Device characteristics of solution-processed molecular floating-gate transistor memories based on ambipolar polymer semiconductors

Abstract

Development of nonvolatile organic field-effect transistor (OFET) memory devices with good solution processability provides an effective way of producing flexible and printable memory arrays by similar processes used for organic integrated circuits. In this study, we fabricate top-gate/bottom-contact (TG/BC) OFET memory devices with molecular floating gates by spin-coating processes and investigate their electrical characteristics. A solution-processable organic composite of 6, 13-bis(triisopropylsilylenthynyl)pentacene (TIPS-pentacene) and polystyrene (PS) is used to form floating gates and tunneling insulator layers simultaneously on a solution-processed organic semiconductor layer composed of an ambipolar semiconductor, poly(N-alkyldiketopyrrolo-pyrrole-dithienylthieno[3,2-b]thiophene) (DPP-DTT). The solution-processed DPP-DTT FET devices exhibit a large threshold voltage shift of over 10 V by programming in the dark because of the deep lowest unoccupied molecular orbital and good electron transport property of the DPP-DTT semiconductor. The memory devices also show stable charge retention characteristics and reproducible operation during the reprogrammable cycles, demonstrating reliable storage of electrons in the solution-processed molecular floating gates.