Laser doping selective emitter with thin borosilicate glass layer for n-type TOPCon c-Si solar cells

Boron laser doping selective emitter (LDSE) has attracted much attention in the current mass-production of n-type tunnel oxide passivated contact (TOPCon) crystalline silicon (c-Si) solar cells. However, boron LDSE technology is limited by the low boron concentration of borosilicate glass (BSG) during boron diffusion, as well as the inefficient doping and laser-induced damage. Here, a thinner BSG layer with high boron concentration has been achieved by adjusting the boron diffusion conditions, which overcomes the insufficient diffusion dynamics caused by the low diffusion and segregation coefficients of boron atoms to improve the surface passivation and promote the laser doping. We have demonstrated that high-temperature annealing has a better repair on laser-induced damage compared with wet etching back due to the surface tension and internal stress after solidification of the silicon molten pool. More importantly, the synergistic effect of high-temperature annealing and wet etching back results in much better results, together with good compatibility with the subsequent cell production processes without increasing production costs. The influence of front emitter parameters has been further quantified theoretically to provide a meaningful guidance for the development of TOPCon c-Si solar cells with front LDSE.