Heat exchanger-ingot casting/slicing process. Silicon sheet growth development for the Large Area Silicon Sheet Task of the Low Cost Silicon Solar Array Project. Final report, Phase I, November 20, 1975--November 20, 1977

Technical Report · Thu Dec 01 00:00:00 EST 1977

DOI:https://doi.org/10.2172/6808792· OSTI ID:6808792

Schmid, F; Khattak, C P

The proof of concept for silicon casting by the Heat Exchanger Method has been established. One of the major hurdles of ingot cracking has been eliminated with the development of graded crucibles. Such crucibles are compatible with the casting process in that the integrity of the container is maintained at high temperature; however, during the cool-down cycle the crucible fails, thereby leaving a crack-free boule. The controlled growth, heat-flow and cool-down has yielded silicon with a high degree of single crystallinity. Even when the seed melted out, very large grains formed. Solar cell samples made from cast material have yielded conversion efficiency of over 9% (AMI). Representative characterizations of silicon grown has demonstrated a dislocation density of less than 100/cm/sup 2/ and a minority carrier diffusion length of 31 ..mu..m. Excellent surface quality, i.e., surface smoothness and 3 to 5 ..mu..m surface damage, was achieved by multiple wire slicing with fixed diamond abrasive. To achieve this, the silicon workpiece was non-synchronously rocked to produce a radial cut profile and minimize wire contact length. Wire wander was reduced an order of magnitude over the original results by supporting and guiding the wires with grooved rollers. Commercially available impregnated wires that were used failed due to diamond pull-out. Plating after impregnation or electroplating diamonds directly on the core minimized diamond pull-out and corresponding loss in cutting effectiveness. Tungsten wire was the best core material tested because of its high strength, high Young's modulus, and resistance to hydrogen embrittlement. A lighter and longer blade carriage can be used for slicing with wire. This will allow the blade carriage to be reciprocated more rapidly to increase the surface speed. A projected add-on cost calculation shows that these methods will yield silicon for solar cell applications within ERDA/JPL cost goals.

• Research Organization: Crystal Systems, Inc., Salem, Mass. (USA)
• DOE Contract Number: NAS-7-100-954373
• OSTI ID: 6808792
• Report Number(s): DOE/JPL/954373-4
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
36 MATERIALS SCIENCE
SILICON
CASTING
SILICON SOLAR CELLS
COST
CUTTING
CARBIDES
CARBON
CARBON COMPOUNDS
CHEMICAL REACTIONS
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
DECOMPOSITION
DIRECT ENERGY CONVERTERS
ELECTRICAL PROPERTIES
ELEMENTS
FABRICATION
LIFETIME
LINE DEFECTS
MACHINING
METALS
MINERALS
NONMETALS
PHOTOELECTRIC CELLS
PHOTOVOLTAIC CELLS
PHYSICAL PROPERTIES
PYROLYSIS
REFRACTORY METALS
SEMIMETALS
SILICON COMPOUNDS
SOLAR CELLS
TRANSITION ELEMENTS
140501* - Solar Energy Conversion- Photovoltaic Conversion
360601 - Other Materials- Preparation & Manufacture