HIGH EFFICIENCY MULTIJUNCTION SOLAR CELLS

1 . A photovoltaic cell comprising, wherein:

at least four subcells, at least one of the subcells having a base layer formed of an alloy of one or more elements from group III on the periodic table, nitrogen, arsenic, and at least one element selected from the group consisting of Sb and Bi; and

each of the at least four subcells is substantially lattice matched to each of the other sub cells.

2 . The photovoltaic cell of claim 1 , wherein each of the at least four subcells is substantially lattice matched to a material selected from the group consisting of Si, Ge, SiGe, GaAs, and InP.

3 . The photovoltaic cell of claim 1 , wherein the at least one subcell is characterized by a bandgap selected from the group consisting of 0.7 eV to 1.1 eV, 0.8 to 0.9 eV, 0.9 eV to 1.0 eV, 0.9 eV to 1.3 eV, 1.0 eV to 1.1 eV, 1.0 eV to 1.2 eV, 1.1 eV to 1.2 eV, 1.1 eV to 1.4 eV, and 1.2 eV to 1.4 eV.

4 . The photovoltaic cell of claim 1 , wherein the base layer of the at least one subcell is formed of an alloy Ga 1-x In x N y As 1-y-z Sb z , in which values for x, y and z are 0≦x≦0.24, 0.001≦y≦0.07 and 0.001≦z≦0.20.

5 . The photovoltaic cell of claim 1 , wherein the base layer of the at least one subcell is formed of an alloy Ga 1-x In x N y As 1-y-z Sb z , in which values for x, y and z are 0.01≦x≦0.18, 0.005≦y≦0.05, and 0.001≦z≦0.03.

6 . The photovoltaic cell of claim 1 , wherein the at least two subcells have a base layer formed of an alloy of one or more elements from group III on the periodic table, nitrogen, arsenic, and at least one element selected from the group consisting of Sb and Bi.

7 . The photovoltaic cell of claim 6 , wherein

one of the at least two subcells is characterized by a first band gap of 0.7 to 1.1 eV; and

a second of the at least two subcells is characterized by a second band gap of 0.9 to 1.3 eV, wherein the band gap of the uppermost of the at least two subcells is greater than the band gap of the other of the at least two subcells.

8 . The photovoltaic cell of claim 6 , wherein each of the at least two subcells has a base layer formed of a material independently selected from the group consisting of GaInNAsSb, GaInNAsBi, GaInNAsSbBi, GaNAsSb, GaNAsBi, and GaNAsSbBi.

9 . The photovoltaic cell of claim 6 , wherein

one of the at least two subcells has a base layer formed of an alloy Ga 1-x In x N y As 1-y-z Sb z , in which values for x, y and z are 0.02≦x≦0.24, 0.015≦y≦0.07 and 0.001≦z≦0.03 and

a second of the at least two subcells has a base layer formed of an alloy Ga 1-x In x N y As 1-y-z Sb z , in which values for x, y and z are 0≦x≦0.18, 0.005≦y≦0.05 and 0.001≦z≦0.03.

10 . The photovoltaic cell of claim 1 , comprising:

a first subcell having a first base layer formed of a material selected from the group consisting of Ge, SiGe(Sn), and an alloy of one or more elements from group III on the periodic table, nitrogen, arsenic, and at least one element selected from the group consisting of Sb and Bi, and characterized by a band gap of 0.7 eV to 1.1 eV;

a second subcell having a second base layer overlying the first subcell, wherein the second base layer is formed of an alloy of one or more elements from group III on the periodic table, nitrogen, arsenic, and at least one element selected from the group consisting of Sb and Bi, and characterized by a band gap of 0.9 eV to 1.3 eV;

a third subcell having a third base layer overlying the second subcell, wherein the third base layer is formed of a material selected from the group consisting of GaInPAs and (Al,In)GaAs, and characterized by a band gap from 1.4 eV to 1.7 eV; and

a fourth subcell having a fourth base layer overlying the third subcell, wherein the fourth base layer is formed of (Al)InGaP and characterized by a band gap from 1.9 eV to 2.2 eV.

11 . The photovoltaic cell of claim 10 , wherein the first base layer, the second layer, or both the first base layer and the second base layer are formed of an alloy Ga 1-x In x N y As 1-y-z Sb z , in which values for x, y and z are 0≦x≦0.24, 0.001≦y≦0.07 and 0.001≦z≦0.20.

12 . The photovoltaic cell of claim 10 , wherein the band gap of the first base layer is 0.7 eV to 0.9 eV, the band gap of the second base layer is 1.0 eV to 1.2 eV, the band gap of the third base layer is 1.5 eV to 1.6 eV, and the band gap of the fourth base layer is 1.9 eV to 2.1 eV.

13 . The photovoltaic cell of claim 1 , comprising:

a first subcell having a first base layer formed of a material selected from the group consisting of Ge, SiGe(Sn) and an alloy of one or more elements from group III on the periodic table, nitrogen, arsenic, and at least one element selected from the group consisting of Sb and Bi, and characterized by a band gap of 0.7 eV to 1.1 eV;

a second subcell having a second base layer overlying the first subcell, wherein the second base layer is formed of an alloy of one or more elements from group III on the periodic table, nitrogen, arsenic, and at least one element selected from the group consisting of Sb and Bi, and characterized by a band gap of 0.9 eV to 1.3 eV;

a third subcell having a third base layer overlying the second subcell, wherein the third base layer is formed of a material selected from the group consisting of GaInPAs, (Al,In)GaAs, and an alloy of one or more elements from group III on the periodic table, nitrogen, arsenic, and at least one element selected from the group consisting of Sb and Bi, and characterized by a band gap of 1.2 eV to 1.6 eV;

a fourth subcell having a fourth base layer overlying the third subcell, wherein the fourth base layer is formed of a material selected from the group consisting of GaInPAs and (Al,In)GaAs, and characterized by a band gap from 1.6 eV to 1.9 eV; and

a fifth subcell having a fifth base layer overlying the fourth subcell, wherein the fifth base layer is formed of (Al)InGaP and characterized by a band gap from 1.9 eV to 2.2 eV.

14 . The photovoltaic cell of claim 13 , wherein one or more of the first base layer, the second layer, and the third base are formed of an alloy Ga 1-x In x N y As 1-y-z Sb z , in which values for x, y and z are 0≦x≦0.24, 0.001≦y≦0.07 and 0.001≦z≦0.20.

15 . The photovoltaic cell of claim 1 , comprising:

a first subcell having a first base layer formed of a material selected from the group consisting of Ge, SiGe(Sn), and an alloy of one or more elements from group III on the periodic table, nitrogen, arsenic, and at least one element selected from the group consisting of Sb and Bi, and characterized by a band gap of 0.7 eV to 1.1 eV;

a second subcell having a second base layer overlying the first subcell, wherein the second base layer is formed of an alloy of one or more elements from group III on the periodic table, nitrogen, arsenic, and at least one element selected from the group consisting of Sb and Bi, and characterized by a band gap of 0.9 eV to 1.3 eV;

a third subcell having a third base layer overlying the second subcell, wherein the third base layer is formed of a material selected from the group consisting of GaInPAs, (Al,In)GaAs, and an alloy of one or more elements from group III on the periodic table, nitrogen, arsenic, and at least one element selected from the group consisting of Sb and Bi, and characterized by a band gap of 1.1 eV to 1.5 eV;

a fourth subcell having a fourth base layer overlying the third subcell, wherein the fourth base layer is formed of a material selected from the group consisting of (Al,In)GaAs and (Al)InGa(P)As, and characterized by a band gap from 1.4 eV to 1.7 eV;

a fifth subcell having a fifth base layer overlying the fourth subcell, wherein the fifth base layer is formed of a material selected from the group consisting of (Al)InGaP and Al(In)Ga(P)As, and characterized by a band gap from 1.6 eV to 2.0 eV; and

a sixth subcell having a sixth base layer overlying the fifth subcell, wherein the sixth base layer is formed of (Al)InGaP, and characterized by a band gap from 1.9 eV to 2.3 eV.

16 . The photovoltaic cell of claim 15 , wherein one or more of the first base layer, the second base layer, and the third base layer is formed of an alloy Ga 1-x In x N y As 1-y-z Sb z , in which values for x, y and z are 0≦x≦0.24, 0.001≦y≦0.07 and 0.001≦z≦0.20.

17 . A photovoltaic system comprising at least one photovoltaic cell of claim 1 .

18 . A method of manufacturing a photovoltaic cell, comprising:

forming one or more semiconductor layers on a substrate; and

forming four or more subcells overlying the one or more semiconductor layers; and

wherein at least one of the subcells has a base layer formed of an alloy of one or more elements from group III on the periodic table, nitrogen, arsenic, and at least one element selected from the group consisting of Sb and Bi;

wherein the photovoltaic cell comprises at least four subcells and each of the at least four subcells is substantially lattice matched to each of the other subcells.

19 . The method of claim 18 , wherein forming the four or more subcells comprises:

forming a first subcell having a first base layer formed of a material selected from the group consisting of Ge, SiGe(Sn), and an alloy of one or more elements from group III on the periodic table, nitrogen, arsenic, and at least one element selected from the group consisting of Sb and Bi, wherein the first subcell is characterized by a band gap from 0.7 eV to 1.1 eV;

forming a second subcell having a second base layer, wherein the second base layer is formed of an alloy of one or more elements from group III on the periodic table, nitrogen, arsenic, and at least one element selected from the group consisting of Sb and Bi, wherein the second subcell is characterized by a band gap from 0.9 eV to 1.3 eV; and

forming at least two additional subcells overlying the second subcell;

wherein the photovoltaic cell comprises at least four subcells and each of the at least four subcells is substantially lattice matched to each of the other subcells.

20 . The method of claim 19 , comprising:

forming one or more layers selected from the group consisting of a buffer layer, a contact layer, an etch stop layer, a release layer, and other semiconductor layer on the substrate in a chamber selected from the group consisting of a third materials deposition chamber and the second materials chamber; and

transferring the substrate to the first materials deposition chamber.