Application of ion implanted emitter in PERC solar cells

Ion-implantation offers numerous advantages (i.e. single side precise control and reproducibility of the dopant, simultaneous SiO2 passivation during annealing, no phosphosilicate glass formation) for solar cell manufacturing. Canadian Solar Inc. (CSI) has developed an average efficiency 19.23% blank emitter solar cell (156mm Cz) process. In order to improve the solar cell efficiency, focus is placed on the well known advanced PERC solar cell architecture with optimized back side passivation. The approach is to combine the surface passivation provided by a thin ALD aluminum oxide layer grown after the post implantation annealing (PIA) process with a deposited capping silicon nitride layer. Laser ablation and proper aluminum paste is also used to locally remove the dielectric layers and to form local contact. Based on this development, implanted emitter and local Al-BSF with Al2O3/SiNx back passivation are integrated in solar cells reaching an average efficiency 19.96%, and champion 20.12%.