Reverse-Offset-Printed, Phase-Separated, Organic Nonvolatile Memory Thin-Film Transistor

Abstract

Reverse-offset-printed organic nonvolatile memory thin-film transistors (TFTs) are fabricated on a large-area substrate for the first time. Finely patterned electrodes (a line width of 15 um and a channel length of 10 um) were reverse-offset-printed through three steps of ink coating, patterning and transfer using Ag-nanoparticle ink. The memory devices were configured in a bottom-gate bottom-contact TFT structure with a high-k gate blocking insulator poly(vinylidene fluoride-co-trifluoroethylene). A blend ink 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 were fabricated using air-pulse nozzle printing. The tunneling layer was formed during an active layer printing process with blend ink by phase separation of small-molecule and polymer. The printed memory TFTs with the phase-separated tunneling layer exhibited significantly improved VTH shifts (≈3 times), programmed/erased current ratio (>103 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.