Reverse-Offset-Printed Organic Nonvolatile Memory Thin-Film Transistor

Abstract

Reverse-offset-printed organic nonvolatile memory thin-film transistors (TFTs) are demonstrated on a large-area substrate for the first time. Finely patterned electrodes are fabricated by reverse-offset printing with 15 um line width and 10um channel length through three steps of ink coating, patterning and transfer using Ag-nanoparticle ink. Memory devices are configured in a bottom-gate bottom-contact TFT structure with a high-k gate blocking insulator poly(vinylidene fluoride-co-trifluoroethylene). A blend ink, which consists of a small-molecule p-type organic semiconductor dithieno[2,3-d;2′,3′-d′]benzo[1,2-b;4,5-b′]dithiophene and a tunneling polymer polystyrene, are fabricated using air-pulse nozzle printing. The tunneling layer is formed during the active layer printing process with blended ink by phase separation of small-molecule and polymer. The printed nonvolatile memory TFTs with the phase-separated tunneling layer exhibited significantly improved VTH shifts (~3 times), programmed/erased current ratio (>10^3 A/A), switching speed (<100 ms) and data retention (>10 y). We believe our finding is applicable to wearable electronics, smart Internet-of-Things devices and neuromorphic computing devices.