# US 2018/0323334 A1 · Photovoltaic Devices and Method of Making

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- Number: US 2018/0323334 A1
- Document ID: US20180323334A1
- Status: Published application
- Kind: A1
- Application number: 16/032,531
- Filed: 2018-07-11
- Published: 2018-11-08
- Earliest claimed: 2013-06-07
- Assignees: First Solar, Inc.
- Applicants: First Solar, Inc.
- Inventors: Holly Ann Blaydes; Kristian William Andreini; William Hullinger Huber; Eugene Thomas Hinners; Joseph John Shiang; Yong Liang; Jongwoo Choi; Adam Fraser Halverson
- Web page: https://patentgrep.com/patent/US20180323334A1

## CPC

- H10F 71/125: {The active layers comprising only Group II-VI materials, e.g. CdS, ZnS or CdTe}
- H10F 10/13: Photovoltaic cells having absorbing layers comprising graded bandgaps
- H10F 10/162: comprising only Group II-VI materials, e.g. CdS/CdTe photovoltaic cells
- H10F 71/1253: {comprising at least three elements, e.g. HgCdTe}
- H10F 77/1237: {having at least three elements, e.g. HgCdTe}
- H10F 77/211: {for photovoltaic cells}
- Y02E 10/543: Solar cells from Group II-VI materials
- 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

Embodiments of a photovoltaic device are provided herein. The photovoltaic device can include a layer stack and an absorber layer disposed on the layer stack. The absorber layer can include a first region and a second region. Each of the first region of the absorber layer and the second region of the absorber layer can include a compound comprising cadmium, selenium, and tellurium. An atomic concentration of selenium can vary across the absorber layer. The first region of the absorber layer can have a thickness between 100 nanometers to 3000 nanometers. The second region of the absorber layer can have a thickness between 100 nanometers to 3000 nanometers. A ratio of an average atomic concentration of selenium in the first region of the absorber layer to an average atomic concentration of selenium in the second region of the absorber layer can be greater than 10.

## Claims

### Claim 1

A photovoltaic device, comprising:
a layer stack; and
an absorber layer disposed on the layer stack, wherein:
the absorber layer comprises a compound comprising cadmium, selenium, and tellurium,
the compound comprising cadmium, selenium, and tellurium has a first region and a second region,
an atomic concentration of selenium varies across the absorber layer;
the first region of the compound comprising cadmium, selenium, and tellurium has a thickness between 100 nanometers to 3000 nanometers,
the second region of the compound comprising cadmium, selenium, and tellurium has a thickness between 100 nanometers to 3000 nanometers, and
a ratio of an average atomic concentration of selenium in the first region of the compound comprising cadmium, selenium, and tellurium to an average atomic concentration of selenium in the second region of the compound comprising cadmium, selenium, and tellurium is greater than 10.

### Claim 2 (depends on 1)

The photovoltaic device of claim 1, wherein a peak of a Se/(Se+Te) ratio of the absorber layer is less than 0.40.

### Claim 3 (depends on 1)

The photovoltaic device of claim 1, wherein an average atomic concentration of selenium in the absorber layer is in a range from 0.001 atomic percent to 40 atomic percent of the absorber layer.

### Claim 4 (depends on 1)

The photovoltaic device of claim 1, wherein the atomic concentration of selenium in the absorber layer has a profile comprising an exponential profile, a top-hat profile, a step-change profile, a saw-tooth profile, a square-wave profile, a power law profile, or combinations thereof.

### Claim 5 (depends on 1)

The photovoltaic device of claim 1, wherein the absorber layer comprises sulfur, oxygen, copper, chlorine, lead, zinc, mercury, or combinations thereof.

### Claim 6 (depends on 1)

The photovoltaic device of claim 1, wherein at least a portion of the compound comprising cadmium, selenium, and tellurium is a ternary compound or a quaternary compound.

### Claim 7 (depends on 1)

The photovoltaic device of claim 1, wherein the compound comprising cadmium, selenium, and tellurium further comprises mercury.

### Claim 8 (depends on 7)

The photovoltaic device of claim 7, an amount of mercury varies across a thickness of the absorber layer.

### Claim 9 (depends on 1)

The photovoltaic device of claim 1, wherein the compound comprising cadmium, selenium, and tellurium further comprises zinc.

### Claim 10 (depends on 9)

The photovoltaic device of claim 9, an amount of zinc varies across a thickness of the absorber layer.

### Claim 11

A photovoltaic device, comprising:
a layer stack comprising a transparent conductive oxide; and
an absorber layer disposed on the layer stack, wherein:
the absorber layer comprises a compound comprising cadmium, selenium, and tellurium,
the compound comprising cadmium, selenium, and tellurium comprising a first region disposed proximate to the layer stack relative to a second region,
the first region of the compound comprising cadmium, selenium, and tellurium is disposed at a front interface of the absorber layer,
the second region of the compound comprising cadmium, selenium, and tellurium is disposed at a back interface of the absorber layer,
the first region of the compound comprising cadmium, selenium, and tellurium has a thickness between 200 nanometers to 1500 nanometers,
the second region of the compound comprising cadmium, selenium, and tellurium has a thickness between 200 nanometers to 1500 nanometers, and
a ratio of an average atomic concentration of selenium in the first region of the compound comprising cadmium, selenium, and tellurium to an average atomic concentration of selenium in the second region of the compound comprising cadmium, selenium, and tellurium is greater than 2.

### Claim 12 (depends on 11)

The photovoltaic device of claim 11, wherein the compound comprising cadmium, selenium, and tellurium further comprises mercury.

### Claim 13 (depends on 12)

The photovoltaic device of claim 12, an amount of mercury varies across a thickness of the absorber layer.

### Claim 14 (depends on 11)

The photovoltaic device of claim 11, wherein the compound comprising cadmium, selenium, and tellurium further comprises zinc.

### Claim 15 (depends on 14)

The photovoltaic device of claim 14, an amount of zinc varies across a thickness of the absorber layer.

### Claim 16 (depends on 11)

The photovoltaic device of claim 11, wherein an average atomic concentration of selenium in the absorber layer is in a range from 0.01 atomic percent to 25 atomic percent of the absorber layer.

### Claim 17 (depends on 16)

The photovoltaic device of claim 16, wherein a peak of a Se/(Se+Te) ratio of the absorber layer is located at the front interface of the absorber layer.

### Claim 18 (depends on 17)

The photovoltaic device of claim 17, wherein the peak of the Se/(Se+Te) ratio of the absorber layer is less than 0.40.

### Claim 19 (depends on 18)

The photovoltaic device of claim 18, wherein the photovoltaic device is substantially free of a cadmium sulfide layer.