Highly Transparent Nanoscale Tunnel Oxide Polysilicon Passivated Contacts: Optimisation, Analysis, and Impact Study

Abstract

The presented work on nanometre scale ultra-thin tunnel oxide passivated contact (UT-TOPCon) technology presents a promising pathway for enhancing power conversion efficiency in Si solar cells by mitigating parasitic optical losses. The in-depth optimisation demonstrates record-low surface recombination currents for a polysilicon layer under 3 nm thick, measuring 0.8 fAcm⁻² on planar and 1.3 fAcm⁻² on textured surfaces. Low specific contact resistivities between 2.5 and 5 mΩcm² were measured on various samples, confirming its excellent carrier transport properties. Furthermore, optical properties were characterised and the opto-electrical inputs were incorporated into a comprehensive numerical simulation study to evaluate the impact of its application for Si-perovskite tandem and various single-junction Si cell architectures. The results indicate significant performance improvements to Si-perovskite tandem devices, and very high efficiency potential of 26.7% in front and rear UT-TOPCon designs and up to 27.5% in interdigitated back-contact UT-TOPCon structures.