# US 9,437,760 B2 · Method of reducing semiconductor window layer loss during thin film photovoltaic device fabrication, and resulting device structure

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- Number: US 9,437,760 B2
- Document ID: US9437760B2
- Status: Granted
- Kind: B2
- Application number: 14/209,589
- Filed: 2014-03-13
- Published: 2014-09-18
- Granted: 2016-09-06
- Earliest claimed: 2013-03-15
- Assignees: First Solar, Inc.
- Applicants: First Solar, Inc.
- Inventors: Daniel Damjanovic; Rick C. Powell; Jigish Trivedi; Zhibo Zhao
- Web page: https://patentgrep.com/patent/US9437760B2

## CPC

- H10F 77/123: comprising only Group II-VI materials, e.g. CdS, ZnS or HgCdTe
- H10F 10/162: comprising only Group II-VI materials, e.g. CdS/CdTe photovoltaic cells
- H10F 71/125: {The active layers comprising only Group II-VI materials, e.g. CdS, ZnS or CdTe}
- H10F 71/1253: {comprising at least three elements, e.g. HgCdTe}
- H10F 77/1237: {having at least three elements, e.g. HgCdTe}
- H10F 77/1696: {the films including Group II-VI materials, e.g. CdTe or CdS}
- H10P 14/22: using physical deposition, e.g. vacuum deposition or sputtering
- H10P 14/3436: {being chalcogenide semiconductor materials not being oxides, e.g. ternary compounds}
- 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
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
- 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 completed photovoltaic device and method forming it are described in which fluxing of a window layer into an absorber layer is mitigated by the presence of a sacrificial fluxing layer.

## Claims

### Claim 1

A method of manufacturing a photovoltaic device, the method comprising:
forming a first electrode;
forming a window layer containing sulfur in electrical association with the first electrode;
forming a first absorber layer adjacent the window layer;
forming a sacrificial layer containing sulfur adjacent the first absorber layer;
forming a second absorber layer adjacent the sacrificial layer;
wherein the sacrificial layer is formed in contact with the first absorber layer and the second absorber layer;
heating the device layers such that at least a portion of the sulfur from the sacrificial layer fluxes into the first and second absorber layers; and,
forming a second electrode in electrical association with the second absorber layer.

### Claim 2 (depends on 1)

The method of claim 1 wherein the fluxing of the sacrificial layer into the absorber layers decreases a fluxing of the sulfur from the window layer into the first absorber layer during the heating.

### Claim 3 (depends on 1)

The method of claim 1, wherein the window layer and the sacrificial layer are formed of the same material.

### Claim 4 (depends on 1)

The method of claim 1, wherein the window layer comprises a material selected from the group consisting of cadmium sulfide and cadmium zinc sulfide.

### Claim 5 (depends on 4)

The method of claim 4, wherein the sacrificial layer comprises a material selected from the group consisting of cadmium sulfide and cadmium zinc sulfide.

### Claim 6 (depends on 1)

The method of claim 1, wherein the first and second absorber layers each comprise cadmium telluride.

### Claim 7 (depends on 1)

The method of claim 1, further comprising treating at least the second absorber layer with a compound comprising chlorine in association with the heating.

### Claim 8 (depends on 7)

The method of claim 7, wherein the sacrificial layer and the first and second absorber layers are formed to thicknesses such that after the treating and heating steps at least a portion of the first and second absorber layers are in contact with each other.

### Claim 9 (depends on 7)

The method of claim 7, wherein the sacrificial layer and first and second absorber layers are formed to thicknesses such that after the treating and heating steps a portion of each of the first and second absorber layers are separated by a portion of the sacrificial layer.

### Claim 10 (depends on 7)

The method of claim 7 wherein the compound comprising chlorine comprises a material selected from the group consisting of CdCl2, NH2Cl, ZnCl2, and TeCl4.

### Claim 11 (depends on 10)

The method of claim 10 wherein, wherein heating the device layers comprises a first heating at a first temperature and a second heating at a second temperature.

### Claim 12 (depends on 11)

The method of claim 11, wherein the first and second temperatures are different.

### Claim 13 (depends on 10)

The method of claim 10, wherein the treating step comprises more than one treatment step with the compound comprising chlorine.

### Claim 14 (depends on 13)

The method of claim 13, wherein the heating steps comprise a first heating to between about 400° C. and about 600° C. for between about 10 seconds and about 2 hours after a first compound comprising chlorine treatment and a second heating to between about 400° C. and about 600° C. for between about 10 seconds and about 2 hours after a second compound comprising chlorine treatment step.

### Claim 15 (depends on 14)

The method of claim 14, wherein the first and second heating steps are each to between about 420° C. and about 450° C. for between about 15 minutes and about 30 minutes.

### Claim 16 (depends on 7)

The method of claim 7, wherein the compound comprising chlorine comprises an aqueous CdCl2 solution having a concentration between about 100 g/L and about 600 g/L.

### Claim 17 (depends on 1)

The method of claim 1, wherein the sacrificial layer is formed to a thickness of between about 50 Å and about 1000 Å.

### Claim 18 (depends on 17)

The method of claim 17, wherein the first absorber layer is formed to a thickness of between about 10 Å and about 50,000 Å.

### Claim 19 (depends on 17)

The method of claim 17, wherein the second absorber layer is formed to a thickness of between about 500 Å and about 50,000 Å.

### Claim 20 (depends on 17)

The method of claim 17, wherein the window layer is formed to a thickness of between about 50 Å and about 2,000 Å.

### Claim 21 (depends on 17)

The method of claim 17, wherein the sacrificial layer is formed to a thickness of between about 100 Å and about 800 Å.

### Claim 22 (depends on 21)

The method of claim 21, wherein the first absorber layer is formed to a thickness of between about 10,000 Å and about 30,000 Å.

### Claim 23 (depends on 21)

The method of claim 21, wherein the second absorber layer is formed to a thickness of between about 10,000 Å and about 40,000 Å.

### Claim 24 (depends on 21)

The method of claim 21, wherein the window layer is formed to a thickness of between about 75 Å and about 1000 Å.

### Claim 25 (depends on 1)

The method of claim 1, wherein heating the device layers comprises heating the device to between about 300° C. and about 600° C.

### Claim 26 (depends on 25)

The method of claim 25, wherein heating the device layers comprises heating the device to between about 400° C. and about 450° C.