Nitroacetylacetone as a Cofuel for the Combustion Synthesis of High-Performance Indium–Gallium–Zinc Oxide Transistors

Abstract

Thin-film combustion synthesis has been utilized for the fabrication of solution processed high-performance metal-oxide thin-film transistors (MOTFTs) at lower temperatures than conventional sol–gel processes. The fuel-oxidizer ensemble in the MO precursor solution/film plays an important role in achieving high-efficiency and low-residual combustion byproducts. However, unlike conventional bulk combustion, only a very limited number of thin-film fuels have been investigated. Here we report the use of an efficient new cofuel, 3-nitroacetylacetone (NAcAcH), incorporating a −NO2 group, for the combustion synthesis of display-relevant indium–gallium–zinc-oxide (IGZO) thin films. Compared to the traditional acetylacetone (AcAcH) fuel, a higher enthalpy of combustion (988.6 vs 784.4 J/g) and a lower ignition temperature (107.8 vs 166.5 °C) are achieved for NAcAcH-based formulations. The resulting NAcAcH-derived IGZO TFTs exhibit far higher average electron mobilities (5.7 cm2 V–1 s–1) than AcAcH-derived TFTs (2.7 cm2 V–1 s–1). More importantly, when combining AcAcH with NAcAcH as cofuels in an optimal molar ratio of 1.5:0.5, an even larger TFT electron mobility (7.5 cm2 V–1 s–1) and more stable devices are achieved. Comprehensive IGZO precursor/film analysis and characterization by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), grazing incidence X-ray diffraction (GIXRD), and X-ray reflectivity (XRR) explain the basis of the film microstructure and TFT performance trends.