Introduction to Light Trapping in Solar Cell and Photo-detector Devices

By Stephen Fonash

New Approaches to Light Trapping in Solar Cell Devices discusses in detail the use of photonic and plasmonic effects for light trapping in solar cells. It compares and contrasts texturing, the current method of light-trapping design in solar cells, with emerging approaches employing photonic and plasmonic phenomena. These new light trapping methods reduce the amount of absorber required in a solar cell, promising significant cost reduction and efficiency.

This book highlights potential advantages of photonics and plasmonics and describes design optimization using computer modeling of these approaches. Its discussion of ultimate efficiency possibilities in solar cells is grounded in a review of the Shockley-Queisser analysis; this includes an in-depth examination of recent analyses building on that seminal work.

• Language: English
• Publisher: Academic Press
• Release date: Sep 15, 2014
• ISBN: 9780124166370

Stephen Fonash

Dr. Stephen Fonash is Bayard D. Kunkle Chair Professor Emeritus of Engineering Sciences at Penn State University and Chief Technology Officer of Solarity LCCM, LLC. His activities at Penn State include serving as the director of Penn State’s Center for Nanotechnology Education and Utilization (CNEU), director of the National Science Foundation Advanced Technology Education Center, and director of the Pennsylvania Nanofabrication Manufacturing Technology Partnership. Prof. Fonash’s education contributions focus on nanotechnology post-secondary education and workforce development. His research activities encompass the processing and device physics of micro- and nanostructures including solar cells, sensors, and transistors. He has published over 300 refereed papers in the areas of education, nanotechnology, photovoltaics, microelectronics devices and processing, sensors, and thin film transistors. His book “Solar Cell Device Physics” has been termed the “bible of solar cell physics” and his solar cell computer modeling code AMPS is used by almost 800 groups around the world. Dr. Fonash holds 29 patents in his research areas, many of which are licensed to industry. He is on multiple journal boards, serves as an advisor to university and government groups, has consulted for a variety of firms, and has co-founded two companies. Prof. Fonash received his Ph.D. from the University of Pennsylvania. He is a Fellow of the Institute of Electrical and Electronics Engineers and a Fellow of the Electrochemical Society

Book preview

Introduction to Light Trapping in Solar Cell and Photo-detector Devices

Stephen J. Fonash

Table of Contents

Cover

Title page

Copyright Page

Dedication

Preface

Chapter 1: A Brief Overview of Phenomena Involved in Light Trapping

Abstract

1.1. Interference

1.2. Scattering

1.3. Reflection

1.4. Diffraction

1.5. Plasmonics

1.6. Refraction

Chapter 2: Modes and Hybridization

Abstract

2.1. Introductory comments

2.2. Radiation modes

2.3. Trapped traveling modes: guided modes

2.4. Trapped traveling modes: Bloch modes

2.5. Trapped localized modes: Mie modes and plasma modes

Chapter 3: Light-Trapping Structures

Abstract

3.1. Introduction

3.2. Planar structures with ARCs

3.3. Planar structures with randomly textured surfaces

3.4. Structures with nanoelement arrays

3.5. Structures with plasmonic effects

Chapter 4: Summary

Abstract

4.1. The current picture

4.2. Some future directions?

4.3. Overview

Appendix A: Yablonovitch Limit Derivation

Appendix B: Fresnel Equations for the Situation of Section 2.2

Appendix C: Index of Refraction, Permittivity, and Absorption Coefficient

References

Copyright Page

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ISBN: 978-0-12-416649-3

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Dedication

To Evan, Nina, Leo, and Alec – and their parents – and to their grandmother Joyce

Preface

I have been very involved in light trapping and carrier collection in solar cells for quite some time. While these two phenomena are really very intertwined, as I discussed in my 2010 Elsevier book Solar Cell Device Physics, this work concentrates on the light-trapping aspect. The attempt here is to look systematically at light trapping and to explore, in a short and concise manner, how it can be accomplished. Polarization effects are only very briefly mentioned since the intent is to capture the essence of light trapping. My interest is solar cells but photo-detectors are mentioned explicitly here and there and the applicability of the discussion to such devices should be obvious.

I am very indebted to Drs Atilla Ozgur Cakmak and Nghia Dai Nguyen here at Penn State for their support and aid in this project. Both contributed to the computer modeling results used, and Dr Cakmak was particularly helpful in looking at special computer cases and in proof-reading the text. My appreciation also goes to Renee Lindenberg for her assistance and patience in getting this book together.

The level intended for this work is that of engineering and science seniors, practicing engineers, and first-year graduate students. I tried to go easy on the mathematics and to concentrate on bare-bones physics. Hopefully I did that effectively.

Chapter 1

A Brief Overview of Phenomena Involved in Light Trapping

Abstract

Light trapping is the capturing of photons for use in applications such as solar cells, sensing, photo-electrochemistry, and thermal photovoltaics. Light enters the structures involved in these applications through refraction, scattering, or the systematic scattering provided by diffraction. The chapter examines these entry paths and the various optical processes that can be present in a light trapping structure.

Keywords

light absorption

light trapping

solar cells

photovoltaics

photodetectors

photons

radiation modes

trapped traveling modes

trapped localized modes

Light trapping is the capturing of as many photons as possible from an impinging electro-magnetic (E-M) wave with the objective of generating heat or charge carriers, excitons, or both [1]. For our purposes, the light being trapped may lie anywhere in that part of the E-M spectrum extending from the infrared to the ultraviolet.