Title:	Limiting Efficiency of an Intermediate Band Solar Cell Under Concentrated AM1.5 Spectrum
Author(s):	S.P. Bremner, S.N. Dahal, C. Honsberg
Topic:	Advanced Photovoltaics
Subtopic:	Fundamental Studies
Event:	23rd European Photovoltaic Solar Energy Conference and Exhibition, 1-5 September 2008, Valencia, Spain
Session:	1AO.4.3
Pages:	37 - 40
ISBN:	3-936338-24-8
Paper DOI:	10.4229/23rdEUPVSEC2008-1AO.4.3
Price:	0,00 EUR
Document(s):	paper

Abstract/Summary:

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Theoretical calculations used for optimum band gap design for intermediate band solar cells have focused on the case of the device under a blackbody spectrum. As yet there has been little attention given to the case of the intermediate band solar cell under a terrestrial spectrum. The piece wise continuous nature of the AM1.5 spectrum in contrast to the smooth continuous nature of a blackbody spectrum should see the variation in efficiency being multi-peaked. Using a rapid flux calculation method the detailed balance efficiency of an intermediate band solar cell has been calculated, over a large range of internal band gaps, under the AM1.5 spectrum at concentrations of 1, 100, 1,000 and 10,000 suns. The results show that there are several peaks in the efficiency and that the location of the peak corresponding to the global maximum depends on the level of concentration. At a concentration of 10,000x there are found to be three peaks of similar value suggesting there are several designs possible of roughly the same merit, in terms of limiting efficiency. These results have clear implications for the selection of materials systems for implementing an intermediate band solar cell since the required smaller internal band gap, corresponding to confinement potential in nanostructure approaches, can be < 0.6 eV for high concentration. Some possible candidate materials systems for a quantum dot approach taking into account these results have been identified using a k.p approach to take into account strain. The resulting systems are presented and briefly discussed.