Study of the microstructures and lifetime of spin-cast silicon sheets for photovoltaics.

Silicon sheets were fabricated by a new fabricating method, spin casting with various rotation speeds of the graphite mold. The microstructure of spin-cast silicon sheets were investigated using an electron probe microanalyzer (EPMA) and scanning electron microscope/electron backscatter diffraction/orientation image micrograph, and the lifetime of the sheets was mapped using microwave photoconductance decay. The silicon sheets were vertically aligned, with sizes ranging from tens of microns to one hundred microns. The as-grown lifetime was measured and found to range from 0.049 micros to 0.250 micros. The ASTM number was plotted against the lifetime using ASTM E112 to estimate the grain size. Approximately half of the grain boundaries seemed electrically inactive with meaning of no recombination center since the grains were growth directionally, especially in a longitudinal aligned. It was confirmed that the lifetime of spin-cast sheets makes them suitably applicable for photovoltaics compared to those produced by alternative ribbon-producing methods.