Design of Epitaxial CdTe Solar Cells on InSb Substrates
Epitaxial CdTe has been shown by others to have a radiative recombination rate approaching unity, high carrier concentration, and low defect density. It has, therefore, become an attractive candidate for high-efficiency solar cells, perhaps becoming competitive with GaAs. The choice of substrate is a key design feature for epitaxial CdTe solar cells, and several possibilities (CdTe, Si, GaAs, and InSb) have been investigated by others. All have challenges, and these have generally been addressed through the addition of intermediate layers between the substrate and CdTe absorber. InSb is an attractive substrate choice for CdTe devices, because it has a close lattice match with CdTe, it has low resistivity, and it is easy to contact. However, the valence-band alignment between InSb and p-type CdTe, which can both impede hole current and enhance forward electron current, is not favorable. Three strategies to address the band-offset problem are investigated by numerical simulation: heavy doping of the back part of the CdTe layer, incorporation of an intermediate CdMgTe or CdZnTe layer, and the formation of an InSb tunnel junction. Lastly, wach of these strategies is predicted to be helpful for higher cell performance, but a combination of the first two should be most effective.
- Research Organization:
- National Renewable Energy Lab. (NREL), Golden, CO (United States)
- Sponsoring Organization:
- USDOE Office of Energy Efficiency and Renewable Energy (EERE), Renewable Power Office. Solar Energy Technologies Office
- Grant/Contract Number:
- UGA-0-41027-18; AC36-08GO28308
- OSTI ID:
- 1825095
- Alternate ID(s):
- OSTI ID: 1235426
- Report Number(s):
- NREL/JA-5J00-64499; 7234833
- Journal Information:
- IEEE Journal of Photovoltaics, Journal Name: IEEE Journal of Photovoltaics Vol. 5 Journal Issue: 6; ISSN 2156-3381
- Publisher:
- Institute of Electrical and Electronics EngineersCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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