Printing of eco-friendly solution based zinc-tin oxide for device applications

Abstract

The research of amorphous metal oxide semiconductors for printed electronics applications, such as transparent and flexible devices, has been increasing to allow the low-cost production, good performance and large area upscaling of these materials. The most commonly used solution-based semiconductors rely on toxic solvents and are indium-based. To avoid this critical raw material ZTO is the preferred alternative. Nevertheless, replacing the toxic solvent and the chloride-based tin precursor wich also contributes to the toxicity of the solution remains a challenge. This work focuses on the development of eco-friendly ZTO precursor solutions to produce electronic devices at low temperature and optimization of flexographic printing of these ZTO inks. ZTO/SiO2 TFTs were successfully produced at 300 °C with non-toxic solvent, presenting a mobility of 2.98 ± 0.05 cm2/V.s and flexoprinted Ag/ZTO/ITO Schottky diodes were successfully produced at low temperature (150 °C + DUV) with a current on/off ratio of 1000. These devices show equivalent performance to the current state-of-the-art of ZTO devices produced with toxic solvents. Finally, TFTs and Schottky diodes using non-toxic solvent and chloride-free ZTO precursors were successfully demonstrated for the first time. This work clearly shows that it is possible to produce 100 % eco-friendly inks for high performance devices at low temperature suitable for large area printing.