Application of ion Implantation 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. has developed an average efficiency 19.23% blank emitter solar cell (156 mm Cz) process using a high-throughput Varian (Applied Materials) Solion ion-implant tool. In order to improve solar cell efficiency, focus is placed on the well-known advanced passivated emitter and rear cell solar cell architecture with optimized backside passivation. The approach is to combine the surface passivation provided by a thin atomic layer deposition aluminum oxide layer grown after the post implantation annealing 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/SiN_x back passivation are integrated in solar cells, reaching an average efficiency of 19.96% and champion 20.12%.