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== Materials == | == Materials == | ||
The III-V alloys have proven to be the most suitable semiconductors for MJ devices for a number of reasons. First, the band gaps of the alloys span the spectral range allowing for maximum photon absorption. Second, the alloys have direct band gaps meaning lattice vibrations (phonons) are not required for electron promotion. This avoids the need for additional layer thickness to produce the phonons thereby reducing material costs. Also, the alloys have large absorption coefficients which is another reason only thin layers are needed. The III-V semiconductors can be grown in high volumes with high crystalline and optoelectronic properties | The III-V alloys have proven to be the most suitable semiconductors for MJ devices for a number of reasons. First, the band gaps of the alloys span the spectral range allowing for maximum photon absorption. Second, the alloys have direct band gaps meaning lattice vibrations (phonons) are not required for electron promotion. This avoids the need for additional layer thickness to produce the phonons thereby reducing material costs. Also, the alloys have large absorption coefficients which is another reason only thin layers are needed. The III-V semiconductors can be grown in high volumes with high crystalline and optoelectronic properties which makes them applicable for large-scale production of commercial solar modules. Finally, the alloys are extremely hard and possess high radiation and temperature resistances making them ideal for space and extreme weather applications. | ||
=== InGaN === | === InGaN === | ||
Indium gallium nitride (InGaN) is a III-V alloy with great potential | Indium gallium nitride (InGaN) is a III-V alloy with great potential for forming cost-effective, high-efficiency MJ solar cells. By varying the indium-gallium ratio in the material its band gap can range from 0.7 eV (InN) to 3.4 eV (GaN) which covers nearly the entire solar spectrum. Since the same three elements are used for different subcells, the large-scale deposition process is simplified with respect to equipment and chamber cleaning. InGaN exhibits nano-columnar growth which increases optical length to enhance light trapping and absorption rates. This columnar structure also reduces strain and defects as well as increasing flexibility and wear resistance on the macro scale. | ||
== References == | == References == |