Laser processing of Ni-B coated Si-wafer: Simultaneous realization of selective emitters and copper barrier layers for TOPCon solar cells

Laser doping selective emitter (LDSE) technology has become a research hotspot in the large-scale production of silicon solar cells (SCs) due to its advantages of room-temperature processing, precise control of doping profiles, and short processing duration. In this study, a Ni-B alloy coating was chemically deposited on the front surface of n-type tunneling oxide passivated contact (TOPCon) crystalline silicon (c-Si) solar cell precursors, through which selective B doping and the formation of NiSi 2 metal seed layer were achieved during laser grooving process. Electrochemical capacitance-voltage (ECV) tests revealed a significant enhancement in carrier concentration, thereby confirming the successful doping of B. This process resulted in the formation of a locally heavily doped (p ++ ) layer, which effectively reduced the contact resistance (R c ) between the metal electrodes and Si substrate. Theoretical calculations indicated that the built-in potential (V bi ) of the pn junction increased, thereby enhancing built-in electric field (E bi ). This enhancement of the built-in electric field contributed to the improvement of both the open-circuit voltage (V oc ) and the short-circuit current density (J sc ), and significantly strengthened the adhesion between the metal electrodes and the Si substrate, ultimately leading to a comprehensive enhancement in the performance of the SCs. This study provides a new technical route to advance the industrial application of laser doping technology. • Simultaneously forming selective emitter and NiSi 2 phase. • This method successfully achieves heavy boron (B) doping, forming a heavily doped layer that strengthens the built-in electric field, thereby improving carrier separation efficiency and reducing recombination losses. • The R c and ρ c are significantly reduced, the adhesion between metal grid electrodes and the Si substrate is enhanced, and the J sc and V oc are remarkably improved.