- Provides an overview of the latest developments and research results in the field of printed electronics - Topics addressed include: organic printable electronic materials, inorganic printable electronic materials, printing processes and equipments for electronic manufacturing, printable transistors, printable photovoltaic devices, printable lighting and display, encapsulation and packaging of printed electronic devices, and applications of printed electronics - Discusses the principles of the above topics, with support of examples and graphic illustrations - Serves both as an advanced introductory to the topic and as an aid for professional development into the new field - Includes end of chapter references and links to further reading
1.1 What is Printed Electronics?
Printed electronics, as the name implies, is a type of electronics that are created by printing technology. To be more specific, it is an electronic science and technology based on conventional printing techniques as the means to manufacture electronics devices and systems. To most people, "printed electronics" is an unfamiliar phrase. Even experts in electronics may not have heard it. Many people may have it confused with conventional printing technology or mixed up with electronic printing. Conventional printing is for printing paper media, such as books, newspapers, and magazines. Even electronic printing is not printed electronics. Electronic printing is still conventional media printing but with more use of computers and electronic typesetting. A closer analogy to printed electronics would be electronics or integrated circuit (IC)-based electronics, rather than conventional printing. The aim of printed electronics is to make integrated electronic systems using printing technology instead of much more expensive and complex IC manufacturing technology.
Silicon-based IC technology has been in use for nearly 60 years. Modern silicon microelectronics and its manufacturing technology have evolved into an extremely complicated process. There are several hundreds of steps involved in producing a silicon IC chip, from the preparation of single crystal silicon substrates to making billions of transistors and getting these transistors interconnected, including repeated thin film deposition, lithography, etching, and packaging . IC manufacturing has become so expensive that the latest deep UV photolithography system can cost tens of millions of dollars, whereas an extreme UV lithography system for making silicon chips at below 32 nm feature size has a price tag of more than $120 million . The IC industry has become so investment intensive that only a handful companies in the world can afford to play in the field. On the other hand, printing is a very simple process compared to the IC manufacturing process, as illustrated in Figure 1.1 In order to turn a functional material into a functional structure or pattern on a silicon substrate, IC manufacturing has to go through thin film deposition, spin-coating photoresist layer, baking, photolithography, baking, developing, etching, and stripping of the photoresist masking layer. If printing is employed, the functional material can be directly printed as patterns onto the substrate. Only a subsequent annealing/sintering process is needed.
Figure 1.1 Comparison of IC manufacturing and printing processes. (a) Conventional IC manufacturing; and (b) printing process
Printing is an additive manufacturing process, similar to the deposition process in micro- and nanofabrication  but combined with patterning. In printed electronics, the components of an electronic device or a system can be made by printing in additive fashion. For example, for a field-effect transistor, the source, drain, and gate electrodes, as well as semiconductor and insulating layers, can all be printed in ink forms and layer by layer onto a substrate. It is very much like color printing in a conventional printing press, where each color ink is printed sequentially and several color layers are overlaid to form the final color print. Because of its similarity to the printing process, the machine to print electronics is not much different from a conventional media printer. Figure 1.2 compares a conventional roll-to-roll paper media printer and an electronics printer. They look almost the same. The only difference is the inks they use. The inks for printing electronics have conducting, semiconducting, or dielectric properties. They are electronic materials, not pigment, which is the key for printing to be used for printed electronic