Production of Solar Grade (SoG) Silicon by Refining Liquid Metallurgical Grade (MG) Silicon: Final Report, 19 April 2001

PDF Version Also Available for Download.

Description

This report summarizes the results of the developed technology for producing SoG silicon by upgrading MG silicon with a cost goal of $20/kg in large-scale production. A Heat Exchanger Method (HEM) furnace originally designed to produce multicrystalline ingots was modified to refine molten MG silicon feedstock prior to directional solidification. Based on theoretical calculations, simple processing techniques, such as gas blowing through the melt, reaction with moisture, and slagging have been used to remove B from molten MG silicon. The charge size was scaled up from 1 kg to 300 kg in incremental steps and effective refining was achieved. After ... continued below

Physical Description

vp.

Creation Information

Khattak, C. P.; Joyce, D. B. & Schmid, F. August 6, 2001.

Context

This report is part of the collection entitled: Office of Scientific & Technical Information Technical Reports and was provided by UNT Libraries Government Documents Department to Digital Library, a digital repository hosted by the UNT Libraries. More information about this report can be viewed below.

Who

People and organizations associated with either the creation of this report or its content.

Sponsor

Publisher

Provided By

UNT Libraries Government Documents Department

Serving as both a federal and a state depository library, the UNT Libraries Government Documents Department maintains millions of items in a variety of formats. The department is a member of the FDLP Content Partnerships Program and an Affiliated Archive of the National Archives.

Contact Us

What

Descriptive information to help identify this report. Follow the links below to find similar items on the Digital Library.

Description

This report summarizes the results of the developed technology for producing SoG silicon by upgrading MG silicon with a cost goal of $20/kg in large-scale production. A Heat Exchanger Method (HEM) furnace originally designed to produce multicrystalline ingots was modified to refine molten MG silicon feedstock prior to directional solidification. Based on theoretical calculations, simple processing techniques, such as gas blowing through the melt, reaction with moisture, and slagging have been used to remove B from molten MG silicon. The charge size was scaled up from 1 kg to 300 kg in incremental steps and effective refining was achieved. After the refining parameters were established, improvements to increase the impurity reduction rates were emphasized. With this approach, 50 kg of commercially available as-received MG silicon was processed for a refining time of about 13 hours. A half life of <2 hours was achieved, and the B concentration was reduced to 0.3 ppma and P concentration to 10 ppma from the original values of 20 to 60 ppma, and all other impurities to <0.1 ppma. Achieving <1 ppma B by this simple refining technique is a breakthrough towards the goal of achieving low-cost SoG silicon for PV applications. While the P reduction process was being optimized, the successful B reduction process was applied to a category of electronics industry silicon scrap previously unacceptable for PV feedstock use because of its high B content (50-400 ppma). This material after refining showed that its B content was reduced by several orders of magnitude, to {approx}1 ppma (0.4 ohm-cm, or about 5x1016 cm-3). NREL's Silicon Materials Research team grew and wafered small <100> dislocation-free Czochralski (Cz) crystals from the new feedstock material for diagnostic tests of electrical properties, C and O impurity levels, and PV performance relative to similar crystals grown from EG feedstock and commercial Cz wafers. The PV conversion efficiency of 1-cm2 devices made from C z crystals grown using the new feedstock were 95% as high as those from Cz crystals grown using EG feedstock and were comparable to those we obtained using commercial <111> Cz wafers. Devices with an efficiency of 7.3% were also made directly on wafers cut from the feedstock that had not gone through a controlled directional solidification. Only a few cells have been processed. Device parameters for this material have not yet been optimized, and additional diagnostic device fabrication, analysis, and verification is under way. The successful B treatment process developed during the program can be used with high-B-doped silicon scrap from the electronics industry thereby making available, for the short term, a new silicon feedstock for an additional 200 MW/year annual production of PV modules. For the future, this approach, when used in an MG silicon production plant, will produce SoG silicon for $7.62/kg, which is less than the goal of $20/kg.

Physical Description

vp.

Source

  • Other Information: PBD: 6 Aug 2001

Language

Item Type

Identifier

Unique identifying numbers for this report in the Digital Library or other systems.

  • Report No.: NREL/SR-520-30716
  • Grant Number: AC36-99GO10337
  • DOI: 10.2172/786367 | External Link
  • Office of Scientific & Technical Information Report Number: 786367
  • Archival Resource Key: ark:/67531/metadc715748

Collections

This report is part of the following collection of related materials.

Office of Scientific & Technical Information Technical Reports

Reports, articles and other documents harvested from the Office of Scientific and Technical Information.

Office of Scientific and Technical Information (OSTI) is the Department of Energy (DOE) office that collects, preserves, and disseminates DOE-sponsored research and development (R&D) results that are the outcomes of R&D projects or other funded activities at DOE labs and facilities nationwide and grantees at universities and other institutions.

What responsibilities do I have when using this report?

When

Dates and time periods associated with this report.

Creation Date

  • August 6, 2001

Added to The UNT Digital Library

  • Sept. 29, 2015, 5:31 a.m.

Description Last Updated

  • March 31, 2016, 7:03 p.m.

Usage Statistics

When was this report last used?

Yesterday: 0
Past 30 days: 1
Total Uses: 6

Interact With This Report

Here are some suggestions for what to do next.

Start Reading

PDF Version Also Available for Download.

Citations, Rights, Re-Use

Khattak, C. P.; Joyce, D. B. & Schmid, F. Production of Solar Grade (SoG) Silicon by Refining Liquid Metallurgical Grade (MG) Silicon: Final Report, 19 April 2001, report, August 6, 2001; Golden, Colorado. (digital.library.unt.edu/ark:/67531/metadc715748/: accessed December 15, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.