1. GaAs and High-Efficiency Space Cells
- Author
-
Vyacheslav M. Andreev
- Subjects
Materials science ,Condensed Matter::Other ,Wavelength range ,Band gap ,business.industry ,Photovoltaic system ,Physics::Optics ,Heterojunction ,Photon energy ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Distributed Bragg reflector ,Condensed Matter::Materials Science ,Lattice (order) ,Optoelectronics ,business ,Surface states - Abstract
Publisher Summary This chapter presents basic concepts related to GaAs and high-efficiency space cells. GaAs has been found to have an optimal bandgap for effective sunlight conversion. In the first solar cells based on AlGaAs/GaAs heterojunctions, the basic narrow bandgap material was GaAs. A wide bandgap window was made of AlGaAs close in the composition to AlAs, which is almost completely transparent to sunlight, making solar cells very sensitive in the short wavelength range of the sun spectrum. Such a cell is illuminated through the window, and the light with photon energy exceeding the bandgap value of GaAs is absorbed in it, while the generated minority carriers are separated by the p–n junction field located in GaAs. Because of the close lattice parameters of the contacting materials, the interface in AlGaAs/GaAs heterojunctions is characterized by a low density of surface states, providing a highly effective accumulation of carriers. This chapter begins with a historical review of III–V solar cells. It then explains single-junction III–V space solar cells. Solar cells based on AlGaAs/GaAs heterostructures are then explained. The chapter also discusses solar cells with internal Bragg reflector and basic concepts related to GaAs-based cells on Ge substrates.
- Published
- 2018
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