Low operating voltage organic transistors and circuits with anodic titanium oxide and phosphonic acid self-assembled monolayer dielectrics

We fabricated organic thin-film transistors (OTFTs) with sub-1 V driving voltage enabled by a hybrid dielectric comprising high-k amorphous titanium oxide (TiO_x) and a phosphonic acid self-assembled monolayer (SAM). The p-type OTFTs show a high on/off ratio (10⁵), a near 0 V threshold voltage (−0.09 V), and a high mobility of 1.2 cm²/Vs when operated at 1 V. These OTFTs are readily employed in circuit applications, and we show pseudo-CMOS and CMOS inverters operating at 0.5 V as basic building blocks of low-voltage advanced organic logic circuits. We fabricate a five-stage CMOS ring oscillator that displays clear oscillation characteristics at a driving voltage of 0.5 V to highlight the potential of our hybrid dielectric for ultra-low-voltage integrated plastic circuitry.