Ni/Cu interface optimization via low-temperature dark annealing for enhancing open-circuit voltage and efficiency of mass-produced electroplated electrode TOPCon solar cells

Electroplated copper electrode technology demonstrates broad application prospects in photovoltaic manufacturing due to its low cost, excellent conductivity, and simplified process. In tunnel oxide passivated contact (TOPCon) solar cells, electroplated copper electrodes are considered a viable alternative to traditional silver electrodes. However, practical applications indicate that copper-plated electrodes significantly improve the fill factor of the device, while the increase in open-circuit voltage and short-circuit current fall short of expectations, resulting in limited improvements in power conversion efficiency. Therefore, enhancing the open-circuit voltage of electroplated copper electrodes in TOPCon cells has become a key research focus. This paper proposes a low-temperature dark annealing post-processing method, aiming to improve the adhesion and contact performance of the Ni/Cu interface, reduce the recombination current density ( J 0 ), and thereby help restore the open-circuit voltage of the device. This method promotes beneficial atomic inter-diffusion at the Ni/Cu electrode interface through low-temperature thermal treatment of the TOPCon cell, significantly improving the contact quality and electrical performance. Through optimization, the low-temperature dark annealing technique maximally reduces the contact resistivity ( ρ c ) of electroplated Ni/Cu electrodes in TOPCon cells by approximately 2.7 mΩ cm 2 , thereby improving the power conversion efficiency by 1.02 % abs. This study not only validates the effectiveness of low-temperature dark annealing in improving electrode contact interface, but also provides a simple and process-compatible technical approach to further enhance the open-circuit voltage and short-circuit current of TOPCon cells, thus providing valuable insights for advancing the application of electroplated copper electrodes in efficient photovoltaic cells. • Low-temperature dark annealing enhances performance of TOPCon solar cells with electroplated Ni/Cu electrodes. • Low-temperature dark annealing promotes Ni-Cu interdiffusion, repairing plating-induced defects at the Ni/Cu interface. • Low-temperature dark annealing reduces contact resistance and improves its spatial uniformity in TOPCon solar cells.