Eco‐Friendly Approach to Ultra‐Thin Metal Oxides‐ Solution Sheared Aluminum Oxide for Half‐Volt Operation of Organic Field‐Effect Transistors

Sol–gel‐based solution‐processed metal oxides have emerged as a key fabrication method for applications in thin film transistors both as a semiconducting and a dielectric layer. Here, a low‐temperature, green solvent‐based, non‐toxic, and cost‐effective solution shearing approach for the fabrication of thin aluminum oxide (AlOx) dielectrics is reported. Optimization of sustainability aspects like energy demand, and selection of chemicals used allows to reduce the environmental impact of the life cycle of the resulting product already in the design phase. Using this approach, ultra‐thin, device‐grade AlOx films of 7 nm are coated—the thinnest films to be reported for any solution‐fabrication method. The metal oxide formation is achieved by both thermal annealing and deep ultra‐violet (UV) light exposure techniques, resulting in capacitances of 750 and 600 nF cm−2, respectively. The structural analysis using microscopy and x‐ray spectroscopy techniques confirmed the formation of smooth, ultra‐thin AlOx films. These thin films are employed in organic field‐effect transistors (OFETs) resulting in stable, low hysteresis devices leading to high mobilities (6.1 ± 0.9 cm2 V−1 s−1), near zero threshold voltage (−0.14 ± 0.07 V) and a low subthreshold swing (96 ± 16 mV dec−1), enabling device operation at only ±0.5 V with a good Ion/Ioff ratio (3.7 × 105).