Why Use Gallium Arsenide Solar Cells?

2017-12-04T19:22:29+00:00 October 31, 2017|

Alta Devices uses Gallium Arsenide (GaAs) as the basis for our solar technology.

It’s a lesser known material so we wanted to share some key information here:

What is Gallium Arsenide?

Gallium Arsenide (GaAs) is a semiconductor material and a compound of Gallium and Arsenic (interconnected cubic lattices). Traditionally it’s an expensive material mostly used in space technologies (satellites/spacecraft), RF ICs, or military applications.

Alta Devices produces a very thin layer of GaAs via an MOCVD (metalorganic chemical vapor deposition) reaction of trimethylgallium and arsine in a proprietary and innovative scaled process. Our solar is made by growing a thin film (1-2 microns thick) of GaAs on top of a high purity GaAs wafer. This thin layer is then separated from the wafer for usage as a solar cell while the wafer is reused. This specialized process makes it vastly more economical to produce and commercially viable for many applications.

Gallium arsenide (GaAs)

Advantages of Gallium Arsenide over Silicon

Low Temperature Coefficient– the temperature coefficient is a measure of performance (efficiency) loss versus temperature relative to 25C. Most solar materials such as Silicon (Si) lose a lot of efficiency when the temperature rises. Gallium Arsenide has a low temperature coefficient and thus experiences very little efficiency loss at higher temperatures. Alta’s GaAs also runs cooler in the first place. If you had GaAs solar on the roof of a car it would produce significantly more electricity and stay cooler during the day compared with Si, resulting in reduced load on the A/C and increased vehicle range.

Good Low Light Performance: In most solar cells, the energy available in weak illumination (low light) leaks away, but not in high quality GaAs. The wide bandgap and low-defect crystal structure also results in a lower leakage current and more rapid voltage buildup with illumination. The wider bandgap of GaAs also means it is much better tuned to the wavelengths of LED and fluorescent light, relative to silicon. So even in an office or warehouse environment, solar power can be generated using GaAs.

High Efficiency– GaAs is the highest efficiency solar material currently available in the world. This means it produces more power for a given surface area than any other solar technology. This is very important when surface area is limited such as on an aircraft, cars or on small satellites. For example, triple junction GaAs solar is 37%+ efficient while silicon solar is (at best) around 21%. So per unit area GaAs produces close to twice the power.

GaAs solar cells hold the world record for the most practical type of solar cell (single-junction). The record solar efficiency is 28.8% (record held by Alta Devices). The NCPV (National Center for Photovoltaics) at the National Renewable Energy Lab (NREL) produces a chart of these record efficiencies here: NREL Solar Efficiency Chart.

Excellent UV, Radiation and Moisture Resistance
– Gallium Arsenide is naturally resistant to damage from moisture, radiation and ultra-violet light. These properties make GaAs an excellent choice for aerospace applications where there is increased UV and radiation.

Flexible and Lightweight– GaAs solar is highly efficient even when very thin layers are used which keeps overall solar material weight low. Alta Devices uses a thin GaAs layer placed on a thin flexible substrate to maintain its lightweight and flexible properties. Si is not as good an absorber of sunlight so a relatively thick layer is required, making it very brittle and heavier. Rigid brittle glass is usually placed on top of the Silicon which further increases weight.

Please reach out if you are interested in learning more about Alta Devices GaAs solar cell technology and applications: info@altadevices.com