Advanced Characterization Techniques for Thin Film Solar Cells E-Book

• Herausgeber: Wiley-VCH
• Kategorie: Fachliteratur
• Sprache: Englisch

Seitenzahl: 1452

Veröffentlichungsjahr: 2016

Beschreibung

The book focuses on advanced characterization methods for thin-film solar cells that have proven their relevance both for academic and corporate photovoltaic research and development. After an introduction to thin-film photovoltaics, highly experienced experts report on device and materials characterization methods such as electroluminescence analysis, capacitance spectroscopy, and various microscopy methods. In the final part of the book simulation techniques are presented which are used for ab-initio calculations of relevant semiconductors and for device simulations in 1D, 2D and 3D.

Building on a proven concept, this new edition also covers thermography, transient optoelectronic methods, and absorption and photocurrent spectroscopy.

Leseprobe

Table of Contents

Cover

Title Page

Copyright

Dedication

List of Contributors

Preface of the Second Edition

Preface of the First Edition

Abbreviations

Part I: Introduction

Chapter 1: Introduction to Thin-Film Photovoltaics

1.1 Introduction

1.2 The Photovoltaic Principle

1.3 Functional Layers in Thin-Film Solar Cells

1.4 Comparison of Various Thin-Film Solar-Cell Types

1.5 Conclusions

Acknowledgments

References

Part II: Device Characterization

Chapter 2: Fundamental Electrical Characterization of Thin-Film Solar Cells

2.1 Introduction

2.2 Current/Voltage Curves

2.3 Quantum Efficiency Measurements

Acknowledgments

References

Chapter 3: Electroluminescence Analysis of Solar Cells and Solar Modules

3.1 Introduction

3.2 Basics

3.3 Spectrally Resolved EL

3.4 Spatially Resolved EL of c-Si Solar Cells

3.5 EL Imaging of Thin-Film Solar Cells and Modules

3.6 Electromodulated Luminescence under Illumination

Acknowledgments

References

Chapter 4: Capacitance Spectroscopy of Thin-Film Solar Cells

4.1 Introduction

4.2 Admittance Basics

4.3 Sample Requirements

4.4 Instrumentation

4.5 CV Profiling and the Depletion Approximation

4.6 Admittance Response of Deep States

4.7 The Influence of Deep States on CV Profiles

4.8 Deep-Level Transient Spectroscopy

4.9 Admittance Spectroscopy

4.10 Drive-Level Capacitance Profiling

4.11 Photocapacitance

4.12 The Meyer–Neldel Rule

4.13 Spatial Inhomogeneities and Interface States

4.14 Metastability

Acknowledgments

References

Chapter 5: Time-of-Flight Analysis

5.1 Introduction

5.2 Fundamentals of TOF Measurements

5.3 Experimental Details

5.4 Analysis of TOF Results

References

Chapter 6: Transient Optoelectronic Characterization of Thin-FilmSolar Cells

6.1 Introduction

6.2 Measurement Setup

6.3 Charge Extraction and Transient Photovoltage

6.4 CE with Linearly Increased Voltage

6.5 Time-Delayed Collection Field Method

Acknowledgment

References

Chapter 7: Steady-State Photocarrier Grating Method

7.1 Introduction

7.2 Basic Analysis of SSPG and Photocurrent Response

7.3 Experimental Setup

7.4 Data Analysis

7.5 Results

7.6 DOS Determination

7.7 Data Collection by Automization and Combination with Other Experiments

7.8 Summary

Acknowledgment

References

Part III: Materials Characterization

Chapter 8: Absorption and Photocurrent Spectroscopy with High Dynamic Range

8.1 Introduction

8.2 Photothermal Deflection Spectroscopy

8.3 Fourier Transform Photocurrent Spectroscopy

Acknowledgment

References

Chapter 9: Spectroscopic Ellipsometry

9.1 Introduction

9.2 Theory

9.3 Ellipsometry Instrumentation

9.4 Data Analysis

9.5 Spectroscopic Ellipsometry for Thin-Film Photovoltaics

9.6 Summary and Outlook

References

Chapter 10: Characterizing the Light-Trapping Properties of Textured Surfaces with Scanning Near-Field Optical Microscopy

10.1 Introduction

10.2 How Does a Scanning Near-Field Optical Microscope Work?

10.3 The Role of Evanescent Modes for Light Trapping

10.4 Analysis of Scanning Near-Field Optical Microscopy Images by Fast Fourier Transformation

10.5 Investigation of Individual Waveguide Modes

10.6 Light Propagation in Thin-Film Solar Cells Investigated with Dual-Probe SNOM

10.7 Conclusion

Acknowledgments

References

Chapter 11: Photoluminescence Analysis of Thin-Film Solar Cells

11.1 Introduction

11.2 Experimental Issues

11.3 Basic Transitions

11.4 Case Studies

Acknowledgments

References

Chapter 12: Electron-Spin Resonance (ESR) in Hydrogenated Amorphous Silicon (a-Si:H)

12.1 Introduction

12.2 Basics of ESR

12.3 How to Measure ESR

12.4 The

g

Tensor and Hyperfine Interaction in Disordered Solids

12.5 Discussion of Selected Results

12.6 Alternative ESR Detection

12.7 Concluding Remarks

Acknowledgments

References

Chapter 13: Scanning Probe Microscopy on Inorganic Thin Films for Solar Cells

13.1 Introduction

13.2 Experimental Background

13.3 Selected Applications

13.4 Summary

Acknowledgments

References

Chapter 14: Electron Microscopy on Thin Films for Solar Cells

14.1 Introduction

14.2 Scanning Electron Microscopy

14.3 Transmission Electron Microscopy

14.4 Sample Preparation Techniques

Acknowledgments

References

Chapter 15: X-ray and Neutron Diffraction on Materials for Thin-Film Solar Cells

15.1 Introduction

15.2 Diffraction of X-Rays and Neutron by Matter

15.3 Grazing Incidence X-Ray Diffraction (GIXRD)

15.4 Neutron Diffraction of Absorber Materials for Thin-Film Solar Cells

15.5 Anomalous Scattering of Synchrotron X-Rays

Acknowledgments

References

Part IV: Materials and Device Modeling

Chapter 16: In Situ Real-Time Characterization of Thin-Film Growth

16.1 Introduction

16.2 Real-Time

In Situ

Characterization Techniques for Thin-Film Growth

16.3 X-Ray Methods for Real-Time Growth Analysis

16.4 Light Scattering and Reflection

16.5 Summary

Acknowledgments

References

Chapter 17: Raman Spectroscopy on Thin Films for Solar Cells

17.1 Introduction

17.2 Fundamentals of Raman Spectroscopy

17.3 Vibrational Modes in Crystalline Materials

17.4 Experimental Considerations

17.5 Characterization of Thin-Film Photovoltaic Materials

17.6 Conclusions

Acknowledgments

References

Chapter 18: Soft X-ray and Electron Spectroscopy: A Unique “Tool Chest” to Characterize the Chemical and Electronic Properties of Surfaces and Interfaces

18.1 Introduction

18.2 Characterization Techniques

18.3 Probing the Chemical Surface Structure: Impact of Wet Chemical Treatments on Thin-Film Solar Cell Absorbers

18.4 Probing the Electronic Surface and Interface Structure: Band Alignment in Thin-Film Solar Cells

18.5 Summary

Acknowledgments

References

Chapter 19: Accessing Elemental Distributions in Thin Films for Solar Cells

19.1 Introduction

19.2 Glow-Discharge Optical Emission Spectroscopy (GD-OES) and Glow-Discharge Mass Spectroscopy (GD-MS)

19.3 Secondary Ion Mass Spectrometry (SIMS)

19.4 Auger Electron Spectroscopy (AES)

19.5 X-Ray Photoelectron Spectroscopy (XPS)

19.6 Energy-Dispersive X-Ray Analysis on Fractured Cross Sections

19.7 Atom Probe Tomography and Correlated Microscopies

Acknowledgments

References

Chapter 20: Hydrogen Effusion Experiments

20.1 Introduction

20.2 Experimental Setup

20.3 Data Analysis

20.4 Discussion of Selected Results

20.5 Comparison with other Experiments

20.6 Concluding Remarks

Acknowledgments

References

Chapter 21: Ab Initio Modeling of Defects in Semiconductors

21.1 Introduction

21.2 DFT and Methods

21.3 Methods Beyond DFT

21.4 From Total Energies to Materials Properties

21.5

Ab initio

Characterization of Point Defects

21.6 Conclusions

Acknowledgments

References

Chapter 22: Molecular Dynamics Analysis of Nanostructures

22.1 Introduction

22.2 Molecular Dynamics Methods

22.3 Vapor Deposition Simulations

22.4 Defect Extraction Algorithms

22.5 Case Study: CdTe/CdS Solar Cells

22.6 Concluding Remarks

Acknowledgments

References

Chapter 23: One-Dimensional Electro-Optical Simulations of Thin-Film Solar Cells

23.1 Introduction

23.2 Fundamentals

23.3 Modeling Hydrogenated Amorphous and Microcrystalline Silicon

23.4 Optical Modeling of Thin Solar Cells

23.5 Tools

Acknowledgments

References

Chapter 24: Two- and Three-Dimensional Electronic Modeling of Thin-Film Solar Cells

24.1 Applications

24.2 Methods

24.3 Examples

24.4 Summary

Acknowledgments

References

Index

End User License Agreement

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Guide

Cover

Table of Contents

Preface of the Second Edition

Part I: Introduction

Begin Reading

List of Illustrations

Chapter 1: Introduction to Thin-Film Photovoltaics

Figure 1.1 (a) Comparison of the AM1.5G spectrum with the blackbody spectrum of a body with a temperature

T

= 5800 K. Both spectra are normalized such that the power density is 100 mW/cm

2

. (b) Using the AM1.5G spectrum and Equation (1.1), we obtain the short-circuit current density

J

sc,SQ

in the Shockley–Queisser limit as a function of the band-gap energy

E

g

of the solar absorber.

Figure 1.2 (a) Power density/voltage curves and (b) current density/voltage (

J

/

V

) curves of three ideal solar cells with band gaps

E

g

= 0.8, 1.4, and 2.0 eV, respectively. The higher the band gap

E

g

, the higher the open-circuit voltage

V

oc

, that is, the intercept of both power density and current density with the voltage axis. However, a higher band gap also leads to a decreased short-circuit current

J

sc

(cf. Figure 1.1b). The curves are calculated using Equation 1.4.

Figure 1.3 (a) Open-circuit voltage and (b) conversion efficiency as a function of the band-gap energy

E

g

in the Shockley–Queisser limit using an AM1.5G spectrum as illumination. The optimum band-gap energies for single-junction solar cells are in the range of 1.1 eV <

E

g

< 1.4 eV with maximum conversion efficiencies around

η

= 33% under unconcentrated sunlight.

Figure 1.4 Absorptance as a function of photon energy for (a) a flat solar cell and (b) a textured solar cell with perfect light trapping. In both cases the absorption coefficient

α

0

from Equation 1.9 is varied. The values are for both subFigure , , . For the same absorption coefficient, the textured solar cell has absorptances that are much closer to the perfect step function than the flat solar cell.

Figure 1.5 Comparison of the short-circuit current density of a flat (solid line) and a textured solar cell (dashed line) as a function of the product of

α

0

and the thickness

d

assuming an absorption coefficient according to Equation 1.9 (with

E

g

= 1.2 eV). Especially for low absorption coefficients relative to the device thickness (low

α

0

d

), light trapping increases the short-circuit current density drastically. The refractive index used for these simulations is

n

= 3.5 independent of photon energy.

Figure 1.6 Simulation of the band diagrams of a (a, d) p

–

n-junction, a (b, e) p

–

i

–

n-junction, and a (c, f) flatband (fb) solar cell under illumination. Every type of geometry is depicted under short-circuit conditions and under an applied forward bias

V

= 0.5 V.

Figure 1.7 Simulated current/voltage curves of the three solar-cell geometries introduced in Figure 1.6 for two charge carrier mobilities, namely, (a)

μ

= 10

−1

cm

2

/V s and (b)

μ

= 10

1

cm

2

/V s. The main influence of a decreased mobility is a lower short-circuit current for the p

–

n-junction solar cell and a lower fill factor for the p

–

i

–

n-junction and the flatband solar cell, which feature voltage-dependent charge carrier collection.

Figure 1.8 Overview over the three basic recombination mechanisms for photogenerated excess carriers in a semiconductor. The excess energy is either transferred to (a) a photon, (b) kinetic energy of an excess electron or hole, or (c) phonons. For case (b), in the so-called Auger recombination, the kinetic energy of the electron is lost by collisions with the lattice, which heats up. In case (c), the emission of phonons becomes possible by the existence of states in the forbidden gap. This recombination mechanism is called Shockley–Read–Hall recombination.

Figure 1.9 Current/voltage curves of (a) a p

–

i

–

n-junction solar cell and (b) a p

–

n-junction solar cell for a constant mobility

μ

= 1 cm

2

/V s (for electrons and holes) and with a varying lifetime

τ

= 1 ns, 10 ns, 100 ns, 1 µs, and 10 µs. All other parameters are defined in Table 1.1. An increasing lifetime helps to increase

V

oc

in both cases up to the level defined by surface recombination alone. In case of the p

–

i

–

n-junction solar cell, the

FF

increases as well.

Figure 1.10 Sketch of the layer sequences to build up the system for thin-film solar cells in superstrate (a) and substrate configuration (b). The minimum number of layers in excess of the supporting sub- or superstrate consists of the transparent and conductive front contact, the absorber layer, and the back contact.

Figure 1.11 (a) Layer-stacking sequence and (b) energy band diagram of a typical ZnO/CdS/Cu(In,Ga)Se

2

heterojunction solar cell.

Figure 1.12 (a) Layer-stacking sequence and (b) energy band diagram of a typical CdTe-based solar cell following Ref. [82].

Figure 1.13 (a) Stacking sequence and (b) band diagram of a typical a-Si:H p

–

i

–

n solar cell. The main absorber layer is intrinsic, while the built-in field is due to the thin doped silicon layers. Due to the asymmetric mobilities between electrons and holes, the p-type layers will always be on the illuminated side, ensuring that the holes with their lower mobility have the shorter way to the contacts.

Chapter 2: Fundamental Electrical Characterization of Thin-Film Solar Cells

Figure 2.1 Semilogarithmic plots (a, c, e, g) of dark

J

/

V

characteristics and linear plots (b, d, f, h) of dark (dashed lines) and illuminated (full lines)

J

/

V

characteristics as well as of the difference

J

ph

=

J

il

−

J

d

(open circles). In (a, b) the characteristics of a p–n-junction diode resulting from radiative recombination is shown leading to an ideal slope of the dark

J

/

V

with an ideality

n

id

= 1 and a voltage-independent photocurrent. (c, d) illustrate the departure from an ideal diode law in case of typical p–n-junction solar cells, where the low-energy part of the dark

J

/

V

features a second slope with a higher ideality factor

n

id

= 1.86 which originates from SRH recombination in the space charge region. (e, f) illustrate the addition of a series and parallel resistance with the gray line representing the case with

R

s

= 0 and

R

p

= ∞ for reference. Note that

J

ph

is voltage dependent despite the fact that carriers are efficiently collected. This can be used to determine the series resistance. (g, h) show a p–i–n junction with a low mobility-lifetime product and a subsequently strongly voltage-dependent photocurrent

J

ph

.

Figure 2.2 Equivalent circuit useful for the description of p–n-junction solar cells consisting of a current source representing the short-circuit current, two diodes for the recombination in the space charge region, and one series and parallel resistance. Note that a representation with an equivalent circuit is difficult for p–i–n-type solar cells, since there the photocurrent is inherently voltage dependent.

Figure 2.3 Schematic of a solar simulator for

J

/

V

measurements under illumination with a spectrum resembling the standard AM1.5G. To better approximate the solar spectrum, a W lamp and a Xe lamp are combined.

Figure 2.4 Dark current density

J

d

(dashed line), illuminated current density

J

il

(solid line), and illumination-dependent short-circuit current density

J

sc

(open squares) as a function of voltage or open-circuit voltage

V

oc

in case of the

J

sc

on a semilogarithmic scale. The

J

il

/

V

curve is shifted by the

J

sc

at AM1.5G conditions at which the

J

il

/

V

curve was measured. From the voltage differences at constant current densities in this plot, the series resistance of a p–n-junction solar cell can be calculated.

Figure 2.5 Schematic band diagram of a CdS/Cu(In,Ga)Se

2

solar cell showing the four main recombination mechanisms that can occur. The four different locations where recombination with different ideality factors and activation energies can take place are (i) the CdS/Cu(In,Ga)Se

2

interface, (ii) the space charge region, (iii) the neutral bulk, and (iv) the back contact (interface between Cu(In,Ga)Se

2

and Mo). The quantities

E

C

and

E

V

stand for the conduction and valence band,

E

fn

and

E

fp

stand for the quasi-Fermi levels of electrons and holes, and Φ

b

is the interface barrier.

Figure 2.6 Temperature dependence of the open-circuit voltage

V

oc

for different Cu(In,Ga)(Se,S)

2

solar cells with different band gap energies due to different In/Ga and Se/S ratios. The open symbols correspond to devices that are grown with a Cu-poor final composition and have a band gap energy (as calculated from the stoichiometry) of

E

g

= 1.49 eV (circles) and 1.22 eV (triangles). The extrapolated open-circuit voltage

V

oc

(

T

= 0 K) roughly follows

E

g

, whereas for the devices grown under Cu-rich conditions

V

oc

(

T

= 0 K) is independent of

E

g

(1.15 eV, circles, and 1.43 eV, triangles). The latter finding points to the fact that recombination in such devices has an activation energy given by the height of the interface barrier Φ

b

.

Figure 2.7 Scheme of two quantum efficiency setups – (a) a monochromator-based setup and (b) a setup with a filter wheel. In both cases, chopped monochromatic light illuminates first the reference (during calibration) and then the sample (during measurement). The current output of reference or sample is converted to voltage and then amplified with a lock-in amplifier triggered by the chopper wheel synchronization output. Temporal variations in intensity of the monochromatic light can be monitored with a monitor diode measuring intensity during calibration and during measurement.

Figure 2.8 Schematic of the two possible approaches when illuminating a solar cell during a quantum efficiency measurement. (a) With a monochromator-based setup, a typical spot size is in the mm range and will be smaller than most investigated cells. Thus, the spot illuminates only a small part of the cell and the quantum efficiency will be a local quantity, which may change when moving the spot. (b) In case of a filter wheel setup, it is possible to illuminate solar cells or small modules homogeneously and thus get an average quantum efficiency.

Figure 2.9 Example for the quantum efficiency of a-Si:H/µc-Si:H tandem cell on textured ZnO:Al superstrates. The quantum efficiencies of top and bottom cell are indicated as solid lines and are measured using a bias light to flood the respective other subcell. In addition, the sum of both is indicated as dashed line and the minimum value is indicated as open circles. The latter indicates the measurement result one would obtain, when measuring without bias light.

Figure 2.10 Bias-dependent quantum efficiency of the top cell in an a-Si:H/µc-Si:H tandem solar cell. (a, c) show the experiment and (b, d) the simulation. (a, b) show the quantum efficiency itself and (c, d) the difference in quantum efficiency compared to the short-circuit situation.

Figure 2.11 Comparison of the typical quantum efficiency of a µc-Si:H solar cell with a textured ZnO (solid line) and a flat ZnO.

Figure 2.12 Comparison of the absorption in the different layers of (a) a typical µc-Si:H solar cell (redrawn from Ref. [44]) and (b) a typical Cu(In,Ga)Se

2

solar cell

Figure 2.13 Using a simulation of an a-Si:H/µc-Si:H tandem solar cell, the losses in the different layers are calculated. The total incident photon flux of the AM1.5G spectrum between 300 and 1100 nm is taken as input leading to 43.51 mA/cm

2

as the maximum

J

sc

for a single-junction solar cell (and 0.5 × 43.51 mA/cm

2

for a tandem solar cell). Losses in the Si layers are denoted as recombination losses, while losses in the front and back contact layers are termed parasitic absorption losses although the distinction between the two is not strict.

Chapter 5: Time-of-Flight Analysis

Figure 5.1 (a) Basic procedure of a time-of-flight experiment. (After Figure 5.1 in Ref. [3].) (b) Ideal photocurrent transient in the absence of any kind of dispersion.

Figure 5.2 Two kinds of dispersive transport [4], p. 16. Obviously, both cases are very different. While (a) consists of a constant phase followed by a sharp drop, (b) exhibits power-law behavior and has a much less distinct

t

T

. Note the logarithmic axes of the right-hand plot.

Edited byDaniel Abou-Ras, Thomas Kirchartz, and Uwe Rau

Advanced Characterization Techniques for Thin Film Solar Cells

Volume 1

Second Edition

Edited byDaniel Abou-Ras, Thomas Kirchartz, and Uwe Rau

Advanced Characterization Techniques for Thin Film Solar Cells

Volume 2

Second Edition

Editors

Dr. Daniel Abou-Ras

Helmholtz Center Berlin for Materials and Energy

Hahn-Meitner-Platz 1

14109 Berlin

Germany

Prof. Dr. Thomas Kirchartz

Forschungszentrum Jülich GmbH

IEK-5 Photovoltaik

Leo-Brandt-Straße

52428 Jülich

Germany

Prof. Dr. Uwe Rau

Forschungszentrum Jülich GmbH

IEK-5 Photovoltaik

Leo-Brandt-Straße

52428 Jülich

Germany

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List of Contributors

Daniel Abou-Ras

Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB)

Hahn-Meitner-Platz 1

14109 Berlin

Germany

Péter Ágoston

Technische Universität Darmstadt

Institut für Materialwissenschaft

Fachgebiet Materialmodellierung

Petersenstr. 23

64287 Darmstadt

Germany

Karsten Albe

Technische Universität Darmstadt

Institut für Materialwissenschaft

Fachgebiet Materialmodellierung

Petersenstr. 23

64287 Darmstadt

Germany

Jacobo Álvarez-García

Universitat de Barcelona

Department d'Electrònica

C. Martí i Franquès 1

08028 Barcelona

Spain

Marcus Bär

Renewable Energy Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB)

Hahn-Meitner-Platz 1

14109 Berlin

Germany

Jan Behrends

Berlin Joint EPR Lab

Institute for Nanospectroscopy Helmholtz-Zentrum Berlin für Materialen und Energie

Albert-Einstein-Str. 15

12489 Berlin

Germany

and

Berlin Joint EPR Lab Fachbereich Physik

Freie Universität Berlin Arnimallee 14

14195 Berlin

Germany

Wolfhard Beyer

Forschungszentrum Jülich GmbH

Institut für Energie- und Klimaforschung (IEK-5)

Photovoltaik

52428 Jülich

Germany

Karsten Bittkau

Forschungszentrum Jülich GmbH

Institut für Energie- und Klimaforschung (IEK-5)

Photovoltaik

52428 Jülich

Germany

Varvara Brackmann

Leibniz Institute for Solid State and Materials Research (IFW) Dresden

Institute for Complex Materials

Helmholtzstraße 20

01069 Dresden

Germany

Torsten Bronger

Forschungszentrum Jülich GmbH

Institut für Energie- und Klimaforschung (IEK-5)

Photovoltaik

52428 Jülich

Germany

Rudolf\, Brüggemann

Carl von Ossietzky Universität Oldenburg

Fakultät V-Institut für Physik

AG GRECO

Carl-von-Ossietzky-Str. 9-11

26111 Oldenburg

Germany

Marc Burgelman

Universiteit Gent

Vakgroep Elektronica en Informatiesystemen (ELIS)

St.-Pietersnieuwstraat 41

9000 Gent

Belgium

Raquel Caballero

Universidad Autónoma de Madrid

Departamento de Física Aplicada

Calle Francisco TomÁs y Valiente 7

28049 Madrid

Spain

Jose Chavez

The University of Texas at El Paso

Department of Electrical and Computer Engineering

500 West University Avenue

El Paso, TX 79968

USA

Oana Cojocaru-Mirédin

RWTH Aachen

I. Physikalisches Institut IA

Sommerfeldstraße 14

52074 Aachen

Germany

and

Max-Planck Institut für Eisenforschung GmbH

Max-Planck Straße 1

40237 Düsseldorf

Germany

Robert W. Collins

University of Toledo

Department of Physics and Astronomy

Wright Center for Photovoltaics Innovation and Commercialization (PVIC)

2801 West Bancroft Street

Toledo, OH 43606

USA

Koen Decock

Universiteit Gent

Vakgroep Elektronica en Informatiesystemen (ELIS)

St.-Pietersnieuwstraat 41

9000 Gent

Belgium

Carsten Deibel

Technische Universität Chemnitz

Institut für Physik

Optik und Photonik kondensierter Materie

insbesondere für Sensorik und Analytik (OPKM/212064)

09107 Chemnitz

Germany

Kaining Ding

Forschungszentrum Jülich GmbH

Institut für Energie- und Klimaforschung (IEK-5)

Photovoltaik

52428 Jülich

Germany

Florian Einsele

Forschungszentrum Jülich GmbH

Institut für Energie- und

Klimaforschung (IEK-5)

Photovoltaik

52428 Jülich

Germany

Matthias Fehr

Berlin Joint EPR Lab

Institut für Silizium-Photovoltaik

Helmholtz-Zentrum Berlin für Materialen und Energie Kekuléstr. 5

12489 Berlin

Germany

Andreas Gerber

Forschungszentrum Jülich GmbH

Institut für Energie- und Klimaforschung (IEK-5)

Photovoltaik

52428 Jülich

Germany

Rene Gunder

Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB)

Hahn-Meitner-Platz 1

14109 Berlin

Germany

Levent Gütay

Carl von Ossietzky University of Oldenburg

Department of Physics

Carl-von-Ossietzky-Straße 9-11

26129 Oldenburg

Germany

Jennifer Heath

Linfield College

900 SE Baker Street

McMinnville, OR 97128

USA

Marc Daniel Heinemann

Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB)

Hahn-Meitner-Platz 1

14109 Berlin

Germany

Clemens Heske

University of Nevada

Las Vegas (UNLV)

Department of Chemistry and Biochemistry

4505 S. Maryland Pkwy

Las Vegas, NV 89154-4003

USA

and

Institute for Photon Science and Synchrotron Radiation (IPS)

Institute for Chemical Technology and Polymer Chemistry (ITCP)

Karlsruhe Institute of Technology (KIT)

ANKA Synchrotron Radiation Facility

Hermann-von-Helmholtz-Platz 1

76344 Eggenstein-Leopoldshafen

Germany

Volker Hoffmann

Leibniz Institute for Solid State and Materials Research (IFW) Dresden

Institute for Complex Materials

Helmholtzstraße 20

01069 Dresden

Germany

Vito Huhn

Forschungszentrum Jülich GmbH

Institut für Energie- und Klimaforschung (IEK-5)

Photovoltaik

52428 Jülich

Germany

Víctor Izquierdo-Roca

IREC-Catalonia Institute for Energy Research

C Jardins de les Dones de Negre 1

08930 Sant Adria del Besos

Barcelona

Spain

Ana Kanevce

National Renewable Energy Laboratory

15013 Denver West Pkwy

Golden, CO 80401-3305

USA

Christian A. Kaufmann

Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB)/Kompetenzzentrum Dünnschicht- und Naontechnologie für Photovoltaik Berlin (PVcomB)

Schwarzschildstrasse 3

12489 Berlin

Germany

Prakash Koirala

University of Toledo

Department of Physics & Astronomy and Wright Center for Photovoltaics Innovation & Commercialization (PVIC)

2801 West Bancroft Street

Toledo, OH 43606

USA

Thomas Kirchartz

Forschungszentrum Jülich GmbH

Institut für Energie- und Klimaforschung (IEK-5)

Photovoltaik

52428 Jülich

Germany

and

Universität Duisburg-Essen

Fakultät für Ingenieurwissenschaften und CENIDE

47057 Duisburg

Germany

Denis Klemm

Sunfire GmbH

Gasanstaltstraße 2

01237 Dresden

Germany

Stephan Lehnen

Forschungszentrum Jülich GmbH

Institut für Energie- und Klimaforschung (IEK-5)

Photovoltaik

52428 Jülich

Germany

Jian Li

University of Toledo

Department of Physics and Astronomy

Wright Center for Photovoltaics Innovation and Commercialization (PVIC)

2801 West Bancroft Street

Toledo, OH 43606

USA

Klaus Lips

Berlin Joint EPR Lab

Institute for Nanospectroscopy Helmholtz-Zentrum Berlin für Materialen und Energie

Albert-Einstein-Str. 15

12489 Berlin

Germany

and

Berlin Joint EPR Lab Fachbereich Physik

Freie Universität Berlin Arnimallee 14

14195 Berlin

Germany

Roland Mainz

Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB)

Hahn-Meitner-Platz 1

14109 Berlin

Germany

Sylvain Marsillac

Old Dominion University

Department of Electrical and Computer Engineering

Virginia Institute of Photovoltaics

231 Kaufman Hall

Norfolk, VA 23529

USA

Wyatt K. Metzger

National Renewable Energy Laboratory

15013 Denver West Pkwy

Golden, CO 80401-3305

USA

Thomas Christian Mathias Müller

Forschungszentrum Jülich GmbH

Institut für Energie- und Klimaforschung (IEK-5)

Photovoltaik

52428 Jülich

Germany

Melanie Nichterwitz

Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB)

Hahn-Meitner-Platz 1

14109 Berlin

Germany

Tim Nunney

Thermo Fisher Scientific

The Birches Industrial Estate Imberhorne Lane

East Grinstead

West Sussex RH19 1UB

UK

Ulrich W. Paetzold

Forschungszentrum Jülich GmbH

Institut für Energie- und Klimaforschung (IEK-5)

Photovoltaik

52428 Jülich

Germany

and

IMEC v.z.w.

Kapeldreef 75

3001 Leuven

Belgium

Alejandro Pérez-Rodríguez

Universitat de Barcelona

Department d'Electrònica

C. Martí i Franquès 1

08028 Barcelona

Spain

and

IREC-Catalonia Institute for Energy Research

C Jardins de les Dones de Negre 1

08930 Sant Adria del Besos

Barcelona

Spain

Bart E. Pieters

Forschungszentrum Jülich GmbH

Institut für Energie- und Klimaforschung (IEK-5)

Photovoltaik

52428 Jülich

Germany

Paul Pistor

IREC-Catalonia Institute for Energy Research

Jardins de les Dones de Negre 1

08930 Sant Adrià de Besòs

Barcelona

Spain

and

Martin Luther University Halle-Wittenberg

Photovoltaics Group/ Institute of Physics

Von-Danckelmann-Platz 3

06120 Halle (Saale)

Germany

Nikolas J. Podraza

University of Toledo

Department of Physics and Astronomy

Wright Center for Photovoltaics Innovation and Commercialization (PVIC)

2801 West Bancroft Street

Toledo, OH 43606

USA

Johan Pohl

Technische Universität Darmstadt

Institut für Materialwissenschaft

Fachgebiet Materialmodellierung

Petersenstr. 23

64287 Darmstadt

Germany

Uwe Rau

Forschungszentrum Jülich GmbH

Institut für Energie- und Klimaforschung (IEK-5)

Photovoltaik

52428 Jülich

Germany

Angus A. Rockett

University of Illinois

Department of Materials Science and Engineering

1304 W. Green Street

Urbana, IL 61801

USA

Manuel J. Romero

National Renewable Energy Laboratory

1617 Cole Blvd.

Golden, CO 80401-3305

USA

Sascha Sadewasser

INL-International Iberian Nanotechnology Laboratory

Laboratory for Nanostructured Solar Cells

Av. Mestre José Veiga s/n

4715-330 Braga

Portugal

Roland Scheer

Martin-Luther-University Halle-Wittenberg

Photovoltaics Group/ Institute of Physics

Von-Danckelmann-Platz 3

06120 Halle (Saale)

Germany

Thomas Schmid

Federal Institute for Materials Research and Testing

Richard-Willstätter-Str. 11

12489 Berlin

Germany

Sebastian S. Schmidt

Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB)

Hahn-Meitner-Platz 1

14109 Berlin

Germany

Susan Schorr

Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB)

Hahn-Meitner-Platz 1

14109 Berlin

Germany

and

Freie Universität Berlin

Department for Geosciences

Malteserstr. 74-100

12249 Berlin

Germany

Michelle N. Sestak

University of Toledo

Department of Physics and Astronomy

Wright Center for Photovoltaics Innovation and Commercialization (PVIC)

2801 West Bancroft Street

Toledo, OH 43606

USA

Rolf Stangl

National University of Singapore

Solar Energy Research Institute of Singapore (SERIS)

Novel Cell Concepts & Simulation

7 Engineering Drive 1

Block E3A, #06-01

117574 Singapore

Singapore

Christiane Stephan

Bundesanstalt für Materialforschung und-prüfung (BAM)

Unter den Eichen 87

12200 Berlin

Germany

Daniel M. Többens

Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB)

Hahn-Meitner-Platz 1

14109 Berlin

Germany

Tobias Törndahl

Uppsala University

Solid State Electronics

PO Box 534

751 21 Uppsala

Sweden

Thomas Unold

Structure and Dynamics of Energy Materials

Helmholtz-Zentrum Berlin für Materialien und Energie GmbH

Hahn-Meitner Platz 1

4109 Berlin

Germany

Cornel Venzago

AQura GmbH

Rodenbacher Chaussee 4

63457 Hanau

Germany

Iris Visoly-Fisher

Ben-Gurion University of the Negev

Swiss Institute for Dryland Environmental and Energy Research

Jacob Blaustein Institutes for Desert Research

Sede Boqer Campus

Department of Solar Energy and Environmental Physics

8499000 Midreshet Ben-Gurion

Israel

Lothar Weinhardt

University of Nevada

4505 S. Maryland Pkwy

Las Vegas (UNLV)

Department of Chemistry and Biochemistry

Las Vegas, NV 89154-4003

USA

and

Institute for Photon Science and Synchrotron Radiation (IPS)

Institute for Chemical Technology and Polymer Chemistry (ITCP)

Karlsruhe Institute of Technology (KIT)

ANKA Synchrotron Radiation Facility

Hermann-von-Helmholtz-Platz 1

76344 Eggenstein-Leopoldshafen

Germany

Thomas Wirth

Bundesanstalt für Materialforschung und-prüfung

Unter den Eichen 87

12205 Berlin

Germany

Pawel Zabierowski

Warsaw University of Technology

Koszykowa 75

00-662 Warsaw

Poland

Xiaowang Zhou

Sandia National Laboratories

Mechanics of Materials Department

7011 East Avenue

Livermore, CA 94550

USA

David Zubia

The University of Texas at El Paso

Department of Electrical and Computer Engineering

500 West University Avenue

El Paso, TX 79968

USA

Preface of the First Edition

Inorganic thin-film photovoltaics is a very old research topic with a scientific record of more than 30 years and tens of thousands of published papers. At the same time, thin-film photovoltaics is an emerging research field due to technological progress and the subsequent tremendous growth of the photovoltaic industry during recent years. As a consequence, many young scientists and engineers enter the field not only because of the growing demand for skilled scientific personnel but also because of the many interesting scientific and technological questions that are still to be solved. As a consequence, there is a growing demand for skilled scientific staff entering the field who will face a multitude of challenging scientific and technological questions. Thin-film photovoltaics aims for the highest conversion efficiencies and lowest possible cost. Therefore, a profound understanding of corresponding solar-cell devices and photovoltaic materials applied is a major prerequisite for any further progress in this challenging field.

In recent years, a wide and continuously increasing variety of sophisticated and rather specialized analysis techniques originating from very different directions of physics, chemistry, or materials science have been applied in order to extend the scientific base of thin-film photovoltaics. This increasing specialization is a relatively new phenomenon in the field of photovoltaics where during the “old days” everyone was (and had to be) able to handle virtually every scientific method personally. Consequently, it becomes nowadays more and more challenging for the individual scientist to keep track with the results obtained by specialized analysis methods, the physics behind these methods, and their implications for the devices.

The need for more communication and exchange especially among scientists and PhD students working in the same field but using very different techniques was more and more rationalized during recent years. As notable consequences, very well-attended “Young Scientist Tutorials on Characterization Techniques for Thin-Film Solar Cells” were established at Spring Meetings of the Materials Research Society and the European Materials Research Society. These tutorials were especially dedicated to mutual teaching and open discussions.

The present handbook aims to follow the line defined by these tutorials, providing concise and comprehensive lecture-like chapters on specific research methods, written by researchers who use these methods as the core of their scientific work and who at the same time have a precise idea of what is relevant for photovoltaic devices. The chapters are intended to focus on the specific methods more than on significant results. This is because these results, especially in innovative research areas, are subject to rapid change and are better dealt with by review articles. The basic message of the chapters in the present handbook focuses more on how to use the specific methods, on their physical background, and especially on their implications for the final purpose of the research, that is, improving the quality of photovoltaic materials and devices.

Therefore, the present handbook is not thought as a textbook on established standard (canonical) methods. Rather, we focus on emerging, specialized methods that are relatively new in the field but have a given relevance. This is why the title of the book addresses “advanced” techniques. However, new methods also need to be judged by their implication for photovoltaic devices. For this reason, an introductory chapter (Chapter 1) will describe the basic physics of thin-film solar cells and modules and also guide to the specific advantages that are provided by the individual methods. In addition, we have made sure that the selected authors not only are established specialists concerning a specific method but also have long-time experience dealing with solar cells. This ensures that in each chapter, the aim of the analysis work is kept on the purpose of improving solar cells.

The choice of characterization techniques is not intended for completeness but should be a representative cross section through scientific methods that have a high level of visibility in the recent scientific literature. Electrical device characterization (Chapter 2), electroluminescence (Chapter 3), photoluminescence (Chapter 7), and capacitance spectroscopy (Chapter 4) not only are standard optoelectronic analysis techniques for solid-state materials and devices but also are well established and of common use in their specific photovoltaic context. In contrast, characterization of light trapping (Chapter 5) is an emerging research topic very specific to the photovoltaic field. Chapters 6, 8, and 9 deal with ellipsometry, the steady-state photocarrier grating method, and time-of-flight analysis, which are dedicated thin-film characterization methods. Steady-state photocarrier grating (Chapter 8) and time-of-flight measurements (Chapter 9) specifically target the carrier transport properties of disordered thin-film semiconductors. Electron spin resonance (Chapter 10) is a traditional method in solid-state and molecule physics, which is of particular use for analyzing dangling bonds in disordered semiconductors.

The disordered nature of thin-film photovoltaic materials requires analysis of electronic, structural, and compositional properties at the nanometer scale. This is why methods such as scanning probe techniques (Chapter 11) as well as electron microscopy and its related techniques (Chapter 12) gain increasing importance in the field. X-ray and neutron diffraction (Chapter 13) and Raman spectroscopy (Chapter 14) contribute to the analysis of structural properties of photovoltaic materials. Since thin-film solar cells consist of layer stacks with interfaces and surfaces, important issues are the analyses of their chemical and electronic properties, which may be studied by means of soft X-ray and electron spectroscopy (Chapter 15). Important information for thin-film solar-cell research and development is the elemental distributions in the layer stacks, analyzed by various techniques presented in Chapter 16. Specifically for silicon thin-film solar cells, knowledge about hydrogen incorporation and stability is obtained from hydrogen effusion experiments (Chapter 17).

For designing photovoltaic materials with specific electrical and optoelectronic properties, it is important to predict these properties for a given compound. Combining experimental results from materials analysis with those from ab initio calculations based on density functional theory provides the means to study point defects in photovoltaic materials (Chapter 18). Finally, in order to come full circle regarding the solar-cell devices treated in the first chapters of the handbook, the information gained from the various materials analyses and calculations may now be introduced into one-dimensional (Chapter 19) or multidimensional device simulations (Chapter 20). By means of carefully designed optical and electronic simulations, photovoltaic performances of specific devices may be studied even before their manufacture.

We believe that the overview of these various characterization techniques is useful not only for colleagues engaged in the research and development of inorganic thin-film solar cells, from which the examples in the present handbook are given, but also for those working with other types of solar cells and optoelectronic, thin-film devices.

The editors would like to thank all authors of this handbook for their excellent and (almost) punctual contributions. We are especially grateful to Ulrike Fuchs and Anja Tschörtner, Wiley-VCH, for helping in realizing this book project.

Berlin, Germany; London, UK; and Jülich, Germany

August 2010

Daniel Abou-Ras,Thomas Kirchartz,and Uwe Rau