Discotic Materials for Organic Electronics Dissertation zur Erlangung des Grades “Doktor der Naturwissenschaften” am Fachbereich Chemie, Pharmazie und Geowissenschaften der Johannes Gutenberg-Universität Mainz Marcel Kastler geboren in Weilburg Mainz, 2006 Dekan: 1. Berichterstatter: 2. Berichterstatter: Tag der mündlichen Prüfung: Herrn Prof. Dr. K. Müllen, unter dessen Anleitung ich die vorliegende Arbeit am Max-Planck Institut für Polymerforschung in Mainz in der Zeit von Dezember 2002 bis Dezember 2005 angefertigt habe, danke ich für seine wissenschaftliche und persönliche Unterstützung sowie seine ständige Diskussionsbereitschaft. Dedicated to my parents Contents 1 Introduction................................................................................................................ 1 1.1 Organic Electronics........................................................................................... 1 1.2 Why Discotics?.................................................................................................. 2 1.3 Polycyclic aromatic hydrocarbons..................................................................... 6 1.3.1 Synthesis 7 1.3.1.1 FRIEDEL-CRAFTS-type Reactions ........................................................... 7 1.3.1.2 DIELS-ALDER Cycloaddition.................................................................. 8 1.3.1.3 Photocyclization .................................................................................... 9 1.3.1.4 Flash Vacuum Pyrolysis (Thermolysis)............................................... 10 1.3.1.5 Extrusion of Heteroatoms .................................................................... 11 1.3.1.6 SCHOLL-Cyclodehydrogenation........................................................... 12 1.4 Supramolecular Organization.......................................................................... 14 1.4.1 Self-assembly 14 1.4.2 Orientation on Substrates 16 1.4.3 Characterization of the Organization 16 1.5 Processing........................................................................................................ 20 1.6 Electronic Devices ........................................................................................... 23 1.6.1 Light Emitting Diode 23 1.6.2 Photovoltaic Element 23 1.6.3 Field-Effect Transistor 25 1.7 References........................................................................................................ 26 2 Motivation and Objective........................................................................................ 31 2.1 References........................................................................................................ 35 3 Hexa-peri-hexabenzocoronenes with Improved Processability .............................. 37 3.1 Synthesis.......................................................................................................... 39 3.2 Self-Assembly.................................................................................................. 43 3.2.1 NMR Investigation 44 3.2.2 Electronic Spectroscopy 51 3.2.3 Conclusion 56 3.3 Processing.........................................................................................................61 3.3.1 Solution Processing 61 3.3.2 Melt Processing 67 3.3.2.1 Morphology..........................................................................................67 3.3.2.2 Characterization of the molecular orientation......................................72 3.3.2.3 Mechanism of the Homeotropic Phase Formation...............................77 3.3.2.4 Zone-Crystallization.............................................................................81 3.3.3 Mechanical Alignment - Structural Investigation 83 3.3.3.1 Thermal Behavior.................................................................................83 3.3.3.2 Mechanically Aligned Fibers ...............................................................85 3.3.3.3 Molecular Dynamics ............................................................................89 3.3.3.4 Manipulation of the Superstructure......................................................93 3.4 Charge Carrier Mobility.................................................................................102 3.4.1 Pulse-Radiolysis Time-Resolved Microwave Conductivity 102 3.4.2 Life-Time of Charge Carriers 104 3.4.3 Time-of-Flight 109 3.5 Implementation in Photovoltaic Devices .......................................................115 3.6 Organization in porous materials – Pyrolysis ................................................119 3.7 Summary ........................................................................................................125 3.8 References ......................................................................................................127 4 Functionalization of Hexa-peri-hexabenzocoronenes............................................135 4.1 Attachment of a Chromophore.......................................................................136 4.2 a posteriori Functionalizations.......................................................................144 4.2.1 Synthesis 145 4.2.2 Supramolecular Organization 148 4.3 “Tailoring” Supramolecular Properties..........................................................153 4.4 Structure-Property Relation............................................................................159 4.5 Chemical Cross-Linking of Hexa-peri-hexabenzocoronene.......................... 161 4.5.1 Fixation of supramolecular organizations 161 4.5.2 Nanostructuring 165 4.6 Summary........................................................................................................ 171 4.7 References...................................................................................................... 172 5 Polycyclic Aromatic Hydrocarbons with Different Peripheries............................ 177 5.1 Nomenclature................................................................................................. 177 5.2 Clar-Rule and Peripheries.............................................................................. 180 5.3 Electronic Spectroscopy of PAHs ................................................................. 182 5.4 Introduction of “zigzag” Sites ....................................................................... 187 5.4.1 Tetrabenzo[bc,ef,hi,uv]ovalene 188 5.4.2 Dibenzo[hi,uv]phenanthro-[3,4,5,6-bcdef]-ovalene 201 5.4.3 Diphenanthro[3,4,5,6-uvabc;3',4',5',6'-efghi]ovalene 211 5.4.4 Dibenzo[ef,hi]phenanthro[3,4,5,6-u,v,a,b,c]ovalene 218 5.4.5 Circumcoronene 221 5.5 Electronic Spectroscopy of the “zigzag” PAHs............................................. 224 5.5.1 Aromatic Core Symmetry 224 5.5.2 Self-Association in Solution 231 5.6 Supramolecular Organization........................................................................ 233 5.6.1 Introduction of a Novel Substitution Pattern 233 5.6.2 Self-Assembly in the Bulk Phase 235 5.6.3 Self-Assembly on Surfaces 239 5.7 Functionalization of PAHs in the Periphery.................................................. 250 5.7.1 3H-Cyclopenta[cde]hexa-peri-hexabenzocoronene 251 5.7.2 Investigation of the Supramolecular Self-Organization 255 5.7.3 Functionalization 261 5.7.4 Other “Reactive” Peripheries 264 5.8 Graphite with “Defects”................................................................................. 268 5.8.1 Synthesis of an Extended PAH with “Hole” 268 5.8.2 Engineering of microporous organic crystals 275 5.8.3 Phase Forming Ring 277 5.8.4 Non-planar PAHs with hole 281 5.8.5 Softlanding 284 5.9 Summary ........................................................................................................287 5.10 References ......................................................................................................289 6 Conclusion and Outlook.........................................................................................299 7 Experimental Part...................................................................................................305 7.1 General methods.............................................................................................305 7.1.1 Chemicals and solvents 305 7.1.2 Chromatography 305 7.1.3 Microwave Assisted Reactions 305 7.1.4 Inert atmosphere 305 7.2 Analytical techniques.....................................................................................306 7.2.1 Mass spectrometry 306 7.2.2 NMR spectroscopy 306 7.2.3 Elemental Analysis 306 7.2.4 UV/vis spectroscopy 306 7.2.5 Photoluminescence spectroscopy 307 7.2.6 Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) 307 7.2.7 Polarization microscopy 307 7.2.8 X-Ray Diffractometry 307 7.2.9 Single crystal analysis 308 7.2.10 Synchrotron experiments 308 7.2.11 Pulse-radiolysis time-resolved microwave conductivity investigation 308 7.2.12 Time-of-flight experiments 309 7.2.13 Electrochemical Characterization 309 7.2.14 Preparation of Photovoltaic Devices 310 7.3 Synthesis.........................................................................................................311 7.3.1 4,4’-Bis(2-ethyl-hexyl)diphenylacetylene (3-11a) 311 7.3.2 Hexa-(4-(2-ethyl-hexyl-))phenylbenzene (3-12a) 311 7.3.3 2,5,8,11,14,17-Hexa(4-(2-ethyl-hexyl-)-hexa-peri-hexabenzocoronene (3-13a) 312 7.3.4 4,4’-Bis(2-hexyl-decyl)diphenylacetylene (3-11b) 313 7.3.5 Hexa-(4-(2-hexyl-decyl-))phenylbenzene (3-12b) 313 7.3.6 2,5,8,11,14,17-Hexa(2-hexyl-decyl)-hexa-peri-hexabenzocoronene (3-13b) 314 7.3.7 2-Decyl-tetradecylbromide (3-10c)