The reduction of laser-damage on the rear surface of the N-type TOPCon solar cells with electroplating electrodes

Abstract

The shortcomings of traditional screen-printed technology in PV industry have rendered it inadequate for the demands of high power conversion efficiency solar cell design, including the low contact performance and the high shading area. Combinating laser ablation pretreatment and Ni/Cu plating can circumvent these issues. However, laser-induced damage significantly influences the further enhancement of power conversion efficiency of the solar cells with electroplating electrodes. In this paper, a simplified physical model of laser ablation on the rear surface dielectric layer for N-type tunnel oxide passivated contacts(TOPCon) solar cells was presented. According to model, the approximate calculation of the laser ablation power was between 0.2 W and 1.6 W, when a 355 nm ps Gaussian pulsed laser was employed on the rear surface of N-type TOPCon solar cells. Subsequently, the optimal laser ablation process parameters for the electroplating process on the rear surface of the wafer were identified through experiments. By modifying the laser ablation process, as far as possible to reduce the damage to the polycrystalline silicon passivation layer caused by the laser on the rear surface of the TOPCon solar cells. Following the modification of the laser ablation procedure, the laser-induced damage was also rectified through high-temperature annealing. Ultimately, a photoelectric conversion efficiency of 24.36 % was attained in the N-type electroplating TOPCon solar cells, representing an enhancement of 0.86%_abs in comparison to that of the TOPCon solar cells with electrodes fabricated by screen-printed on the rear surface.