High-quality p-type emitter using boron aluminum source for n-type TOPCon solar cells

Abstract

In the current landscape of n-type Tunnel Oxide Passivated Contact (TOPCon) solar cell production, challenges persist with conventional gas boron sources used for the fabrication of p-type emitters, including their influence on emitter recombination and metal-semiconductor contact recombination. This research introduces a novel approach involving the diffusion of a boron-aluminum source via spin-coating, proposed as a replacement for the conventional gas boron source. This method facilitates a higher quality p-type emitter, at drive-in temperature of 900 °C and 30 min. The surface doping concentration of the p-type layer reached 3.18 × 10¹⁹ cm⁻³, with a peak doping concentration of 5.36 × 10¹⁹ cm⁻³. Studies show that the p-type emitter prepared with boron-aluminum source can reduce metal-semiconductor contact recombination and Auger recombination, due to its high surface doping concentration and shallow junction depth. Moreover, the overall process temperature for preparing p-type emitters with the boron-aluminum source is low, and the duration is short, which is advantageous for reducing energy consumption. Additionally, Quokka3 simulation results show that the efficiency of TOPCon solar cells prepared with the boron-aluminum source is 0.43 % higher than that of TOPCon cells prepared with the gaseous boron source.