# US 10,374,112 B2 · Inverted metamorphic multijunction solar cell including a metamorphic layer

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- Number: US 10,374,112 B2
- Document ID: US10374112B2
- Status: Granted
- Kind: B2
- Application number: 15/045,641
- Filed: 2016-02-17
- Published: 2016-06-30
- Granted: 2019-08-06
- Earliest claimed: 2007-09-24
- Assignees: SolAero Technologies Corp.
- Applicants: SolAero Technologies Corp.
- Inventors: Arthur Cornfeld; Pravin Patel; Mark A. Stan; Benjamin Cho; Paul R. Sharps; Daniel J. Aiken; John Spann
- Web page: https://patentgrep.com/patent/US10374112B2

## CPC

- H10F 10/1425: {Inverted metamorphic multi-junction [IMM] photovoltaic cells}
- H10F 10/19: Photovoltaic cells having multiple potential barriers of different types, e.g. tandem cells having both PN and PIN junctions
- H10F 71/1272: {comprising at least three elements, e.g. GaAlAs or InGaAsP}
- H10F 71/139: {using temporary substrates}
- Y02E 10/544: Solar cells from Group III-V materials
- Y02E 10/548: Amorphous silicon PV cells
- Y02P 70/50: Manufacturing or production processes characterised by the final manufactured product
- H10F: INORGANIC SEMICONDUCTOR DEVICES SENSITIVE TO INFRARED RADIATION, LIGHT, ELECTROMAGNETIC RADIATION OF SHORTER WAVELENGTH OR CORPUSCULAR RADIATION
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS

## Abstract

A multijunction solar cell includes an upper first solar subcell, a second solar subcell adjacent to the first solar subcell, a third solar subcell adjacent to the second solar subcell, and a graded interlayer adjacent to the third solar subcell. The graded interlayer has a band gap that is greater than the band gap of the third solar subcell and is composed of a compositionally step-graded series of (InxGa1-x)yAl1-yAs layers with monotonically changing lattice constant, with x and y having respective values such that the band gap of the graded interlayer remains constant throughout its thickness, and wherein 0<x<1 and 0<y<1. A fourth solar subcell is adjacent to the graded interlayer and is lattice mismatched with respect to the third solar subcell. The graded interlayer provides a transition in lattice constant from the third solar subcell to the fourth solar subcell. A lower fifth solar subcell is adjacent to the fourth solar subcell.

## Claims

### Claim 1

A multijunction solar cell comprising:
an upper first solar subcell having a first band gap;
a second solar subcell adjacent to the first solar subcell and having a second band gap smaller than the first band gap of the first solar subcell;
a third solar subcell adjacent to the second solar subcell and having a third band gap smaller than the second band gap of the second solar subcell;
a graded interlayer adjacent to the third solar subcell, the graded interlayer having a fourth band gap that is greater than the third band gap of the third solar subcell, wherein the graded interlayer is composed of a compositionally step-graded series of (InxGa1-x)yAl1-yAs layers with monotonically changing lattice constant, with x and y having respective values such that the band gap of the graded interlayer remains constant throughout its thickness, and wherein 0<x<1 and 0<y<1;
a fourth solar subcell adjacent to the graded interlayer, the fourth solar subcell having a fifth band gap smaller than the third band gap of the third solar subcell wherein the fourth solar subcell is lattice mismatched with respect to the third solar subcell, and wherein the graded interlayer provides a transition in lattice constant from the third solar subcell to the fourth solar subcell; and
a lower fifth solar subcell adjacent to the fourth solar subcell and having a sixth band gap smaller than the fifth band gap of the fourth solar subcell.

### Claim 2 (depends on 1)

The multijunction solar cell of claim 1 further comprising a barrier layer adjacent the graded interlayer.

### Claim 3 (depends on 2)

The multijunction solar cell of claim 2 wherein the barrier layer is composed of (Al)GaInP.

### Claim 4 (depends on 2)

The multijunction solar cell of claim 2 wherein the barrier layer has a thickness of about 0.5 micron.

### Claim 5 (depends on 1)

The multijunction solar cell of claim 1 wherein the graded interlayer is disposed between first and second barrier layers.

### Claim 6 (depends on 5)

The multijunction solar cell of claim 5 wherein the first barrier layer has a composition different from a composition of the second barrier layer.

### Claim 7 (depends on 1)

The multijunction solar cell of claim 1 wherein the fourth band gap of the graded interlayer is constant at 1.5 eV throughout the thickness of the graded interlayer.

### Claim 8 (depends on 7)

The multijunction solar cell of claim 7 wherein:
the third band gap of the third solar subcell is in a range of 1.3 eV-1.5 eV; and
the fifth band gap of the fourth solar subcell is in a range of 1.0 eV-1.2 eV.

### Claim 9 (depends on 1)

The multijunction solar cell of claim 1 wherein the upper first solar subcell comprises an AlGaInP emitter region and an AlGaInP base region.

### Claim 10 (depends on 1)

The multijunction solar cell of claim 1 wherein the second solar subcell comprises:
an emitter region composed of AlGaAs, GaAs, GaInP, GalnAs, GaAsSb or GaInAsN; and
a base region composed of AlGaAs, GaAs, GalnAs, GaAsSb or GaInAsN.

### Claim 11 (depends on 1)

The multijunction solar cell of claim 1 wherein the third solar subcell comprises a GaInP emitter region and a GaAs base region.

### Claim 12 (depends on 1)

The multijunction solar cell of claim 1 wherein the fourth solar subcell comprises a GaInP emitter region and a AlGaInAs base region.

### Claim 13 (depends on 1)

The multijunction solar cell of claim 1 wherein the fifth solar subcell comprises a GaInP emitter region and a GalnAs base region.

### Claim 14 (depends on 1)

The multijunction solar cell of claim 1 wherein each of the first, second, third, fourth and fifth solar subcells comprises an emitter region and a base region each of which is composed of GaAs and at least one of In, P or As.

### Claim 15

A method of manufacturing a solar cell, the method comprising:
providing a first substrate;
forming, on the first substrate, a first solar subcell having a first band gap;
forming a second solar subcell adjacent to the first solar subcell and having a second band gap smaller than the first band gap of the first solar subcell;
forming a third solar subcell adjacent to the second solar subcell and having a third band gap smaller than the second band gap of the second solar subcell;
forming a graded interlayer adjacent to the third solar subcell, the graded interlayer having a fourth band gap that is greater than the third band gap of the third solar subcell, wherein the graded interlayer is composed of a compositionally step-graded series of (InxGa1-x)yAl1-yAs layers with monotonically changing lattice constant, with x and y having respective values such that the band gap of the graded interlayer remains constant throughout its thickness, and wherein 0<x<1 and 0<y<1;
forming a fourth solar subcell adjacent to the graded interlayer, the fourth solar subcell having a fifth band gap smaller than the third band gap of the third solar subcell wherein the fourth solar subcell is lattice mismatched with respect to the third solar subcell, and wherein the graded interlayer provides a transition in lattice constant from the third solar subcell to the fourth solar subcell;
forming a fifth solar subcell adjacent to the fourth solar subcell and having a sixth band gap smaller than the fifth band gap of the fourth solar subcell;
mounting a surrogate substrate over the fifth solar subcell; and
subsequently removing the first substrate.

### Claim 16 (depends on 15)

The method of claim 15 including providing a metal contact layer over the fifth solar subcell before mounting the surrogate substrate.

### Claim 17 (depends on 15)

The method of claim 15 wherein the fourth band gap of the graded interlayer is constant at 1.5 eV throughout the thickness of the graded interlayer.

### Claim 18 (depends on 15)

The method of claim 15 including:
forming a first barrier layer over the third solar subcell, wherein the first barrier layer has a composition different from a composition of an adjoining layer of the third solar subcell;
forming the graded interlayer over the first barrier layer; and
forming a second barrier layer over the graded interlayer before forming the fourth solar subcell, wherein the second barrier layer has a composition different from a composition of the graded interlayer, and
wherein the first and second barrier layers are designed to prevent threading dislocations from propagating in a direction of growth of the solar cell or opposite the direction of growth.

### Claim 19 (depends on 18)

The method of claim 18 including forming the second barrier layer to have a composition different from the composition of the first barrier layer.

### Claim 20 (depends on 19)

The method of claim 19 including:
depositing the graded interlayer on the first barrier layer; and
depositing the second barrier on the graded interlayer.