Inverted multijunction solar cells with distributed bragg reflector

Patent metadata

Field	Value
Publication number	US-11063168-B1
Application number	US-201916667687-A
Country	US
Kind code	B1
Filing date	Oct 29, 2019
Priority date	Dec 17, 2008
Publication date	Jul 13, 2021
Grant date	Jul 13, 2021

Abstract

An inverted metamorphic multijunction solar cell comprising: an upper first solar subcell having a first band gap; a middle second solar subcell disposed adjacent to the upper first solar subcell and having a second band gap smaller than said first band gap; a graded interlayer disposed adjacent to the middle second solar subcell and having a band gap that remains constant throughout its thickness; a lower third solar subcell disposed adjacent to said graded interlayer and having a fourth band gap that is smaller than said second band gap such that said third solar subcell is lattice mismatched with respect to said second solar subcell; a back surface field (BSF) layer disposed directly adjacent to the base layer of said lower third solar subcell; at least one distributed Bragg reflector (DBR) layer disposed directly adjacent to the back surface field (BSF) layer.

First claim

The invention claimed is:

1. An inverted metamorphic multijunction solar cell comprising:
an upper first solar subcell having a first band gap;
a middle second solar subcell disposed adjacent to the upper first solar subcell and having a second band gap smaller than said first band gap;
a graded interlayer disposed adjacent to the middle second solar subcell and having a band gap that remains constant throughout its thickness;
a lower third solar subcell disposed adjacent to said graded interlayer and having a fourth band gap that is smaller than said second band gap such that said third solar subcell is lattice mismatched with respect to said second solar subcell; the lower third solar subcell having an emitter layer and a base layer disposed below the emitter layer;
a back surface field (BSF) layer disposed directly adjacent to the base layer of said lower third solar subcell;
at least one distributed Bragg reflector (DBR) layer disposed directly adjacent to the back surface field (BSF) layer that is disposed directly adjacent the base layer of said lower third solar subcell;
a spacer layer composed of p+ InGaAlAs disposed directly adjacent the at least one distributed Braff reflector layer; and
a high band gap contact layer composed of InGaAlAs disposed directly adjacent to the spacer layer.

2. A multijunction solar cell as defined in claim 1 , wherein the at least one distributed Bragg reflector layer is composed of a plurality of alternating layers of lattice matched materials with discontinuities in their respective indices of refraction.

3. A multijunction solar cell as defined in claim 1 , wherein the at least one DBR layer includes a first DBR layer composed of p type Al x Ga 1-x As and a second directly adjacent DBR layer disposed over the first DBR layer and composed of p type Al y Ga 1-y As, where 0<x<1, 0<y<1, and y is greater than x.

4. A multijunction solar cell as defined in claim 1 , wherein said graded interlayer is composed of any of the As, N, Sb based III-V compound semiconductors subject to the constraints of having the in-plane lattice parameter greater or equal to that of the upper first solar subcell and less than or equal to that of the middle second solar subcell, and having a band gap energy greater than that of the second solar subcell, and the band gap of said graded interlayer remains constant at approximately 1.50 eV throughout its thickness.

5. A multijunction solar cell as defined in claim 1 , wherein said graded interlayer is composed of (In x Ga 1-x ) y Al 1-y As with 0<x<1, 0<y<1, and x and y selected such that the band gap of said graded interlayer remains constant throughout its thickness; and wherein said graded interlayer is deposited using trimethylgallium, trimethylindium, and arsine as precursor compounds in the MOCVD process.

6. A multijunction solar cell as defined in claim 1 , wherein the middle second solar subcell is composed of an GaInP, GaAs, GaInAs, GaInAsN emitter region and an GaAs, GaInAs, GaAsSb, or GaInAsN base region, and the lower third solar subcell is composed of InGaAs base and emitter regions.

7. A multijunction solar cell as defined in claim 1 , wherein the lower third solar subcell is composed of an InGaP emitter layer and an InGaAs base layer, or a InGaAs emitter layer and a InGaAs base layer.

8. A multijunction solar cell as defined in claim 1 , wherein the upper first solar subcell is grown on a first substrate is composed of gallium arsenide or germanium.

9. A method of manufacturing a multijunction solar cell as defined in claim 8 , wherein the first substrate is removed after growth of all of the semiconductor layers by grinding, lapping, or etching.

10. An inverted metamorphic multijunction solar cell including an upper solar subcell, a middle solar subcell, and a lower solar subcell comprising:
an upper first solar subcell having a first band gap
a middle second solar subcell disposed adjacent to the upper first solar subcell and having a second band gap smaller than said first band gap, and having an emitter layer and a base layer disposed below the emitter layer;
a first back surface field (BSF) layer disposed directly adjacent the base layer of said middle second solar subcell;
a first distributed Bragg reflector (DBR) layer disposed directly adjacent the first back surface field (BSF) layer that is directly adjacent the base layer of said middle second solar subcell;
a graded interlayer over the first distributed Bragg reflector layer wherein a band gap of the interlayer remains constant throughout its thickness;
a lower third solar subcell disposed adjacent to said graded interlayer and having a fourth band gap smaller than said second band gap such that said third solar subcell is lattice mismatched with respect to said middle second solar subcell;
a second back surface field (BSF) layer disposed directly adjacent a base layer of said lower third solar subcell;
a second distributed Bragg reflector disposed directly adjacent the second back surface field (BSF) layer that is directly adjacent the base layer of said lower third solar subcell;
a spacer layer composed of p+ InGaAlAs disposed directly adjacent the second distributed Bragg reflector layer;
a high band gap contact layer composed of InGaAlAs disposed directly adjacent the spacer layer;
wherein light can enter the upper first solar subcell, pass through the middle second solar subcell and the directly adjacent back surface field (BSF) layer, and be reflected by the first directly adjacent distributed Bragg reflector layer back into the middle second solar subcell; and
wherein light can enter the upper first solar subcell, pass through the middle second solar subcell, the lower third solar subcell, and the directly adjacent back surface field (BSF) layer, and be reflected by the second directly adjacent distributed Bragg reflector layer back into the lower third solar subcell.

11. A multijunction solar cell as defined in claim 10 , wherein the upper first solar subcell is composed of InGa(Al)P.

12. A multijunction solar cell as defined in claim 10 , wherein the middle second solar subcell is composed of an GaAs, GaInP, GaInAs, GaAsSb, or GaInAsN emitter region and a GaAs, GaInAs, GaAsSb, or GaInAsN base region.

13. A multijunction solar cell as defined in claim 10 , wherein the lower third solar subcell is composed of an InGaAs base and emitter layer, or InGaAs base layer and a InGaP emitter layer.

14. A multijunction solar cell as defined in claim 10 , wherein the graded interlayer is compositionally graded to lattice match the middle second solar subcell on one side and the lower third solar subcell on the other side, and is composed of (In x Ga 1-x ) y Al 1-y As with 0<x<1, 0<y<1, and x and y selected such that the band gap of the interlayer remains constant throughout its thickness and greater than said second band gap; and
wherein said graded interlayer is deposited using trimethylgallium, trimethylindium, and arsine as precursor compounds in an MOCVD process.

15. A multijunction solar cell as defined in claim 10 , wherein the graded interlayer has approximately a 1.5 eV band gap throughout its thickness.

16. A multijunction solar cell as defined in claim 10 , wherein the graded interlayer is composed of any of the As, N, Sb based III-V compound semiconductors subject to the constraints of having the in-plane lattice parameter greater or equal to that of the middle second solar subcell and less than or equal to that of the lower third solar cell, and having a band gap energy greater than that of the middle second solar subcell.

Assignees

• Solaero Tech Corp

Inventors

• Stan Mark A
• Cornfeld Arthur

Classifications

• H10F77/492

  Spectrum-splitting means, e.g. dichroic mirrors · CPC title

• H10F77/80

  Arrangements for preventing damage to photovoltaic cells caused by corpuscular radiation, e.g. for space applications · CPC title

• H10F77/48

  Back surface reflectors [BSR] · CPC title

• H10F71/1272 Primary

  comprising at least three elements, e.g. GaAlAs or InGaAsP · CPC title

• H10F10/1425

  Inverted metamorphic multi-junction [IMM] photovoltaic cells · CPC title