Table Of ContentSpringer Series in
MATERIALS SCIENCE 38
Springer-Verlag Berlin Heidelberg GmbH
ONUNE LlBRARY
Physics and Astronomy
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Springer Series in
MATERIALS SCIENCE
Editors: R. HuB R. M. Osgood, Ir. H. Sakaki A. Zunger
The Springer Series in Materials Science covers the complete spectrum of materials physics,
induding fundamental principles, physical properties, materials theory and design. Recognizing
the increasing importance of materials science in future device technologies, the book titles in this
series reflect the state-of-the-art in understanding and controlling the structure and properties
of all important dasses of materials.
26 Gas Source Molecular Beam Epitaxy 33 Supercarbon
Growth and Properties of Phosphorus Synthesis, Properties and Applications
Containing III-V Heterostructures Editors: S. Yoshimura and R. P. H. Chang
By M. B. Panish and H. Temkin
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Principles and Applications New Aspects
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30 Process Technology
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Crystal Growth and Microprocesses ofAmorphousSilicon
By K. Iga and S. Kinoshita Editor: R. A. Street
31 Nanostructures and Quantum Effects 38 Fullerene Polymers
By H. Sakaki and H. Noge and Fullerene Polymer Composites
Editors: P. C. Eklund and A. M. Rao
32 Nitride Semiconductors and Devices
ByH.Morkos;
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Peter C. Eklund Apparao M. Rao (Eds.)
Fullerene Polymers
and Fullerene Polymer
Composites
With 224 Figures and 19 Tables
, Springer
Professor Dr. Peter C. Eklund
Dr. Apparao M. Rao
Department of Physics and Astronomy
and Center for Applied Energy Research
University of Kentucky
Lexington, KY 40506-0055
USA
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University ofVirginia Institute ofIndustrial Science
Dept. of Materials Science and Engineering University of Tokyo
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Library of Congress Cataloging-in-Publication Data
Fullerene polymers and fullerene polymer composites / [edited by] Peter C. Eklund and
Apparao M. Rao.
p. cm. -- (Springer series in materials science, ISSN 0933-033X ; 38)
Includes bibliographical references and index.
I. Fullerene polymers. 2. Polymerie composites. I. Eklund, P. C. II. Rao, Apparao M.,
1961-III. Springer series in materials science; v. 38.
QD383.F84 F85 1999
620.1 '92--dc21
99-050347
ISSN 0933-033x
ISBN 978-3-642-08441-6 ISBN 978-3-662-04269-4 (eBook)
DOI 10.1007/978-3-662-04269-4
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Preface
The discovery of carbon cage moleeules C2n (or "fullerenes"), by Smalley,
Kroto and coworkers in 1985, launched an intensive interdisciplinary inquiry
into the fundamental properties of these highly symmetrie molecules. The
subsequent observation by Kratschmer, Huffman and coworkers that C and
60
C could be produced in large enough quantities to be studied in the solid
70
state opened up this research area to physicists, chemists and materials sci
entists, and the field of fullerene-based materials was born. In addition to
the interesting chemieal, physieal and photophysieal properties of the iso
lated molecules, many exciting materials properties were discovered when
they were assembled in the solid state.
In this research monograph, we have attempted to collect important re
sults in the partieular sub-field of fullerenes devoted to polymerie materials
containing, or built from, C60 and C70. These materials can be sub-divided
into three main classes: (1) "all-fullerene" polymers formed by inducing co
valent connections (bonds) between the cages, (2) polymers formed by the
chemieal addition of C to the backbone of a conventional polymer, and (3)
60
composite materials formed by the physieal mixt ure of C and conventional
60
polymers.
Herein will be found eleven chapters written by internationally recog
nized researchers in this sub-field of fullerene research. The first two chapters
provide introductory material for the non-experts. Chapter 1, "Fundamen
tal Properties of Fullerenes", provides an overview of the structure, bond
ing, electronie and vibrational states, and physical properties of fullerene
moleeules and fullerene solids. Chapter 2, "Introduction to Electronic, Opti
cal and Transport properties of Conducting Polymers and Fullerene Polymer
Composites", serves as a second cornerstone for the book, introducing some
of the key photophysical and transport concepts from the perspective of poly
mer scientists. Of the remaining ni ne chapters, three are contributions from
prominent theorists. They have applied molecular dynamics and state-of-the
art electronic energy band calculations to explain the structural, electronic
and vibrational properties of C dimers, trimers and various C polymer
60 60
systems. This information has proven useful in identifying the various poly
merie phases obtained under different experimental conditions. Theoretical
discussion ofth e polymerization mechanism(s) is also presented in these chap-
VI Preface
ters. Three chapters are devoted to the observed properties of "all-fullerene"
polymers, where polymerization (or covalent bonding between molecules) was
driven either by the application of light, heat and press ure , or charge trans
fer doping. The remaining three chapters deal with the unusual physical and
photophysical properties of composites of C60 - polymer systems, formed by
the physical mixture of C60 with various conventional polymers; photodevice
applications based on these materials are also discussed.
The authors are indebted to Dr. G. Sumanasekera for help with the prepa
ration of the final electronic file of the text, and to the United States National
Science Foundation for partial support during the preparation and editing of
this manuscript. We gratefully acknowledge many helpful discussions with
Prof. M.S. Dresselhaus and Dr. G. Dresselhaus yielding furt her insight into
the properties of these novel materials.
November 1999 Peter C. Eklund
Apparao M. Rao
Contents
1. Fundamental Properties of Fullerenes
M.S. Dresselhaus, G. Dresselhaus ................................. 1
1.1 Introduction to Fullerenes as Polymerie Materials
and Composites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1.1 Historieal Background to Fullerenes. . . . . . . . . . . . . . . . . . . . 1
1.1.2 Historieal Background to Fullerene Polymers
and Fullerene-Polymer Composites . . . . . . . . . . . . . . . . . . . . . 3
1.2 Structural Properties of Fullerene Molecules . . . . . . . . . . . . . . . . . . . 3
1.2.1 Structure of C60 .•........................•.......... 3
1.2.2 Structure of C and Higher Mass Fullerenes. . . . . . .. . . . . 6
70
1.2.3 Structure of Metallofullerenes. . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.3 Synthesis.................................................. 7
1.4 Structure in Condensed Phases .............................. 8
1.4.1 Crystalline C60 ...•...........•.•.............••..... 9
1.4.2 Crystalline C70 .....................................• 11
1.4.3 Crystalline Phases for Higher Mass Fullerenes ........... 11
1.4.4 Intercalated Fullerene Structures . . . . . . . . . . . . . . . . . . . . . .. 12
1.5 Polymerized Fullerenes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 14
1.5.1 Photopolymerization of C60 ........................... 15
1.5.2 Electron Beam-Induced Polymerization of C60 . . . . . . . . . .. 17
1.5.3 Pressure-Induced Polymerization of C60 . . . . . . . . . . . . . . . .. 17
1.5.4 Plasma-Induced Polymerization of C60 . . . . . . . . . . . . . . . . .. 18
1.5.5 Photopolymerization of C Films. . . . . . . . . . . . . . . . . . . . .. 18
70
1.6 Vibrational Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 19
1.6.1 Infrared-active Modes in C60 ...............•.......... 21
1.6.2 Raman-active Modes in C60 . . . . . . . . . . . . . . . . . . . . . . . . . .. 21
1.6.3 Silent Modes in C60 . . . . . . . . . . . • • . . . . . . . . . . . . . . . . . . . .. 24
1.6.4 Vibrational Spectra for C70 .................•..••..... 24
1.6.5 Vibrational Modes in Doped Fullerene Solids . . . . . . . . . . .. 24
1.6.6 Vibrational Properties of Phototransformed Fullerenes. . .. 27
1.7 Electronie Properties ....................................... 31
1.8 Optieal Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 35
1.8.1 Introduction to Molecular Photophysics. . . . . . . . . . . . . . . .. 35
1.8.2 Optical Transitions in Photopolymerized C60 . . . . . . . . . . .. 44
VIII Contents
1.9 Transport and Photoconductivity ..... . . . . . . . . . . . . . . . . . . . . . .. 46
1.9.1 Electrical Conductivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 46
1.9.2 Photoconductivity................................... 48
1.10 Superconductivity.......................................... 52
1.11 Concluding Remarks ....................................... 57
References ................................................... .. 58
2. Introduction to Electronic, Optical,
and Transport Properties of Conducting Polymers
and Fullerene-Polymer Composites
P.A. Lane, Z.V. Vardeny ......................................... 69
2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 69
2.2 Electronic States in Conducting Polymers . . . . . . . . . . . . . . . . . . . .. 69
2.3 Absorption Studies of Conducting Polymers. . . . . . . . . . . . . . . . . .. 76
2.4 Excited State Optical Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 79
2.5 Optical Studies of t-(CH)x .................................. 81
2.6 Optical Studies of Polythiophene . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 84
2.7 Optical Properties of C60: Polymer Composites ................ 89
2.8 Transport Properties of Conducting Polymers. . . . . . . . . . . . . . . . .. 91
2.9 Device Applications of Conducting Polymers. . . . . . . . . . . . . . . . . .. 94
2.10 Summary................................................. 97
References ..................................................... 98
3. Supramolecular Photophysics and Photovoltaic Devices
of Fullerene-Conjugated Polymer Composites
N.S. Sariciftci .................................................. 101
3.1 Introduction ............................................... 101
3.1.1 Semiconducting, Conjugated Polymers
as Photoexcited Electron Donors ....................... 101
3.1.2 Buckminsterfullerene, C60, as Electron Acceptor ......... 102
3.2 Experimental Results: Ultrafast, Reversible,
Photoinduced Electron Transfer
in Conjugated Polymer/Fullerene Composite Films ............. 104
3.2.1 Linear Absorption and Photoluminescence .............. 104
3.2.2 Near Steady State Photoinduced Absorption ............ 107
3.2.3 Sub-Picosecond Photoinduced Absorption ............... 111
3.2.4 Sub-Picosecond Photoinduced Dichrosim ................ 120
3.2.5 Steady State Infrared Photoinduced Absorption .......... 123
3.2.6 Sensitization of Photoconductivity ..................... 124
3.2.7 Direct Experimental Evidence for the Metastable Charge
Separation: Light Induced Electron Spin Resonance
(LESR) ............................................. 127
3.3 Effect of the Surrounding Medium: Solution Studies ............ 129
Contents IX
3.4 Photovoltaic and Photodetector Applications:
A Molecular Approach to High Efficiency Photovoltaic Cells
Using Photoinduced Electron 'fransfer ........................ 130
3.4.1 Conjugated Polymer/C6o Heterojunction Photodiodes .... 131
3.4.2 Diodes Made of Conjugated Polymer Composites
with a Network of Internal Heterojunctions .............. 135
3.5 Future Areas ............. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 139
References ..................................................... 140
4. Optical Studies of Covalently Linked C Solids
60
A.M. Rao, P.C. Eklund .......................................... 145
4.1 Introduction ............................................... 145
4.2 Pristine C60 ............................................... 147
4.3 Vibrational Modes of Solid C60 .............................. 149
4.4 Polymerized C60 Structures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 152
4.4.1 Photopolymerized C60 ................................ 153
4.4.2 Cha,rge 'fransfer Excitons: a Possible 'frigger Mechanism
for Photopolymerization .............................. 163
4.4.3 Theoretical Predictions ............................... 165
4.4.4 Experimental Evidence for CT Excitons in C60 .......... 166
4.5 Photo-induced Hardening of C60 Crystals ..................... 168
4.6 Pressure-induced C60 Polymers .............................. 169
4.7 M1C60 Polymers ........................................... 178
4.7.1 Na4C60 Polymer ..................................... 180
References ..................................................... 182
5. First-Principles Molecular Dynamical Studies
of Polymerized C
60
G.B. Adams, J.B. Page .......................................... 185
5.1 Method: First-Principles Quantum Molecular Dynamics ......... 185
5.2 Simulation One: Polymerized C60 ............................ 188
5.2.1 Structure and Energy ................................. 188
5.2.2 Vibrational Properties ................................ 197
5.2.3 Electronic Eigenvalues ................................ 210
5.2.4 Energy Barrier to Dimer Separation .................... 212
5.2.5 Summary for Photopolymerized C60 .................... 213
5.2.6 Other Forms of Polymerized C60 .......•............... 215
5.3 Simulation Two: CUg ....................................... 216
5.3.1 Predicting the Structure .............................. 216
5.3.2 Properties of the Predicted Structure ................... 219
5.3.3 Summary for CUg ................................... 222
References ..................................................... 224
X Contents
6. Covalent Bonding Between Fullerenes
M. Menon, KR. Subbaswamy .................................... 229
6.1 Introduetion ............................................... 229
6.2 Theoretieal Methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230
6.3 Covalent Bonding Between Fullerenes. . . . . . . . . . . . . . . . . . . . . . . . . 230
6.3.1 C Dimer .......................................... 230
60
6.3.2 C Dimer .......................................... 235
70
6.3.3 Curvature Dependenee of Covalent Bonding ............. 238
6.3.4 Summary ........................................... 238
Referenees ..................................................... 239
7. Polymerized Fullerite Structures: Experiment and Theory
M. Nunez-Regueiro, L. Marques, J.L. Rodeau, C.R. Xu, G.E. Seuseria . 241
7.1 Introduetion ............................................... 241
7.2 Bonding Under Pressure .................................... 242
7.2.1 Organie Moleeules Under Pressure ..................... 242
7.2.2 Carbon Under Pressure and New Possible
Carbon Struetures ................................... 243
7.2.3 C Under Pressure .................................. 244
60
7.2.4 Polymerizing C60 •........................•....•..... 246
7.2.5 C Dimers ......................................... 247
60
7.3 The Polymerized Fullerite Struetures ......................... 250
7.3.1 1-D Polymers ........................................ 251
7.3.2 2-D Polymers ........................................ 255
7.3.3 3-D Polymers ........................................ 257
7.4 Conelusions ............................................... 260
Referenees ..................................................... 261
8. Polymerization of Charged Cao Moleeules
R. Kuzmany, J. Winter .......................................... 265
8.1 Introduetion ............................................... 265
8.2 Phases of AC60, A = K, Rb, Cs .............................. 266
8.2.1 Phase Separation Versus Struetural Phase Transition
to the Orthorhombie Phase for AC60 ..••............... 267
8.2.2 Strueture of the Polymerie Phase ...................... 271
8.3 Physieal Properties of the Polymerie Phases ................... 274
8.3.1 Vibrational Speetra and Optieal Transitions ............. 274
8.3.2 Magnetie Resonanee .................................. 283
8.3.3 Transport ........................................... 287
8.4 Eleetronie Structure of AC60 ................................ 289
8.5 Stability Versus Atmospherie Conditions ...................... 291
8.6 Dimerie Phases and Annealing After Quenehing of AC60 ........ 292
