Structuring Interdigitated Back Contact Solar Cells Using the Enhanced Oxidation Characteristics Under Laser-Doped Back Surface Field Regions

Abstract

Interdigitated back contact (IBC) architecture can yield among the highest silicon wafer-based solar cell conversion efficiencies. Since both polarities are realized on the rear side, there is a definite need for a patterning step. Some of the common patterning techniques involve photolithography, inkjet patterning, and laser ablation. This work introduces a novel patterning technique for structuring the rear side of IBC solar cells using the enhanced oxidation characteristics under the locally laser-doped n++ back surface field (BSF) regions with high-phosphorous surface concentrations. Phosphosilicate glass layers deposited via POCl3 diffusion serve as a precursor layer for the formation of local heavily laser-doped n++ BSF regions. The laser-doped n++ BSF regions exhibit a 2.6-fold increase in oxide thickness compared to the nonlaser-doped n+ BSF regions after undergoing high-temperature wet thermal oxidation. The utilization of oxide thickness selectivity under laser-doped and nonlaser-doped regions serves two purposes in the context of the IBC solar cell, first patterning rear side and second acting as a masking layer for the subsequent boron diffusion. Proof-of-concept solar cells are fabricated using this novel patterning technique with a mean conversion efficiency of 20.41%.