SiOx/polysilicon selective emitter prepared by PECVD-deposited amorphous silicon plus one-step firing enabling excellent J0,met of < 235 fA/cm2 and ρc of < 2 mΩ·cm2

Abstract

Boron(B)-doped polysilicon (poly-Si) is the key element to achieve high efficiency and low-cost bifacial tunnel oxide passivated contact (TOPCon) silicon solar cells. In this work, we explore the feasibility of using a plasma-enhanced chemical vapor deposition (PECVD) system to prepare the high-performance poly-Si fingers as selective emitters (poly-finger SE) through depositing nano SiOx and B-doped amorphous silicon plus one-step annealing process. It is found that the poly-finger SE not only reduces the recombination current density under metal contacts (J_0,met) from ∼ 1300 fA/cm² to ∼ 230 fA/cm², while maintaining a low contact resistivity (ρ_c) of ∼ 1.6 mΩ·cm². Additionally, numerical simulations indicate that n-type Si solar cells with poly-finger SE can achieve a high efficiency of 25.36% based on the most advanced device manufacturing technology and the above-mentioned passivation and contact performances. The open-circuit voltage (V_oc) increased by 11.1 mV and 4.8 mV compared to controlled and laser SE TOPCon solar cells, manifesting the efficiency increase of 0.39% and 0.20%. Overall, this work presents a new method to enhance the efficiency of TOPCon devices.