Impact of laser-enhanced contact optimization on n-TOPCon solar cells' performance and efficiency: Experimental and simulated insights

Abstract

The laser-enhanced contact optimization (LECO) process, instead of the conventional high-temperature sintering process on the tunnel oxide passivated contact (TOPCon) solar cells, is being migrated to mainstream technology, with ongoing improvements in recent years. This study examines the impact of various process parameters—including sintering temperature, laser power, and reverse voltage—within the LECO process on the metallization-induced recombination current density associated with metal contact (denoted as J₀,_metal), contact resistivity (represented as ρ_c), and current-voltage (I-V) characteristics. On the basis of the experiment, COMSOL simulations were introduced to model the changes in charge carrier dynamics during LECO. The influence of laser power and reverse voltage on the front surface electron concentration was systematically investigated and confirmed. The findings indicated that appropriately reducing the sintering temperature can significantly decrease metallization recombination. At the same time, the open-circuit voltage (V_oc) showed a negative correlation with both the laser energy and reverse voltage. Conversely, the fill factor (FF) and contact resistivity (ρ_c) positively correlated with these factors. Data from ρ_c and I-V measurements demonstrated that adequate laser energy is crucial for achieving sufficient carrier concentrations, which is necessary for minimizing ρ_c. However, excessively high laser energy may harm the passivation layer. Simulation analysis confirmed that the laser in the LECO process generates electron-hole pairs, while the reverse voltage separates the electrons and holes. We implemented the LECO process utilizing a sintering temperature of 790 °C, laser power of 18 W, and a reverse voltage of 16 V to enhance the maximum efficiency. (E_ff) of 25.97 %, corresponding to a short-circuit current density (J_sc) of 42.05 mA/cm², a V_oc of 731.5 mV, and a fill factor (FF) of 84.42 %. The findings presented herein provide valuable insights that will inform the subsequent investigation of novel cell structures.