Impurity Precipitation, Dissolution, Gettering and Passivation in PV Silicon: Final Technical Report, 30 January 1998--29 August 2001

Weber, E. R.

National Renewable Energy Laboratory (U.S.)

关键词: Pv;    Multicrystalline Silicon;    Solar Cells;    36 Materials Science;    Precipitation;   

DOI  :  10.2172/15000243
RP-ID  :  NREL/SR-520-31528
RP-ID  :  AC36-99-GO10337
RP-ID  :  15000243

美国|英语

来源: UNT Digital Library

【 摘 要 】

This report describes the major progress in understanding the physics of transition metals in silicon and their possible impact on the efficiency of solar cells that was achieved during the three-year span of this subcontract. We found that metal-silicide precipitates and dissolved 3d transition metals can be relatively easily gettered. Gettering and passivating treatments must take into account the individuality of each transition metal. Our studies demonstrated how significant is the difference between defect reactions of copper and iron. Copper does not significantly affect the minority-carrier diffusion length in p-type silicon, at least as long as its concentration is low, but readily precipitates in n-type silicon. Therefore, copper precipitates may form in the area of p-n junctions and cause shunts in solar cells. Fortunately, copper precipitates are present mostly in the chemical state of copper-silicide and can relatively easily be dissolved. In contrast, iron was found to form clusters of iron-oxides and iron-silicates in the wafers. These clusters are thermodynamically stable even in high temperatures and are extremely difficult to remove. The formation of iron-silicates was observed at temperatures over 900C.