This textbook introduces the physical concepts required for a comprehensive understanding of p-n junction devices, light emitting diodes and solar cells. Semiconductor devices have made a major impact on the way we work and live. Today semiconductor p-n junction diode devices are experiencing substantial growth: solar cells are used on an unprecedented scale in the renewable energy industry; and light emitting diodes (LEDs) are revolutionizing energy efficient lighting. These two emerging industries based on p-n junctions make a significant contribution to the reduction in fossil fuel consumption. This book covers the two most important applications of semiconductor diodes - solar cells and LEDs - together with quantitative coverage of the physics of the p-n junction. The reader will gain a thorough understanding of p-n junctions as the text begins with semiconductor and junction device fundamentals and extends to the practical implementation of semiconductors in both photovoltaic and LED devices. Treatment of a range of important semiconductor materials and device structures is also presented in a readable manner. Topics are divided into the following six chapters: Semiconductor Physics The PN Junction Diode Photon Emission and Absorption The Solar Cell Light Emitting Diodes Organic Semiconductors, OLEDs and Solar Cells Containing student problems at the end of each chapter and worked example problems throughout, this textbook is intended for senior level undergraduate students doing courses in electrical engineering, physics and materials science. Researchers working on solar cells and LED devices, and those in the electronics industry would also benefit from the background information the book provides.

This textbook introduces the physical concepts requiredfor a comprehensive understanding of p-n junction devices, lightemitting diodes and solar cells.Semiconductor devices have made a major impact on the way wework and live. Today semiconductorp-n junction diode devices are experiencing substantial growth:solar cells are used on an unprecedented scale in the renewableenergy industry; and light emitting diodes (LEDs) arerevolutionizing energy efficient lighting. These two emergingindustries based on p-n junctions make a significant contributionto the reduction in fossil fuel consumption.This book covers the two most important applications ofsemiconductor diodes - solar cells and LEDs - together withquantitative coverage of the physics of the p-n junction. Thereader will gain a thorough understanding of p-n junctions as thetext begins with semiconductor and junction device fundamentals andextends to the practical implementation of semiconductors in bothphotovoltaic and LED devices. Treatment of a range ofimportant semiconductor materials and device structures is alsopresented in a readable manner.Topics are divided into the following six chapters:* Semiconductor Physics* The PN Junction Diode* Photon Emission and Absorption* The Solar Cell* Light Emitting Diodes* Organic Semiconductors, OLEDs and Solar CellsContaining student problems at the end of each chapter andworked example problems throughout, this textbook is intended forsenior level undergraduate students doing courses in electricalengineering, physics and materials science. Researchers working onsolar cells and LED devices, and those in the electronics industrywould also benefit from the background information the bookprovides.

Introduction xiAcknowledgements xv1 Semiconductor Physics 11.1 Introduction 21.2 The Band Theory of Solids 21.3 The Kronig-Penney Model 31.4 The Bragg Model 81.5 Effective Mass 81.6 Number of States in a Band 101.7 Band Filling 121.8 Fermi Energy and Holes 141.9 Carrier Concentration 151.10 Semiconductor Materials 251.11 Semiconductor Band Diagrams 261.12 Direct Gap and Indirect Gap Semiconductors 291.13 Extrinsic Semiconductors 351.14 Carrier Transport in Semiconductors 401.15 Equilibrium and Non-Equilibrium Dynamics 431.16 Carrier Diffusion and the Einstein Relation 451.17 Quasi-Fermi Energies 481.18 The Diffusion Equation 501.19 Traps and Carrier Lifetimes 531.20 Alloy Semiconductors 561.21 Summary 59Suggestions for Further Reading 61Problems 632 The PN Junction Diode 692.1 Introduction 702.2 Diode Current 722.3 Contact Potential 752.4 The Depletion Approximation 782.5 The Diode Equation 852.6 Reverse Breakdown and the Zener Diode 972.7 Tunnel Diodes 1002.8 Generation/Recombination Currents 1012.9 Ohmic Contacts, Schottky Barriers and Schottky Diodes 1042.10 Heterojunctions 1132.11 Alternating Current (AC) and Transient Behaviour 1152.12 Summary 117Suggestions for Further Reading 118Problems 1193 Photon Emission and Absorption 1233.1 Introduction to Luminescence and Absorption 1243.2 Physics of Light Emission 1253.3 Simple Harmonic Radiator 1283.4 Quantum Description 1293.5 The Exciton 1323.6 Two-Electron Atoms 1353.7 Molecular Excitons 1413.8 Band-to-Band Transitions 1443.9 Photometric Units 1483.10 Summary 152Suggestions for Further Reading 153Problems 1554 The Solar Cell 1594.1 Introduction 1604.2 Light Absorption 1624.3 Solar Radiation 1644.4 Solar Cell Design and Analysis 1644.5 Thin Solar Cells 1724.6 Solar Cell Generation as a Function of Depth 1764.7 Solar Cell Efficiency 1794.8 Silicon Solar Cell Technology: Wafer Preparation 1844.9 Silicon Solar Cell Technology: Solar Cell Finishing 1874.10 Silicon Solar Cell Technology: Advanced Production Methods 1914.11 Thin Film Solar Cells: Amorphous Silicon 1924.12 Telluride/Selenide/Sulphide Thin-Film Solar Cells 1994.13 High-Efficiency Multijunction Solar Cells 2004.14 Concentrating Solar Systems 2034.15 Summary 204Suggestions for Further Reading 205Problems 2075 Light Emitting Diodes 2155.1 Introduction 2165.2 LED Operation and Device Structures 2175.3 Emission Spectrum 2205.4 Non-Radiative Recombination 2215.5 Optical Outcoupling 2235.6 GaAs LEDs 2255.7 GaAs1-xPx LEDs 2265.8 Double Heterojunction AlxGa1-xAs LEDs 2285.9 AlGaInP LEDs 2345.10 Ga1-xInxN LEDs 2365.11 LED Structures for Enhanced Outcoupling and Power Output 2445.12 Summary 247Suggestions for Further Reading 248Problems 2496 Organic Semiconductors, OLEDs and Solar Cells 2536.1 Introduction to Organic Electronics 2546.2 Conjugated Systems 2556.3 Polymer OLEDs 2606.4 Small-Molecule OLEDs 2666.5 Anode Materials 2706.6 Cathode Materials 2706.7 Hole Injection Layer 2716.8 Electron Injection Layer 2726.9 Hole Transport Layer 2726.10 Electron Transport Layer 2756.11 Light Emitting Material Processes 2766.12 Host Materials 2786.13 Fluorescent Dopants 2796.14 Phosphorescent Dopants 2836.15 Organic Solar Cells 2836.16 Organic Solar Cell Materials 2896.17 Summary 292Suggestions for Further Reading 294Problems 295Appendix 1: Physical Constants 301Appendix 2: Properties of Semiconductor Materials 303Appendix 3: The Boltzmann Distribution Function 305Index 309