Precursor- route ZnO films from mixed casting solvent for high performance aqueous electrolyte- gated transistors

We significantly improved the properties of semiconducting zinc oxide (ZnO) films resulting from the thermal conversion of a soluble precursor, zinc acetate (ZnAc), by using a mixed casting solvent for the precursor. ZnAc dissolves more readily in a 1:1 mix of ethanol (EtOH) and acetone than in either pure EtOH, pure acetone, or pure isopropanol, and ZnO films converted from mixed solvent cast ZnAc are more homogeneous. When gated with a biocompatible electrolyte, phosphate buffered saline (PBS), ZnO thin film transistors (TFTs) derived from mixed solvent cast ZnAc give 7 times larger field effect current than similar films derived from ZnAc cast from pure EtOH. Sheet resistance at VG = VD = 1V is 18 kΩ/▢, lower than for any organic TFT, and lower than for any water- gated ZnO TFT, reported to date.