Organic Molecular Crystals: Their Electronic States

1. Introduction: Characteristic Features of Organic Molecular Crystals.- 1.1 Interaction Forces in Molecular Crystals.- 1.2 The Atom-Atom Potential Method.- 1.3 Aromatic Hydrocarbons - Model Compounds of Organic Molecular Crystals.- 1.3.1 Anthracene.- Anthracene as Model Compound.- Molecular Structure.- Basic Molecular Parameters.- Crystal Structure.- Elastic and Optical Properties.- Metastable Phases in Anthracene.- 1.3.2 Naphthalene.- Molecular Structure.- Basic Molecular Parameters.- Crystal Structure.- Elastic and Optical Properties.- 1.3.3 Higher Linear Polyacenes.- Tetracene and Pentacene.- Hexacene.- 1.3.4 Other Model Aromatic Compounds.- 1.4 Specific Properties of Electronic States in a Molecular Crystal.- 1.5 Basic Characteristics of Electronic Conduction States in Molecular Crystals.- 1.5.1 Band Theory Approach.- 1.5.2 Hopping Versus Band Model.- 1.5.3 Band-to-Hopping Transition.- 1.5.4 Electronic Polarization and Charge Carrier Self-Energy.- 1.5.5 Other Types of Interaction.- 2. Electronic States of an Ideal Molecular Crystal.- 2.1 Neutral Excited States in a Molecular Crystal.- 2.2 Ionized States in a Molecular Crystal.- 2.2.1 The Lyons Model of Ionized States.- 2.2.2 A Modified Lyons Model.- 2.3 Electronic Polarization of a Molecular Crystal by a Charge Carrier.- 2.3.1 Some General Considerations.- 2.3.2 Dynamic and Microelectrostatic Approaches to Electronic Polarization in Molecular Crystals.- 2.4 Electrostatic Methods of Electronic Polarization Energy Calculation in Molecular Crystals.- 2.4.1 Microelectrostatic Methods of Zero-Order Approximation.- 2.4.2 Method of Self-Consistent Polarization Field.- 2.5 Determination of Molecular Polarizability Tensor.- 2.5.1 Experimental Methods.- 2.5.2 Theoretical Methods.- 2.6 Selection of Molecular Polarizability Components bi. for Electronic Polarization Energy Calculations.- 2.7 Extended Polarization Model of Ionized States in Molecular Crystal s.- 2.7.1 Intrinsic Electronic Polarization of a Molecule by a Localized Charge Carrier.- 2.7.2 Vibronic Relaxation and Ionic State Formation.- 2.7.3 Extended Polarization Model Including Ionic States of Electronic Conductivity.- 2.7.4 Dynamic Electronic Polaron States in a Molecular Crystal.- 2.8 Charge Transfer (CT) States in Molecular Crystals.- 2.8.1 General on CT States.- 2.8.2 Evaluation of CT-State Energies in Anthracene and Naphthalene Crystals.- 2.8.3 CT States in Photogeneration Processes.- 2.8.4 CT States in Recombination Processes.- 2.9 Experimental Determination of Energy Structure Parameters in Molecular Crystals.- 2.10 Energy Structure of an Anthracene Crystal.- 2.11 Energy Structure of Aromatic and Heterocyclic Molecular Crystals.- 3. Role of Structural Defects in the Formation of Local Electronic States in Molecular Crystals.- 3.1 Statistical Aspects of the Formation of Local States of Polarization Origin.- 3.2 General Considerations on the Role of Specific Structural Defects.- 3.3 Point Defects (Vacancies) in Molecular Crystals, Their Crystallographic and Electronic Properties.- 3.4 Dislocation Defects, Their Role in Local State Formation.- 3.5 Energetics of Dislocations in Molecular Crystals.- 3.5.1 Discrete Configuration of Dislocations.- 3.5.2 Basic Elastic Properties of Anthracene and Naphthalene Crystals.- 3.5.3 Energy Estimates for Basal Edge Dislocations in an Anthracene Crystal.- 3.6 Atomic and Molecular Models of the Dislocation Core.- 3.6.1 Models of Spherical Atoms and Molecules.- 3.6.2 Polyatomic Molecular Models.- 3.7 Dislocation Alignments and Aggregations, Their Configurational and Energetic Properties.- 3.7.1 Interaction Between Dislocations.- 3.7.2 Dislocation Alignments.- 3.7.3 Dislocation Ensembles.- 3.8 Grain Boundaries, Their Energetic Characteristics.- 3.8.1 Energy of Grain Boundaries in Molecular Crystals.- 3.8.2 Relative Lattice Compression on Grain Boundaries of an Anthracene Crystal.- 3.9 Stacking Faults in Molecular Crystals.- 3.9.1 General on Stacking Faults.- 3.9.2 Stacking Faults in Anthracene-Type Crystals, Their Energetic Characteristics.- 3.9.3 Calculations of Equilibrium Configuration of Molecules in Stacking Faults of an Anthracene Crystal.- 3.10 Formation of Predimer States in the Regions of Extended Structural Defects of Anthracene-Type Crystals.- 3.11 Some More Complex Two- and Three-Dimensional Lattice Defects in Molecular Crystals.- 3.12 Observation of Structural Defects in Molecular Crystals.- 3.12.1 Optical Low Resolution Technique.- 3.12.2 Electron Microscopy and Diffraction Techniques.- 3.12.3 X-Ray Methods.- 3.13 Main Characteristics of Dislocation Defects in Some Model Molecular Crystals.- 3.13.1 Dominant Types of Dislocatioas in Anthracene Space Group Crystal s.- 3.13.2 Density of Dislocations in Anthracene Crystals, Its Dependence on Crystal Growth and Treatment.- 4. Local Trapping Centers for Excitons in Molecular Crystals.- 4.1 Theory of Exciton States in a Deformed Molecular Crystal.- 4.2 Electron Level Shifts in Hydrostatically Compressed Molecular Crystal s.- 4.3 Formation of Local Exciton Trapping Centers in Structural Defects of a Crystal.- 5. Local Trapping States for Charge Carriers in Molecular Crystals.- 5.1 Electronic Polarization Energy of a Compressed Anthracene Crystal.- 5.2 Formation of Local Trapping Centers for Charge Carriers in Structural Defects of a Real Molecular Crystal.- 5.3 Energy Spectrum of Local States of Polarization Origin in Stacking Faults of an Anthracene Crystal.- 5.4 Local Surface States of Polarization Origin in Molecular Crystals.- 5.5 Local States of Polarization Origin in the Vicinity of a Lattice Vacancy.- 5.6 Local Charge Carrier Trapping in Covalent, Ionic and Molecular Crystal s.- 5.7 Randomizing Factors Determining Gaussian Distribution of Local States of Structural Origin.- 5.8 Investigation of Local Trapping States by Method of Space Charge Limited Currents (SCLC).- 5.8.1 General Considerations.- 5.8.2 Injecting and Blocking Contacts.- 5.8.3 Conventional SCLC Theories of Discrete and Exponential Approximation of Trap Distribution.- SCLC Theory for an Insulator With Discrete Trap Distribution.- SCLC Theory for an Insulator With Exponential Trap Distribution.- Applicability Limits of Diffusion-Free SCLC Theory Approximation.- 5.8.4 Criteria for Validity of SCLC Conditions.- 5.8.5 Difficulties in Interpreting Experimental CV Characteristics in Terms of Discrete and Exponential Trap Distribution Models.- 5.9 Phenomenological SCLC Theory for Molecular Crystals with Gaussian Distribution of Local Trapping States.- 5.9.1 Conceptual Basis.- 5.9.2 Basic SCLC Theory Equations.- 5.9.3 Validity Range for Different Analytical SCLC Approximations.- 5.9.4 SCLC Dependence on Dispersion Parameter a.- 5.9.5 SCLC Temperature Dependences for Ge (E) and Gg (E) Distributions.- 5.9.6 SCLC Dependence on Et Value.- 5.9.7 Validity Criteria for Exponential and Gaussian Approximations.- 5.9.8 CV Characteristics for Two Sets of Gaussian Trap Distribution.- 5.10 Gaussian SCLC Approximations of Experimental CV Characteristics.- 5.10.1 Analytical Approximations.- 5.10.2 Differential Method of Analysis of CV Characteristics.- 5.11 SCLC Theory for Spatially Nonuniform Trap Distribution.- 5.12 Investigation of Local Trapping States by Thermally Activated Spectroscopy Techniques.- 5.13 Other Experimental Methods for Local Trapping State Study.- 5.14 Correlations Between Distribution Parameters of Local Trapping States and Crystalline Structure.- 5.15 Local Lattice Polarization by Trapped Charge Carrier in Molecular Crystals.- 5.16 Guest Molecules as Trapping Centers in a Host Lattice.- 6. Summing Up and Looking Ahead.- References.- Additional References with Titles.