Optimal design of high-efficiency tandem cellsComputer analysis indicates that a substantial increase in solar cell conversion efficiencies can be achieved by using two-cell, multi-bandgap tandem structures instead of single-junction cells. Practical AM1 efficiencies of about 30 percent at one sun and over 30 percent at multiple suns are to be expected. The further increases in efficiency calculated for a three-cell tandem structure are much smaller and may not justify the added complexity. For inexpensive two-cell tandem modules, Si is preferred for the bottom cell, and the top-cell material should have a bandgap of 1.75 to 1.80 eV. The GaAs-AlAs and GaAs-GaP systems are very attractive candidates for the top cell. Significant advances have been achieved in growing GaAs on Ge-coated Si substrates (for the two-terminal, two-cell structure) and in growing free-standing ultrathin GaAs layers (for the two-terminal or four-terminal structures). These advances should be transferable to the GaAs-AlAs and GaAs-GaP systems.
Document ID
19840040263
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Fan, J. C. C. (Massachusetts Inst. of Tech. Cambridge, MA, United States)
Tsaur, B.-Y. (Massachusetts Inst. of Tech. Cambridge, MA, United States)
Palm, B. J. (MIT, Lincoln Laboratory, Lexington MA, United States)