7 - Thermal processes

Abstract

As illustrated in Fig. 1.2, thermal treatment is always a part of printed electronics processes. Ink form of electronic materials has to be dried after solution processing (coating or printing). In most cases, the electronic properties of these inks will not be realized without thermal annealing. This is particularly true for metal oxides. Precursor inks rely on thermal annealing to convert into metal oxides. Nanoparticular inks rely on thermal annealing to remove dispersant impurities. Unfortunately, the annealing temperature is usually quite high for metal oxides, which prohibits the use of cheap flexible plastic substrates. Therefore, most of development work on solution processing of metal oxides have been focused on how to lower the annealing temperatures, which is also the focus of this chapter. Two approaches to lowering annealing temperature have been introduced in the chapter, including assisted by internal chemical reactions or by external physical conditions. Some application examples of metal oxides based flexible electronics are also given.