Tackling one of the hottest topics in renewables, thin-film photovoltaics, the authors present the latest updates, technologies, and applications, offering the most up-to-date and thorough coverage available to the engineer, scientist, or student.
It appears rather paradoxical that thin-film photovoltaics (PVs) are made of materials that seem unacceptable from the classical PV perspective, and yet they often outperform classical PV. This exciting new volume solves that paradox by switching to a new physics paradigm.
Many concepts here fall beyond the classical PV scope. The differences lie in device thinness (microns instead of millimeters) and morphology (non-crystalline instead of crystalline). In such structures, the charge carriers can reach electrodes without recombination. On the other hand, thin disordered structures render a possibility of detrimental lateral nonuniformities (“recombination highways”), and their energy spectra give rise to new recombination modes. The mechanisms of thermal exchange and device degradation are correspondingly unique.
The overall objective of this book is to give a self-contained in-depth discussion of the physics of thin-film systems in a manner accessible to both researchers and students. It covers most aspects of the physics of thin-film PV, including device operations, material structure and parameters, thin-film junction formation, analytical and numerical modeling, concepts of large area effects and lateral non-uniformities, physics of shunting (both shunt growth and effects), and device degradation. Also, it reviews a variety of physical diagnostic techniques proven with thin-film PV. Whether for the veteran engineer or the student, this is a must-have for any library.
This outstanding new volume: - Covers not only the state-of-the-art of thin-film photovoltaics, but also the basics, making this volume useful not just to the veteran engineer, but the new-hire or student as well - Offers a comprehensive coverage of thin-film photovoltaics, including operations, modeling, non-uniformities, piezo-effects, and degradation - Includes novel concepts and applications never presented in book format before - Is an essential reference, not just for the engineer, scientist, and student, but the unassuming level of presentation also makes it accessible to readers with a limited physics background - Is filled with workable examples and designs that are helpful for practical applications - Is useful as a textbook for researchers, students, and faculty for understanding new ideas in this rapidly emerging field
Audience:
Industrial professionals in photovoltaics, such as engineers, managers, research and development staff, technicians, government and private research labs; also academic and research universities, such as physics, chemistry, and electrical engineering departments, and graduate and undergraduate students studying electronic devices, semiconductors, and energy disciplines
Table of Contents
Preface xi
Part I General and Thin Film PV 1
I. Introduction to Thin Film PV 1
A. The Origin of PV. Junctions 1
B. Fundamental Material Requirements 3
C. Charge Transport. Definition of Thin Film PV 4
D. Distinctive Features of Thin Film PV 7
References 11
Part II One-Dimensional (1D) Diodes and PV 13
II. 1D Diode 13
A. Metal-Insulator-Metal Diode 13
B. Schottky, Reach-Through, and Field-Compensation Diodes 19
1. Schottky Diode 19
2. Reach Through Diodes 21
3. Field Compensation Diode 23
C. P-N Homo-Junctions 24
D. Heterojunctions 26
E. Other Relevant Types of Diodes 28
F. Field Reversal Diode: A Counterintuitive Case 29
G. Cat’s Whisker Diode 30
III. 1D Solar Cell 32
A. 1D Solar Cell Base Model 32
B. Numerical Modeling of 1D PV 38
1. Governing Equations 39
2. Device Model Parameters 40
3. Some Modeling Results 42
IV. Photovoltaic Parameters 43
A. Second-Level Parameters 44
B. Practical Solar Cells and Third-Level Metrics 46
C. Indicative Facts 49
D. Phenomenological Interpretation. Ideal Diode with Other Circuitry Elements 52
V. Case Study 54
A. Field Reversal PV 54
1. Analytical Approach 55
2. Numerical Modeling of the Field Reversal Device Operations 60
B. Miraculous Back Contact 68
References 72
Part III Beyond 1D: Lateral Effects in Thin Film PV 79
VI. Examples of Multidimensional Numerical Modeling 79
VII. Introduction to Random Multidimensional Phenomena 81
VIII. Lateral Screening Length 84
A. Shunt Screening 84
B. Bias Screening 85
C. Quantitative Approach and Linear Screening Regime 88
IX. Schottky Barrier Nonuniformities 91
X. Semi-Shunts 93
XI. Random Diodes 96
A. Weak Diodes 96
B. Random Diode Arrays in Solar Cells 99
C. Random Diode Arrays in PV Modules and Fields 105
XII. Nonuniformity Observations 109
A. Cell Level Observations 109
B. Module Level Observations 118
XIII. Nonuniformity Treatment 121
References 125
Part IV Electronic Processes in Materials of Thin Film PV 131
XIV. Morphology, Fluctuations, and the Density of States 132
A. The Materials of Thin Film PV are Fundamentally Different 132
B. Noncrystalline Morphology 134
C. Long Range Fluctuations of Potential Energy 136
D. Random Potential in Very Thin Structures 139
E. Numerical Estimates and Implications 142
XV. Electronic Transport 144
A. Band Transport in Random Potential 144
B. Hopping Transport Through Thin Noncrystalline Films 147
1. Hopping Between Ideal Electrodes 149
2. Hopping Between Resistive Electrodes 151
3. Critical Area and Mesoscopic Fluctuations 153
XVI. Recombination in Quasi-Continuous Spectrum 155
XVII. Noncrystalline Junctions 161
XVIII. Piezo and Pyro-PV 164
A. The Nature of Piezo-PV 164
B. Piezo-PV Observations 169
C. The Significance of Piezo-PV 171
References 174
Part V Electro-Thermal Instabilities in Thin Film PV 181
XIX. The Two-Diode Model 182
A. Linear Stability Analysis 183
B. The Two-Diode Modeling: Numerical Estimates and Scaling 184
XX. Distributed Diode Model 186
A. Introduction 186
B. Linear Stability Analysis 187
XXI. Simplistic Numerical Modeling 188
XXII. Spontaneous Hot Spots 190
A. Introduction 190
B. Observations 191
C. Numerical Modeling 195
1. Electrical Model 195
2. Thermal Model 199
D. Modeling Results 200
E. Approximate Analytical Model 205
XXIII. Related Work 207
XXIV. Conclusions on the Electro-Thermal Instabilities in Thin Film PV 209
References 210
Part VI Degradation of Thin Film PV 213
XXV. Thin Film vs Crystalline PV Degradation Processes 213
XXVI. Observations 215
A. Cell Degradation 216
B. Module Degradation 222
XXVII. Categories of Degradation 225
A. General Categories 225
B. Thin-Film PV Instabilities 227
1. Shunting Instability 227
2. Contact Delamination Instability 229
XXVIII. Accelerated Life Testing 231
A. Examples of Very Strong ALT: HALT 232
1. EBIC HALT 232
2. LBIC HALT 234
B. Actuarial Approach to ALT 235
C. Concluding Remarks on Degradation 236
References 237
Appendix. Some Methodological Aspects of Device Modeling 243
Appendix A: Model of Series Connection 243
Appendix B: The Diffusion Approximation 245
Appendix C: Long Range Potential 248
1. Point Changes 248
2. Columnar Charges 251
References 253
Index 255
