Earth-Abundant Materials for Solar Cells

Preface
Abbreviations and Acronyms
1 Introduction
1.1 Natural Abundance of Elements in the Earth's Crust
1.1.1 Chemical Elements
1.1.2 Solar Cells and Earth-Abundant Materials
1.2 Solar Radiation Spectrum
1.3 Shockley?{Queisser Efficiency Limit
1.4 Fundamental Properties of Photovoltaic Semiconductor Materials
1.5 Solar Cell Device Characteristics
1.6 Prediction of Physical Properties for Complex Material System
1.6.1 An Effective-Medium Approximation
1.6.2 An Interpolation Scheme
References
2 Structural Properties
2.1 Grimm?{Sommerfeld Rule
2.2 Crystal Structure
2.2.1 Crystal Structure
2.2.2 Theoretical Phase Stability
2.3 Lattice Constant and Related Parameters
2.3.1 Bulk Material
(a) Quaternary material
(b) Solid solution
(c) External perturbation effect
(d) Heteroepitaxy
2.3.2 Nanocrystalline Material
(a) Quaternary material
(b) Solid solution
2.4 Structural Phase Transition
References
3 Thermal Properties
3.1 Phase Diagram
3.1.1 Cu2Zn?{IV?{VI4 Quaternary
3.1.2 Cu2Cd?{IV?{VI4 Quaternary
3.1.3 Cu2Hg?{IV?{VI4 Quaternary
3.1.4 Cu2?{II?{IV?{VI4 Solid Solution
3.2 Melting Point
3.3 Specific Heat
3.4 Debye Temperature
3.5 Thermal Expansion Coefficient
3.6 Thermal Conductivity
3.6.1 Quaternary Material
3.6.2 Alloy Material
(a) Theoretical model
(b) Analysis
3.7 Thermal Duffusivity
References and Notes
4 Elastic, Mechanical and Lattice Dynamic Properties
4.1 Elastic Constant
4.1.1 General Remark
4.1.2 Theoretical Value
4.1.3 Yang's Modulus, Poisson's Ratio and Similar
4.1.4 Sound Velocity
4.2 Microhardness
4.3 Lattice Dynamic Properties
4.3.1 Phonon Dispersion Relation
4.3.2 Raman Scattering: Tetragonal Lattice
4.3.3 Raman Scattering: Orthorhombic Lattice
4.3.4 Effect of Atomic Mass on Phonon Frequency
4.3.5 Raman Scattering: Solid Solution
(a) General remark
(b) Experimental data
4.3.6 Raman Scattering: Excitation Wavelength Dependence
(a) Theoretical consideration
(b) Experimental data
4.3.7 Far-IR Spectroscopy
4.3.8 External Perturbation Effect
(a) Theoretical consideration
(b) Experimental data
4.3.8 Nanocrystalline Material
(a) General remark
(b) Experimental data
References
5 Electronic Energy-Band Structure
5.1 General Remark
5.1.1 Energy-Band Structure
(a) Tetragonal material
(b) Orthorhombic material
5.1.2 ?·-Point Energy-Band Scheme
5.1.3 Band-Gap Energy: External Perturbation and Doping Effects
(a) Temperature effect
(b) Pressure effect
(c) Doping effect
5.1.4 Effective Mass: External Perturbation and Doping Effects
5.2 Lowest Indirect and Direct Band-Gap Energies
5.2.1 Quaternary Material
5.2.2 Solid Solution
5.3 Higher-Lying Band-Gap Energy
5.4 External Perturbation Effect on the Band-Gap Energy: Experimental Data
5.5 Effective Mass
5.5.1 Electron Effective Mass
5.5.2 Hole Effective Mass
5.6 Nanocrystalline Band-Gap Energy
5.6.1 Quaternary Material
5.6.2 Solid Solution
5.7 Heterojunction Band Offset
5.7.1 General Consideration
5.7.2 Theoretical Value
5.7.3 Experimental Value
(a) Window/buffer heterojunction material system
(b) Buffer/absorber heterojunction material system
(c) Window/buffer/Cu2?{II?{IV?{VI4 solar cell structure
5.8 Electron Affinity
5.9 Schottky Barrier Height
References
6 Optical Properties
6.1 General Remark
6.1.1 Dielectric Permittivity: Tensor Representation
6.1.2 Optical Dispersion Relation
(a) Basic expression
(b) Optical sum rule
6.1.3 Optical Spectrum: Classification into Several Regions
6.2 The Reststrahlen Region
6.2.1 Static and High-Frequency Dielectric Constants
6.2.2 Reststrahlen Spectrum
(a) Theoretical expression
(b) Experimental data
6.3 At or Near the Fundamental Absorption Edge
6.3.1 Exciton Parameter
(a) Theoretical expression
(b) Experimental data
6.3.2 Optical Absorption
(a) Free-carrier, IVB and ICB absorptions
(b) At the direct absorption edge: Theoretical expression
(c) At the indirect absorption edge: Theoretical expression
(d) Urbach's tail
(e) Experimental data
6.3.3 Refractive Index
(a) Theoretical expression
(b) Experimental data
6.4 The Interband Transition Region
6.4.1 Model Dielectric Function
6.4.2 Optical Spectrum and MDF Analysis
6.4.3 Optical Absorption Spectrum
6.4.4 Optical Constant in the 0?n?{?n10000 eV Spectral Region
References
7 Carrier Transport Properties
7.1 Electron Transport Properties
7.2 Hole Hall Mobility
7.2.1 General Remark
7.2.2 Room-Temperature Value
7.2.3 Temperature Dependence
7.2.4 Effect of Stoichiometry, Alloying and Foreign Atom Doping
(a) Effect of stoichiometry
(b) Effect of alloying
(c) Affect of foreign atom doping
7.3 Electrical Resistivity
7.3.1 Free-Hole Conduction
(a) Quaternary material
(b) Solid solution
7.3.2 Hopping Conduction
7.3.3 Transport in Degenerate Band
7.3.4 Insulator-to-Metal Transition
7.4 Minority-Carrier Transport
7.4.1 Minority-Electron Mobility
7.4.2 Minority-Electron Lifetime and Diffusion Length
(a) Quaternary material
(b) Solid solution
7.5 Effect of Grain Boundary
7.6 Proposal: Graded-Absorber Solar Cell Structure
7.7 Proposal: Controlling Transport Properties of Bulk Material by Heat Treatment
References
Appendix A Summary: Physical Properties of CZTS and CZTSe
Appendix B Summary: Physical Properties of c-CdS, w-CdS and ZnO
References
Appendix C Optical Constants of Some Cu2?{II?{IV?{VI4 Quaternary Semiconductors:
In Tables
References
Appendix D Optical Constants of c-CdS, w-CdS and ZnO
References
Subject Index