Two-junction photovoltaic devices
The present disclosure relates to a photovoltaic (PV) device that includes a first junction constructed with a first alloy and having a bandgap between about 1.0 eV and about 1.5 eV, and a second junction constructed with a second alloy and having a bandgap between about 0.9 eV and about 1.3 eV, where the first alloy includes III-V elements, the second alloy includes III-V elements, and the PV device is configured to operate in a thermophotovoltaic system having an operating temperature between about 1500° C. and about 3000° C.
1. A thermophotovoltaic (TPV) device comprising, in order:
a first junction having a first composition comprising Al x Ga 1-x As;
a tunnel junction having a second composition comprising at least one of GaAs or AlGaAs;
a buffer layer having a third composition comprising at least one of Ga y In 1-y P or Al a Ga b In 1-a-b As; and
a second junction having a fourth composition comprising Ga c In 1-c As, wherein:
the first junction has a bandgap between 1.3 eV and 1.5 eV,
the second junction has a bandgap between 1.1 eV and 1.3 eV,
0≤x≤0.45,
0.20<y<0.51,
0.15≤a≤0.70,
0.25≤b≤0.60,
0.70≤c≤0.95, and
the TPV device is configured to absorb light from a blackbody operating at a temperature, T w , between 1500° C. and 3000° C.
2. The TPV device of claim 1 , wherein the first composition is GaAs.
3. The TPV device of claim 1 , wherein the third composition is Ga y In 1-y P and 0.32≤y≤0.51.
4. The TPV device of claim 1 , wherein the buffer layer is a compositionally graded buffer (CGF) layer.
5. The TPV device of claim 4 , wherein:
the CGF layer comprises between 2 and 15 graded layers,
each graded layer comprises the third composition, and
the graded layer adjacent to the second junction is lattice-matched to the second junction.
6. The TPV device of claim 1 , wherein the fourth composition is substantially equal to Ga 0.85 In 0.15 As.
7. The TPV device of claim 1 , wherein T w is between 1900° C. and 2400° C.
8. The TPV device of claim 1 , further comprising:
a substrate comprising at least one of GaAs or Ge, wherein:
the first junction is positioned between the substrate and the tunnel junction.