MULTIJUNCTION SOLAR CELLS
High efficiency multijunction solar cells formed primarily of III-V semiconductor alloys and methods of making high efficiency multijunction solar cells are disclosed.
1 . A multijunction solar cell comprising:
a first group of one or more subcells; and
a second group of one or more subcells, wherein each of the subcells is lattice matched to a second substrate 1 ;
wherein:
the second group of subcells is bonded to the first group of subcells;
the multijunction solar cell comprises at least three subcells; and
at least one of the at least three subcells comprises a base layer comprising an alloy of elements of group IIIA, group IV, and group VA on the periodic table.
2 . The multijunction solar cell of claim 1 , wherein each of the first group of subcells is lattice matched to a first substrate.
3 . The multijunction solar cell of claim 2 , wherein the first substrate comprises a material selected from Ge, GaAs, and p-type Ge.
4 . The multijunction solar cell of claim 2 , wherein the first substrate comprises a material selected from Ge, SiGe, GaAs, and InP.
5 . The multijunction solar cell of claim 2 , wherein the first substrate comprises a material selected from Ge and GaAs; and the first group of subcells comprises a III-AsNV subcell grown on the first substrate.
6 . The multijunction solar cell of claim 5 , wherein at least one III-AsNV subcell comprises a GaInAsSb alloy.
7 . The multijunction solar cell of claim 1 , wherein the first group of subcells comprises an epitaxial Ge substrate overlying a Si substrate.
8 . The multijunction solar cell of claim 1 , wherein
the second substrate comprises a thinned substrate; and
the thinned substrate is bonded to the first group of subcells.
9 . The multijunction solar cell of claim 1 , wherein,
the second substrate is removed from the second group of subcells; and
the second group of subcells is bonded to the first group of subcells.
10 . The multijunction solar cell of claim 1 , wherein,
the first group of subcells is annealed at a first condition;
the second group of subcells is annealed at a second condition; and
the first condition is different than the second condition.
11 . The multijunction solar cell of claim 1 , wherein the second substrate is thinned before annealing the second group of subcells.
12 . The multijunction solar cell of claim 1 , wherein the second substrate is removed before annealing the second group of subcells.
13 . The multijunction solar cell of claim 1 , wherein the first group of subcells further comprises a diffused junction layer overlying the uppermost subcell.
14 . The multijunction solar cell of claim 1 , wherein the second group of subcells further comprises an As-containing layer underlying the lowermost subcell.
15 . The multijunction solar cell of claim 1 , wherein,
the first group of subcells comprises a p-type Ge substrate;
the second group of subcells comprises a thinned substrate; and
the thinned substrate is bonded to the Ge substrate.
16 . The multijunction solar cell of claim 1 , wherein,
the first group of subcells comprises a p-type Ge substrate;
the second group of subcells comprises an As-containing layer underlying the lowermost subcell; and the As-containing layer is bonded to the Ge substrate.
17 . The multijunction solar cell of claim 1 , wherein,
the first group of subcells comprises a p-type Ge substrate;
the second group of subcells comprises a phosphorous-containing layer selected from InGaP, InP, and GaP underlying the lowermost subcell; and
the phosphorous-containing layer is bonded to p-type Ge substrate.
18 . The multijunction solar cell of claim 1 , wherein the second substrate comprises a material selected from GaAs and Ge.
19 . The multijunction solar cell of claim 1 , wherein the second group of subcells is grown on a release layer overlying the second substrate.
20 . The multijunction solar cell of claim 19 , wherein the release layer comprises a material selected from AlAs and AlGaAs, wherein the Al content is greater than 80%.
21 . The multijunction solar cell of claim 1 , wherein the first group of subcells comprises a subcell selected from a Ge subcell and a SiGe subcell.
22 . The multijunction solar cell of claim 1 wherein each of the at least three subcells comprises a base layer independently selected from Al)InGaP, (Al)GaAs, InGaAsP, AlInGaAs, InGaAs, InP, Ga(In)As, and (Al)GaAs.
23 . The multijunction solar cell of claim 1 , wherein the second substrate comprises a material selected from Ge, SiGe, GaAs, and InP
24 . A method of manufacturing a multijunction solar cell, comprising:
forming a first group of one or more subcells;
forming a second group of one or more subcells, wherein each of the one or more subcells is lattice matched to a second substrate;
thinning the second substrate; and
bonding the thinned second substrate to a top subcell of the first group of subcells, to form a multijunction solar cell;
wherein:
the multijunction solar cell comprises at least three subcells; and
at least one of the at least three subcells comprises a base layer comprising an alloy of elements of group IIIA, group IV, and group VA on the periodic table.
25 . The method of claim 24 , wherein each of the one or more subcells of the first group of subcells is lattice matched to a first substrate.
26 . The method of claim 24 , comprising attaching a carrier substrate d to a top subcell of the second group of subcells before thinning the second substrate.
27 . The method of claim 24 , wherein the first group of subcells is annealed at a first condition; and the second group of subcells is annealed at a second condition before bonding.
28 . A method of manufacturing a multijunction solar cell, comprising:
forming a first group of one or more subcells;
forming a second group of one or more subcells overlying a release layer, wherein the release layer overlies a second substrate, and each of the one or more subcells is lattice matched to the second substrate;
attaching a carrier substrate to a top subcell of the second group of subcells;
releasing the second group of subcells from the second substrate; and
bonding the second group of subcells to a top subcell of the first group of subcells, to form a multijunction solar cell;
wherein:
the multijunction solar cell comprises at least three subcells; and
at least one of the at least three subcells comprises a base layer comprising an alloy of elements of group IIIA, group IV, and group VA on the periodic table.
29 . The method of claim 28 , wherein each of the one or more subcells of the first group of subcells is lattice matched to a first substrate.
30 . The method of claim 28 , wherein forming the second group of subcells comprises forming the second group of subcells on the release layer.
31 . The method of claim 28 , wherein bonding comprises bonding a subcell having the lowest bandgap of the second group of subcells to a top subcell of the first group of subcells,
32 . The method of claim 28 , wherein the second group of subcells is formed in a non-inverted order.
33 . The method of claim 28 , wherein the second group of subcells is formed in an inverted order.
34 . The method of claim 28 , wherein,
the first group of subcells is annealed at a first condition; and
the second group of subcells is annealed at a second condition before bonding.
35 . The method of claim 28 , further comprising:
forming an As-containing layer overlying the release layer;
forming the second group of subcells comprises forming the second group of subcells on the As-containing layer; and
bonding comprises bonding the As-containing layer to the top subcell of the first group of subcells.
36 . The method of claim 28 , further comprising:
forming an P-containing layer overlying the release layer;
forming the second group of subcells comprises forming the second group of subcells on the P-containing layer; and
bonding comprises bonding the P-containing layer to the top subcell of the first group of subcells.
37 . The method of claim 36 wherein the P-containing layer comprises an alloy selected from InGaP, InP, and GaP.