Gallium arsenide, a III-V semiconductor that has six times higher electron mobility than silicon, allows a faster operation and lower thermal noise.
Based on Malachite’s calculations, the silicon/gallium-arsenide tandem solar cell converts 38% of solar energy into electricity, which is about 1.5 times greater than that of Si/III-V tandem made by Sunpower (24% efficiency).
However, gallium arsenide is more expensive and brittle than silicon. The processes involved in fabricating silicon/gallium-arsenide tandem solar cell are also expensive. That makes cost reduction as the next challenge for this innovation.