage (V-T) organic thin-film transistor (OTFT) process suitable for flexible large-area integrated circuits is presented. The near-room-temperature (<= 95 degrees C) process produces integrated dual V-T pentacene-based p-channel transistors. The two V-T's are enabled by using two gate metals of low (aluminum) and high (platinum) work function. The Al and Pt gate OTFTs exhibit nominally identical current-voltage transfer curves shifted by an amount Delta V-T. The availability of a high-V-T device enables area-efficient zero-V-GS high-output-resistance current sources, enabling high-gain inverters. We present positive noise margin inverters and rail-to-rail ring oscillators powered by a 3-V supply-one of the lowest supply voltages reported for OTFT circuits. These results show that integrating n- and p-channel organic devices is not mandatory to achieve functional area-efficient low-power organic integrated circuits.