FROM APPLICATION OF ORGANIC THIN MULTILAYER FILMS IN 3D OPTICAL DATA STORAGE TO THEIR FABRICATION FOR ORGANIC ELECTRONIC DEVICES by ANUJ SAINI Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy Dissertation Adviser: Dr. Kenneth D. Singer Department of Physics CASE WESTERN RESERVE UNIVERSITY May, 2016 CASE WESTERN RESERVE UNIVERSITY SCHOOL OF GRADUATE STUDIES We hereby approve the thesis/dissertation of Anuj Saini candidate for the degree of Doctor of Philosophy*. Committee Chair Dr. Kenneth D. Singer Committee Member Dr. Giuseppe Strangi Committee Member Dr. Rolfe Petschek Committee Member Dr. Lei Zhu Date of Defense March 21, 2016 *We also certify that written approval has been obtained for any proprietary material contained therein. ii Dedication To my parents and to my wife, Kailash iii Contents List of Figures … ix List of Tables … xv Acknowledgements … xvi List of Abbreviations … xvii Abstract … xx 1. Introduction … 1 1.1. Motivation 1.2. Optical Data Storage 1.2.1. A Brief History of Optical Data Storage 1.2.2. Searching for Newer Techniques 1.2.3. 3D Optical Data Storage 1.2.4. Multilayered Films for Data Storage Media 1.3. Fabrication of Organic Electronic Devices 1.3.1. A Short Review of Film Forming Techniques 1.3.2. The Ideal Film Forming Process 1.3.3. The Process of Electrocoating 2. Roll-to-Roll Fabrication of Multilayer Films for High Capacity Optical Data Storage. … 23 2.1. Introduction 2.2. Experimental iv 2.2.1. Materials 2.2.2. Co-extrusion 2.2.3. Absorption and Fluorescence 2.2.4. Writing and Reading 2.3. Results 2.3.1. Materials and Data Storage Medium 2.3.2. Writing and Reading of Data 2.3.3. Spot Size and Cross-Talk 2.4. Conclusions 2.A. Calculations of the layer cross-talk 3. Non-linear fluorescence modulation of an organic dye for optical data storage … 42 3.1. Introduction 3.2. Experimental 3.3. Results and Discussion 3.3.1. Bleaching with μs pulses 3.3.2. Bleaching at Equal Fluences 3.3.3. Bleaching Power Dependence of Single ns-Pulses 3.3.4. Bleaching vs. Time and Concentration 3.3.5. Photophysical Mechanisms 3.4. Conclusions 4. Threshold behavior for 3D Optical Data Storage by Photo thermal Bleaching … 61 v 4.1. Introduction 4.2. Experimental 4.2.1. Materials and their Optical Properties 4.2.2. Writing and Reading 4.2.3. Thermogravimetric analysis (TGA) 4.2.4. Scanning Electron Microscopy (SEM) 4.2.5. Atomic Force Microscopy (AFM) 4.2.6. Solar Simulator Exposure 4.3. Theory and Simulations 4.3.1. Surface Heating of Polymer by Laser Pulses (Analytical Solution) 4.3.2. Temperature Change by Finite Element Analysis (Numerical Simulations) 4.4. Results and Discussion 4.4.1. Temperature and bleaching 4.4.1.1. Simulation vs Experiment 4.4.2. Topography of the bleached spots 4.4.3. Bleached bit size 4.4.4. Solar Simulator Exposure 4.5. Conclusion 5. Aqueous deposition of a semiconducting polymer by electrocoating … 84 5.1. Introduction 5.2. Electrocoating Functionalized P3AT 5.2.1. Kinetics of Anodic Potentiostatic Electrocoating 5.2.2. Depositing Films by Anodic Potentiostatic electrocoating vi 5.3. Characterization of the Electrocoated films 5.3.1. Physical and Optical Characterization of the Electrocoated films 5.3.2. Broadband Dielectric spectroscopy 5.3.3. Photoconductivity Measurements 5.3.4. Time of Flight 5.4. Conclusions 5.A. Electrocoating of Porous Film, Film Dissolution and Limiting Film Thickness 6. Electrocoated Graphene Oxide thin Layers over Transparent Electrodes and Progress towards Electrocoated Optoelectronic Device. … 110 6.1. Introduction 6.2. Fabricating Graphene Oxide Thin Films by Electrocoating 6.3. Kinetics of Film Growth 6.4. Characterization of the Graphene Oxide Films 6.4.1. Physical Characterization of the Films 6.4.2. Optical and Electrical Characterization of the Films 6.5. Electrocoating P3AT Thin Films over Transparent Electrodes 6.5.1. Physical and Optical Characterization of the Electrocoated device 6.6. Conclusions 7. Future Work … 126 7.1. 3D Optical Data Storage 7.1.1. Enhancing the photo-thermal bleaching by using additives 7.1.2. Extending the Thermal Decomposition Studies 7.1.3. Understanding of Photo-Chemical Bleaching Phenomena vii 7.2. Organic Electronic Devices 7.2.1. Electrocoated Organic Photovoltaic Device Comprehensive Bibliography …131 viii List of Figures 2.1 Schematic of the co-extruder used to the manufacture the films, and the resulting roll of film. … 25 2.2 Fluoresence image (false color) of the crossection of the 64 layer film and plot profile of the crossection shows 23 FL peaks within 150 microns. … 28 2.3 The difference between aparent depth and real depth of the focus. … 29 2.4 Chemical structure of the dye (C18-RG). Absorption (red) of the entire 200 μm thick ML film, containing 64 active layers, and the FL spectra of a single layer before (blue) and after (green) writing indicating a typical level of FL reduction induced by writing. ... 30 2.5 Patterned images stored in the 23 layer film (false color) and cross-section of two layers after writing complementary images. ... 32 2.6 Cross-section of single written line in a 5 μm thick single active layer and intensity profile of the spot at the waist, with a FWHM of 380 nm. ... 33 2.7 FL images of a series bits in layer 1 after recording layer 1 itself (top), layers 1-5 (middle), and layers 1-10 (bottom). The curves in (b) show the modulation signal of the images in (a). The experimentally measured CBR of layer 1 versus the number of layers of recorded, along with theoretical predictions. ... 35 3.1 Absorption spectra of films with varying dye concentrations, normalized to the peak values, showing no significant dimer formation. FL spectra of same films, ix normalized only to thickness and beam intensity. There is a large bathochromic shift indicative of FL absorption and re-emission. … 45 3.2 Integrated FL and absorption from spectra in Fig. 1. Absorption increases linearly with concentration but FL saturates, indicating a reduction in FL QY expected from the FL re-emission. Inset: Calculated relative QY versus concentration. … 46 3.3 Bleaching for different exposure times in the 1.0 wt.% sample. … 48 3.4 Bleaching for different exposure times in the 1.0 wt.% sample. The excitation power is altered to keep the fluence constant. This shows that there are bleaching pathways being activated at higher powers that dominant any response from S1/T1 states. Similar bleaching trends seen with C18-RG/PETG system. … 49 3.5 False color confocal FL image of spots written in the 1.0 wt.% sample at 400ns and 36 MW/cm2. Scale bar is 2m. Bleaching versus power in the 1.0 wt.% sample at various exposure times demonstrating ability to write for short times and with a non-linear response. … 51 3.6 FWHM of the bleached spots, obtained from Gaussian fits, versus bleaching. FWHM of the writing beam was measured to be 580nm, and accounting for diffraction, written spots are no larger than the writing beam. … 53 3.7 Bleaching versus exposure time for multiple concentrations and power. Only high concentrations and large absorbed powers will yield measurable response for sub- μs times. Circled points are discussed explicitly in the manuscript. An incident power of 80mW gives an intensity of 30 MW/cm2. … 55 x 4.1 Molecular structures and molecular weights of the dyes under study. … 64 4.2 Extinction spectra (a) of the dyes showing the absorption bands of the dyes and fluorescence spectra (b) of the dyes showing the emission bands. … 65 4.3 False color confocal FL image of the spots written in the Perylene Orange/SAN25 (0.033mM) sample with 200ns laser pulses of different intensities. … 66 4.4 An image of temperature rise by a heat source was placed at the center of the dye/polymer system in COMSOL. … 71 4.5 Bleaching with sub-microsecond exposures vs surface temperature rise at the center of the laser pulse for the dye+polymer systems studied here, for two different molar concentrations – 0.033mM (a) and 0.044mM (b) … 72 4.6 Bleaching with sub-microsecond exposures vs temperature as calculated by COMSOL simulations at the center of the laser pulse for the dye+polymer systems studied here, for two different molar concentrations – a) 0.033mM and b) 0.044mM. c) Plot shows all the data for 0.044mM near the threshold region. Plot d) shows different bleaching levels for dyes at the same exposure time (300 ns), thus having different intensity thresholds. … 73 4.7 Evidence of photo-chemical bleaching: Bleaching with long exposures, low intensities vs temperature as calculated by COMSOL simulations. X axis represents the change in temperature is from the room temperature (293 K). … 74 4.8 TGA of the polymer and dye/polymer systems. … 75 xi 4.9 Comparison of SEM (top row) images of the bleached spots made at 300 ns exposure time in a PO/SAN25 film to the FL bleached spots (bottom row). … 76 4.10 a) Comparing surface topography of the films using AFM (right) with the FL (left) bleaching spots. These spots are made in 0.022mM PO/SAN25 film using the 90 mW/cm2 power at different exposure times. b) Zoomed in AFM image of the spots made at low exposure times showing the bumps or hills on the surface. … 77 4.11 FL profile (blue) of the time resolved spots shown in the figure 4.10 compared to the topography (red) of the spots.