HIGH-EFFICIENCY SPACE AND TERRESTRIAL MULTIJUNCTION SOLAR CELLS THROUGH BANDGAP CONTROL IN CELL STRUCTURES Richard R. King, Chris M. Fetzer, Peter C. Colter, Ken M. Edmondson, James H. Ermer, Hector L. Cotal, Hojun Yoon, Alex P. Stavrides, Geoff Kinsey, Dimitri D. Krut, N. H. Karam Presented at the 29 th IEEE Photovoltaic Specialists Conference – New Orleans, Louisiana, May 20-24, 2002 Presented by Parth Bhide
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Richard R. King, Chris M. Fetzer, Peter C. Colter, Ken M. Edmondson, James H. Ermer, Hector L. Cotal, Hojun Yoon, Alex P. Stavrides, Geoff Kinsey, Dimitri.
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HIGH-EFFICIENCY SPACE AND TERRESTRIAL MULTIJUNCTION SOLAR CELLS THROUGH BANDGAP CONTROL IN CELL STRUCTURES
Richard R. King, Chris M. Fetzer, Peter C. Colter, Ken M. Edmondson, James H. Ermer, Hector L. Cotal, Hojun Yoon, Alex P. Stavrides, Geoff Kinsey, Dimitri D. Krut, N. H. Karam
Presented at the 29th IEEE Photovoltaic Specialists Conference – New Orleans, Louisiana, May 20-24, 2002
Presented by Parth Bhide
WHAT ARE MULTIJUNCTION SOLAR CELLS
Multijunction cells employ a tandem of individual cells wired together each with its own bandgap.
The varying bandgaps allow for a wider range of absorbed photon wavelengths. The bandgap is the amount
of energy required to liberate an electron into the conduction band.
Photovoltaic (PV) Cells- The scientific name for solar panels.
Current (I)- The amount of particles moving in an electric circuit.
Voltage(V)- The strength of the electric circuit.
King, R. R., A. Boca, X. Q. Liu, D. Bhusari, D. Larrabee, K. M. Edmondson, D. C. Law, C. M. Fetzer, S. Mesropian, W. Hong, and N. H. Karam. "Band-gap-engineered Architectures for High-efficiency Multijunction Concentrator Solar Cells." 24th European Photovoltaic Solar Energy Conference and Exhibition, Hamburg, Germany, 21-25 Sep. 2009 (2009): n. pag. Web.
KEY TERMS
Doping- An impurity is intentionally added to a material.
Minority Carrier- The carrier of the electrical charge which is opposite to the doping of the layer in which the carrier is created.
Carrier Lifetime- The average amount of time before two carriers rejoin after separated.
Irradiance- The amount of incoming energy in an area. 1 sun is 0.100 W/cm3. Irradiance is adjusted by concentrator PV systems.
PARTS OF A MULTIJUNCTION PHOTOVOLTAIC CELL
Base The bases are responsible for
current generation. The bases are GaInP/GaInAs/Ge.
Tunnel Junction Areas with high doping and high
bandgaps which limit photogeneration. These are situated between bases to act as a separator.
Other layers, such as the back-surface field and the window layers are similarly done as tunnel junctions.
REVIEW OF LITERATURE R. R. King, N. H. Karam, J. H. Ermer, M. Haddad, P. C. Colter, T. Isshiki, H. Yoon, H. L. Cotal, D. E. Joslin,
D. D. Krut, R. Sudharsanan, K. M. Edmondson, B. T. Cavicchi, and D. R. Lillington, "Next-Generation, High-Efficiency III-V Multijunction Solar Cells," Proc. 28th IEEE Photovoltaic Specialists Conf. (IEEE, New York, 2000), p. 998.
The efficiency of multijunction solar cells benefits from a combination of varying bandgaps.
R. R. King, M. Haddad, T. Isshiki, P. C. Colter, J. H. Ermer, H. Yoon, D. E. Joslin, and N. H. Karam, "Metamorphic GaInP/GaInAs/Ge Solar Cells," Proc. 28th IEEE Photovoltaic Specialists Conf. (IEEE, New York, 2000), p. 982.
A greater current production can occur in the middle cell if the bandgap is lower due to the excess current in the bottom cell.
REVIEW OF LITERATURE
M. W. Wanlass, T. J. Coutts, J. S. Ward, K. A. Emery, T. A. Gessert, and C. A. Osterwald, "Advanced High-Efficiency Concentrator Tandem Solar Cells," Proc. 22nd IEEE Photovoltaic Specialists Conf. (IEEE, New York, 1991), p. 38.
An optimal bandgap for the top layer is 1.9eV for the terrestrial spectrum.
PURPOSE
To improve the efficiency of multijunction PV cells by altering the material composition and the bandgap of the bases and of the auxiliary layers.
MATERIALS
Multijunction photovoltaic cells with a GaInP/GaInAs/Ge composition.
Different ratios were tested to determine which had the greatest efficiency.
Properties of 4- and 5- junction cells. Fine tuning bandgaps for three and
more layers. Increasing irradiance levels. Controlling SRH recombination. Maintaining voltage, current, and
resistance values.
REFERENCES
King, Richard R., Chris M. Fetzer, Peter C. Colter, Ken M. Edmonson, James H. Ermer, Hector L. Cotal, Hojun Yoon, Alex P. Starvides, Geoff Kinsey, Dimitri D. Krut, and N. H. Karam. "High-Efficiency Space and Terrestrial Multijunction Solar Cells Through Bandgap Control in Cell Structures." 29th IEEE Photovoltaic Specialists Conference – New Orleans, Louisiana, May 20-24, 2002 (2002): n. pag. Print.
King, R. R., A. Boca, X. Q. Liu, D. Bhusari, D. Larrabee, K. M. Edmondson, D. C. Law, C. M. Fetzer, S. Mesropian, W. Hong, and N. H. Karam. "Band-gap-engineered Architectures for High-efficiency Multijunction Concentrator Solar Cells." 24th European Photovoltaic Solar Energy Conference and Exhibition, Hamburg, Germany, 21-25 Sep. 2009 (2009): n. pag. Web.
M. W. Wanlass, T. J. Coutts, J. S. Ward, K. A. Emery, T. A. Gessert, and C. A. Osterwald, "Advanced High-Efficiency Concentrator Tandem Solar Cells," Proc. 22nd IEEE Photovoltaic Specialists Conf. (IEEE, New York, 1991), p. 38.
R. R. King, M. Haddad, T. Isshiki, P. C. Colter, J. H. Ermer, H. Yoon, D. E. Joslin, and N. H. Karam, "Metamorphic GaInP/GaInAs/Ge Solar Cells," Proc. 28th IEEE Photovoltaic Specialists Conf. (IEEE, New York, 2000), p. 982.
R. R. King, N. H. Karam, J. H. Ermer, M. Haddad, P. C. Colter, T. Isshiki, H. Yoon, H. L. Cotal, D. E. Joslin, D. D. Krut, R. Sudharsanan, K. M. Edmondson, B. T. Cavicchi, and D. R. Lillington, "Next-Generation, High-Efficiency III-V Multijunction Solar Cells," Proc. 28th IEEE Photovoltaic Specialists Conf. (IEEE, New York, 2000), p. 998.