| CPC H01L 31/0725 (2013.01) [C12P 19/56 (2013.01); H01L 31/065 (2013.01); H01L 31/0735 (2013.01); H01L 31/184 (2013.01)] | 20 Claims |

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1. A multijunction solar cell comprising:
a first solar subcell, having an emitter layer and a base layer which form a photoelectric junction;
a second solar subcell disposed below and adjacent to the first solar subcell, having an emitter layer and a base layer which form a photoelectric junction; and
a third solar subcell disposed below the second solar subcell, having an emitter layer and a base layer which form a photoelectric junction;
wherein the base layer and the emitter layer of at least a particular one of the first solar subcell, the second solar subcell, and the third solar subcell has a graded band gap throughout at least a portion of a thickness of the emitter layer in a first region in the emitter layer adjacent to the photoelectric junction, and throughout at least a portion of a thickness of the base layer in a second region in the base layer spaced apart from the first region and adjacent to the photoelectric junction, with the band gap in the first region and the band gap in the second region being in the range of 20 to 300 meV greater than the band gap away from the photoelectric junction in the emitter layer and the base layer in the at least a particular one of the first solar subcell, the second solar subcell and the third solar subcell, and
wherein the thickness of the first region is less than the thickness of the second region.
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