Investigation of the Ag–Si contact characteristics of boron emitters for n‐TOPCon solar cells metallized by laser‐assisted current‐injection treatment

Laser‐assisted current injection treatment, also known as laser‐enhanced contact optimization (LECO), has great potential to reduce front contact resistance and metal‐induced recombination of n‐type tunnel oxide‐passivated contact (n‐TOPCon) solar cells, thereby improving the cell efficiency. Herein, the interfacial Ag–Si contact characteristics on boron‐doped p + emitters and the electrical properties of industrial n‐TOPCon solar cells that feature a LECO treatment and a specific Ag paste are investigated and compared with those of n‐TOPCon solar cells with a standard Ag/Al paste process. LECO causes some current‐fired contacts that, when removed by sequential selective etching, leave bowl‐shaped imprints on the emitter, indicating that isotropic alloying behavior occurs between Ag and Si at these local positions during LECO. Unlike the standard Ag/Al metallization process, the LECO process does not significantly damage the passivation layer or emitter. More interestingly, the n‐TOPCon solar cells prepared with the specific Ag paste do not initially form an effective metal–semiconductor contact, with an average efficiency of only 0.14%, which increases to 25.65% after LECO treatment, even 0.2% abs higher than that of the reference counterparts with standard Ag/Al electrodes. Ultimately, a physical model of LECO‐induced Ag–Si contact formation on boron emitters is proposed.