HIGH-EFFICIENCY MULTICRYSTALLINE SILICON SOLAR-CELLS

A detailed investigation of quality enhancement techniques, such as PE CVD SiO2/SiN deposition and forming gas anneal (FGA) for defect passiv ation, and Al treatment for defect and impurity gettering, was conduct ed 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 up on 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 alo ne, and 1.2% from Al diffusion and FGA interaction. Cells fabricated o n various multicrystalline materials were in the efficiency range of 1 4.0-17.7% with highest efficiency on cast silicon from Osaka Titanium Corporation.