Organic Molecular Solids

Abstract

1 Introduction. 1.1 What are Organic Solids? 1.2 What are the Special Characteristics of Organic Solids? 1.3 Goals and Future Outlook. Problems for Chapter 1. Literature. 2 Forces and Structures. 2.1 Forces. 2.1.1 Inductive Forces. 2.1.2 Van der Waals Forces. 2.1.3 Repulsive Forces. 2.1.4 Intermolecular Potentials. 2.1.5 Coulomb Forces. 2.2 Structures. 2.2.1 Crystals of Nonpolar Molecules. 2.2.2 Crystals of Molecules with Polar Substituents. 2.2.3 Crystals with a Low Packing Density, Clathrates. 2.2.4 Crystals of Molecules with Charge Transfer, Radical-ion Salts. 2.3 Polymer Single Crystals: Diacetylenes. 2.4 Thin Films. 2.5 Inorganic-Organic Hybrid Crystals. Problems for Chapter 2. Literature. 3 Purification of Materials, Crystal Growth and Preparation of Thin Films. 3.1 Purification. 3.2 Highest Purity. 3.3 Crystal Growth. 3.4 Mixed Crystals. 3.5 Epitaxy, Ultrathin Films. Problems for Chapter 3. References. 4 Impurities and Defects. 4.1 Foreign Molecules, Impurities, and X traps. 4.2 Structural Defects. 4.2.1 Point Defects. 4.2.2 Dislocations. 4.2.3 Grain Boundaries. 4.2.4 Dipolar Disorder. 4.3 Characterisation and Analysis of Impurities. 4.4 Characterisation of Defects. Literature. 5 Molecular and Lattice Dynamics in Organic Molecular Crystals. 5.1 Introduction. 5.2 Intramolecular Vibrations. 5.3 Phonons. 5.3.1 The Eigenvector. 5.3.2 The Wavevector. 5.3.3 The Frequencies (K). 5.3.4 Excitations. 5.4 Experimental Methods. 5.4.1 Inelastic Neutron Scattering. 5.4.2 Raman Scattering and Infrared Absorption. 5.5 The 12 External Phonons of the Naphthalene Crystal. 5.5.1 Dispersion relations. 5.5.2 Pressure and Temperature Dependencies. 5.6 Analytic Formulation of the Lattice Dynamics in Molecular Crystals. 5.7 Phonons in other Molecular Crystals. 5.8 Hindered Rotation and Diffusion. 5.8.1 Nuclear Magnetic Resonance. 5.8.2 Benzene Crystals. 5.8.3 Methyl Groups. 5.8.4 Diffusion. Problems for Chapter 5. References. 6 Electronic Excited States, Excitons, Energy Transfer. 6.1 Introduction. 6.2 Some historical remarks. 6.3 Optical Excited States in Crystals. 6.4 Davydov Splitting and Mini-Excitons. 6.5 Frenkel Excitons. 6.5.1 Excitonic States, Fundamental Equations. 6.5.2 Polarisation and Band Structure. 6.5.3 Coherence. 6.6 Charge Transfer (CT) Excitons. 6.7 Surface Excitons. 6.8 Excimers. 6.9 Exciton Processes, Energy Conduction. 6.9.1 Sensitised Fluorescence. 6.9.2 Delayed Fluorescence by Triplet Excitons. 6.9.3 Excitonic Processes. 6.10 Excitonic Processes in other Systems. 6.11 Future Developments. Problems for Chapter 6. Literature. 7 Structure and Dynamics of Triplet States. 7.1 Introduction and Historical Remarks. 7.2 Spin Quantisation in Triplet States. 7.3 The Dipole-Dipole Interaction, Fine Structure. 7.3.1 Zero Field (B0 = 0). 7.3.2 Zeeman Splitting (B0 = 0). 7.3.3 Powder Spectra. 7.4 Mini-Excitons. 7.5 Triplet Excitons. 7.5.1 Anthracene and Naphthalene Crystals: Two-dimensional Triplet Excitons. 7.5.2 Dibromonaphthalene Crystals: coherent, one-dimensional Triplet Excitons. 7.6 Optical Spin Polarisation (OEP). 7.7 Optical Nuclear-Spin Polarisation (ONP). 7.8 Perspectives. Problems for Chapter 7 Literature. 8 Organic Semiconductors. 8.1 Preliminary Historical Remarks. 8.2 Conductivity and Mobility of nearly-free Charge Carriers. 8.3 Charge Carriers in Organic Semiconductors: Polarons, Shallow Traps and Deep Traps. 8.4 Generation of Charge Carriers and Charge Transport: Experimental Methods. 8.4.1 The TOF Method: Gaussian Transport. 8.4.2 Photogeneration of Charge Carriers. 8.4.3 Contacts, Injection, Ejection, and Dark Currents. 8.4.4 Space-Charge Limited Currents. 8.5 Charge-Carrier Mobilities in Organic Molecular Crystals. 8.5.1 Band- or Hopping Conductivity? 8.5.2 Temperature Dependence and Anisotropy of the Mobilities. 8.5.3 Electric-field Dependence. 8.5.4 Band Structures. 8.5.5 Charge-Carrier Traps. 8.6 Charge Transport in Disordered Organic Semiconductors. 8.6.1 The Bassler Model. 8.6.2 Mobilities in High-Purity Films: Temperature, Electric-Field, and Time Dependence. 8.6.3 Binary Systems. 8.6.4 Discotic Liquid Crystals. 8.6.5 Stationary Dark Currents. Problems for Chapter 8. Literature. 9 Organic Crystals of High Conductivity. 9.1 Donor-Acceptor Systems. 9.2 Strong CT Complexes, Radical-ion Salts. 9.3 The Organic Metal TTF-TCNQ - Peierls Transition and Charge-Density Waves. 9.4 Other Radical-ion Salts and CT Complexes. 9.5 Radical-Anion Salts of DCNQI. 9.6 Radical-Cation Salts of the Arenes. 9.6.1 Direct-current Conductivity. 9.6.2 X-Ray Scattering. 9.6.3 Optical Reflection Spectrum. 9.6.4 Magnetic Susceptibility. 9.6.5 Spin Resonance of the Conduction Electrons (ESR). 9.6.6 Charge-Density-Wave Transport. Problems for Chapter 9. Literature. 10 Organic Superconductors. 10.1 Introduction. 10.2 Mainly One-dimensional Charge-Transfer Salts as Superconductors Bechgaard Salts. 10.3 Quasi-Two-dimensional Charge-Transfer Systems as Superconductors. 10.4 The Nature of the Superconducting State in Organic Salts. 10.5 Three-dimensional Superconductivity in Fullerene Compounds. Literature. 11 Electroluminescence and the Photovoltaic Effect. 11.1 Electroluminescence: Organic Light-Emitting Diodes (OLEDs). 11.1.1 Historical Remarks. 11.1.2 The Principle of the OLED. 11.1.3 Multilayer OLEDs. 11.1.4 Electro-optical Properties. 11.2 Photovoltaic Effect: Organic Photovoltaic Cells. 11.2.1 Exciton Dissociation. 11.2.2 Photovoltaic Characteristics. 11.2.3 CuPc/C60 Solar Cells. Literature. 12 Towards a Molecular Electronics. 12.1 What is Molecular Electronics and What Will it Do? 12.2 Molecules as Switches, Photochromic Effects. 12.3 Molecular Wires. 12.4 Light-Induced Phase Transitions. 12.5 Molecular Rectifiers. 12.6 Molecular Transistors. 12.7 Molecular Storage Units. Appendix: Coloured Plates. Index.