Conjugated polymer and molecular interfaces: science and technology for photonic and optoelectronic applications

883 Pages·2002·6.114 MB·English

by  William R Salaneck

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ISBN: 0-8247-0588-2
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Foreword
Although it would be difficult to describe in detail the evolution of the
science of condensed organic molecular solids over the past century, rec-
ognizable periods of activity can be identified.An abbreviatedoutlineofthe
lineage might be as follows: Evolving from a diverse array of work from
many different backgrounds and disciplines, there was a surge in interest in
the 1970s in the metallic one-dimensional charge transfer salts, as repre-
sented by the molecular crystal TTF-TCNQ, and in parallel, in the interca-
lated graphites. Based initially on these two classes of materials, the ter-
minology synthetic metals was coined. The discovery of electrically
conducting organic polymers in the late 1970s provided a new focus for the
field and resulted in a natural scientific reorganization. During the 1980s,
conductingpolymersmaturedasauniqueclassofmaterials:stableelectronic
materials that combined the electrical and optical properties of metals and
semiconductors with the processing advantage and mechanical propertiesof
polymers. Organic (small-molecule) light-emitting devices (OLEDs)
emergedinthe1980sandbecameanewfocusforresearchanddevelopment
in the 1990s. Light-emitting devices based on luminescent, semiconducting
polymers (PLEDs) evolved in the 1990s along with the more general de-
velopment of ‘‘plastic electronics,’’ including photodiodes, photovoltaic
cells, thin-film transistors, and lasers. Although we have only just entered
the first decade of the new century, it seems that a principal focus will be
on the use of advanced printing technologies to fabricate such plastic elec-
tronic devices.
These developments in electronic applications of organic molecular
and polymericmaterialsarediscussedinthisbook.Novelelectronicdevices
iii
iv Foreword
fabricated from conjugated polymers or from organic molecular solids are
emerging in the marketplace. The role of interfaces in this context iscentral
tothedeviceapplications,fortheinterfacescontrolthecarrierinjection.The
editors have solicited contributions from many of the world’s leading sci-
entists, and they have succeeded in pulling together in one place a compre-
hensive collection of presentations that address the main issues in this di-
verse field. The basic scientific content will be useful to students and
beginners, as well as a resource for practitioners in the area.The significant
emphasisonrealdevicesisaparticularlyinterestingfeatureofthecollection
of chapters in this volume. This ‘‘real device’’ emphasis will be important
to people entering thearea and to thosealreadyinvolvedintheoptimization
of device peformance.
This book is unique in its emphasis on interfaces in electronicdevices
fabricatedfromorganicmaterials.InthiscontextIrecommendit.Sincesuch
interfacestypicallylimittheperformanceoftheelectronicandoptoelectronic
devices that are responsible for the ongoing revolution in ‘‘plastic electron-
ics,’’the reader will find this book to be a resource that is both useful and
relevant.
Alan J. Heeger
Co-recipient of the Noble Price in Chemistry, 2000
Professor, Physics Department and Materials Department
Institute for Polymers and Organic Solids
University of California, Santa Barbara
Santa Barbara, California
Preface
Electronicdevicesbasedonorganicmaterialshaverecentlymadetheirdebut
in the marketplace. Many companies, especially new and small ones, are
entering the field. Novel materials in pure, well-characterized form have
been generated, especially over the last decade. The organic materials can
be classified broadly as falling into one of two categories: (1) conjugated,
orsemiconducting,polymersand(2)so-called‘‘smallmolecules.’’Thelatter
termissomewhatmisleading,since‘‘smallmolecules’’refersmainlytomol-
ecules smaller than polymeric macromolecules but otherwise still relatively
large.Althoughsomefundamentaldifferencesexistbetweenthesematerials,
there are also many underlying similarities. In terms of applications, these
materials have many common target markets.
It may safely be stated that, should progress in the development of
new materials suddenly come to a halt, device performance could continue
to improve through engineering of the interfaces, in particular the cathode
andanodeinterfaces.Manyscientistsbelievethattheinterfaceissuesrelated
to organic molecular-based devices are, at this particular moment, some of
the most important with regard to the overall device concept and perfor-
mance. Engineering moreefficientinterfacesmaybedeterminantinkeeping
up with the rate of progress in the development of polymer- and small-
molecule-based electronic devices. This book provides an up-to-date fun-
damentalunderstandingofthepropertiesoforganicinterfacesandapractical
approach to the formation and improvement of these interfaces.
We initially intended to divide the chapters into groups reflecting
chemistry, physics, engineering, and other subjects. In the process of com-
piling the manuscript, however, we realized that even with a directivetothe
v
vi Preface
authors it would be impossible to categorize all the chapters in such a man-
ner. This issue in itself indicates the interdisciplinary nature of the field of
polymericandmolecularorganicsemiconductorsinelectronicsapplications.
Similarly, we had hoped to assemble a chapter for beignners. This also
proved almost impossible, as it appeared that each group of authors had
their own special set of procedures. However, the sample preparation sec-
tions in each of the device-oriented chapters will serve as a guideline for
beginners.
Aconsiderable amount of work on organic interfaceshasbeenaccom-
plished over the past few years and the time is right to present some of the
principal work in the field in this book. We have prevailed on some of the
eminent leaders involved in work on interfaces in electronic devices based
on organic materials. These scientists, from around the world, have contrib-
uted chapters to this book by gathering together their specialist expertise in
interface science. The content of these chapters spans a considerable range
of issues from basic or fundamental materials science through device appli-
cations,pointingouttheroleofinterfacesineachcase.Wehaveendeavored
to represent all subfactions in the field as fairly as possible. The result es-
tablishes a snapshot in time, representing the state of the art in interface
scienceintheareaofelectronicapplicationsoforganicmaterials.Essentially
all the problems met in practicing the art of interface science with these
organic materials are represented.We hopethatthe readersofthisbookwill
come away with the same general opinions.
Finally, we thank allthose who have contributedtothisbook,fortheir
timeandefforts,andforthescientificdexterityittooktocarryouttheworks
reported. There are numerous financial sources that need to be acknowl-
edged, which is done at the end of each chapter.
William R. Salaneck
Kazuhiko Seki
Antoine Kahn
Jean-Jacques Pireaux
Contents
Foreword Alan J. Heeger iii
Preface v
Contributors xi
1. Functional Dendritic Thin Films and Monolayers 1
Albertus P. H. J. Schenning, J. W. Weener, and E. W. Meijer
2. ATheoretical Study of Electrical Contacts to Self-Assembled
Molecular Wires on Conducting Substrates 23
Sven Stafstro¨m, A˚sa Johansson, and Ma˚rten Bjo¨rketun
3. ATheoretical Insight into Organic Interfaces in Electro-Optic
Devices 39
Je´roˆme Cornil, Donizetti dos Santos, Roberto Lazzaroni,
Massimo Malagoli, and Jean-Luc Bre´das
4. Photoelectron Spectroscopy of Interfaces for Polymer-Based
Electronic Devices 73
Michael Lo¨gdlund, Grzegorz Greczynski, Annica Crispin,
Mats Fahlman, William R. Salaneck, and Thomas Kugler
5. Role of Interfaces in Semiconducting Polymer
Optoelectronic Devices 113
Paul F. van Hutten, Victor V. Krasnikov, and
Georges Hadziioannou
vii
viii Contents
6. Studies of Organic Thin Films and Interfaces by Various
Electron Spectroscopies: Molecular Orientation, Electronic
States, and Reactions 153
Nobuo Ueno, Koji Kamiya Okudaira, Yasushi Azuma,
Satoshi Kera, and Shinji Hasegawa
7. Organic–Metal Interfaces: From Physisorption to
Covalent Bonding 205
Norbert Koch, Gu¨nther Leising, Aparna Rajagopal, and
Jean-Jacques Pireaux
8. Electronic Structure of Interfaces Between Organic Molecules
and van der Waals Surfaces 241
Toshihiro Shimada and Atsushi Koma
9. Indium-Tin-Oxide Thin Films for Characterization of
Electrochemical Processes in MolecularAssemblies:
Surface Characterization and Surface Modification 269
Carrie L. Donley, Darren Dunphy, Rebecca A. P. Zangmeister,
Kenneth W. Nebesny, and Neal R. Armstrong
10. Energy LevelAlignment at Organic–Metal Interfaces 293
Hisao Ishii and Kazuhiko Seki
11. Organic Molecular Interfaces: Investigations of Electronic
Structure, Chemistry, and Carrier Injection Properties 351
Chongfei Shen, Antoine Kahn, and Ian Hill
12. Metal–Polyfluorene Interface and Surface: Structures
and Stability 401
Liang-Sheng Liao, C. S. Lee, Shuit Tong Lee, M. Inbasekaran,
and W. W. Wu
13. Femtosecond Photoemission Study of Relaxation and Interface
Charge Transfer Dynamics in Organic Photoreceptors 443
Antti J. Ma¨kinen, Stephan Schoemann, Yongli Gao,
Max G. Mason, Annabel A. Muenter, and Andrew R. Melnyk
14. STM-Excited Electroluminescence and Spectroscopy of
Conjugated Polymers 473
Santos F. Alvarado
Contents ix
15. Contact-Limited Hole Current in Poly(p-phenylenevinylene) 505
P. W. M. Blom, D. W. Black, and M. C. J. M. Vissenberg
16. Organic Light-Emitting Diodes Using Akaline-Earth Fluorides
as an Electron Injection Layer 525
Shizuo Tokito, Hisayoshi Fujikawa, Tomohiko Mori, and
Yasunori Taga
17. Characterization of Metal Interfaces to Molecular Media from
Analysis of Transient and Steady-State Electrical Measurements 545
Martin A. Abkowitz
18. Molecular-Sized Structural Trap at Organic–Metal Interface
and Photocurrent Multiplication Phenomenon 585
Masahiro Hiramoto, Ken-ichi Nakayama, Masaaki Yokoyama,
and Tadashi Katsume
19. Charge Injection into Disordered Organic Semiconductors 613
Vladimir I. Arkhipov, Ulrich Wolf, Siegfried Barth,
and Heinz Ba¨ssler
20. Energy Structures of Molecular Thin-Film/Metal Interfaces
in Air 651
Yutaka Harima and Kazuo Yamashita
21. Metal–Organic Schottky Energy Barriers: Measurements
and Device Implications 693
I. H. Campbell and Darryl L. Smith
22. Nanometric Electrostatic Phenomena at Molecular Interfaces 733
Mitsumasa Iwamoto
23. Modifying Interfaces to Semiconducting Polymers: PEDOT in
Polymer Microelectronics 777
Lucimara Stolz Roman and Olle Ingana¨s
24. Electron and Hole Injection Processes in OLEDs Consisting
of Low Molecular Weight Materials 793
Michio Matsumura