Improved Passivation of Silicon Solar Cells Using Combined Low-Energy Hydrogen Implantation and Optical Processing

ABSTRACTAn improved technique for impurity/defect passivation of silicon solar cells is described. A low-energy hydrogen implantation is performed from the back side of solar cells to produce a deep hydrogen diffusion. The deep diffusion is believed to be caused by the formation of a mobile hydrogen-vacancy (H-V) complex. Next, a layer of Al is deposited on the hydrogenated side and an Optical Processing (OP) step is performed. The OP step accomplishes several objectives that include formation of an ohmic contact, dissociation of H-V complexes to release hydrogen that can participate in further passivation, and dissolution and regrowth of the highly defected surface layer.