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 two junction thermophotovoltaic (TPV) device comprising, in order:
a first junction having a first composition comprising Al x Ga y In 1-x-y As or Ga a In 1-a As b P 1-b ;
a tunnel junction having a second composition comprising at least one of GaInAs or GaAsSb; and
a second junction having a third composition comprising Ga c In 1-c As, wherein:
the first junction has a bandgap between 1.1 eV and 1.4 eV,
the second junction has a bandgap between 0.9 eV and 1.2 eV,
0.05≤ x≤ 0.25,
0.45≤ y≤ 0.65,
0.40≤ a≤ 0.60,
0.45≤ b≤ 0.70,
0.60≤ c≤ 0.80, 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 two junction TPV device of claim 1 , wherein the first composition is substantially equal to Al 0.15 Ga 0.55 In 0.3 As or Ga 0.5 In 0.5 As 0.57 P 0.43 .
3. The two junction TPV device of claim 1 , wherein the third composition is substantially equal to Ga 0.7 In 0.3 As.
4. The two junction TPV device of claim 1 , wherein T w is between 1900° C. and 2400° C.
5. The two junction 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.
6. The two junction TPV device of claim 5 , further comprising:
a buffer layer having a fourth composition comprising Ga w In 1-w P or Al u Ga v In 1-u-v As, wherein:
0.20≤ w≤ 0.51,
0.15 ≤u≤ 0.70,
0.25≤ v≤ 0.60, and
the buffer layer is positioned between the substrate and the first junction.
7. The two junction TPV device of claim 6 , wherein:
the buffer layer is a compositionally graded buffer (CGF) layer,
the CGF layer comprising between 2 and 15 graded layers,
each graded layer comprises the fourth composition, and
the graded layer adjacent to the first junction is lattice-matched to the first junction.
8. The two junction TPV device of claim 1 , wherein the first junction and second junction each have a lattice constant of about 5.78 Å.
9. The two junction TPV device of claim 1 , wherein the first junction, the second junction, and the tunnel junction are substantially lattice matched.