Tunnel Heterojunctions in Group IV/ Group II-VI Multijunction Solar Cells

• US 20200135955A1
• Filed: 07/01/2019
• Published: 04/30/2020
• Est. Priority Date: 12/10/2009
• Status: Active Grant

• Current Assignee: Epic Technology
• Original Assignee: Epic Technology
• Inventors: SIVANANTHAN, Sivalingam, CARMODY, Michael, BOWER, Robert W., MALLICK, Shubhrangshu, GRALAND, James
• Granted Patent: US 11,257,973 B2
• Time in Patent Office: Days
• CPC Class Codes: H01L 29/267 in different semiconductor regions , e.g. heterojunctions H01L29/263 takes precedence
• CPC Class Codes: H01L 31/0687 Multiple junction or tandem solar cells
• CPC Class Codes: H01L 31/0725 Multiple junction or tandem 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: H01L 31/18 Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
• CPC Class Codes: Y02E 10/50 Photovoltaic [PV] energy
• CPC Class Codes: Y02E 10/543 Solar cells from Group II-VI materials
• CPC Class Codes: Y02E 10/544 Solar cells from Group III-V materials
• CPC Class Codes: Y02E 10/547 Monocrystalline silicon PV cells

Abstract

A photovoltaic cell comprises a first subcell formed of a Group IV semiconductor material, a second subcell formed of a Group II-VI semiconductor material, and a tunnel heterojunction interposed between the first and second subcells. A first side of the tunnel heterojunction is formed by a first layer that is adjacent to a top surface of the first subcell. The first layer is of a first conductivity type, is comprised of a highly doped Group IV semiconductor material. The other side of the tunnel heterojunction is formed by a second layer that adjoins the lower surface of the second subcell. The second layer is of a second conductivity type opposite the first conductivity type, and is comprised of a highly doped Group II-VI semiconductor material. The tunnel heterojunction permits photoelectric series current to flow through the subcells.

Claims

1. A photovoltaic cell, comprising:

a first subcell formed of a Group IV semiconductor material and having an upper surface;

a second subcell formed of a Group II-VI semiconductor material and having a bottom surface; and

a tunnel heterojunction interposed between the upper surface of the first subcell and the bottom surface of the second subcell, the tunnel heterojunction including

a first layer comprising a highly doped Group IV semiconductor material, the first layer having a first conductivity type and disposed adjacent the upper surface of the first subcell, the first layer forming one side of a tunnel heterojunction; and

a second layer comprising a highly doped Group II-VI semiconductor material, the second layer having a second conductivity type opposite the first conductivity type, the second layer disposed to adjoin the first layer and to be adjacent to the bottom surface of the second subcell, the second layer forming the other side of the tunnel heterojunction.

2. The cell of claim 1, wherein the first conductivity type is (n).

3. The cell of claim 1, wherein the first conductivity type is (p).

4. The cell of claim 1, wherein the first subcell comprises an emitter having the first conductivity type and a base having the second conductivity type and being adjacent to the emitter.

5. The cell of claim 1, wherein the first subcell comprises a base formed to be of the second conductivity type and adjoining the first layer of the tunnel junction, the first layer of the tunnel heterojunction acting as an emitter of the first subcell.

6. The cell of claim 1, wherein the second subcell is formed from a Group II-VI semiconductor material that is selected from the group consisting of CdS, CdTe, CdSe, ZnTe, ZnSe, ZnS, MgTe, CdSeTe, CdZnTe, CdMnTe, CdMgTe, CdHgTe, and composites thereof.

7. The cell of claim 1, wherein the first subcell is formed from a Group IV semiconductor material that is selected from the group consisting of silicon, strained silicon-germanium, and silicon-germanium.

8. The cell of claim 1, wherein the first layer of the tunnel heterojunction comprises a Group IV semiconductor material selected from the group consisting of silicon, strained silicon-germanium, and silicon-germanium.

9. The cell of claim 1, wherein the second layer of the tunnel heterojunction comprises a Group II-VI semiconductor material selected from the group consisting of ZnTe, ZnS, MgTe, CdMgTe and composites thereof.

10. A method for passing photovoltaic current between a second subcell formed from a Group II-VI semiconductor material and a first subcell formed from a Group IV semiconductor material, comprising the steps of:

forming a tunnel heterojunction between the first subcell and the second subcell, said step of forming including the substeps of

forming a first layer to be adjacent to an upper surface of the first subcell, the first layer comprising a highly doped Group IV semiconductor material, the first layer having a first conductivity type and forming one side of a tunnel heterojunction;

forming a second layer to adjoin the first layer and to be adjacent to a bottom surface of the second subcell, the second layer comprising a Group II-VI semiconductor material and having a second conductivity type opposite the first conductivity type, the second layer forming the other side of the tunnel heterojunction; and

responsive to said step of forming the heterojunction, tunneling carriers formed by light incident on the first and second subcells through the tunnel heterojunction, thereby permitting a photoelectric series current to flow through the first and second subcells.

11. The method of claim 10, wherein the first conductivity type is (n).

12. The method of claim 10, and further comprising the step of forming the first subcell to have an emitter of the first conductivity type and a base having the second conductivity type and being adjacent to the emitter.

13. The method of claim 10, and further comprising the steps of

forming the first subcell to have a base of the second conductivity type and to adjoin the first layer of the tunnel junction;

and

using the first layer of the tunnel junction to be an emitter of the first subcell.

14. The method of claim 10, and further comprising the steps of forming the first layer of the tunnel heterojunction to be comprised of a Group IV semiconductor material selected from the group consisting of silicon, silicon-germanium and strained silicon-germanium.

15. The method of claim 10, and further comprising the steps of forming the second layer of the tunnel heterojunction to be comprised of a Group II-VI semiconductor material selected from the group consisting of ZnTe, ZnS, MgTe, CdMgTe and composites thereof.