# US 8,541,048 B1 · Formation of photovoltaic absorber layers on foil substrates

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- Number: US 8,541,048 B1
- Document ID: US8541048B1
- Status: Granted
- Kind: B1
- Application number: 12/437,539
- Filed: 2009-05-07
- Granted: 2013-09-24
- Earliest claimed: 2004-09-18
- Assignees: Nanosolar, Inc.
- Applicants: Craig Leidholm; Brent Bollman
- Inventors: Craig Leidholm; Brent Bollman
- Web page: https://patentgrep.com/patent/US8541048B1

## CPC

- H10F 77/126: {comprising only Group I-III-VI chalcopyrite materials, e.g. CuInSe2, CuGaSe2 or CuInGaSe2 [CIGS]}
- H10F 71/128: {Annealing}
- H10F 77/169: Thin semiconductor films on metallic or insulating substrates
- H10F 77/1694: {the films including Group I-III-VI materials, e.g. CIS or CIGS}
- H10F 77/1696: {the films including Group II-VI materials, e.g. CdTe or CdS}
- H10F 77/1698: {the metallic or insulating substrates being flexible}
- H10F 77/1699: {the films including Group I-III-VI materials, e.g. CIS or CIGS on metal foils or polymer foils}
- H10P 14/203: {using transformation of metal, e.g. oxidation or nitridation}
- H10P 14/265: {using solutions}
- H10P 14/2922: {being non-crystalline insulating materials, e.g. glass or polymers}
- H10P 14/2923: {being conductive materials, e.g. metallic silicides}
- H10P 14/3241: {being conductive materials}
- H10P 14/3436: {being chalcogenide semiconductor materials not being oxides, e.g. ternary compounds}
- H10P 14/3461: {Nanoparticles}
- Y02E 10/541: CuInSe2 material PV cells
- 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

An absorber layer of a photovoltaic device may be formed on an aluminum or metallized polymer foil substrate. A nascent absorber layer containing one or more elements of group IB and one or more elements of group IIIA is formed on the substrate. The nascent absorber layer and/or substrate is then rapidly heated from an ambient temperature to an average plateau temperature range of between about 200° C. and about 600° C. and maintained in the average plateau temperature range 1 to 30 minutes after which the temperature is reduced.

## Claims

### Claim 1

A method comprising:
continuous processing of an elongate flexible metal substrate coated with a nascent absorber layer, the continuous processing occurring as the substrate passes through an elongate furnace in a non-oxygen group VIA vapor atmosphere in a non-vacuum process to incorporate the group VIA element into the nascent absorber layer without damaging or destroying the metal substrate and without generating substantial hydrogen selenide, wherein the elongate flexible metal substrate comprises a bulk portion comprised of aluminum and a first, electrically conductive diffusion barrier on a top surface of the aluminum and a second diffusion barrier layer on a bottom surface of the substrate, wherein the first diffusion barrier layer is between the substrate and an electrode layer.

### Claim 2 (depends on 1)

The method of claim 1 wherein the nascent absorber layer and/or substrate passing through the elongate furnace is: a) rapidly heated from an ambient temperature to a plateau temperature range of between about 200° C. and about 600° C., the rapid thermal heating occurring at a ramp rate between about 5° C.°/sec and about 150° C.°/sec, b) maintained at the plateau temperature for between about 2 minutes and 10 minutes; and c) lowered to a reduced temperature.

### Claim 3 (depends on 1)

The method of claim 1 wherein processing the nascent absorber layer includes depositing the nascent absorber layer from a solution of nanoparticulate precursor materials.

### Claim 4 (depends on 3)

The method of claim 3 further comprising, incorporating one or more group VIA elements into the nascent absorber layer either before or during the step of rapidly heating the nascent absorber layer and/or substrate.

### Claim 5 (depends on 4)

The method of claim 4 wherein the group VIA vapor atmosphere includes sulfur.

### Claim 6 (depends on 3)

The method of claim 3 wherein rapidly heating the nascent absorber layer and/or substrate is performed by radiant heating of the nascent absorber layer and/or substrate.

### Claim 7 (depends on 6)

The method of claim 6 wherein one or more infrared lamps apply the radiant heating.

### Claim 8 (depends on 3)

The method of claim 3 wherein the continuous processing of the nascent absorber layer takes place as the substrate passes through roll-to-roll processing.

### Claim 9 (depends on 3)

The method of claim 3 further comprising, incorporating one or more group VIA elements into the nascent absorber layer after rapidly heating the nascent absorber layer and/or substrate.

### Claim 10 (depends on 3)

The method of claim 3, further comprising, incorporating an intermediate layer between a layer of molybdenum and the metal substrate, wherein the intermediate layer inhibits inter-diffusion of molybdenum and metal during heating.

### Claim 11 (depends on 10)

The method of claim 10 wherein, the intermediate layer includes, chromium, vanadium, tungsten, glass, and/or nitrides, tantalum nitride, tungsten nitride, and silicon nitride, oxides, or carbides.

### Claim 12 (depends on 4)

The method of claim 4 wherein the group VIA vapor atmosphere includes selenium.

### Claim 13 (depends on 1)

The method of claim 1 wherein processing the nascent absorber layer includes depositing a film of an ink containing elements of groups IB and IIIA on the substrate.

### Claim 14 (depends on 1)

The method of claim 1, further comprising disposing a layer of molybdenum between the metal substrate and the nascent absorber layer.

### Claim 15 (depends on 1)

The method of claim 1 wherein the elongate furnace comprises a tube furnace.

### Claim 16

A method comprising:
continuous processing of an elongate flexible metal substrate coated with a nascent absorber layer in two or more processing stages, the processing occurring as the substrate passes through an elongate furnace,
wherein at least one of the foregoing stages occurs in a non-oxygen group VIA vapor in a non-vacuum process and a total time spent above ambient temperature in such vapor is sufficient to incorporate the non-oxygen group VIA material into the absorber layer without damaging or destroying the metal substrate while continuously moving the substrate through the furnace, wherein the elongate flexible metal substrate comprises a bulk portion comprised of aluminum and a first electrically conductive diffusion barrier on a top surface of the aluminum and a second diffusion barrier layer on a bottom surface of the substrate, wherein the first diffusion barrier layer is between the substrate and an electrode layer.

### Claim 17 (depends on 16)

The method of claim 16 wherein the nascent absorber layer and/or substrate passing through the elongate furnace is at one stage rapidly heated from an ambient temperature to a plateau temperature range of between about 200° C. and about 600° C., the rapid thermal heating occurring at a ramp rate between about 5° C.°/sec and about 150° C.°/sec, at another stage maintained at the plateau temperature for between about 2 minutes and 10 minutes; and at yet another stage lowered to a reduced temperature.

### Claim 18 (depends on 17)

The method of claim 17 wherein the substrate is moved using a roll-to-roll system.