Handbook of
`Photovoltaic Science
`and Engineering
`
`Edited by
`
`Antonio Luque
`Instituto de Energ´ıa Solar, Universidad Polit´ecnica de Madrid, Spain
`
`Steven Hegedus
`Institute of Energy Conversion, University of Delaware, USA
`
`and
`
`HANWHA 1020
`
`

`

`Copyright © 2003
`
`John Wiley & Sons Ltd, The Atrium, Southern Gate, Chichester,
`West Sussex PO19 8SQ, England
`Telephone (+44) 1243 779777
`
`Email (for orders and customer service enquiries): cs-books@wiley.co.uk
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`All Rights Reserved. No part of this publication may be reproduced, stored in a retrieval system or
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`
`Library of Congress Cataloging-in-Publication Data
`
`Handbook of photovoltaic science and engineering / edited by Antonio Luque and Steven Hegedus.
`p. cm.
`Includes bibliographical references and index.
`ISBN 0-471-49196-9 (alk. paper)
`1. Photovoltaic cells. 2. Photovoltaic power generation. I. Luque, A. (Antonio) II.
`Hegedus, Steven.
`
`TK8322 .H33 2003
`(cid:2)
`621.31
`244 – dc21
`
`2002191033
`
`British Library Cataloguing in Publication Data
`
`A catalogue record for this book is available from the British Library
`
`ISBN 0-471-49196-9
`
`Typeset in 10/12 Times by Laserwords Private Limited, Chennai, India
`Printed and bound in Great Britain by Antony Rowe Ltd, Chippenham, Wiltshire
`This book is printed on acid-free paper responsibly manufactured from sustainable forestry
`in which at least two trees are planted for each one used for paper production.
`
`

`

`We dedicate this book to all those who have worked so hard for half a century to bring
`solar electricity to where it is today, and to our colleagues present and future who must
`work even harder in the next half century to make sure that it fulfills its potential as a
`widely available clean energy source.
`
`The editors also owe much appreciation to the authors of the chapters contained in this
`book. Their long hours spent writing the best possible chapter covering their field of
`expertise, and then suffering through a storm of editorial criticisms, has hopefully made
`this a high-quality publication of lasting value.
`
`Finally, we want to express our gratitude to our loved ones (Carmen, Ignacio, Sof´ıa,
`Victoria, In´es, and Debbie, Jordan, Ariel) for the many hours stolen from family life
`while working on this book.
`
`AL & SH
`December 2, 2002
`
`

`

`List of Contributors
`
`Jes´us Alonso
`Departamento de I+D
`ISOFOTON
`C/Caleta de Velez, 52
`Pol. Ind. Santa Teresa
`29006 Malaga
`Spain
`Phone: +3495 224 3790
`Fax: +3495 224 3449
`email: j.alonso@isofoton.es
`
`Hironori Arakawa
`National Institute of Advanced
`Industrial Science and Technology
`(AIST)
`1-1-1 Higashi, Tsukuba, Ibaraki
`305-8565, Japan
`Phone: 29-861-4410
`Fax: 29-856-3445
`email: h.arakawa@aist.go.jp
`
`Sheila Bailey
`NASA Lewis Research Center
`MS 302-1, 21000 Brookpark Road
`Cleveland, OH 44135
`USA
`Phone: +1 216 433 2228
`Fax: +1 216 433 6106
`email: Sheila.bailey@lerc.nasa.gov
`
`Carlos del Ca˜nizo
`Instituto de Energ´ıa Solar
`Universidad Polit´ecnica de Madrid
`
`E.T.S.I. Telecomunicaci´on
`28040 Madrid
`Spain
`Phone: +34 91 544 1060
`Fax: +34 91 544 6341
`email: canizo@ies-def.upm.es
`
`Bruno Ceccaroli
`Silicon Technologies AS
`P.O. Box 8309 Vaagsbygd
`N-4676 Kristiansand
`Norway
`Phone: +47 38 08 58 81
`Fax: +47 38 11 99 61
`email: br-c@online.no
`
`Xunming Deng
`Department of Physics and
`Astronomy
`University of Toledo
`Toledo, OH 43606
`USA
`Phone: +1 419 530 4782
`Fax: +1 419 530 2723
`email: dengx@physics.utoledo.edu
`
`Michael T. Eckhart
`Solar Bank Program
`Solar International
`Management Inc.
`1825 I Street, NW, Suite 400
`Washington, DC 20006 USA
`USA
`
`

`

`xxiv
`
`LIST OF CONTRIBUTORS
`
`Phone: +1 202-429-2030
`Fax: +1 202-429-5532
`email: eckhart@solarbank.com
`
`Keith Emery
`NREL
`1617 Cole Boulevard
`Golden, CO 80401-3393
`USA
`Phone: +1 303 384 6632
`Fax: +1 303 384 6604
`email: keith−emery@nrel.gov
`
`Arthur Endr¨os
`Corporate R&D department
`Siemens and Shell Solar GmbH
`Siemens AG
`Munich, Germany
`
`Dieter Franke
`ACCESS e.V.
`Aachen
`Germany
`
`D. J. Friedman
`NREL
`1617 Cole Boulevard
`Golden, CO 80401-3393
`USA
`
`Jeffery L. Gray
`Purdue University
`West Lafayette
`Indiana
`USA
`email: grayj@ecn.purdue.edu
`
`Lalith Gunaratne
`Solar Power & Light Co, Ltd
`338 TB Jayah Mawatha
`Colombo 10
`Sri Lanka
`
`Phone: +94 014 818395
`Fax: + 94 014 810824
`email: laithq@sri.lanka.net
`
`Christian Haessler
`Central Research Physics
`Bayer AG Krefeld
`Germany
`email: christian.haessler@
`bayerpolymers.com
`
`Steven S. Hegedus
`Institute of Energy Conversion
`University of Delaware
`Newark DE 19716
`USA
`email: ssh@udel.edu
`
`Jorge Huacuz
`Unidad de Energ´ıas no
`Convencionales
`Instituto de Investigaciones
`El´ectricas
`P.O. Box 1-475
`Cuernavaca, Morelos
`62490 Mexico
`Phone/Fax: +52 73 182 436
`email: jhuacuz@iie.org.mx
`
`J. A. Hutchby
`Semiconductor Research
`Corporation
`P.O. Box 12053
`Research Triangle Park
`North Carolina 27709
`USA
`
`S. A. Johnston
`P.O. Box 12194
`Research Triangle Park
`North Carolina 27709
`USA
`
`

`

`Juris Kalejs
`RWE Schott Solar Inc.
`4 Suburban Park Drive
`Billerica, MA 01821 USA
`Phone: 978-947-5993
`Fax: 978-663-2868
`email: jkalejs@asepv.com
`
`Wolfgang Koch
`Central Research, Physics
`(ZF-FPM), Photonic Materials
`Chemicals-Bayer Solar, (CH-BS),
`Projects
`Bayer AG
`Geb.R82, PF111107
`D-47812 Krefeld
`Germany
`Phone: +492151-883370
`Fax: +492151-887503
`email: wolfgang.koch.wk2@bayer-ag.de
`
`Hara Kohjiro
`National Institute of Advanced
`Industrial Science and Technology
`(AIST)
`1-1-1 Higashi, Tsukuba, Ibaraki
`305-8565, Japan
`Phone: 29-861-4494
`Fax: 29-861-6771
`email: k-hara@aist.go.jp
`
`Sarah Kurtz
`NREL
`1617 Cole Boulevard
`Golden, CO 80401-3393
`USA
`Phone: +1 303 384 6475
`Fax: +1 303 384 6531
`email: sarah−kurtz@nrel.gov
`
`Otto Lohne
`Norwegian University of Science
`and Technology
`
`LIST OF CONTRIBUTORS
`
`xxv
`
`Department of Materials
`Technology
`N-7491 Trondheim
`Norway
`Phone: +47 73 59 27 94
`Fax: +47 43 59 48 89
`email: Otto.Lohne@sintef.no
`
`Eduardo Lorenzo
`Instituto de Energ´ıa Solar
`Universidad Polit´ecnica de Madrid
`E.T.S.I. Telecomunicaci´on
`Ciudad Universitaria
`28040 Madrid
`Spain
`Phone: +3491 366 7228
`Fax: +3491 544 6341
`email: lorenzo@ies-def.upm.es
`
`Antonio Luque
`Instituto de Energ´ıa Solar
`Universidad Polit´ecnica de Madrid
`E.T.S.I. Telecomunicaci´on
`28040 Madrid
`Spain
`Phone: +34 91 336 7229
`Fax: +34 91 544 6341
`email: luque@ies-def.upm.es
`
`Joachim Luther
`Fraunhofer Institute for Solar
`Energy Systems ISE
`Heidenhofstrasse 2
`79110 Freiburg
`Germany
`Phone: +49 (0) 761 4588-5120
`Fax: +49 (0) 761 4588-9120
`email: luther@ise.fhg.de
`
`Antonio Mart´ı
`Instituto de Energ´ıa Solar
`Universidad Polit´ecnica de Madrid
`E.T.S.I. Telecomunicaci´on
`
`

`

`xxvi
`
`LIST OF CONTRIBUTORS
`
`28040 Madrid
`Spain
`Phone: +34 91 544 1060
`Fax: +34 91 544 6341
`email: amarti@etsit.upm.es
`
`Brian McCandless
`Institute of Energy Conversion
`University of Delaware
`Newark, DE 19716
`USA
`Phone: +1 302 831 6240
`Fax: +1 302 831 6226
`email: bem@udel.edu
`
`H. J. Moeller
`Institut f¨ur Experimentelle Physik
`TU Bergakademie Freiberg
`Silbermannstr. 1
`09599 Freiberg
`Germany
`Phone: +493731-392896
`Fax: +493731-394314
`email: moeller@physik.tu-freiberg.de
`
`J. M. Olson
`NREL
`1617 Cole Boulevard
`Golden, CO 80401-3393
`USA
`
`Klaus Preiser
`Produktion Energie badenova
`AG & Co. KG
`Tullastraße 61
`79108 Freiburg i.Br.
`Telefon 0761/279-2207
`Telefax 0761/279-2731
`Mobil 0160/7154879
`email: klaus.preiser@badenova.de
`www.badenova.de
`
`Ryne Raffaelle
`Rochester Institute of Technology
`
`84 Lomb Memorial Drive
`Rochester, NY 14623-5603
`USA
`
`Tjerk Reijenga
`BEAR Architecten
`Gravin Beatrixstraat 34
`NL 2805 PJ Gouda
`The Netherlands
`Phone: +31 182 529 899
`Fax: +31 182 582 599
`email: Tjerk@bear.nl
`
`Keith Rutledge
`Renewable Energy Development
`Institute
`Willits, CA 95490
`USA
`
`Dirk Uwe Sauer
`Electrical Energy Systems -
`Storage Systems
`Fraunhofer Institut f¨ur Solare
`Energiesysteme ISE
`Heidenhofstrasse 2
`D-79110 Freiburg
`Germany
`Phone: +49 761 4588 5219
`Fax: +49 761 4588 9217
`email: sauer@ise.fhg.de
`
`Eric A. Schiff
`Department of Physics
`Syracuse University
`Syracuse, New York 13244-1130
`USA
`http://physics.syr.edu/∼schiff
`
`J¨urgen Schmid
`ISET–Institut f¨ur Solare
`Energieversorgungstechnik e.V.,
`Universit¨at Kassel
`K¨onigstor 59
`
`

`

`34119 Kassel
`Germany
`Phone: +49 (0)5 61/72 94-3 45
`Fax: +49 (0)5 61/72 94-3 00
`email: jschmid@iset.uni-kassel.de
`
`Heribert Schmidt
`Fraunhofer Institut f¨ur Solare
`Energiesysteme ISE, Freiburg
`Heidenhofstr. 2
`79110 Freiburg
`Germany
`Phone: +49 (0)7 61/45 88-52 26
`Fax: +49 (0)7 61/45 88-92 26
`email: heri@ise.fhg.de
`
`William Shafarman
`Institute of Energy Conversion
`University of Delaware
`Newark, DE 19716
`USA
`Phone: 1 302 831 6215
`Fax: 1 302 831 6226
`email: wns@udel.edu
`
`James Sites
`Department of Physics
`Colorado State University
`Fort Collins, CO 80523-1875
`USA
`Phone: +1 970 491 5850
`Fax: +1 970 491 7947
`email: sites@lamar.colostate.edu
`
`Bushan Sopori
`NREL
`1617 Cole Boulevard
`Golden, CO 80401-3393
`USA
`Phone: +1 303 384 6683
`Fax: +1 303 384 6684
`email: bsopori@nrel.gov
`
`LIST OF CONTRIBUTORS
`
`xxvii
`
`Lars Stolt
`˚Angstr¨om Solar Center
`Uppsala University
`P.O. Box 534
`SE-751 21 Uppsala
`Sweden
`Phone: +46 18 471 3039
`Fax: +46 18 555 095
`email: Lars.Stolt@angstrom.uu.se
`
`Jack L. Stone
`NREL
`1617 Cole Boulevard
`Golden, CO 80401-3393
`USA
`
`Richard Swanson
`SUNPOWER Corporation
`435 Indio Way
`Sunnyvale, CA 94086
`USA
`Phone: +1 408 991 0900
`Fax: +1 408 739 7713
`email: Rswanson@sunpowercorp.com
`
`Ignacio Tob´ıas
`Instituto de Energ´ıa Solar
`Universidad Polit´ecnica de Madrid
`ETSI Telecomunicaci´on
`Ciudad Universitaria
`28040 Madrid
`Spain
`Phone: +3491 5475700-282
`Fax: +3491 5446341
`email: Tobias@ies-def.upm.es
`
`Richard A. Whisnant
`Parameters, Inc.
`1505 Primrose Lane
`Cary, NC 27511
`(919) 467-8710 (phone, fax)
`(919) 523-0456 (cell phone)
`
`

`

`Contents
`
`List of Contributors
`
`xxiii
`
`1 Status, Trends, Challenges and the Bright Future of Solar Electricity
`from Photovoltaics
`Steven S. Hegedus and Antonio Luque
`1.1 The Big Picture
`1.2 What Is Photovoltaics?
`1.3 Six Myths of Photovoltaics
`1.4 History of Photovoltaics
`1.5 PV Costs, Markets and Forecasts
`1.6 What Are the Goals of Today’s PV Research and Manufacturing?
`1.7 Global Trends in Performance and Applications
`1.8 Crystalline Silicon Progress and Challenges
`1.9 Thin Film Progress and Challenges
`1.10 Concentration PV Systems
`1.11 Balance of Systems
`1.12 Future of Emerging PV Technologies
`1.13 Conclusions
`References
`
`2 Motivation for Photovoltaic Application and Development
`Joachim Luther
`2.1 Characteristics of Photovoltaic Energy Conversion
`2.2 A Long-term Substitute for Today’s Conventional Electricity
`Production – The Ecological Dimension of Photovoltaics
`2.2.1 In Summary
`2.3 A Technological Basis for Off-grid Electricity Supply – The
`Development Dimension of Photovoltaics
`2.3.1 In Summary
`2.4 Power Supply for Industrial Systems and Products – The
`Professional Low Power Dimension
`2.5 Power for Spacecraft and Satellites – the Extraterrestrial Dimension
`of Photovoltaics
`References
`
`1
`
`1
`3
`5
`11
`15
`19
`20
`23
`27
`31
`32
`37
`39
`41
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`45
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`45
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`48
`54
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`54
`57
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`57
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`59
`60
`
`

`

`viii
`
`CONTENTS
`
`3 The Physics of the Solar Cell
`Jeffery L. Gray
`3.1 Introduction
`3.2 Fundamental Properties of Semiconductors
`3.2.1 Crystal Structure
`3.2.2 Energy Band Structure
`3.2.3 Conduction-band and Valence-band Densities of State
`3.2.4 Equilibrium Carrier Concentrations
`3.2.5 Light Absorption
`3.2.6 Recombination
`3.2.7 Carrier Transport
`3.2.8 Semiconductor Equations
`3.2.9 Minority-carrier Diffusion Equation
`3.3 PN -Junction Diode Electrostatics
`3.4 Solar Cell Fundamentals
`3.4.1 Solar Cell Boundary Conditions
`3.4.2 Generation Rate
`3.4.3 Solution of the Minority-carrier Diffusion Equation
`3.4.4 Terminal Characteristics
`3.4.5 Solar Cell I – V Characteristics
`3.4.6 Properties of Efficient Solar Cells
`3.4.7 Lifetime and Surface Recombination Effects
`3.4.8 An Analogy for Understanding Solar Cell Operation: A
`Partial Summary
`3.5 Additional Topics
`3.5.1 Efficiency and Band gap
`3.5.2 Spectral Response
`3.5.3 Parasitic Resistance Effects
`3.5.4 Temperature Effects
`3.5.5 Concentrator Solar Cells
`3.5.6 High-level Injection
`3.5.7 p-i-n Solar Cells
`3.5.8 Detailed Numerical Modeling
`3.6 Summary
`References
`
`4 Theoretical Limits of Photovoltaic Conversion
`Antonio Luque and Antonio Mart´ı
`4.1 Introduction
`4.2 Thermodynamic Background
`4.2.1 Basic Relationships
`4.2.2 The Two Laws of Thermodynamics
`4.2.3 Local Entropy Production
`4.2.4 An Integral View
`4.2.5 Thermodynamic Functions of Radiation
`4.2.6 Thermodynamic Functions of Electrons
`4.3 Photovoltaic Converters
`
`61
`
`61
`64
`64
`65
`66
`67
`70
`74
`78
`81
`82
`83
`87
`87
`89
`89
`89
`92
`95
`96
`
`98
`99
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`102
`104
`106
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`109
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`111
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`113
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`113
`114
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`116
`116
`117
`117
`119
`120
`
`

`

`CONTENTS
`
`ix
`
`4.3.1 The Balance Equation of a PV Converter
`4.3.2 The Monochromatic Cell
`4.3.3 Thermodynamic Consistence of the Shockley–Queisser
`Photovoltaic Cell
`4.3.4 Entropy Production in the Whole Shockley–Queisser
`Solar Cell
`4.4 The Technical Efficiency Limit for Solar Converters
`4.5 Very High Efficiency Concepts
`4.5.1 Multijunction Solar Cells
`4.5.2 Thermophotovoltaic Converters
`4.5.3 Thermophotonic Converters
`4.5.4 Higher-than-one Quantum Efficiency Solar Cells
`4.5.5 Hot Electron Solar Cells
`4.5.6 Intermediate Band Solar Cell
`4.6 Conclusions
`References
`
`5 Solar Grade Silicon Feedstock
`Bruno Ceccaroli and Otto Lohne
`5.1 Introduction
`5.2 Silicon
`5.2.1 Physical Properties of Silicon Relevant to Photovoltaics
`5.2.2 Chemical Properties Relevant to Photovoltaics
`5.2.3 Health Factors
`5.2.4 History and Applications of Silicon
`5.3 Production of Metallurgical Grade Silicon
`5.3.1 The Carbothermic Reduction of Silica
`5.3.2 Refining
`5.3.3 Casting and Crushing
`5.3.4 Economics
`5.4 Production of Semiconductor Grade Silicon (Polysilicon)
`5.4.1 The Siemens Process
`5.4.2 The Union Carbide Process
`5.4.3 The Ethyl Corporation Process
`5.4.4 Economics and Business
`5.5 Current Silicon Feedstock to Solar Cells
`5.6 Requirements of Silicon for Crystalline Solar Cells
`5.6.1 Solidification
`5.6.2 Effect of Crystal Imperfections
`5.6.3 Effect of Various Impurities
`5.7 Routes to Solar Grade Silicon
`5.7.1 Crystallisation
`5.7.2 Upgrading Purity of the Metallurgical Silicon Route
`5.7.3 Simplification of the Polysilicon Process
`5.7.4 Other Methods
`5.8 Conclusions
`References
`
`120
`124
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`126
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`129
`131
`132
`132
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`136
`140
`141
`144
`148
`149
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`153
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`201
`201
`202
`
`

`

`x
`
`CONTENTS
`
`6 Bulk Crystal Growth and Wafering for PV
`W. Koch, A. L. Endr¨os, D. Franke, C. H¨aßler, J. P. Kalejs
`and H. J. M¨oller
`6.1 Introduction
`6.2 Bulk Monocrystalline Material
`6.2.1 Cz Growth of Single-crystal Silicon
`6.2.2 Tri-crystalline Silicon
`6.3 Bulk Multicrystalline Silicon
`6.3.1 Ingot Fabrication
`6.3.2 Doping
`6.3.3 Crystal Defects
`6.3.4 Impurities
`6.4 Wafering
`6.4.1 Multi-wire Wafering Technique
`6.4.2 Microscopic Process of Wafering
`6.4.3 Wafer Quality and Saw Damage
`6.4.4 Cost and Size Considerations
`6.5 Silicon Ribbon and Foil Production
`6.5.1 Process Description
`6.5.2 Productivity Comparisons
`6.5.3 Manufacturing Technology
`6.5.4 Ribbon Material Properties and Solar Cells
`6.5.5 Ribbon/Foil Technology – Future Directions
`6.6 Numerical Simulations of Crystal Growth Techniques
`6.6.1 Simulation Tools
`6.6.2 Thermal Modelling of Silicon Crystallisation Techniques
`6.6.3 Simulation of Bulk Silicon Crystallisation
`6.6.4 Simulation of Silicon Ribbon Growth
`6.7 Conclusions
`6.8 Acknowledgement
`References
`
`7 Crystalline Silicon Solar Cells and Modules
`Ignacio Tob´ıas, Carlos del Ca˜nizo and Jes´us Alonso
`7.1 Introduction
`7.2 Crystalline Silicon as a Photovoltaic Material
`7.2.1 Bulk Properties
`7.2.2 Surfaces
`7.3 Crystalline Silicon Solar Cells
`7.3.1 Cell Structure
`7.3.2 Substrate
`7.3.3 The Front Surface
`7.3.4 The Back Surface
`7.3.5 Size Effects
`7.3.6 Cell Optics
`7.3.7 Performance Comparison
`
`205
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`255
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`255
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`257
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`259
`260
`263
`266
`266
`268
`270
`
`

`

`CONTENTS
`
`xi
`
`7.4 Manufacturing Process
`7.4.1 Process Flow
`7.4.2 Screen-printing Technology
`7.4.3 Throughput and Yield
`7.5 Variations to the Basic Process
`7.5.1 Thin Wafers
`7.5.2 Back Surface Passivation
`7.5.3 Improvements to the Front Emitter
`7.5.4 Rapid Thermal Processes
`7.6 Multicrystalline Cells
`7.6.1 Gettering in mc Solar Cells
`7.6.2 Passivation with Hydrogen
`7.6.3 Optical Confinement
`7.7 Other Industrial Approaches
`7.7.1 Silicon Ribbons
`7.7.2 Heterojunction with Intrinsic Thin Layer
`7.7.3 Buried Contact Technology
`7.8 Crystalline Silicon Photovoltaic Modules
`7.8.1 Cell Matrix
`7.8.2 The Layers of the Module
`7.8.3 Lamination and Curing
`7.8.4 Postlamination Steps
`7.8.5 Special Modules
`7.9 Electrical and Optical Performance of Modules
`7.9.1 Electrical and Thermal Characteristics
`7.9.2 Fabrication Spread and Mismatch Losses
`7.9.3 Local Shading and Hot Spot Formation
`7.9.4 Optical Properties
`7.10 Field Performance of Modules
`7.10.1 Lifetime
`7.10.2 Qualification
`7.11 Conclusions
`References
`
`8 Thin-film Silicon Solar Cells
`Bhushan Sopori
`8.1 Introduction
`8.2 A Review of Current Thin-film Si Cells
`8.2.1 Single-crystal Films Using Single-crystal Si Substrates
`8.2.2 Multicrystalline-Si Substrates
`8.2.3 Non-Si Substrates
`8.3 Design Concepts of TF-Si Solar Cells
`8.3.1 Light-trapping in Thin Si Solar Cells
`8.3.2 Description of PV Optics
`8.3.3 Electronic Modeling
`8.3.4 Methods of Making Thin-Si Films for Solar Cells
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`xii
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`CONTENTS
`
`8.3.5 Methods of Grain Enhancement of a-Si/μc-Si
`Thin Films
`8.3.6 Processing Considerations for TF-Si Solar Cell
`Fabrication
`8.4 Conclusion
`References
`
`9 High-Efficiency III-V Multijunction Solar Cells
`J. M. Olson, D. J. Friedman and Sarah Kurtz
`9.1 Introduction
`9.2 Applications
`9.2.1 Space Solar Cells
`9.2.2 Terrestrial Energy Production
`9.3 Physics of III-V Multijunction and Single-junction Solar Cells
`9.3.1 Wavelength Dependence of Photon Conversion Efficiency
`9.3.2 Theoretical Limits to Multijunction Efficiencies
`9.3.3 Spectrum Splitting
`9.4 Cell Configuration
`9.4.1 Four-terminal
`9.4.2 Three-terminal Voltage-matched Interconnections
`9.4.3 Two-terminal Series-connected (Current Matched)
`9.5 Computation of Series-Connected Device Performance
`9.5.1 Overview
`9.5.2 Top and Bottom Subcell QE and JSC
`9.5.3 Multijunction J – V Curves
`9.5.4 Efficiency versus Band Gap
`9.5.5 Top-cell Thinning
`9.5.6 Current-matching Effect on Fill Factor and VOC
`9.5.7 Spectral Effects
`9.5.8 AR Coating Effects
`9.5.9 Concentration
`9.5.10 Temperature Dependence
`9.6 Materials Issues Related to GaInP/GaAs/Ge Solar Cells
`9.6.1 Overview
`9.6.2 MOCVD
`9.6.3 GaInP Solar Cells
`9.6.4 GaAs Cells
`9.6.5 Ge Cells
`9.6.6 Tunnel-junction Interconnects
`9.6.7 Chemical Etchants
`9.6.8 Materials Availability
`9.7 Troubleshooting
`9.7.1 Characterization of Epilayers
`9.7.2 Transmission Line Measurements
`9.7.3 I -V Measurements of Multijunction Cells
`9.7.4 Evaluation of Morphological Defects
`9.7.5 Device Diagnosis
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`9.8 Future-generation Solar Cells
`9.8.1 Refinements to the GaInP/GaAs/Ge Cell
`9.8.2 Mechanical Stacks
`9.8.3 Growth on Other Substrates
`9.8.4 Spectrum Splitting
`9.9 Implementation into Terrestrial Systems
`9.9.1 Economic Issues
`9.9.2 Concentrator Systems
`9.9.3 Terrestrial Spectrum
`References
`
`10 Space Solar Cells and Arrays
`Sheila Bailey and Ryne Raffaelle
`10.1 The History of Space Solar Cells
`10.1.1 Vanguard I to Deep Space I
`10.2 The Challenge for Space Solar Cells
`10.2.1 The Space Environment
`10.2.2 Thermal Environment
`10.2.3 Solar Cell Calibration and Measurement
`10.3 Silicon Solar Cells
`10.4 III-V Solar Cells
`10.4.1 Thin-film Solar Cells
`10.5 Space Solar Arrays
`10.5.1 Body-mounted Arrays
`10.5.2 Rigid Panel Planar Arrays
`10.5.3 Flexible Fold-out Arrays
`10.5.4 Thin-film or Flexible Roll-out Arrays
`10.5.5 Concentrating Arrays
`10.5.6 High-temperature/Intensity Arrays
`10.5.7 Electrostatically Clean Arrays
`10.5.8 Mars Solar Arrays
`10.5.9 Power Management and Distribution (PMAD)
`10.6 Future Cell and Array Possibilities
`10.6.1 Low Intensity Low Temperature (LILT) Cells
`10.6.2 Quantum Dot Solar Cells
`10.6.3 Integrated Power Systems
`10.6.4 High Specific Power Arrays
`10.6.5 High-radiation Environment Solar Arrays
`10.7 Power System Figures of Merit
`References
`
`11 Photovoltaic Concentrators
`Richard M. Swanson
`11.1 Introduction
`11.1.1 The Concentrator Dilemma
`11.2 Basic Types of Concentrators
`11.2.1 Types of Optics
`11.2.2 Concentration Ratio
`
`CONTENTS
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`xiii
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`xiv
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`CONTENTS
`
`11.2.3 Types of Tracking
`11.2.4 Static Concentrators
`11.3 Historical Overview
`11.3.1 The Sandia National Laboratories Concentrator Program
`(1976 to 1993)
`11.3.2 The Martin Marietta Point-focus Fresnel System
`11.3.3 The Entech Linear-focus Fresnel System
`11.3.4 Other Sandia Projects
`11.3.5 The Concentrator Initiative
`11.3.6 Early Demonstration Projects
`11.3.7 The EPRI High-concentration Program
`11.3.8 Other Concentrator Programs
`11.3.9 History of Performance Improvements
`11.4 Optics of Concentrators
`11.4.1 Basics
`11.4.2 Reflection and Refraction
`11.4.3 The Parabolic Concentrator
`11.4.4 The Compound Parabolic Concentrator
`11.4.5 The V-trough Concentrator
`11.4.6 Refractive Lenses
`11.4.7 Secondary Optics
`11.4.8 Static Concentrators
`11.4.9 Innovative Concentrators
`11.4.10 Issues in Concentrator Optics
`11.5 Current Concentrator Activities
`11.5.1 Amonix
`11.5.2 Australian National University
`11.5.3 BP Solar and the Polytechnical University of Madrid
`11.5.4 Entech
`11.5.5 Fraunhofer-Institut fur Solare Energiesysteme
`11.5.6 Ioffe Physical-Technical Institute
`11.5.7 National Renewable Energy Laboratory
`11.5.8 Polytechnical University of Madrid
`11.5.9 Solar Research Corporation
`11.5.10 Spectrolab
`11.5.11 SunPower Corporation
`11.5.12 University of Reading
`11.5.13 Tokyo A&T University
`11.5.14 Zentrum fur Sonnenenergie und Wasserstoff Forschung
`Baden Wurttenberg (ZSW)
`References
`
`12 Amorphous Silicon–based Solar Cells
`Xunming Deng and Eric A. Schiff
`12.1 Overview
`12.1.1 Amorphous Silicon: The First Bipolar Amorphous
`Semiconductor
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`12.1.2 Designs for Amorphous Silicon Solar Cells: A Guided Tour
`12.1.3 Staebler–Wronski Effect
`12.1.4 Synopsis of this Chapter
`12.2 Atomic and Electronic Structure of Hydrogenated Amorphous
`Silicon
`12.2.1 Atomic Structure
`12.2.2 Defects and Metastability
`12.2.3 Electronic Density-of-states
`12.2.4 Bandtails, Bandedges, and Band Gaps
`12.2.5 Defects and Gap States
`12.2.6 Doping
`12.2.7 Alloying and Optical Properties
`12.3 Depositing Amorphous Silicon
`12.3.1 Survey of Deposition Techniques
`12.3.2 RF Glow Discharge Deposition
`12.3.3 Glow Discharge Deposition at Different Frequencies
`12.3.4 Hot-wire Chemical Vapor Deposition
`12.3.5 Other Deposition Methods
`12.3.6 Hydrogen Dilution
`12.3.7 Alloys and Doping
`12.4 Understanding a-Si pin Cells
`12.4.1 Electronic Structure of a pin Device
`12.4.2 Photocarrier Drift in Absorber Layers
`12.4.3 Absorber Layer Design of a pin Solar Cell
`12.4.4 The Open-circuit Voltage
`12.4.5 Optical Design of a-Si:H Solar Cells
`12.4.6 Cells under Solar Illumination
`12.4.7 Light-soaking Effects
`12.5 Multiple-Junction Solar Cells
`12.5.1 Advantages of Multiple-junction Solar Cells
`12.5.2 Using Alloys for Cells with Different Band Gaps
`12.5.3 a-Si/a-SiGe Tandem and a-Si/a-SiGe/a-SiGe Triple-junction
`Solar Cells
`12.5.4 Microcrystalline Silicon Solar Cells
`12.5.5 Micromorph and Other μc-Si-based Multijunction Cells
`12.6 Module Manufacturing
`12.6.1 Continuous Roll-to-roll Manufacturing on Stainless Steel
`Substrates
`12.6.2 a-Si Module Production on Glass Superstrate
`12.6.3 Manufacturing Cost, Safety, and Other Issues
`12.6.4 Module Performance
`12.7 Conclusions and Future Projections
`12.7.1 Status and Competitiveness of a-Si Photovoltaics
`12.7.2 Critical Issues for Further Enhancement and Future
`Potential
`12.8 Acknowledgments
`References
`
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`xvi
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`CONTENTS
`
`13 Cu(InGa)Se2 Solar Cells
`William N. Shafarman and Lars Stolt
`13.1 Introduction
`13.2 Material Properties
`13.2.1 Structure and Composition
`13.2.2 Optical Properties
`13.2.3 Electrical Properties
`13.2.4 The Surface and Grain Boundaries
`13.2.5 Substrate Effects
`13.3 Deposition Methods
`13.3.1 Substrates
`13.3.2 Back Contact
`13.3.3 Coevaporation of Cu(InGa)Se2
`13.3.4 Two-step Processes
`13.3.5 Other Deposition Approaches
`13.4 Junction and Device Formation
`13.4.1 Chemical Bath Deposition
`13.4.2 Interface Effects
`13.4.3 Other Deposition Methods
`13.4.4 Alternative Buffer Layers
`13.4.5 Transparent Contacts
`13.4.6 Buffer Layers
`13.4.7 Device Completion
`13.5 Device Operation
`13.5.1 Light-generated Current
`13.5.2 Recombination
`13.5.3 The Cu(InGa)Se2/CdS Interface
`13.5.4 Wide and Graded Band Gap Devices
`13.6 Manufacturing Issues
`13.6.1 Processes and Equipment
`13.6.2 Module Fabrication
`13.6.3 Module Performance
`13.6.4 Production Costs
`13.6.5 Environmental Concerns
`13.7 The Cu(InGa)Se2 Outlook
`References
`
`14 Cadmium Telluride Solar Cells
`Brian E. McCandless and James R. Sites
`14.1 Introduction
`14.2 CdTe Properties and Thin-film Fabrication Methods
`14.2.1 Condensation/Reaction of Cd and Te2 Vapors on a Surface
`14.2.2 Galvanic Reduction of Cd and Te Ions at a Surface
`14.2.3 Precursor Reaction at a Surface
`14.3 CdTe Thin-Film Solar Cells
`14.3.1 Window Layers
`14.3.2 CdTe Absorber Layer and CdCl2 Treatment
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`xvii
`
`14.3.3 CdS/CdTe Intermixing
`14.3.4 Back Contact
`14.3.5 Solar Cell Characterization
`14.3.6 Summary of CdTe-cell Status
`14.4 CdTe Modules
`14.5 The Future of CdTe-based Solar Cells
`14.6 Acknowledgments
`References
`
`15 Dye-sensitized Solar Cells
`Kohjiro Hara and Hironori Arakawa
`15.1 Introduction to Dye-Sensitized Solar Cells (DSSC)
`15.1.1 Background
`15.1.2 Structure and Materials
`15.1.3 Mechanism
`15.1.4 Charge-transfer Kinetics
`15.1.5 Characteristics
`15.2 DSSC Fabrication (η = 8%)
`15.2.1 Preparation of TiO2 Colloid
`15.2.2 Preparation of the TiO2 Electrode
`15.2.3 Dye Fixation onto the TiO2 Film
`15.2.4 Redox Electrolyte
`15.2.5 Counter Electrode
`15.2.6 Assembling the Cell and Cell Performance
`15.3 New Developments
`15.3.1 New Oxide Semiconductor Film Photoelectrodes
`15.3.2 New Dye Photosensitizers
`15.3.3 New Electrolytes
`15.3.4 Quasi-solid-state and Solid-state DSSCs
`15.4 Approach to Commercialization
`15.4.1 Stability of the DSSC
`15.4.2 Module Fabrication and Other Subjects for
`Commercialization
`15.5 Summary and Prospects
`References
`
`16 Measurement and Characterization of Solar Cells and Modules
`Keith Emery
`16.1 Introduction
`16.2 Rating PV Performance
`16.2.1 Standard Reporting Conditions
`16.2.2 Alternative Peak Power Ratings
`16.2.3 Energy-based Performance Rating Methods
`16.2.4 Translation Equations to Reference Conditions
`16.3 Current Versus Voltage Measurements
`16.3.1 Measurement of Irradiance
`16.3.2 Simulator-based I – V Measurements: Theory
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`CONTENTS
`
`16.3.3 Primary Reference Cell Calibration Methods
`16.3.4 Uncertainty Estimates in Reference Cell Calibration
`Procedures
`16.3.5 Intercomparison of Reference Cell Calibration
`Procedures
`16.3.6 Multijunction Cell Measurement Procedures
`16.3.7 Cell and Module I – V Systems
`16.3.8 Solar Simulators
`16.4 Spectral Responsivity Measurements
`16.4.1 Filter-based Systems
`16.4.2 Grating-based Systems
`16.4.3 Spectral Responsivity Measurement Uncertainty
`16.5 Module Qualification and Certification
`Acknowledgements
`References
`
`17 Photovoltaic Systems
`Klaus Preiser
`17.1 Introduction to PV Systems and Various Forms of Application
`17.2 Principles of photovoltaic Power System Configuration and their
`Application
`17.2.1 Grid-independent Photovoltaic Systems for Small Devices
`and Appliances
`17.2.2 Photovoltaic Systems for Remote Consumers of Medium
`and Large Size
`17.2.3 Decentralised Grid-connected Photovoltaic Systems
`17.2.4 Central Grid-connected Photovoltaic Systems
`17.2.5 Space Application
`17.3 Components for PV Systems
`17.3.1 Battery Storage
`17.3.2 Charge Controller
`17.3.3 Inverters
`17.3.4 Auxiliary Generators
`17.3.5 System Sizing
`17.3.6 Energy-saving Domestic Appliances
`17.4 Future Developments in Photovoltaic System Technology
`17.4.1 Future Developments in Off-grid Power Supply with
`Photovoltaics
`17.4.2 Future Developments in Grid-connected Photovoltaic
`Systems
`References
`
`18 Electrochemical Storage for Photovoltaics
`Dirk Uwe Sauer
`18.1 Introduction
`18.2 General Concept of Electrochemical Batteries
`18.2.1 Fundamentals of Electrochemical Cells
`
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`18.2.2 Batteries with Internal and External Storage
`18.2.3 Commonly Used Technical Terms and Definitions
`18.2.4 Definitions of Capacity and State of Charge
`18.3 Typical Operation Conditions of Batteries in PV Applications
`18.3.1 An Example of an Energy Flow Analysis
`18.3.2 Classification of Battery-operating Conditions in PV
`Systems
`18.4 Secondary Electrochemical Accumulators with Internal Storage
`18.4.1 Overview
`18.4.2 NiCd Batteries
`18.4.3 Nickel-metal Hydride (NiMH) Batteries
`18.4.4 Rechargeable Alkali Mangan (RAM) Batteries
`18.4.5 Lithium-ion and Lithium-polymer Batteries
`18.4.6 Double-layer Capacitors
`18.4.7 The Lead Acid Battery
`18.5 Secondary Electrochemical Battery Systems with External Storage
`18.5.1 Redox-flow Batteries
`18.5.2 Hydrogen/Oxygen Storage Systems
`18.6 Investment and Lifetime Cost Considerations
`18.7 Conclusion
`References
`
`19 Power Conditioning for Photovoltaic Power Systems
`J¨urgen Schmid, Heribert Schmidt
`19.1 Charge Controllers and Monitoring Systems for Batteries in PV
`Power Systems
`19.1.1 Charge Controllers
`19.1.2 Charge Equaliser for Long Battery Strings
`19.2 Inverters
`19.2.1 General Characteristics of PV Inverters
`19.2.2 Inverters for Grid-connected Systems
`19.2.3 Inverters for Stand-alone Operation
`19.2.4 Inverter Principles
`19.2.5 Power Quality of Inverters
`19.2.6 Active Quality Control in the Grid
`19.2.7 Safety Aspects with Grid-connected Inverters
`19.3 Acknowledgement
`References
`
`20 Energy Collected and Delivered by PV Modules
`Eduardo Lorenzo
`20.1 Introduction
`20.2 Movement between Sun and Earth
`20.3 Solar Radiation Components
`20.4 Solar Radiation Data and Uncertainty
`20.4.1 Clearness Index
`20.5 Radiation on Inclined Surfaces
`
`8