**2.1. Introduction**

In this section, we focus on the low-temperature solution deposition of high-quality oxide dielectric thin films for the fabrication of active electronic devices such as thin-film transistors (TFTs). Highly stable oxide dielectric materials are of paramount importance as implemented through sophisticated additive processing with the other components of a TFT. However, compared to vacuum-based deposited oxide films, solution-processed counterparts are generally found to be inferior due to their deposition, metal precursors, morphological characteristics, and performance limitations. Although realizing capabilities to print and integrate solution-processed device-quality oxide dielectrics poses a very significant challenge, success is very likely to open many opportunities in fabricating active electronics as well as in providing new approaches to the production of various unique optical and optoelectronic devices. In addition, solution processing of oxide dielectric thin films at a temperature well below 300°C, which likely opens the door to flexible electronics, has remained challenging. By various approaches including tailoring precursor solution or functional solution chemistry, deposition, annealing/heating profile, activation of amorphous film, such as photo-assisted annealing (UV), solvothermal synthesis, and so on, low-temperature solution-processed oxide dielectric thin films have become possible now.
