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Past Work
Silicon Info


Past Work:  Silicon Thin-Layer Growth by LPE

We developed a thin-layer Si growth method with large grain size and high Si film quality based on vertical dipping liquid phase epitaxy (LPE).  See top figure. Cu/Al solvent was shown to provide native oxide removal, good nucleation, impurity/dopant gettering, smooth isotropic growth on different grains of an MG-Si substrate (see middle figure), and rapid growth.  The P-type resistivity could be adjusted between 0.01-0.2 .cm by using various Cu/Al ratios to modify the uptake of Al.  Cu concentrations in the Si film are <1x1016 cm-3 - less than the cell degradation onset.  LPE Si layers grown from Cu on single crystal substrates do not substantially degrade solar cell efficiency (see bottom figure). 

A growth rate ~ 1 μm/min was used for temperatures of 850-950 C.  30-μm-thick LPE-grown layers on MG-Si had 4.5 μs lifetime.

Improvements in substrate quality are necessary for epi-layer quality consistency and efficient PV cells.  SiC particles in the MG-Si substrate can act as shunts in the solar cell.

Theodore F. Ciszek and Tihu Wang, "Crystallization from High Temperature Solutions of Si in Cu/Al Solvent," U.S. Patent 5,544,616 (1996).

T.H. Wang, T.F. Ciszek, C.R. Schwerdtfeger, H. Moutinho, and R. Matson, "Growth of silicon thin layers on cast MG-Si from metal solution for solar cells," Solar Energy Mat. and Solar Cells 41/42, (1996) pp. 19-30.


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