Polymer Electronics

Citation

Goosey, M. (2014), "Polymer Electronics", Circuit World, Vol. 40 No. 1. https://doi.org/10.1108/CW-10-2013-0043

Polymer Electronics

Article Type: Book review From: Circuit World, Volume 40, Issue 1

Mark Geoghegan and Georges Hadziioannou
Oxford University Press
Oxford
2013
ISBN: 978-0-199-953382-4 (hardback) and 978-0-199-953383-1 (paperback)

Polymer Electronics has been developing over a number of years and the global market is now predicted to exceed $8 billion dollars by 2018. It is currently the basis of several important new technological developments including flexible electronics, novel types of displays, printed lighting and photovoltaic devices. The technology also has the potential to enable radical innovations in a whole range of electronic products that find widespread everyday use. Polymer Electronics thus covers a broad range of subject matter and there is clearly a need for a work that presents the subject in a clear and concise manner to those who have broad interest or may be starting to work in the area. This book by Mark Geoghegan and Georges Hadziioannou has exactly the intention of addressing these needs and it is published as part of the Oxford Master Series in Condensed Matter Physics. Books in this series are aimed at the final year undergraduate/initial post graduate level and have the intention of providing straightforward introductions to key subjects in physics.

This 250 page book is divided into ten discrete chapters and begins with an introduction and overview of Polymer Electronics, covering history and applications along with the challenges that will influence broader exploitation. There is then a chapter covering the theory that gives rise to semiconducting behaviour and how it applies to polymers; it begins with an overview of conductivity and the free electron model, which can be used to predict conductivity in many different materials. It then covers band theory and energy bands in polymers, with an introduction to doping and the influence it has on both inorganic and organic semiconductors.

The doping of polyacteylene with iodine was first investigated in the 1970s and since then a wide range of other materials has subsequently been investigated. Well known examples include polyaniline, polythiophene, polypyrrole and poly(p-phenylene vinylene), but more recently there has also been growing interest in carbon nanotubes, graphene, buckminsterfullerene and many other novel materials. Chapter 3 of this book is entitled "Beyond polyacteylene" and it gives a brief introduction to several examples from this diverse range of materials that are of potential interest in Polymer Electronics.

The preparation of a high efficiency green light-emitting polymer based organic light emitting diodes in the 1990s generated a whole new wave of interest in Polymer Electronics and one of the key areas receiving attention in recent years has been associated with the use of these new materials in display applications. It is not surprising, therefore, that a chapter of this work is dedicated to "Optoelectronic properties" and Chapter 4 covers the main subject areas of interest including photoconduction, photoluminescence, electroluminescence and the structure of a basic light emitting device.

Charge transport is fundamental to the fabrication of viable transistors and opto-electronic devices and understanding the factors that influence electron and hole transport mechanisms in polymers is key to the successful selection of materials for Polymer Electronics applications. Chapter 5 focuses on "Charge transport" and covers band transport, hopping, and a number of other key factors including injection and the nature of the electrodes that are so important when constructing functional devices.

The next two chapters alternate between the chemistry and physics of conducting polymers. In Chapter 6 on "Synthesis and macromolecular design", the book moves more towards the chemistry side of Polymer Electronics with coverage of polymerisation and a discussion of polymer solubility, doping and band gap control in the context of macromolecular design. This is then followed by details of the synthesis of a number of key conducting polymers such polyaniline. There is also mention of the electrochemical synthesis of poly (3, 4-ethylene dioxythiophene), which has found widespread application due to its high stability and optical transparency in the conducting state. Chapter 7 then covers "The physics of polymers", although this is achieved by also considering their structure and crystallinity.

Chapter 8 considers "Surfaces and interfaces" and begins with a discussion of interfacial energy before moving on to a consideration of polymers at surfaces, which is key to achieving the required performance and functionality from polymer electronic devices such as light emitting diodes or solar cells. Methods of depositing films are then described. These include the conventional approaches such as dip coating, spin coating and doctor blading, along with techniques that enable layer by layer deposition. The last part of the chapter is dedicated to surface analysis and covers methods that can be used to provide chemical structure or topographical information.

The first eight chapters of the book have focussed more on the fundamental properties, processing and characterisation of the novel materials used in Polymer Electronics, but Chapters 9 and 10 cover their actual use in electronic and optoelectronic devices. Chapter 9 is dedicated to "Polymer transistors" while Chapter 10 is on "Optoelectronic devices". Polymer transistors have very different characteristics to the conventional silicon-based devices that are found in most electronics and, while they are unlikely to ever compete on speed and the levels of integration seen with silicon, they are ideal for applications where silicon devices are unsuitable. Typical examples of potential applications for polymer transistors would be in large area and flexible displays, as well is in RFID tags. This chapter gives a good overview of the thin film field effect transistors that are made from organic materials, rather than silicon and its inorganic analogues. The basics of the field effect transistor and the key important properties are described, along with details of how they can be optimised. The chapter concludes with an introduction to logic circuits. Organic light emitting devices have many attractive features including their good processability and low costs. Chapter 10 provides information on a range of optoelectronics devices; not just organic light emitting diodes but also light emitting transistors and photovoltaics.

At the end of most chapters there are number of exercises aimed at testing the reader on their understanding of the particular subject matter covered. Answers to these problems are given in one of the four appendices to the main body of the work; the other three covering descriptions of "Schottky barriers", "dispersity in step-growth polymerisation" and the "regular solution theory". Instead of providing a list of references at the end of each chapter, the book concludes with a bibliography that provides recommended further reading material.

In summary, Polymer Electronics provides an excellent introduction and overview of all of the key aspects of this new and important area of electronics. It is pitched at a level which provides sufficient detail for those who are likely to find themselves working on the subject, but it is also at a level where those with a more general interest will also find the book not overly complex and off-putting. The book presents a thorough introductory discussion of both the physics and chemistry of Polymer Electronics and should appeal to all those with an interest in this exciting new field.

September 2013

Martin Goosey
IeMRC, Loughborough University, Loughborough, UK