Controllable Growth of Silver Crystallites on the Rear Ag–Si Contact Interface of TOPCon Solar Cells Through an Electrochemical Reduction Reaction Triggered by Laser‐Enhanced Contact Optimization

Achieving a balance between passivation and contact has always been crucial for enhancing crystalline silicon (c‐Si) solar cells, especially for the currently mainstream N‐type TOPCon solar cells. The laser‐enhanced contact optimization (LECO) technology improved both the quality and reliability of the front‐side Ag–Si contacts in TOPCon solar cells. However, its impact on the rear‐side Ag–Si contacts has been overlooked. By investigating LECO, its impact was revealed that electrochemical reduction reaction occurred at the rear‐side Ag–Si interface during LECO. This reaction makes it possible for the controlled directional growth of Ag crystallites, thereby optimizing the Ag–Si contact quality. By adjusting the sintering temperature and applying LECO, a balance between passivation and conductivity is achieved, enabling the fabrication of TOPCon solar cells with high open‐circuit voltage (V_oc) and low series resistor (R_s). This study not only clarifies the role of LECO in optimizing the rear‐side Ag–Si contact of TOPCon solar cells but also provides valuable guidance for metallization optimization and power conversion efficiency enhancement of devices.