High efficiency InAlN-based solar cells

The band gap energies of the In
1−x
Al
x
N alloys are continuously tunable across the solar spectrum, making them good candidates for high efficiency solar cells. In particular, multijunction solar cells could be fabricated entirely from different compositions of this one alloy system. From modeling experimental measurements of the optical absorption coefficient in alloys with 0 ≤ × ≤ 0.6, a band gap bowing parameter of 4.8 ± 0.5 eV is found for the alloy system. With this number, the alloy compositions for two and three junction tandem cells with maximum theoretical power conversion efficiencies can be determined. Two junction InAlN / Si solar cells are also promising structures for high efficiency solar cells, due to the properties of the interface between n-type InAlN and p-type Si, as well as the band gaps of the respective materials. The theoretical efficiency (detailed balance) for the In
0.60
Al
0.40
N / Si tandem cell is 41%.