Impact of iron contamination in multicrystalline silicon solarcells: origins, chemical states, and device impacts
Synchrotron-based microprobe techniques have been applied to study the distribution, size, chemical state, and recombination activity of Fe clusters in two types of mc-Si materials: block cast mc-Si, and AstroPower Silicon Film(TM) sheet material. In sheet material, high concentrations of metals were found at recombination-active, micron-sized intragranular clusters consisting of micron and sub-micron sized particles. In addition, Fe nanoparticles were located in densities of {approx}2'107 cm-2 along recombination-active grain boundaries. In cast mc-Si,two types of particles were identified at grain boundaries: (1) micron-sized oxidized Fe particles accompanied by other metals (Cr, Mn, Ca, Ti), and (2) a higher number of sub-micron FeSi2 precipitates that exhibited a preferred orientation along the crystal growth direction. In both materials, it is believed that the larger Fe clusters are inclusions of foreign particles, from which Fe dissolves in the melt to form the smaller FeSi2 nanoprecipitates, which by virtue of their more homogeneous distribution are deemed more dangerous to solar cell device performance. Based on this understanding, strategies proposed to reduce the impact of Fe on mc-Si electrical properties include gettering, passivation, and limiting the dissolution of foreign Fe-rich particles in the melt.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE Director. Office of Science. Office of Basic EnergySciences. Contracts DE-AC03-76SF00098 and W-31-109-ENG-38,NationalRenewable Energy Laboratory subcontract AAT-2-31605-03; AG-Solar projectof the government of Northrhein-Westfalia. Fraunhofer Institute for SolarEnergy Systems of Germany, Deutsche Forschungsgemeinschaft
- DOE Contract Number:
- DE-AC02-05CH11231
- OSTI ID:
- 861507
- Report Number(s):
- LBNL-55330; R&D Project: 80JE01; TRN: US200601%%888
- Resource Relation:
- Conference: 19th photovoltaic solar energy conference, Paris,France, 06/07/2004 - 06/11/2004
- Country of Publication:
- United States
- Language:
- English
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