Photoconductivity and Photoconductive Materials, 2 Volume Set

Safa Kasap, PhD, DSc, is a Distinguished Professor in Electronic and Optoelectronic Materials and Devices at the University of Saskatchewan in Canada. He has over 35 years' experience in optoelectronic materials and is Editor-in-Chief for Journal of Materials Science: Materials in Electronics.

• Volume 1Preface xiiiSeries Preface xviList of Contributors xvii1 Photoconductivity: Fundamental Concepts 1Safa O. KasapAbbreviations 11.1 Introduction 21.2 Major Photoconductivity Classifications 101.3 Dark Current and Electrical Contacts 131.3.1 Injecting Contacts 131.3.2 Noninjecting Contacts 181.4 Shockley–Ramo Theorem 241.5 Major Recombination Mechanism 271.5.1 Direct Recombination 271.5.2 Indirect Recombination in Semiconductors: Shockley–Read–Hall Model 301.5.2.1 Weak Photogeneration 331.5.2.2 Strong Photogeneration 361.5.3 Impact or Auger Recombination 371.6 Quasi-Fermi Levels and Distribution of Recombination Centers in Energy 391.6.1 Quasi-Fermi Levels for Free Carriers 391.6.2 Quasi-Fermi Levels (QFLs) for Trapped Carriers in the Presence of Localized States 401.6.3 Demarcation Energy and Dead Carriers 461.7 Elementary Photoconductor with Ohmic Contacts and Absorption Transverse to Applied Field 471.7.1 Elementary Photoconductivity Without Diffusion 471.7.2 Elementary Photoconductivity with Diffusion 511.8 Elementary Photoconductor with Noninjecting Contacts and Optical Absorption Along the Field 531.9 Absorbed Light Intensity with Rear Reflection 561.10 Photoconductive Gain 581.11 Effects of Traps on Photoconductivity 601.12 Sinusoidally Modulated Photoexcitation: Frequency-Resolved Photoconductivity 621.13 Noise in Photoconductors 69Ackowledgments 78References 782 Characterization of Semiconductors from Photoconductivity Techniques: Uniform and Monochromatic Illumination 89Christophe Longeaud, Javier Schmidt, and Jean-Paul Kleider2.1 Introduction 892.2 Steady-State Photoconductivity (SSPC) 922.2.1 Basic Equations 932.2.2 DOS Determination 962.2.3 Illustration by Means of Simulations 972.3 Modulated Photocurrent (MPC) 1002.3.1 High-Frequency Regime (HF-MPC) 1042.3.2 Low-Frequency Regime (LF-MPC) 1062.3.3 Summary of the Two MPC Regimes 1072.3.4 Illustration by Means of Simulations 1082.3.5 Experimental Results 1142.3.5.1 Application to a Crystalline Material 1142.3.5.2 Application to Amorphous Thin Films 1162.4 Conclusion 119Symbols and Abbreviations 120Acknowledgments 122References 1223 Characterization of Semiconductors from Photoconductivity Techniques: Uniform and Polychromatic Illumination 125Christophe Longeaud, Javier Schmidt, and Jean-Paul Kleider3.1 Introduction 1253.2 The Constant Photocurrent Method (CPM) 1263.2.1 CPM Principle 1263.2.2 Absolute CPM 1303.2.3 Determination of the DOS from a CPM Spectrum 1313.2.3.1 Deconvolution of a CPM Spectrum 1313.2.3.2 Calculation of the Excess Absorption 1323.2.3.3 Absorption at a Single Energy 1323.2.4 Limits of the CPM 1333.2.5 AC CPM vs. DC CPM 1333.3 The Fourier-Transform Photocurrent Spectroscopy (FTPS) 1343.3.1 FTPS Bases 1343.3.2 FTPS Bench 1373.3.3 Experimental Results 1383.3.3.1 Comparison of Calibrations with Transmitted or Direct Flux 1383.3.3.2 Comparison of FTPS Performed on Thin Films and Solar Cells 1403.3.3.3 Application of FTPS to the Study of Perovskite Thin Films 1433.4 Conclusion 147Symbols and Abbreviations 147Acknowledgments 148References 1494 Characterization of Semiconductors from Photoconductivity Techniques: Photocarrier Grating Techniques 151Christophe Longeaud, Javier Schmidt, and Jean-Paul Kleider4.1 Introduction 1514.2 Steady-State Photocarrier Grating (SSPG) 1544.2.1 Fundamentals 1544.2.2 Description of an Automated SSPG Bench 1574.2.3 Use of the SSPG Technique to Derive the DOS 1594.3 Modulated Photocarrier Grating (MPG) 1624.4 Moving Grating Technique (MGT) 1644.5 Oscillating Photocarrier Grating (OPG) 1674.6 DOS Determination from the Small Signal Recombination Lifetime 1714.7 Conclusions 174Symbols and Abbreviations 175Acknowledgments 177References 1775 Time-of-Flight Transient Photoconductivity Technique 179Safa O. Kasap5.1 Basic Principles 1795.2 Shallow Traps, Effective Drift Mobility, and Effective Lifetime 1875.2.1 Effective Drift Mobility 1875.2.2 Deep Trapping in the Presence of Shallow Traps 1925.3 Exponential Absorption: exp(−αx) 1955.4 Continuity Equation Formalism Under Multiple Trapping 1975.5 Generalized Quasi-equilibrium Transport 2025.6 Anomalous Dispersion and Thickness Dependent TOF Drift Mobility 2065.7 Experimental Implementation and Artifacts 2125.7.1 Single-Shot TOF Experiments and Apparatus 2135.7.2 Operational Definition of Transit Time 2155.7.3 Finite Photogeneration Depth (δ) 2195.7.4 Finite Photoexcitation Duration 2205.7.5 Maximum I-Mode and V -Mode Signals 2215.7.6 RC Time Constant and Instrument Bandwidth 2225.8 Xerographic Time-of-Flight Experiment 2235.9 Lateral or Coplanar Time-of-Flight (CTOF) 2265.10 Time-of-Flight Study of Recombination: Double Photoexcitation 2285.11 Interrupted Field Time-of-Flight (IFTOF) 2315.12 Space Charge Perturbed Photocurrents 2345.13 Charge Collection Efficiency (CCE) 2375.14 Monte Carlo Simulation of Carrier Transport 241Acknowledgments 245References 2456 Transient Photocurrent of Disordered Semiconducting Thin Films with Coplanar Electrode Configurations 253Hayate Fujimura, Takashi Nagase, and Hiroyoshi Naito6.1 Introduction 2536.2 Theory of Laplace Transform Methods 2556.2.1 Determination of Localized-State Distribution 2556.2.2 Determination of Localized-State Distribution with High Energy Resolution 2586.2.3 Determination of Free Carrier Lifetime 2596.2.4 Determination of Drift Mobility 2606.2.4.1 Uniform Optical Excitation Between Coplanar Electrodes with a Blocking Contact 2606.2.4.2 Optical Excitation Near an Electrode 2616.3 Numerical Calculation of Transient Photocurrent 2616.3.1 Localized-State Distribution 2616.3.2 Free Carrier Lifetime 2666.3.3 Drift Mobility 2666.3.3.1 Uniform Excitation 2666.3.3.2 Local Excitation 2686.4 Experimental Results 2696.4.1 Localized-State Distribution 2696.4.2 Free Carrier Lifetime 2706.4.3 Drift Mobility 2716.4.3.1 Uniform Excitation 2716.4.3.2 Local Excitation 2716.5 Conclusions 272References 2737 Organic Photoconductors: Photogeneration, Transport, and Applications in Printing 275David S. Weiss7.1 Introduction: Organic Photoconductors (OPC) 2757.1.1 OPC Structure, Photodischarge Physics, and Process Considerations 2767.2 History of Electrophotography and OPC Developments 2817.2.1 Electrophotography 2817.2.2 Electrophotographic Copying and Printing 2827.2.3 OPC Development 2837.3 OPC Photogeneration Efficiency and Mechanisms 2877.3.1 OPC Charge Generation: Hole Transporting Materials (Aromatic Amines) 2897.3.2 OPC Charge Generation: Molecular Complexes 2907.3.2.1 PVK–TNF 2917.3.2.2 Dye–Polymer Aggregate 2947.3.3 OPC Charge Generation: Pigments 2957.3.3.1 Azo Pigments 2967.3.3.2 Phthalocyanine Pigments 2977.3.3.3 Perylene Pigments 3007.3.3.4 Squaraine Pigments 3017.3.4 Summary of Charge Generation Mechanism in OPCs 3017.4 Dark Conductivity 3037.5 Charge Transport 3047.5.1 Charge Transport Experimental Methods 3047.5.2 Theory: Charge Transport in Organic Semiconductors 3077.5.3 Charge Transport in Molecularly Doped Polymers (MDP) and Polymers 3127.5.3.1 Hole Transport: MDPs and Polymers 3127.5.3.2 Electron Transport: MDPs and Polymers 3147.5.3.3 Bipolar Transport: MDPs and Polymers 3157.6 Charge Transport Disruptions 3177.6.1 Medium and Polarity Effects 3177.6.2 Charge Trapping 3187.7 OPC Charge Transport 3187.7.1 Disruptions of OPC Functionality 3207.7.1.1 OPC Photofatigue 3217.7.1.2 OPC Corona Chemical Fatigue 3227.8 OPC New Materials Applications 3247.9 OPC New Printing Applications and Future Developments 3267.9.1 Current OPC Printing Applications 3267.9.2 New OPC Printing Applications 327References 3288 Charge Extraction by Linearly Increasing Voltage (CELIV) Method for Investigation of Charge Carrier Transport and Recombination in Disordered Materials 339Oleksandr Grynko, Gytis Juška, and Alla Reznik8.1 Introduction 3398.2 Charge Extraction by Linearly Increasing Voltage (CELIV) Technique 3418.2.1 Dark-CELIV 3418.2.2 Dark-CELIV Measurements in Low-Conductivity Materials 3448.2.3 Dark-CELIV Measurements in High-Conductivity Materials 3458.3 Photo-CELIV 3498.3.1 Photo-CELIV: Surface vs. Bulk Photogeneration 3518.3.2 Photo-CELIV in the Case of Langevin Recombination 3548.3.3 Photo-CELIV in the Case of Electric Field-Dependent Mobility 3578.3.4 Analysis of Photo-CELIV for Dispersive Transport 3598.4 i-CELIV 3618.5 Summary 367References 3679 Terahertz Photoconductivity 369David G. Cooke9.1 THz Pulses 3699.2 Drude Conductivity of Free Charges 3719.3 ac Conductivity of Bound Charges: Lorentz Response 3739.4 Generation and Detection Techniques 3739.4.1 Photoconductive Switches 3739.4.2 Nonlinear Generation and Detection of THz Pulses 3759.4.3 Tilted Pulse Front Optical Rectification 3769.4.4 Ultra-Broadband THz Pulses 3789.4.5 Air Plasma Generation and Detection 3789.5 Terahertz Spectroscopy 3799.5.1 Time-Domain THz Spectroscopy 3799.5.2 Time-Resolved THz Spectroscopy 3819.6 Transient Photoconductivity: Semiconductors 3849.6.1 Carrier Trapping and Diffusion 3879.6.2 Plasmon and Optical Phonon Dynamics 3889.6.3 Polarons 3909.6.4 Excitons 3929.6.5 Semiconductor Nanostructures 3949.7 Conclusions 396References 397Volume 2Preface xiiiSeries Preface xviiList of Contributors xix10 Photoconductive Materials 399Alan Owens11 Photoconductivity of Nanowire Systems 493Harry E. Ruda12 Photoconductivity of Semiconductor Nanocrystals 523Richard J. Curry13 Persistent Photocurrents and Defects 549Ruben J. Freitas and Koichi Shimakawa14 Photoconductivity in the Infrared: Mercury Cadmium Telluride 577Peter Capper15 X-ray Photoconductivity and Typical Large-Area X-ray Photoconductors 613Zahangir Kabir16 Progress in Lead Oxide X-Ray Photoconductive Layers 643Oleksandr Grynko and Alla Reznik17 Diamond Radiation Detectors 689Gabriele Chiodini and Maurizio Martino18 Doped and Stabilized Amorphous Selenium Single and Multilayer Photoconductive Layers for X-Ray Imaging Detector Applications 715Safa O. Kasap19 Metal Halide Perovskites for Photodetection 781Qianqian Lin20 Photoconductive Antennas for Terahertz Applications 807Roger Lewis21 Phthalocyanines: A Class of Organic Photoconductive Materials 831Asim K. Ray, Debdyuti Mukherjee, and Sujoy SarkarIndex 853