Zone‐melting recrystallization of silicon thin films for solar cell application

Zone‐melting recrystallization (ZMR) has been applied successfully to fabricate a thin‐film silicon solar cell with high conversion efficiency that also has the potential to lower the material cost. It is found that seeding from an Si substrate during ZMR is not necessary for high‐quality thin‐film Si with a low defect density and the dominant (100) crystallographic orientation. This feature is very important because one can separate the thin‐film Si from the substrate in order to obtain a flexible solar cell and the substrate can be recycled. Lowering the scanning speed of the upper movable carbon strip heater has proved to be most effective for high‐quality crystal. In order to realize thin‐film Si solar cells, a 60‐μm thick Si active layer is deposited by chemical vapour deposition on recrystallized Si film. Pyramidal shape formation at the surface for light confinement by using (100) orientation and low‐energy H+ ion irradiation for the passivation of crystal defects has been applied to the fabrication of thin‐film Si solar cells and we achieved high conversion efficiencies of more than 14% for a 10 × 10 cm2 cell and 16% for a 2 × 2 cm2 cell.