Today, we are taking a look at one of the highest performing solar cell materials available – Gallium Arsenide.
Gallium Arsenide (GaAs) is a combination of the elements gallium and arsenic. It is used in the manufacturing of common items such as integrated circuits, light emitting diodes, and also solar cells.
The reason that GaAs is such a great material for making solar cells is because of its band gap value of 1.39 eV. This is very close to the ideal value of 1.34, and allows GaAs solar cells to almost achieve the optimal efficiency of 33.7%. Some multi-junction solar cells can collectively achieve an overall efficiency of over 33.7%. However, this requires putting multiple solar cells on top of each other, and no single solar cell can be over 33.7% efficient.
Here is what a GaAs solar cell looks like.
One thing you will notice about the solar cell in the image above is that is is very small. One of the main reasons for this is that GaAs is very expensive, and the cost will have to come down dramatically before this technology can be commercially viable.
Unlike silicon solar cells, there is no economical supply of GaAs wafers. The main factors that contribute to the high costs are:
- High cost of the wafer (can be over $7/W if we assume each wafer can be used 20 times).
- Additional cost of polishing of the wafers.
- High cost of depositing the GaAs (can be over $2/W).
Some of the things that can potentially bring the cost of GaAs technology down are:
- Large reduction (on the order of 10x-100x) in material deposition cost.
- Economic utilization of light trapping to reduce the required film thickness.
- Use of concentrators to direct more light onto the solar cell.
Due to their high efficiency and light weight, GaAs solar cells have become very popular in the niche of portable applications. For example, GaAs solar cells have more than doubled the flight time of drones.
If the cost of GaAs solar cells can be reduced, then it will be able to dominate the solar cell market that is currently led by silicon-based cells.