HIGH-EFFICIENCY MULTICRYSTALLINE SILICON SOLAR-CELLS

A detailed investigation of quality enhancement techniques, such as PECVD SiO2/SiN deposition and forming gas anneal (FGA) for defect passivation, and Al treatment for defect and impurity gettering, was conducted on several promising multicrystalline Si materials. The PECVD SiO2/SiN coating increased the bulk lifetime by a factor of 1.3 to 1.7, and decreased the surface recombination by a factor of 5-22, depending upon the multicrystalline material. FGA in conjunction with Al treatment improved the EFG sheet Si cells efficiency by 5.3% absolute, with 2.6% improvement resulting from the FGA alone, 1.5% from Al gettering alone, and 1.2% from Al diffusion and FGA interaction. Cells fabricated on various multicrystalline materials were in the efficiency range of 14.0-17.7% with highest efficiency on cast silicon from Osaka Titanium Corporation.