Cost Reduction of IMM Solar Cells by Recycling Substrates Using Wet Chemical Etching, Phase II

Metadata Updated: February 28, 2019

The goal of the program is to reduce the cost of substrate reclaim for high-efficiency solar cells fabricated by an epitaxial lift-off (ELO) process, and to increase the number of reuse cycles for a given substrate. If successful, this will result in a reduction in the cost of GaAs-based multi-junction solar cells, in which the cost of the substrate accounts for approximately 50% of the total cost. The cost reduction is achieved by introducing a new multi-layer etch-stop structure into a inverted metamorphic (IMM) triple-junction cell. The etch-stop structure is grown between the original GaAs substrate and the ELO release layer, thereby becoming the effective substrate surface after the ELO process. The etch-stop structure prevents pits and surface damage that occur during ELO from damaging the surface of the GaAs substrate. The standard method of reclaiming the GaAs substrate after ELO is to employ chemo-mechanical polishing (CMP) to remove the defect-ridden GaAs surface and chemically polish the underlying GaAs to yield a surface that is suitable for epitaxial growth. The CMP process works but reduces the substrate thickness and causes minor wafer damage itself, which requires further polishing. These factors accumulate, in practice limiting the number of reclaim cycles to 5 - 10 for a given substrate. With the incorporation of the proposed etch-stop structure, the defects are isolated in the etch-stop structure, which can be dissolved by successive selective wet chemical etches to produce the original pristine GaAs surface on a substrate of the original thickness. All mechanical polishing is eliminated in this proposed work, ensuring a constant substrate thickness through repeated substrate reclaim cycles and reducing the estimated cost of the recycling process to <$1 per substrate. The Phase I program demonstrated that this method for substrate reclaim works; in Phase II we will develop the reclaim into an optimized batch process.

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Public: This dataset is intended for public access and use. License: U.S. Government Work

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Metadata Created Date August 1, 2018
Metadata Updated Date February 28, 2019

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Harvested from NASA Data.json

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Resource Type Dataset
Metadata Created Date August 1, 2018
Metadata Updated Date February 28, 2019
Publisher Space Technology Mission Directorate
Unique Identifier TECHPORT_17847
Maintainer Email
Public Access Level public
Bureau Code 026:00
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Catalog Describedby
Harvest Object Id 10a1fed3-6136-42be-b8aa-316cee33f051
Harvest Source Id 39e4ad2a-47ca-4507-8258-852babd0fd99
Harvest Source Title NASA Data.json
Data First Published 2017-08-01
Homepage URL
Data Last Modified 2018-07-19
Program Code 026:027
Source Datajson Identifier True
Source Hash 992f7e2d627e8b17b65f3e99b8a31f9c64ce46b7
Source Schema Version 1.1

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