# US 2017/0288073 A1 · Photovoltaic device and methods of forming the same

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- Number: US 2017/0288073 A1
- Document ID: US20170288073A1
- Status: Published application
- Kind: A1
- Application number: 15/619,674
- Filed: 2017-06-12
- Published: 2017-10-05
- Earliest claimed: 2013-06-27
- Assignees: First Solar, Inc.
- Applicants: First Solar, Inc.
- Inventors: Benyamin Buller; Markus Gloeckler; Akhlesh Gupta; Rick Powell; Rui Shao; Gang Xiong; Ming Lun Yu; Zhibo Zhao
- Web page: https://patentgrep.com/patent/US20170288073A1

## CPC

- H10F 77/211: {for photovoltaic cells}
- H10F 10/162: comprising only Group II-VI materials, e.g. CdS/CdTe photovoltaic cells
- H10F 10/167: comprising Group I-III-VI materials, e.g. CdS/CuInSe2 [CIS] heterojunction photovoltaic cells
- Y02E 10/541: CuInSe2 material PV 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

Methods and devices are described for a photovoltaic device. The photovoltaic device includes a glass substrate, a semiconductor absorber layer formed over the glass substrate, a metal back contact layer formed over the semiconductor absorber layer, and a p-type back contact buffer layer formed from one of MnTe, Cd1-xMnxTe, and SnTe, the buffer layer disposed between the semiconductor absorber layer and the metal back contact layer.

## Claims

### Claim 1

A method of manufacturing a photovoltaic device comprising the steps of:
depositing a semiconductor absorber layer on a substrate, wherein the semiconductor absorber layer is formed from CdTe;
depositing a p-type back contact buffer layer on the semiconductor absorber layer, wherein the p-type back contact buffer layer is formed from MnTe, and wherein the depositing a p-type back contact buffer layer step is an evaporation step whereby the MnTe back contact buffer layer is deposited on the semiconductor absorber layer by impinging evaporated MnTe onto the semiconductor absorber layer, the evaporated MnTe generated by heating a source of MnTe; and
depositing a back contact layer on the p-type back contact buffer layer.

### Claim 2 (depends on 1)

The method of claim 1, wherein the evaporation step is performed at a temperature of up to about 1200° C.

### Claim 3 (depends on 1)

The method of claim 1, wherein the MnTe is doped up to about 1019 cm−3.

### Claim 4

A method of manufacturing a photovoltaic device comprising the steps of:
depositing a semiconductor absorber layer on a substrate, wherein the semiconductor absorber layer is formed from CdTe;
depositing a p-type back contact buffer layer on the semiconductor absorber layer, wherein the depositing a p-type back contact buffer layer step is a sputtering step whereby the MnTe back contact buffer layer is deposited on the semiconductor absorber layer by sputtering MnTe with a MnTe target onto the semiconductor absorber layer; and
depositing a back contact layer on the p-type back contact buffer layer.

### Claim 5 (depends on 4)

The method of claim 4, wherein the sputtering step is performed at a temperature of up to about 300° C.

### Claim 6 (depends on 4)

The method of claim 4, wherein the MnTe is doped up to about 1019 cm−3.

### Claim 7

A method of manufacturing a photovoltaic device comprising the steps of:
depositing a semiconductor absorber layer on a substrate, wherein the semiconductor absorber layer is formed from CdTe;
depositing a p-type back contact buffer layer on the semiconductor absorber layer, wherein the depositing a p-type back contact buffer layer step is a chemical reaction step involving:
a. depositing MnI2 solution onto the semiconductor absorber layer by one of application of liquid MnI2 thereon and evaporating MnI2 onto thereon; and
b. annealing the MnI2-coated semiconductor absorber layer to form the p-type back contact; and
depositing a back contact layer on the p-type back contact buffer layer.

### Claim 8 (depends on 7)

The method of claim 7, wherein the annealing step is conducted at a temperature of from about 400° C. to about 650° C. in an oxygen-deficient environment.

### Claim 9 (depends on 7)

The method of claim 7, wherein the annealing step is conducted in the presence of a flow of an inert gas to remove annealing byproduct gases.

### Claim 10 (depends on 7)

The method of claim 7, wherein the p-type back contact buffer layer is formed from SnTe.

### Claim 11 (depends on 10)

The method of claim 10, wherein the depositing a p-type back contact buffer layer step is a sputtering step whereby the SnTe back contact buffer layer is deposited on the semiconductor absorber layer by sputtering SnTe with a SnTe target onto the semiconductor absorber layer.

### Claim 12 (depends on 10)

The method of claim 10, wherein the depositing a p-type back contact buffer layer step is a vapor transport deposition step whereby SnTe is deposited on the semiconductor absorber layer.

### Claim 13 (depends on 10)

The method of claim 10, wherein the SnTe back contact buffer layer has a thickness from about 10 nm to about 500 nm.

### Claim 14 (depends on 7)

The method of claim 7, wherein the p-type back contact buffer layer is formed from Cd1-xMnxTe.

### Claim 15 (depends on 14)

The method of claim 14, wherein the Cd1-xMnxTe comprises Cd0.5Mn0.5Te.