«PATTERNING OF CONJUGATED POLYMERS FOR ELECTROCHROMIC DEVICES By AVNI ANIL ARGUN A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF ...»
PATTERNING OF CONJUGATED POLYMERS FOR ELECTROCHROMIC
AVNI ANIL ARGUN
A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY
UNIVERSITY OF FLORIDACopyright 2004 by Avni A. Argun To Evrim
ACKNOWLEDGMENTSAs I look back upon the years that have led to this dissertation, I have been fortunate to have been surrounded by the help and influence of numerous exceptional people. First, I sincerely thank my advisor, Professor John R. Reynolds, for his inspiring and patient guidance throughout this enjoyable, yet challenging journey. He has served as a great mentor and friend from whom I have learned plenty. He allowed me to pursue the research that I have completed and kept me on the right track with his deep insight and unique enthusiasm.
I wish to thank my supervisory committee members Professors Kenneth B.
Wagener and David B. Tanner for their guidance and valuable discussions throughout my graduate studies, and Professors Alexander Angerhofer and Elliot P. Douglas for their interests in serving on my committee. I extend my thanks to Professor Alan G.
MacDiarmid and Dr. Nicolas J. Pinto for welcoming me to their lab at the University of Pennsylvania to teach me the line patterning method presented in Chapter 4. I also thank the funding agencies AFOSR (F49620-03-1-0091) and the ARO/MURI (DAAD19-99-1for their financial support and Agfa-Gevaert for donation of EDOT and PEDOT/PSS used in this work.
Several coworkers and friends have had an important role during my graduate studies in Gainesville with their discussions and companionships. Thanks go to Dr.
Pierre-Henri Aubert, Dr. Ali Cirpan, Mathieu Berard, and Melanie Disabb for their ongoing friendship and working closely with me on several of the projects presented in iv this dissertation. I would like to thank Ben Reeves and Christophe Grenier for the synthesis of PXDOTs and their contributions in collecting some of the data presented in Chapter 6. Other members of the Reynolds Group who deserve acknowledgement include Dr. Mohamed Bouguettaya, Dr. Said Sadki, Dr. Irina Schwendeman, Dr. Gursel Sonmez, Barry Thompson, and Nisha Ananthakrishnan for being helpful when I needed it. I also thank Maria Nikolou, my collaborator from Dr. Tanner’s Group in Physics, for enjoyable discussions. My time here would not have been the same without the social diversions provided by all my friends in Gainesville. I am particularly thankful to Enes Calik and Omer Ayyer for their continuous friendship and Sertac Ozcan for his pool parties.
For their contributions to my interest in polymer science, I thank my undergraduate advisor Prof. Şefik Süzer at Bilkent University and Prof. Levent Toppare at Middle East Technical University. They taught me valuable life lessons and prepared me well for graduate school. I also thank Emrah Ozensoy who has been my best friend during undergraduate years.
I thank my parents Ayşe and Hasan for allowing me to make my own decisions since I was a little child and preparing me to tackle life wherever it may take me. It is not easy to send a child away from home when he is only 10 years old and expect him to endure the complexities of life. I thank my sister Seher for being a fine example to me since the day she taught me how to read. I also wish to thank Aunt Şadiye for her moral support during my four years in Ankara.
Finally, I give my special thanks to my wife, Evrim, for her true love and support no matter how unbearable I get. She is the source of my inspiration and my ultimate “life improvement.”
LIST OF TABLES
LIST OF FIGURES
CHAPTER 1 INTRODUCTION
Electrochromism of Materials
Fundamentals of Electrochromism
The Origin of Electrochromism in Conjugated Polymers
Characterization of Electrochromic Polymers – Methods
Multi-Color Electrochromic Polymers – Color Control
Polymer Electrochromic Devices
General Patterning Methods
Electron Beam (e-beam) Lithography
Scanning Probe Lithography
Microcontact Printing (µCP)
Patterning of ECDs
Structure of Dissertation
vi2 EXPERIMENTAL METHODS
Chemicals and Materials
Preparation of Electrodes
Metal Vapor Deposition
Electroless Metal Plating
Electrochromic Polymer Deposition
Single Wavelength Transient Absorption
3 PATTERNING OF REFLECTIVE ECDS USING SHADOW MASKS..................49
Reflective ECDs from Microporous Gold Electrodes
Device Design and Construction
Electrochromic Switching and Stability
Composite Coloration Efficiency (CCE)
Open Circuit Memory
Pixelated Lateral ECDs
Reflective ECDs from Microporous Nickel Electrodes
Back-Side Electrical Contacts for Patterned ECDs
4 LINE PATTERNING OF METALLIC ELECTRODES FOR LATERAL ECDS....77
Preparation of Patterned Electrodes
Lateral ECDs Using Interdigitated Electrodes (IDEs)
PEDOT-PBEDOT-Cz Lateral ECDs
Lateral ECDs with Varying IDE Spacing
Other Applications of Line Patterning
vii5 ALL ORGANIC ECDS
Line Patterned PEDOT/PSS Electrodes
Highly Conducting PEDOT/PSS Electrodes
EC Polymers on PEDOT-HAPSS Electrodes
All Organic Electrochromic Devices
6 ECDS BASED ON PROCESSABLE DIOXYTHIOPHENE POLYMERS............114
Spray Coated Electrochromic Polymer Films
Thickness Dependence of PProDOT-(EtHx)2 Films
Overall Summary and Perspective
LIST OF REFERENCES
1-1 Patterning methods, the highest resolution values achieved from these methods, and their brief description.
3-1 Components used in construction of the reflective electrochromic devices..............53 3-2 Optical reflectivity contrast in the visible (∆%RVIS) and the NIR range (∆%RNIR) for the devices D1-D5..
3-3 Energy consumption data for D1 and D5 type devices
3-4 Metal candidates to be used in reflective ECD applications
5-1 Surface resistance (Rs) and surface resistivity (ρs) values of PEDOT/PSS coated films
5-2 Conductivity enhancement of PEDOT/PSS using additives
5-3 Surface resistivity values of PEDOT-HAPSS
5-4 Coloration efficiency values of a PProDOT-(Me)2/PBEDOT-NMeCz device........110 6-1 Peaks (nm) and Optical Band-gaps (eV) from the UV-Vis spectroscopy of PProDOT derivatives.
6-2 Electrochromic properties of spray cast films
6-3 Optical and electrochemical data for coloration efficiency measurements.............132
1-1 Doping mechanism for PProDOT: (a) Neutral form, (b) Slightly doped radical cation, (c) Fully doped dication
1-2 Spectroelectrochemistry of a PProDOT-(Et)2 film on ITO/Glass at applied potentials between (a) -0.1V and (o) +0.9V vs. Ag/Ag+ with 50 mV increments
1-3 Representative electrochromic polymers. Color swatches are representations of thin films based on measured CIE 1931 Yxy color coordinates.
2-1 Schematic representation of high vacuum metal vapor deposition process.............36 2-2 Line patterning of plastic substrates: (a) PEDOT-PSS electrodes, (b) Electroless gold deposition.
2-3 (a) Surface resistivity measurement of a thin film and (b) Four-probe conductivity measurement setup.
2-4 Potentiodynamic deposition of PProDOT-(Hx)2 on Pt button electrode (Electrode area = 0.02 cm2)
2-5 (a) Schematic representation of an absorption/transmissive type device. (b) A reflective device scheme using porous electrodes
2-6 Chronocoulometry experiment of a PProDOT-(EtHx)2 film on ITO: (a) The potential step, (b) Current and charge curves as a function of time.
2-7 Integrating sphere used for reflective characterization of surface active ECDs......47 3-1 (a) Schematic representation of a reflective type electrochromic device (ECD) using a porous membrane electrode and (b) Cross section of the ECD
3-2 (a) Two gold pixels patterned on a polycarbonate membrane, (b) A 2 x 2 gold pattern, (c) Magnification (80x) of the metallized membrane, and (d) Image of the pattern on the glass backing plate
3-3 (a) Reflectivity contrast (∆%R = %Rneutral - %Roxidized) spectra of D2 PEDOT (A), D3 PProDOT (B), and D5 PProDOT-(Me)2 (C) devices and (b) The two photographs represent (left) the oxidized and (right) the neutral appearance of the active layer...55 x 3-4 Spectroelectrochemistry of a PProDOT-(Me)2 active layer in a D5-inert type reflective device: (a) –0.8V, (b) –0.6V, (c) –0.4V, (d) –0.2V, (e) 0.0V, (f) +0.2V, and (g) +0.4V.
3-5 (a) Temporal change in %R (1540 nm) during electrochromic switching of a D3 type reflective device between –1V and +1V every 1 second and (b) A single transition illustrating the switching time of the same device (-1V to +1V, λ=558 nm).............58 3-6 Long-term switching stability of a D5-inert type device switching between –1V and +1V every 3 seconds.
3-7 Open circuit memory of a D5-inert type device monitored by single-wavelength reflectance spectroscopy. (a) Visible memory at 558 nm and (b) NIR memory at 1540 nm.
3-8 (a) Photographs of EC switching of PEDOT and PBEDOT-B(OR)2 on a 2 x 2 pixel gold/membrane electrode. (b) A 2 x 2 pixels device using the patterned electrodes described above.
3-9 a) Accumulative deposition of PEDOT on a nickel coated microporous polycarbonate membrane (Electrode area = 1.7 cm2). (b) EC switching of a PEDOT device comprising nickel electrodes. Left:
-1.0V, right: +1.0V
3-10 (a) An ion track etched membrane with well-defined pores (left) and a fiber-like porous membrane (right). (b) Reflective optical micrograph of a track-etched membrane. (c) Reflective optical micrograph of a laboratory filter paper...............70 3-11 A reflective type ECD scheme using back-site addressed electrodes. i- Transparent window, ii- PProDOT-(Me)2, iii- Au, iv- Porous membrane, v- Back-side contact, vi- An porous separator, vii- Polymer counter electrode, viii- Au/plastic...............72 3-12 In-situ reflectance spectroelectrochemistry of a PProDOT-(Me)2 ECD. Applied voltages: (a) -1.0V, (b)-0.8V, (c) -0.6V, (d) -0.2V, (e) 0 V, (f) 0.2V, (g) 0.4V, (h)
0.7V, and (i) 1.0V
3-13 Machine-cut masks used to pattern gold on front (a) and back (b) sides of porous membranes. c) Photograph of a 7-pixel electrochromic numeric display device showing the number “5”. Device dimensions: 3cm x 5cm.
4-1 Preparation of line patterned, gold electrodes. (a) Computer generated designs (negative patterns), (b) Photographs of an interdigitated electrode (IDE) and a 3x3 pixels pattern, and (c) Reflective optical micrographs of the electrodes...................79 4-2 Optical micrograph of a 100x magnified line patterned gold substrate to show the resolution limit is down to 30 µm.
4-3 “Color averaging” in lateral type ECDs. (a) Electrochemical deposition of polymer films, (b) EC switching of the resulting ECD.
4-5 Electrochemical switching of a PEDOT/PBEDOT-Cz device with PBEDOT-Cz being the working electrode. (a) Multi-voltage sweep of the device between -0.5V and +1.2V. (b) Chronoamperometry and chronocolulometry of the device..............84 4-6 Negative computer images of IDEs with varying finger widths.
4-7 Multi-sweep CV electropolymerization of (a) PProDOT-(Me)2 and (b) PBEDOT-Cz from their monomer electrolyte solutions onto a 2-lane IDE
4-8 Voltage sweep of 2-lane (black), 4-lane (red), and 6-lane (green) lateral ECDs comprising PProDOT-(Me)2 (working electrode) and PBEDOT-Cz (counter electrode) as the complementary colored polymer pair.
4-9 (a) The %R changes of the 2-lane, 4-lane, and 6-lane devices as a function of time as they are switched from -1.0V to +0.8V. (b) Switching time to reach the 85% of the full contrast as a function of the distance between the anode and the cathode..........88 4-10 EC switching between an absorptive blue state (-1.0V, left) and a reflective state (+0.8V, right).
4-11 EC switching of a cross patterned PEDOT device to yield high contrast (left, -1.0V) and no contrast (right, -0.2V) surfaces.
4-12 EC switching of PEDOT on line patterned, interdigitated ITO/Plastic electrodes..91 5-1 Chemical structure of PEDOT/PSS
5-2 Schematic representation of a PEDOT/PSS (Baytron P) coated, interdigitated plastic electrode.
5-3 %Transmittance of PEDOT/PSS coated substrates vs. air
5-4 Optical microscope pictures of EC PEDOT film on PEDOT/PSS: (a) EC PEDOT film deposited between micro-printed lines, (b) EC PEDOT – PEDOT/PSS interface at the meniscus, (c) Magnification of the interface to show the short