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Title: Environmental, health and safety issues related to commercializing CuInSe{sub 2}-based photovoltaics

Abstract

Photovoltaics technology is rapidly evolving towards a new generation of low-cost thin film technologies. One of the most promising materials in this new generation is copper indium selenide (CuInSe{sub 2} or CIS). As with any new material, successful commercialization of CIS photovoltaic (PV) technology will require attention to environmental, health and safety issues, including consideration of the sources, usage, and end-of-product-life disposal and/or recycling of the constituent materials. This work focuses on three specific environmental, health and safety (EH and S) issues related to CIS PV: (1) economics are analyzed to determine their impact on materials use and re-use; (2) Federal and California State environmental disposal and waste handling regulations are analyzed to evaluate their impact on PV module manufacturing and end-of-life module handling; and (3) the logistics and economics of product recycling and waste disposal by industries with comparable EH and S issues are examined to quantify the corresponding options available for handling, disposing of and/or recycling manufacturing by-products and end-of-life modules.

Authors:
 [1]; ;  [2]
  1. UNISUN, Newbury Park, CA (United States)
  2. Brookhaven National Lab., Upton, NY (United States)
Publication Date:
Research Org.:
Brookhaven National Lab., Upton, NY (United States)
Sponsoring Org.:
USDOE, Washington, DC (United States)
OSTI Identifier:
373859
Report Number(s):
BNL-63334
ON: DE96014890; TRN: AHC29619%%42
DOE Contract Number:
AC02-76CH00016
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: Jul 1996
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION; COPPER SELENIDE SOLAR CELLS; WASTE MANAGEMENT; RECYCLING; INDIUM SELENIDE SOLAR CELLS; PHOTOVOLTAIC POWER SUPPLIES; HEALTH HAZARDS; POLLUTION REGULATIONS; COMMERCIALIZATION; ECONOMIC IMPACT

Citation Formats

Eberspacher, C., Fthenakis, V.M., and Moskowtiz, P.D. Environmental, health and safety issues related to commercializing CuInSe{sub 2}-based photovoltaics. United States: N. p., 1996. Web. doi:10.2172/373859.
Eberspacher, C., Fthenakis, V.M., & Moskowtiz, P.D. Environmental, health and safety issues related to commercializing CuInSe{sub 2}-based photovoltaics. United States. doi:10.2172/373859.
Eberspacher, C., Fthenakis, V.M., and Moskowtiz, P.D. Mon . "Environmental, health and safety issues related to commercializing CuInSe{sub 2}-based photovoltaics". United States. doi:10.2172/373859. https://www.osti.gov/servlets/purl/373859.
@article{osti_373859,
title = {Environmental, health and safety issues related to commercializing CuInSe{sub 2}-based photovoltaics},
author = {Eberspacher, C. and Fthenakis, V.M. and Moskowtiz, P.D.},
abstractNote = {Photovoltaics technology is rapidly evolving towards a new generation of low-cost thin film technologies. One of the most promising materials in this new generation is copper indium selenide (CuInSe{sub 2} or CIS). As with any new material, successful commercialization of CIS photovoltaic (PV) technology will require attention to environmental, health and safety issues, including consideration of the sources, usage, and end-of-product-life disposal and/or recycling of the constituent materials. This work focuses on three specific environmental, health and safety (EH and S) issues related to CIS PV: (1) economics are analyzed to determine their impact on materials use and re-use; (2) Federal and California State environmental disposal and waste handling regulations are analyzed to evaluate their impact on PV module manufacturing and end-of-life module handling; and (3) the logistics and economics of product recycling and waste disposal by industries with comparable EH and S issues are examined to quantify the corresponding options available for handling, disposing of and/or recycling manufacturing by-products and end-of-life modules.},
doi = {10.2172/373859},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Jul 01 00:00:00 EDT 1996},
month = {Mon Jul 01 00:00:00 EDT 1996}
}

Technical Report:

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  • Cu(In,Ga)Se 2 (CIGS) thin film photovoltaic technology is in the early stages of commercialization with an annual manufacturing capacity over 1 GW and has demonstrated the highest module efficiency of any of the thin film technologies. However there still is a lack of fundamental understanding of the relationship between the material properties and solar cell device operation. It is well known that the incorporation of a small amount of Na into the CIGS film during processing is essential for high efficiency devices. However, there are conflicting explanations for how Na behaves at the atomic scale. This report investigates how Namore » is incorporated into the CIGS device structure and evaluates the diffusion of Na into CIGS grain boundaries (GBs) and bulk crystallites. Participants: This project was carried out at the Institute of Energy Conversion at the University of Delaware, collaborating with the Rockett group at the University of Illinois Urbana-Champagne. Significant Findings: The significant outcomes of this project for each task include; Task 1.0: Effect of Na in Devices Fabricated on PVD Deposited CIGS; Na diffusion occurs through the Mo back contact via GBs driven by the presence of oxygen; Na reversibly compensates donor defects in CIGS GBs,Task 2.0: Na Incorporation in Single Crystal CIGS; and bulk Na diffusion proceeds rapidly such that grains are Na-saturated immediately following CIGS thin film manufacture. Industry Guidance: The presented results offer interesting concepts for modification of manufacturing processes of CIGS-based PV modules. Possible approaches to improve control of Na uptake and uniformly increase levels in CIGS films are highlighted for processes that employ either soda-lime glass or NaF as the Na source. Concepts include the potential of O 2 or oxidative based treatments of Mo back contacts to improve Na diffusion through the metal film and increase Na uptake into the growing CIGS. This project has also offered fundamental understanding of the behavior of Na in CIGS grains and GBs, particularly the confirmation that CIGS grains will be saturated with Na immediately following manufacture Summary of Results: Most commercially available CIGS modules are fabricated on soda-lime glass coated with Mo as the back electric contact, and Na in the glass diffuses through the Mo layer into the CIGS during film growth. In Task 1 the transport of Na through Mo was evaluated using x-ray photoelectron surface spectroscopy along with diffusion modeling to obtain diffusion coefficients at several temperatures. It was determined that Na diffusion in Mo only occurs along GBs and that oxygen provides an additional driving force to enhance Na transport. Device data revealed that older Mo substrates with a greater amount of surface oxide resulted in slightly higher efficiencies due to enhanced Na incorporation caused by the oxide. This finding shows that Mo substrates could potentially undergo an oxidation treatment prior to CIGS deposition to further improve and control the incorporation of Na. To determine if in-grain Na affects device performance, in Task 1 Na was selectively removed from GBs using heat/rinse cycles. Due to the low temperature of this treatment, Na at GBS remained mobile while diffusion within the bulk was too slow for Na removal from the grain interiors. Changes in electrical properties were evaluated using conductivity and Seebeck coefficient measurements, with both decreasing as Na was removed to reach values similar to Na-free controls samples. This can be explained by the compensation of donor defects by Na, causing an increase in the free carrier concentration. Devices showed a decrease in open-circuit voltage after Na removal confirming that the beneficial effects of GB Na. The findings of this project will provide guidance for rational optimization of Na incorporation procedures in the manufacturing of CIGS solar cells. While it is known that Na segregates at CIGS GBs, the nature and role of Na diffusion into grain interiors was less clear. In Task 2, single crystal CuInSe 2 was used as a model system to represent the grain interiors of CIGS. Crystals processed by two different methods of different compositions and dislocation densities, were evaluated. Diffusion coefficients were obtained at two temperatures after Na diffusion, giving near identical values, ~2x10 11 cm 2/s and ~6x10 11 cm2/s at 420°C and 480°C, respectively, for each crystal. Characterization confirmed that dislocation densities were too low to significantly impact the effective diffusion coefficient. The Cu-poor crystal had a higher solubility suggesting that Na diffusion is mediated by Cu-vacancies, but was not accompanied by an expected increase in diffusion coefficient. The activation energy for diffusion was similar to values expected for interstitial diffusion, but the large size of Na + ions should result in a solubility that is much lower than what was experimentally measured. A hybrid interstitial-substitutional mechanism is proposed that combines the fast diffusion of interstitial atoms with the high solubility common for substitutional impurities. Lattice diffusion of Na proceeds fast enough that CIGS grain interiors will have Na concentrations near the solubility limit of 1018 cm -3 when manufactured under standard conditions. Na and K treated epitaxial CIS films showed a significant increase in cathodoluminescence emission intensity, indicating a reduction of non-radiative recombination pathways, which is consistent with improvements in CIGS device performance, though the mechanism is not clear. Pathways forward: Despite the success of this project, there are a number of questions remaining related to further the understanding of the chemistry of Na in CIGS films and devices. These include further elucidation of the mechanisms of Na passivation in CIGS GBs, with identification of which defects are involved and confirmation of the possible effects of in-grain Na on device performance. To complete analysis of the cell structure, conformation of the presence and possible chemistries of Na at the CIGS/CdS junction and/or in the front transparent contacts, and its effects on device performance, is needed.« less
  • Substituting alternative transportation fuels for gasoline and diesel fuel may improve air quality in the United States. Before the 'best' fuel can be identified, each fuel's impact on a variety of environmental factors must be assessed and compared. In addition to considering the direct effect on traditional air quality problems such as ozone attainment, a comprehensive evaluation should also address new concerns about air toxics, acidic deposition and global warming. There may also be health and safety risks associated with the production, marketing, and use of alternative fuels. The fuels of interest are methanol, natural gas, and LPG.
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  • One of the most promising materials for low-cost thin film photovoltaic cells is copper indium selenide (CuInSe{sub 2} or CIS). As with any new material, successful commercialization of CIS photovoltaic (PV) technology will require attention to environmental issues related to the sources of raw materials, their usage, and the disposal and/or recycling of products at the end of their useful life. This paper focuses on three specific environmental issues related to CIS technology: (i) Economics of the use and re-use of materials; (ii) regulations on environmental disposal and waste handling, and (iii) logistics and economics of recycling and disposing ofmore » products by industries faced with comparable environmental issues.« less
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