Integration of aluminum contacts in TOPCon solar cells: A pathway to reduce silver usage

Abstract

The high silver consumption in Tunnel Oxide Passivated Contact (TOPCon) solar cells presents significant challenges regarding material costs and availability. This work demonstrates the feasibility of replacing silver (Ag) contacts with aluminum (Al) contacts on the rear side of industrial n-type TOPCon cells. Our findings indicate that specially formulated Al pastes effectively suppress excessive alloying with the poly-Si layer, achieving much lower contact recombination (J_{0, metal}) compared to conventional Al pastes. The contact mechanisms between Al pastes and n⁺ poly-Si layers under varying firing conditions were systematically investigated, leading to the identification of optimised firing conditions that achieve low contact resistivity (${\rho }_c$) while maintaining high surface passivation quality. The rear-Al champion cell achieved a promising efficiency of 22.9 %, exhibiting a 0.8 % efficiency gap with the 23.7 % rear-Ag reference cell. Additionally, numerical simulation has identified key pathways to enhance rear-Al cell performance, providing a roadmap to achieve the efficiency of reference cells with Ag contacts. These findings highlight the potential for aluminum pastes as a cost-effective and sustainable alternative for significantly reducing silver consumption in terawatt-scale photovoltaic manufacturing.