Modelling and Design of Nanostructured Optoelectronic Devices: Solar Cells and Photodetectors

Preface
	Optoelectronic Design: State of the Art and Challenges
	Model-Based Design of Experiments
	The Finite Element Method of Simulation
Synopsis
Contents
About the Authors
List of Figures
List of Tables
1 Introduction
	1.1 Photonic Components: A Historical Perspective and Examples from Nature
		1.1.1 Light Sources
		1.1.2 Light Sensing Elements
		1.1.3 Light Transporting Elements
	1.2 Introduction to Semiconductor Optoelectronic Devices
		1.2.1 Light Sources
		1.2.2 Light Sensing Devices
		1.2.3 Optical Interconnects
	1.3 Summary
	References
2 Nanomaterials in Optoelectronics
	2.1 Introduction
	2.2 Light Management for Improved Absorption
		2.2.1 Dielectric Structures
		2.2.2 Metallic Gratings
		2.2.3 Metallic Nanoparticles
	2.3 Hierarchical Structures in Photonics and Optoelectronics
	2.4 Outlook: The Need for Numerical Design Approaches
	References
3 Introduction to Photovoltaic Devices
	3.1 Working Principles of Photovoltaic Devices
		3.1.1 Charge Generation
		3.1.2 Charge Separation
		3.1.3 Charge Collection
	3.2 Types of Photovoltaic Devices
		3.2.1 p-n Junction Solar Cells
		3.2.2 Thin-Film Solar Cells
	3.3 Photovoltaic Device Performance
		3.3.1 Measurements Under Broadband Excitation
		3.3.2 Measurements Under Spectrally Resolved Optical Excitation
		3.3.3 Parasitic Resistances
	3.4 Equivalent Circuit Models of Photovoltaic Devices
	3.5 Theoretical Limits to Performance and Ways to Extend These Limits
		3.5.1 Optical Losses
		3.5.2 Charge Carrier Losses
		3.5.3 Thermal Losses
	3.6 Other Operational and Environmental Factors
	3.7 Summary
	References
4 Introduction to Photodetectors
	4.1 Types of Photodetectors and Working Principles
		4.1.1 p-n Junction Photodetectors
		4.1.2 p-i-n Photodetectors
		4.1.3 Avalanche Photodetectors
	4.2 Photodetector Performance
		4.2.1 Shunt Resistance
		4.2.2 Quantum Efficiency
		4.2.3 Responsivity
		4.2.4 Response Time
		4.2.5 Bandwidth
		4.2.6 Noise Characteristics
		4.2.7 Spectral Uniformity
		4.2.8 Linearity
	4.3 Theoretical Limits to Performance and Ways to Extend These Limits
		4.3.1 Optical Losses
		4.3.2 Electrical Losses
		4.3.3 Thermal Losses
	4.4 Summary
	References
5 Waves and Electromagnetics
	5.1 Introduction to Waves
		5.1.1 Plane Waves
		5.1.2 Applicability of Plane Wave Solutions: Need for Numerical Solution Methods
	5.2 Electromagnetic Waves and Maxwell’s Equations
		5.2.1 Maxwell’s Equations
		5.2.2 The Electromagnetic Wave Equations for General Anisotropic Media
		5.2.3 Electromagnetic Waves in Isotropic Media
		5.2.4 Time Harmonic Solutions in Isotropic Materials
		5.2.5 Plane Waves in Isotropic Materials
		5.2.6 Electromagnetic Material Properties
	5.3 Boundary Conditions in Electromagnetic Simulations
		5.3.1 Perfect Electric Conductor and Perfect Magnetic Conductor Boundary Conditions
		5.3.2 Boundary Conditions for the Normal Components of Fields
		5.3.3 Periodic Boundaries
		5.3.4 Transparent Boundary Conditions
		5.3.5 Input Boundaries
	5.4 Poynting’s Theorem: Energy, Power, Link to Exciton Generation
	5.5 Summary
	References
6 The Semiclassical Charge Transport Model and Its Extension to Organic Semiconductors
	6.1 Introduction
	6.2 Describing Charge Transport
		6.2.1 The Quantum Mechanical Approach
		6.2.2 The Semiclassical Particle Approach
		6.2.3 The Ensemble Semiclassical Approach
	6.3 The Boltzmann Transport Equation
	6.4 From the BTE to the Equations of Charge Transport
	6.5 The Drift–Diffusion Model for Charge Transport
	6.6 Boundary Conditions
		6.6.1 Contact Boundaries
		6.6.2 Non-contact Boundaries
		6.6.3 The Physical Implications of Ideal Boundary Conditions
	6.7 Validity of the Semiclassical Charge Transport Model
	6.8 Charge Transport Modeling for Organic Photovoltaic Devices
	6.9 Summary
	References
7 Finite Element Modeling of Organic Photovoltaic Devices
	7.1 Introduction
	7.2 Modeling Approach
		7.2.1 Assumptions
	7.3 Device Geometry, Equations, and Boundary Conditions
		7.3.1 Optical Transport Simulations
		7.3.2 Charge Transport Simulations
	7.4 Material Properties
		7.4.1 Optical Properties: Refractive Index Spectra
		7.4.2 Electronic Properties
	7.5 Finite Element Model Implementation
	7.6 Physical Quantities of Interest
		7.6.1 Exciton Generation Rate
		7.6.2 Optical Absorptance
		7.6.3 Absorbed Photon Flux
		7.6.4 The J-V Curve
	7.7 Simulation of Optoelectronic Behavior of a Planar BHJ Solar Cell
		7.7.1 Simulation Parameters
		7.7.2 Mesh Convergence
		7.7.3 Analysis of Results
	7.8 Summary
	References
8 Bio-inspired Nanostructures for Optoelectronic Enhancement in Photovoltaics
	8.1 Introduction
	8.2 Nanostructured Photovoltaic Design: Motivation and Preliminary Analyses
		8.2.1 Why a Nanostructured Substrate?
	8.3 Bio-inspired Nanostructured Design for OPVs
		8.3.1 Device Architectures
		8.3.2 Morphological Characteristics of the Monolithic Nanostructured Substrates
		8.3.3 Optical Characteristics of the Molded Nanostructured Substrates
		8.3.4 Design Rules for Enhanced Optoelectronic Performance
		8.3.5 Experimental Validation of Optoelectronic Performance
		8.3.6 Enhancement Mechanisms
	8.4 Summary
	References
9 Hierarchical Structures and Multiscale Optical Design: Unconventional Modes of Confined Optical Transport for Better Photodetectors
	9.1 Introduction
	9.2 Hierarchically Structured Materials
		9.2.1 General Overview
		9.2.2 Hierarchical Structures in Photonics and Optoelectronics
	9.3 Defective Nanoscale Arrays with Microscale Discontinuities
	9.4 Optoelectronic Spectral Shaping Using Multiscale Hierarchical Structures
		9.4.1 Motivation
		9.4.2 Nanostructured and Hierarchically Structured Waveguide Substrates: Multiscale Optical Coupling for Better Spectral Uniformity
		9.4.3 Multiscale Optical Transport: Strain-Assisted Fabrication, Optical Measurements, and Optoelectronic Spectral Measurements
	9.5 Summary
	References
10 Summary and Concluding Remarks
Appendix A Understanding Perfectly Matched Layers
Reference
Appendix B Fabrication Procedure: Planar and Nanostructured Molded Transparent Substrates and Organic Photovoltaic Devices
B.1 Fabrication of Molded Nanostructured Substrates
B.2 Fabrication of Organic Photovoltaic Devices on the Epoxy Substrates
Reference