N-PERT solar cell using oxidation etch-back selective-BSF process

N-type passivated emitter, rear totally diffused (N-PERT) solar cells are receiving substantial scholarly attention as next-generation solar cells. The demand for high-efficiency solar cells that can reduce photovoltaic installation costs is increasing. This investigation demonstrates the feasibility of an N-PERT solar cell with a selective back-surface field (BSF) structure. For the BSF formation, first, the backside surface was heavily doped as n-type through POCl3 diffusion; subsequently, the back surface was etched back by a thermal oxidation process, with a mask covering the finger and busbar area. The sheet resistance of the lightly doped region was set to approximately 90 Ω/square and that of the heavily doped region was set to 30 Ω/square. This oxidation etch-back process improved the quality and uniformity of the BSF and improved the performance of the solar cell. The photovoltaic performance was improved mainly in terms of short-circuit current. The absolute efficiency was increased up to approximately 0.3% with a 125 mm × 125 mm cell. An analysis of quantum efficiency revealed an increase in the response in the long-wavelength region.