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Solar Cell Radiation Handbook

Electronics, Instrumentation Design and Engineering

Solar Cell Radiation Handbook
J. R. Carter, Jr.
TRW Systems Group
National Aeronautics and
Space Administration
Jet Propulsion Laboratory
California Institute of Technology
396 Pages

Open: Solar Cell Radiation Handbook
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The purpose of this document is to detail a method of predicting the degradation of a solar array in a space radiation environment. The text contains a discussion of solar cell technology which emphasizes the cell parameters which degrade in a radiation environment. The experimental techniques used in the evaluation of radiation effects are discussed. In Chapter 3, the theoretical aspects of radiation damage are discussed, and the experimental d a t a , on which the concept of damage equivalent 1-MeV electron influence is based, are presented. In Chapter 4, the methods of developing relative damage coefficients from the experimental data are detailed. In this regard, it was found necessary to institute two separate equivalent fluences to properly describe the changes of solar cell parameters under space proton irradiation.

Chapter 5 concerns the nature of the space radiation environment and contains predicted solar flare proton fluences for the twenty-first solar cycle based on a proposed model . In Chapter 6 , the method of calculating equivalent fluence from electron and proton energy spectrums and re1ative damage coefficients is detailed. In addition, computercalculated equivalent fluence contributions from trapped electrons and protons are tabulated for an extensive series of circular earth orbits. The estimated annual equivalent fluence contributions due to solar flare protons are tabulated for the remainder of the current solar cycle. The estimation of degraded solar cell output characteristics from equivalent fluence values is discussed. In Chapter 7, flight data from satellites is compared with estimated degradation.

TOC

PREFACE TO THE FIRST EDITION
TABLE OF CONTENTS
FIGURES
TABLES xv
1.0 THEORY OF THE SILICON SOLAR CELL
1 1 Semi conductor Theory
1.1.1 Thermal Equil i briurn Relationships and Excess Densities
1.2 The P-N Junction
1.3 Silicon Solar Cell Theory
1.4 Solar Cell Coatings and Contacts
1.5 Improvement o f Solar Cell Efficiency
1.5.1 Considerations for Photovol tai c Materials
1.5.2 Violet Cell
1.5.3 Back Surface Field (BSF) Cells
1.5.4 Textured Surface (or Black) Cel ls

2.0 INSTRUMENTATION TECHNIQUES FOR MEASUREMENT OF SOLAR CELL PARAMETERS
2.1 Light Sources and Solar Simulators
2.2 Current-Vol tage Characteristics
2.3 Spectral Response Measurements
2.4 Irradiation Methods
2.5 Diffusion Length Measurement
2.6 S t a t i s t i c a l and Error Analysis

3.0 RADIATION EFFECTS
3.7 The Theory bf Radiation Damage
3.2 Theory of S i l i c o n Solar C e l l Damage
3.3 The Concept o f Damage Equivalence
3.4 One MeV Electron I r r a d i a t i o n o f S i l i c o n Solar Cells . .
3.5 E f f e c t o f Electron Energy on Solar Cell Degradation . .
3.6 Effect o f Proton Energy on Solar Cell Degradation
3.7 Additional Effects of Low Energy Protons
3.8 Effects o f Temperature and Ill urnination I n t e n s i t y on Radiation Damage
3.8.1 Unirradiated Cells
3.8.2 Irradiated Cells
3.9 Effects o f Neutron and Gamma Radiation on Solar Cells
3.10 Lithium Doped Solar Cells
3.11 Radiation Effects on Shielding Materials
3.12 Solar Cell Degradation vs 1 MeV Electrons

4.0 RELATIVE DAMAGE COEFFICIEI4TS FOR SPACE RADIATION
4.7 Geometrical Aspects of Radiation Fluence
4.2 Effect of Shielding on Radiation
4.3 Electron Space Radiation Effects
4.4 Proton Space Effects
4.5 Alpha Particle Space Radiation Effects
4.6 A1ternative Approaches

5.0 THE SPACE RADIATION ENVIRONMENT
5.1 Geomagnetically Trapped Radiation
5.1.1 Trapped Protons
5.1.2 Trapped Electrons
5.2 Orbital Integration
5.2.2 Trajectories Other Than Circular Orbits
5.3 Cosmic-Ray (Galactic Cosmic-Ray) Radiation
5.4 Solar Flare (Solar Cosmic-Ray) Radiation

6.0 SOLAR ARRAY DEGRADATION CALCULATIONS
6.1 General Procedure. Equivalent Fluence
6.2 Effect of Reduced Light Transmission on Solar Cell Response
6.3 Rough Degradation Calculations
6.4 Computer Calculated Equivalent Fluence
6.5 Solar Array Degradation

7.0 FLIGHT DATA 7-1
7.7 Flight Data at Synchronous O r b i t . . . . . . . . . . . 7-3
7.2 Flight Data at Other Than Synchronous O r b i t . . . . . . 7-15
REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-23
APPENDIX A: SHIELDING THICKNESS CONVERSIONS . . . . . . . . . . . A-1
APPENDIX B: CONSTANTS. PROPERTIES AND VALUES . . . . . . . . . . 3-1
APPENDIX C: SOLAR CELL TYPES . . . . . . . . . . . . . . . . . . C-1
APPENDIX D: COMPUTER PROGRAM. EQFRUX D-1