# US 8,772,623 B2 · Low-bandgap, monolithic, multi-bandgap, optoelectronic devices

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- Number: US 8,772,623 B2
- Document ID: US8772623B2
- Status: Granted
- Kind: B2
- Application number: 13/664,142
- Filed: 2012-10-30
- Published: 2013-05-09
- Granted: 2014-07-08
- Earliest claimed: 2012-10-30
- Assignees: Alliance for Sustainable Energy, LLC
- Applicants: Alliance for Sustainable Energy, LLC
- Inventors: Mark W. Wanlass; Jeffrey J. Carapella
- Web page: https://patentgrep.com/patent/US8772623B2

## CPC

- H10F 19/31: having multiple laterally adjacent thin-film photovoltaic cells deposited on the same substrate
- H10F 10/142: comprising multiple PN homojunctions, e.g. tandem cells
- H10F 10/1425: {Inverted metamorphic multi-junction [IMM] photovoltaic cells}
- H10F 19/20: comprising photovoltaic cells in arrays in or on a single semiconductor substrate, the photovoltaic cells having planar junctions (having multiple thin-film photovoltaic cells deposited on the same substrate H10F19/31)
- H10F 19/40: comprising photovoltaic cells in a mechanically stacked configuration
- Y02E 10/544: Solar cells from Group III-V materials
- 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

## Abstract

Low bandgap, monolithic, multi-bandgap, optoelectronic devices (10), including PV converters, photodetectors, and LED's, have lattice-matched (LM), double-heterostructure (DH), low-bandgap GaInAs(P) subcells (22, 24) including those that are lattice-mismatched (LMM) to InP, grown on an InP substrate (26) by use of at least one graded lattice constant transition layer (20) of InAsP positioned somewhere between the InP substrate (26) and the LMM subcell(s) (22, 24). These devices are monofacial (10) or bifacial (80) and include monolithic, integrated, modules (MIMs) (190) with a plurality of voltage-matched subcell circuits (262, 264, 266, 270, 272) as well as other variations and embodiments.

## Claims

### Claim 1

A monolithic, multi-bandgap, photovoltaic converter, comprising:
a first subcell comprising GaInAs(P) with a first bandgap and a first lattice constant;
a second subcell comprising GaInAs(P) with a second bandgap and a second lattice constant, wherein the second bandgap is less than the first bandgap and the second lattice constant is greater than the first lattice constant, and further, wherein the second lattice constant is equal to a lattice constant of a InAsyP1-y alloy with a bandgap greater than the first bandgap; and
a lattice constant transition material positioned between the first subcell and the second subcell, said lattice constant transition material comprising InAsyP1-y alloy with a lattice constant that changes gradually from the first lattice constant to the second lattice constant.

### Claim 2 (depends on 1)

The monolithic, multi-bandgap, photovoltaic converter of claim 1, wherein the lattice constant transition material is grown epitaxially on the first subcell with a gradually increasing value for y.

### Claim 3 (depends on 1)

The monolithic, multi-bandgap, photovoltaic converter of claim 1, wherein the second subcell is grown epitaxially on the lattice constant transition material,

### Claim 4 (depends on 1)

The monolithic, multi-bandgap, photovoltaic converter of claim 1, wherein the first subcell is a lattice-matched, double-heterostructure, comprising homojunction layers of GaInAs(P) clad by InAsyP1-y cladding layers wherein the InAsyP1-y cladding has a value for y in a range of o<y<1, such the InAsyP1-y cladding layers of the first subcell have a lattice constant equal to the first lattice constant.

### Claim 5 (depends on 4)

The monolithic, multi-bandgap, photovoltaic converter of claim 4, wherein the second subcell is a lattice-matched, double-heterostructure comprising homojunction layers of GaInAs(P) clad by InAsyP1-y cladding layers, wherein the InAsyP1-y cladding has a value for y in a range of o<y<1, such that the InAsyP1-y cladding layer of the second subcell have a lattice constant equal to the second lattice constant.

### Claim 6 (depends on 1)

The monolithic, multi-bandgap, photovoltaic converter of claim 1, including a InP substrate, and wherein the first subcell is grown epitaxially on the InP substrate.

### Claim 7 (depends on 1)

The monolithic, multi-bandgap, photovoltaic converter of claim 1, including a tunnel junction positioned between the first subcell and the second subcell.

### Claim 8 (depends on 7)

The monolithic, multi-bandgap, photovoltaic converter of claim 7, wherein the tunnel junction is positioned between the first subcell and the lattice constant transition layer.

### Claim 9 (depends on 1)

The monolithic, multi-bandgap, photovoltaic converter of claim 1, wherein the lattice constant of the lattice constant transition material is graded.

### Claim 10 (depends on 1)

The monolithic, multi-bandgap, photovoltaic converter of claim 1, wherein the lattice constant of the lattice constant transition material changes in steps of multiple, discrete, increments.

### Claim 11 (depends on 1)

The monolithic, multi-bandgap, photovoltaic converter of claim 1, wherein the first bandgap is 0.74 eV.

### Claim 12 (depends on 6)

The monolithic, multi-bandgap, photovoltaic converter of claim 6, wherein the first subcell is grown epitaxially on a front surface of the InP substrate, the lattice constant transition layer is grown epitaxially on a back surface of the InP substrate, and the second subcell is grown epitaxially on the lattice constant transition layer.

### Claim 13 (depends on 12)

The monolithic, multi-bandgap, photovoltaic converter of claim 12, wherein the InP substrate is doped with deep acceptor atoms to make the substrate more electrically insulating than InP, which is not doped with deep acceptor atoms.

### Claim 14 (depends on 1)

The monolithic, multi-bandgap, photovoltaic converter of claim 1, including a InP substrate positioned between the first subcell and the second subcell.

### Claim 15 (depends on 14)

The monolithic, multi-bandgap, photovoltaic converter of claim 14, wherein the InP substrate is positioned between the first subcell and the lattice constant transition material.

### Claim 16 (depends on 1)

The monolithic, multi-bandgap, photovoltaic converter of claim 1, including an isolation layer positioned between the first subcell and the second subcell.

### Claim 17 (depends on 16)

The monolithic, multi-bandgap, photovoltaic converter of claim 16, wherein the isolation layer is positioned between the first subcell and the lattice constant transition material.

### Claim 18 (depends on 16)

The monolithic, multi-bandgap, photovoltaic converter of claim 16, including a InP substrate positioned between the first subcell and the second subcell.

### Claim 19 (depends on 18)

The monolithic, multi-bandgap, photovoltaic converter of claim 18, wherein the InP substrate is positioned between the second subcell and the isolation layer.

### Claim 20 (depends on 18)

The monolithic, multi-bandgap, photovoltaic converter of claim 18, wherein the InP substrate is positioned between the first subcell and the isolation layer.

### Claim 21 (depends on 14)

The monolithic, multi-bandgap, photovoltaic converter of claim 14, including a first isolation layer positioned between the InP substrate and the first subcell, and including a second isolation layer positioned between the InP substrate and the second subcell.

### Claim 22

A monolithic, multi-bandgap, photovoltaic converter, comprising:
a InP substrate with a substrate lattice constant;
a first subcell comprising GaInAs(P) with a first bandgap and a first lattice constant, wherein the first lattice constant is greater than the substrate lattice constant;
a lattice constant transition material positioned between the InP substrate and the first subcell, said lattice constant transition material comprising InAsyP1-y alloy with a lattice constant that changes from the substrate lattice constant to the first lattice constant; and
a second subcell comprising GaInAs(P) positioned behind the first subcell, said GaInAs(P) of the second cell having a second bandgap, which is less than the first bandgap, and a second lattice constant.

### Claim 23 (depends on 22)

The monolithic, multi-bandgap, photovoltaic converter of claim 22, wherein the second lattice second lattice constant is equal to the first lattice constant.