Intrinsic Poly-Si layer thickness: Its role in pinhole contact formation and interface passivation in poly-silicon on oxide solar cells

Abstract

Tunnel oxide passivating contact (TOPCon) solar cells are characterized by high surface passivation and electrical transport efficiency due to the chemical passivation and field effect of the tunnel oxide and doped poly-silicon layers, respectively. Nevertheless, the passivation quality, implied open-circuit voltage (iV_oc), and device lifetime are adversely affected by high-temperature processing, leading to Auger recombination and pinhole defects in the tunnel oxide layer. This study aimed to explore the introduction of intrinsic poly-silicon as an interlayer to improve thermal stability and assesses its effect on the passivation of the tunnel oxide interface. Findings indicate that an intrinsic poly-silicon interlayer with a minimum thickness of 18 nm prevents passivation degradation at elevated temperatures. Additionally, the incorporation of this interlayer facilitates the tuning of the doping profile in crystalline silicon, resulting in a diminished pinhole density and an enhanced iV_oc of 714.9 mV. These results advance our understanding of TOPCon solar cell performance and provide a foundation for their further optimization.