Heterojunction V-groove multijunction solar cell

• US 4,295,002 A
• Filed: 06/23/1980
• Issued: 10/13/1981
• Est. Priority Date: 06/23/1980
• Status: Expired due to Term

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Woodall, Jerry M., Chappell, Terry I.
• Primary Examiner(s): Weisstuch, Aaron
• Application Number:
  US06/161,820
• Time in Patent Office: 477 Days
• Field of Search: 136/244, 136/246, 136/249, 136/255, 136/261, 136/262, 357/30
• US Class Current: 136/244
• CPC Class Codes: H01L 31/035281 Shape of the body
• CPC Class Codes: H01L 31/043 Mechanically stacked PV cells
• CPC Class Codes: H01L 31/047 PV cell arrays including PV cells having multiple vertical junctions or multiple V-groove junctions formed in a semiconductor substrate
• CPC Class Codes: H01L 31/0725 Multiple junction or tandem solar cells
• CPC Class Codes: H01L 31/0735 comprising only AIIIBV compound semiconductors, e.g. GaAs/AlGaAs or InP/GaInAs solar cells
• CPC Class Codes: H01L 31/074 comprising a heterojunction with an element of Group IV of the Periodic Table, e.g. ITO/Si, GaAs/Si or CdTe/Si solar cells
• CPC Class Codes: Y02E 10/544 Solar cells from Group III-V materials

Abstract

A solar cell is disclosed with V-grooves which are series connected, but electrically isolated, indirect bandgap solar cells which are responsive to different light frequencies on both sides of a semi-insulating optically transparent substrate. The device has a very high conversion efficiency of approximately 40% and high open-circuit voltage and low series resistance. An exemplary structure in accordance with this disclosure has a series of silicon V-groove cells on one side and another series of GaAlAs V-groove cells on the other side. The cells are of generally trapezoidal cross-section. The difference between the characteristics of the Si cell and the GaAlAs cell is matched by control of the number of V-grooves.

Claims

1. A solar energy converter comprising:

a first solar cell comprising first multiple p-n heterojunctions in association with a first type of optically active semiconductor material on one side of an insulating substrate; and

a second solar cell comprising second multiple p-n heterojunctions in association with a second type of optically active semiconductor material on the opposite side of the insulating substrate;

said first type of semiconductor material is GaAlAs, said second type of semiconductor material is Si, and said insulating substrate is semi-insulating GaP.

2. A solar energy converter comprising:

a first solar cell comprising first multiple p-n heterojunctions in association with a first type of optically active semiconductor material A on one side of an insulating substrate; and

a second solar cell comprising second multiple p-n heterojunctions in association with a second type of optically active semiconductor material B on the opposite side of the insulating substrate;

wherein said material A has an indirect bandgap and carrier lifetime limited by Auger recombination,

one side of A has a heterojunction with a material A_n '"'"' which is doped to n+ type conductivity, has a larger bandgap than A, and is lattice matched to A,

the other side of A has a heterojunction with a material A_p '"'"' doped to p-type conductivity, and has a larger bandgap than A, and is lattice matched to A;

wherein said insulating substrate comprises an insulation layer adjacent to A_p '"'"' whose bandgap is greater than or equal to the bandgap of said A material and whose interfaces between said first and second cells are atomically compatible;

and wherein said material B has an indirect bandgap less than material A and carrier lifetime limited by Auger recombination,

one side of B has a heterojunction with a material B_n '"'"' doped to n-type conductivity and lattice matched with B, and

the other side of B has a heterojunction with a material B_p '"'"' doped to p-type conductivity and lattice matched with B.

3. A solar energy converter as set forth in claim 2 wherein:

said first material A is Ga_1-x Al_x As,

A'"'"'n is n-Ga_1-y Al_y As,

A'"'"'p is p-Ga_1-y Al_1-y As,

said second material B is Si,

one side of B has a heterojunction with material B_n '"'"' which is n-GaP and is lattice matched with B and the other side of B has a heterojunction with material B_p '"'"' which is p-GaP and is lattice matched with B.

4. A solar energy converter as set forth in claim 3 wherein:

said first material A has an indirect bandgap lying lower in energy than its direct bandgap, thereby having a high carrier lifetime and also having high optical absorption of photons slightly greater in energy than said indirect bandgap.

5. A solar energy converter as set forth in claim 4 wherein

said material A is a ternary semiconductor material compound of an indirect bandgap semiconductor material and a direct bandgap semiconductor material.

6. A solar energy converter as set forth in claim 5 wherein

said material A is a group III-V ternary semiconductor material.

7. A solar energy converter as set forth in claim 6 wherein

said first material A is Ga_1-x Al_x As and x is approximately 0.5.

8. A solar energy converter as set forth in claim 6 wherein A is Ga_1-x Al_x As and x is 0.4≦

×

≦

0.6.

9. A solar energy converter comprising:

a region of a first semiconductor material, which is responsive to light of a first frequency, having indirect bandgap and being carrier lifetime limited by Auger recombination, and having a first quantity of p-n heterojunctions with semiconductor material which has a larger bandgap than said first material and is lattice matched thereto.

a region of a second semiconductor material, which is responsive to light of a second frequency, having indirect bandgap and being carrier lifetime limited by Auger combination and having a second quantity of p-n heterojunctions with a semiconductor material which has a larger bandgap than said second material and is lattice matched thereto,

said first quantity of junctions and second quantity of junctions being operable to provide comparable electrical characteristics from the p-n heterojunctions in said first and said second semiconductor materials,

said first and second regions being conterminous with and separated by a substrate having

electrical isolation properties and

being optically transparent at least to light of said second frequency.

10. A solar energy converter having a

first material A having indirect bandgap and carrier lifetime limited by Auger recombination,

one side of A has a heterojunction with a material A_n '"'"' which is doped to n+ type conductivity, has a larger bandgap than A, and is lattice matched to A,

the other side of A has a heterojunction with a material A_p '"'"' which is doped to p-type conductivity, has a larger bandgap than A, and is lattice matched to A.

11. A solar energy converter as set forth in claim 10 wherein

said first material A has an indirect bandgap lying lower in energy than its direct bandgap thereby having a high carrier lifetime and also having high optical absorption of photons just slightly greater in energy than said indirect bandgap.

12. A solar energy converter as set forth in claim 11 wherein

said material A is a ternary semiconductor material compound comprised of an indirect bandgap semiconductor material and a direct bandgap semiconductor material.

13. A solar energy converter as set forth in claim 12 wherein

said material A is a group III-V ternary semiconductor material.

14. A solar energy converter as set forth in claim 13 wherein

said first material A is Ga_1-x Al_x As and x is approximately 0.5.

15. A solar energy converter as set forth in claim 13 wherein A is Ga_1-x Al_x As and x is 0.4≦

×

≦

0.6.

16. A solar energy converter having

a semiconductor material A with indirect bandgap and carrier lifetime limited by Auger recombination,

one side of A has a heterojunction with semiconductor material A_n doped to n-type conductivity and another side of A has a heterojunction with a semiconductor material A_p which is doped to p-type conductivity,

said material A_n and said material A_p having a larger bandgap than said material A.

17. A solar energy converter as set forth in claim 16 wherein:

said semiconductor material A is silicon,

said semiconductor material A_n is gallium phosphide doped to n-type conductivity, and

said semiconductor material A_p is gallium phosphide doped to p-type conductivity.