# US 10,109,761 B2 · Fabricating thin-film optoelectronic devices with modified surface

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- Number: US 10,109,761 B2
- Document ID: US10109761B2
- Status: Granted
- Kind: B2
- Application number: 15/312,718
- Filed: 2015-05-21
- Published: 2017-05-11
- Granted: 2018-10-23
- Earliest claimed: 2014-05-23
- Assignees: Flisom AG; Empa
- Applicants: Flisom AG; Empa
- Inventors: Patrick Reinhard; Fabian Pianezzi; Benjamin Bissig; Stephan Buecheler; Ayodhya Nath Tiwari
- Web page: https://patentgrep.com/patent/US10109761B2

## CPC

- H10F 71/128: {Annealing}
- H10F 10/167: comprising Group I-III-VI materials, e.g. CdS/CuInSe2 [CIS] heterojunction photovoltaic cells
- H10F 19/30: comprising thin-film photovoltaic cells
- H10F 77/126: {comprising only Group I-III-VI chalcopyrite materials, e.g. CuInSe2, CuGaSe2 or CuInGaSe2 [CIGS]}
- H10F 77/1265: {characterised by the dopants}
- H10F 77/148: {Shapes of potential barriers}
- H10F 77/1698: {the metallic or insulating substrates being flexible}
- H10F 77/211: {for photovoltaic cells}
- H10P 14/3241: {being conductive materials}
- H10P 14/3436: {being chalcogenide semiconductor materials not being oxides, e.g. ternary compounds}
- H10P 14/38: {characterised by treatments done after the formation of the materials}
- Y02E 10/541: CuInSe2 material PV cells
- 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

## Abstract

A method (200) for fabricating thin-film optoelectronic devices (100), the method comprising: providing a substrate (110), forming a back-contact layer (120); forming at least one absorber layer (130) made of an ABC chalcogenide material, adding at least one alkali metal (235), and forming at least one cavity (236, 610, 612, 613) at the surface of the absorber layer wherein forming of said at least one cavity is by dissolving away from said surface of the absorber layer at least one crystal aggregate comprising at least one alkali crystal comprising at least one alkali metal. The method (200) is advantageous for more environmentally-friendly production of photovoltaic devices (100) on flexible substrates with high photovoltaic conversion efficiency and faster production rate.

## Claims

### Claim 1

A method of fabricating thin-film optoelectronic devices, the method comprising:
providing a substrate;
forming a back-contact layer;
forming at least one absorber layer, which absorber layer is made of an ABC chalcogenide material, wherein A represents one or more elements selected from a group consisting of Cu and Ag, B represents one or more elements selected from a group consisting of In, Ga, and Al, and C represents one or more elements selected from a group consisting of S, Se, and Te;
adding at least one alkali metal; and
forming at least one cavity at a surface of the absorber layer by dissolving away from said surface of the absorber layer at least one crystal aggregate comprising at least one alkali crystal comprising at least one alkali metal.

### Claim 2 (depends on 1)

The method according to claim 1, wherein the at least one alkali metal comprises potassium.

### Claim 3 (depends on 1)

The method according to claim 1, further comprising a step of aqueous wetting of at least the surface of the absorber layer with a diluted aqueous ammonia solution with a diluted ammonia molarity in a range from 0.1 to 20 M.

### Claim 4 (depends on 1)

The method according to claim 1, further comprising a step of treating the surface of the absorber layer by adding oxidation state +1/+2 elements to the surface of the absorber layer.

### Claim 5 (depends on 1)

The method according to claim 1, wherein the at least one absorber layer is Cu(In,Ga)Se2.

### Claim 6 (depends on 1)

The method according to claim 1, further comprising forming at least one front-contact layer.

### Claim 7 (depends on 1)

The method according to claim 1, wherein a reflectance of the thin-film optoelectronic device is adjusted by adjusting an amount of at the least one alkali metal in the step of adding the at least one alkali metal.

### Claim 8 (depends on 1)

The method according to claim 1, wherein said substrate is conveyed between a delivery roll and a take-up roll of a roll-to-roll manufacturing apparatus.

### Claim 9

A method of fabricating thin-film optoelectronic devices, the method comprising:
providing a substrate;
forming a back-contact layer;
forming at least one absorber layer, which absorber layer is made of an ABC chalcogenide material, wherein A represents one or more elements selected from a group consisting of Cu and Ag, B represents one or more elements selected from a group consisting of In, Ga, and Al, and C represents one or more elements selected from a group consisting of S, Se, and Te;
adding at least one alkali metal, wherein adding the at least one alkali metal causes at least one crystal aggregate comprising at least one alkali crystal to form on a surface of the absorber layer;
forming at least one cavity at the surface of the absorber layer by dissolving away from said surface of the absorber layer the at least one alkali crystal, wherein the forming at least one cavity comprises:
wetting at least the surface of the absorber layer with an aqueous solution comprising ammonia; and
then forming a buffer layer over the surface of the absorber layer, wherein the buffer layer comprises an element selected from the group of cadmium, zinc, indium and gallium.

### Claim 10 (depends on 9)

The method of claim 9, wherein the at least one alkali metal comprises potassium.

### Claim 11 (depends on 10)

The method of claim 10, wherein the adding at least potassium comprises adding at least one of the group consisting of KF, KCl, KBr, KI, K2S, and K2Se.

### Claim 12 (depends on 9)

The method of claim 9, wherein the solution comprising ammonia comprises a solution with a diluted ammonia molarity in a range from 0.1 to 20 M.

### Claim 13 (depends on 9)

The method of claim 9, wherein forming the least one cavity at the surface of the absorber layer further comprises treating the surface of the absorber layer with a solution comprising cadmium and ammonia before forming the buffer layer over the surface of the absorber layer.

### Claim 14 (depends on 13)

The method of claim 13, wherein the solution comprising cadmium and ammonia comprises an ammonia solution molarity in the range of 1 mol/L to 30 mol/L.

### Claim 15 (depends on 13)

The method of claim 13, wherein the solution comprising cadmium and ammonia comprises a cadmium solution molarity in the range of 0.00001 mol/L to 10 mol/L.

### Claim 16 (depends on 13)

The method of claim 13, wherein the forming at least one cavity further comprises adding oxidation state +1/+2 elements to the surface of the absorber layer.

### Claim 17 (depends on 9)

The method of claim 9, wherein the solution comprising ammonia comprises a diluted aqueous ammonia solution with a diluted ammonia molarity in a range from 0.1 to 20 M.

### Claim 18 (depends on 9)

The method of claim 9, wherein the substrate comprises polyimide.

### Claim 19 (depends on 9)

The method of claim 9, wherein the adding at least one alkali metal is done in the presence of at least one or more elements selected from a group consisting of S, Se, and Te.