Next generation photovoltaics: high efficiency through full spectrum utilization

344 Pages·2004·4.66 MB·English

by  A. Martí, A. Luque

Series in Optics and Optoelectronics
Next Generation Photovoltaics
High efficiency through full spectrum utilization
Edited by
Antonio Mart´ı and Antonio Luque
Istituto de Energia Solar—ETSIT,
Universidad Polite´cnica de Madrid, Spain
Institute of Physics Publishing
Bristol and Philadelphia
Next Generation Photovoltaics
High efficiency through full spectrum utilization
Series in Optics and Optoelectronics
Series Editors: R G W Brown, University of Nottingham, UK
E R Pike, Kings College, London, UK
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⃝c IOP Publishing Ltd 2004
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British Library Cataloguing-in-Publication Data
A catalogue record for this book is available from the British Library.
ISBN 0 7503 0905 9
Library of Congress Cataloging-in-Publication Data are available
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Production Editor: Simon Laurenson
Production Control: Sarah Plenty
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A
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Contents
Preface xi
1 Non-conventional photovoltaic technology: a need to reach goals
Antonio Luque and Antonio Mart´ı 1
1.1 Introduction 1
1.2 On the motivation for solar energy 2
1.3 Penetration goals for PV electricity 7
1.4 Will PV electricity reach costs sufficiently low to permit a wide
penetration? 9
1.5 The need for a technological breakthrough 14
1.6 Conclusions 17
References 18
2 Trends in the development of solar photovoltaics
Zh I Alferov and V D Rumyantsev 19
2.1 Introduction 19
2.2 Starting period 20
2.3 Simple structures and simple technologies 21
2.4 Nanostructures and ‘high technologies’ 23
2.5 Multi-junction solar cells 28
2.6 From the ‘sky’ to the Earth 34
2.7 Concentration of solar radiation 35
2.8 Concentrators in space 43
2.9 ‘Non-solar’ photovoltaics 44
2.10 Conclusions 47
References 48
3 Thermodynamics of solar energy converters
Peter Wu¨rfel 50
3.1 Introduction 50
3.2 Equilibria 50
3.2.1 Temperature equilibrium 51
3.2.2 Thermochemical equilibrium 52
vi Contents
3.3 Converting chemical energy into electrical energy:
the basic requirements for a solar cell 57
3.4 Concepts for solar cells with ultra high efficiencies 59
3.4.1 Thermophotovoltaic conversion 60
3.4.2 Hot carrier cell 60
3.4.3 Tandem cells 60
3.4.4 Intermediate level cells 61
3.4.5 Photon up- and down-conversion 61
3.5 Conclusions 62
References 63
4 Tandem cells for very high concentration
A W Bett 64
4.1 Introduction 64
4.2 Tandem solar cells 66
4.2.1 Mechanically stacked tandem cells 67
4.2.2 Monolithic tandem cells 72
4.2.3 Combined approach: mechanical stacking of monolithic
cells 77
4.3 Testing and application of monolithic dual-junction concentrator
cells 77
4.3.1 Characterization of monolithic concentrator solar cells 77
4.3.2 Fabrication and characterization of a test module 80
4.3.3 FLATCON module 82
4.3.4 Concentrator system development 83
4.4 Summary and perspective 85
Acknowledgments 87
References 88
5 Quantum wells in photovoltaic cells
C Rohr, P Abbott, I M Ballard, D B Bushnell, J P Connolly,
N J Ekins-Daukes and K W J Barnham 91
5.1 Introduction 91
5.2 Quantum well cells 91
5.3 Strain compensation 94
5.4 QWs in tandem cells 96
5.5 QWCs with light trapping 97
5.6 QWCs for thermophotovoltaics 99
5.7 Conclusions 102
References 103
6 The importance of the very high concentration in third-generation
solar cells
Carlos Algora 108
6.1 Introduction 108
Contents vii
6.2 Theory 109
6.2.1 How concentration works on solar cell performance 109
6.2.2 Series resistance 112
6.2.3 The effect of illuminating the cell with a wide-angle cone
of light 115
6.2.4 Pending issues: modelling under real operation conditions 118
6.3 Present and future of concentrator third-generation solar cells 120
6.4 Economics 122
6.4.1 How concentration affects solar cell cost 122
6.4.2 Required concentration level 124
6.4.3 Cost analysis 126
6.5 Summary and conclusions 134
Note added in press 136
References 136
7 Intermediate-band solar cells
A Mart´ı, L Cuadra and A Luque 140
7.1 Introduction 140
7.2 Preliminary concepts and definitions 142
7.3 Intermediate-band solar cell: model 148
7.4 The quantum-dot intermediate-band solar cell 150
7.5 Considerations for the practical implementation of the QD-IBSC 155
7.6 Summary 160
Acknowledgments 162
References 162
8 Multi-interface novel devices: model with a continuous substructure
Z T Kuznicki 165
8.1 Introduction 165
8.2 Novelties in Si optoelectronics and photovoltaics 167
8.2.1 Enhanced absorbance 168
8.2.2 Enhanced conversion 168
8.3 Active substructure and active interfaces 169
8.4 Active substructure by ion implantation 170
8.4.1 Hetero-interface energy band offset 173
8.4.2 Built-in electric field 174
8.4.3 Built-in strain field 176
8.4.4 Defects 178
8.5 Model of multi-interface solar cells 178
8.5.1 Collection efficiency and internal quantum efficiency 181
8.5.2 Generation rate 181
8.5.3 Carrier collection limit 181
8.5.4 Surface reservoir 182
8.5.5 Collection zones 183
8.5.6 Impurity band doping profile 184
viii Contents
8.5.7 Uni- and bipolar electronic transport in a multi-interface
emitter 184
8.5.8 Absorbance in presence of a dead zone 186
8.5.9 Self-consistent calculation 187
8.6 An experimental test device 189
8.6.1 Enhanced internal quantum efficiency 190
8.6.2 Sample without any carrier collection limit (CCL) 191
8.7 Concluding remarks and perspectives 192
Acknowledgments 193
References 194
9 Quantum dot solar cells
A J Nozik 196
9.1 Introduction 196
9.2 Relaxation dynamics of hot electrons 199
9.2.1 Quantum wells and superlattices 201
9.2.2 Relaxation dynamics of hot electrons in quantum dots 206
9.3 Quantum dot solar cell configuration 214
9.3.1 Photoelectrodes composed of quantum dot arrays 216
9.3.2 Quantum dot-sensitized nanocrystalline TiO2 solar cells 216
9.3.3 Quantum dots dispersed in organic semiconductor
polymer matrices 217
9.4 Conclusion 218
Acknowledgments 218
References 218
10 Progress in thermophotovoltaic converters
Bernd Bitnar, Wilhelm Durisch, Fritz von Roth, Gu¨nther Palfinger,
Hans Sigg, Detlev Gru¨ tzmacher, Jens Gobrecht, Eva-Maria Meyer,
Ulrich Vogt, Andreas Meyer and Adolf Heeb 223
10.1 Introduction 223
10.2 TPV based on III/V low-bandgap photocells 224
10.3 TPV in residential heating systems 225
10.4 Progress in TPV with silicon photocells 227
10.4.1 Design of the system and a description of the components 227
10.4.2 Small prototype and demonstration TPV system 228
10.4.3 Prototype heating furnace 230
10.4.4 Foam ceramic emitters 231
10.5 Design of a novel thin-film TPV system 235
10.5.1 TPV with nanostructured SiGe photocells 240
10.6 Conclusion 243
Acknowledgments 243
References 243
Contents ix
11 Solar cells for TPV converters
V M Andreev 246
11.1 Introduction 246
11.2 Predicted efficiency of TPV cells 247
11.3 Germanium-based TPV cells 251
11.4 Silicon-based solar PV cells for TPV applications 254
11.5 GaSb TPV cells 256
11.6 TPV cells based on InAs- and GaSb-related materials 260
11.6.1 InGaAsSb/GaSb TPV cells 261
11.6.2 Sub-bandgap photon reflection in InGaAsSb/GaSb TPV
cells 263
11.6.3 Tandem GaSb/InGaAsSb TPV cells 263
11.6.4 TPV cells based on low-bandgap InAsSbP/InAs 264
11.7 TPV cells based on InGaAs/InP heterostructures 266
11.8 Summary 268
Acknowledgments 269
References 269
12 Wafer-bonding and film transfer for advanced PV cells
C Jaussaud, E Jalaguier and D Mencaraglia 274
12.1 Introduction 274
12.2 Wafer-bonding and transfer application to SOI structures 274
12.3 Other transfer processes 277
12.4 Application of film transfer to III–V structures and PV cells 279
12.4.1 HEMT InAlAs/InGaAs transistors on films transferred
onto Si 280
12.4.2 Multi-junction photovoltaic cells with wafer bonding
using metals 281
12.4.3 Germanium layer transfer for photovoltaic applications 281
12.5 Conclusion 283
References 283
13 Concentrator optics for the next-generation photovoltaics
P Ben´ıtez and J C Min˜ano 285
13.1 Introduction 285
13.1.1 Desired characteristics of PV concentrators 286
13.1.2 Concentration and acceptance angle 287
13.1.3 Definitions of geometrical concentration and optical
efficiency 288
13.1.4 The effective acceptance angle 290
13.1.5 Non-uniform irradiance on the solar cell:
How critical is it? 296
13.1.6 The PV design challenge 305
13.1.7 Non-imaging optics: the best framework for concentrator
design 309
x Contents
13.2 Concentrator optics overview 312
13.2.1 Classical concentrators 312
13.2.2 The SMS PV concentrators 314
13.3 Advanced research in non-imaging optics 319
13.4 Summary 320
Acknowledgments 321
Appendix: Uniform distribution as the optimum illumination 321
References 322
Appendix: Conclusions of the Third-generation PV workshop
for high efficiency through full spectrum utilization 326
Index 328