Beyond silver: Comparative performance analysis of alternative metallization strategies in silicon solar cells

Veysel Unsur, Seda Kilickaya, Melisa Korkmaz Arslan

Center for Solar Energy Research and Application (ODTU-GUNAM), Turkiye

E-mail: veysel.unsur@odtugunam.org

Abstract

The photovoltaic industry’s reliance on silver (Ag) for silicon solar cell metallization faces critical challenges due to Ag scarcity, cost volatility, and sustainability concerns. This study systematically evaluates advanced metallization strategies to reduce or eliminate Ag usage while maintaining high-performance solar cell operation. We investigate fine-line printing, hybrid/core-shell architectures, and alternative materials such as copper (Cu), aluminum (Al), and nickel (Ni). Fine-line printing enables Ag finger widths as narrow as >10µm, reducing front-side Ag consumption by up to 25% (9 mg/W) without compromising efficiency. However, sub-10 µm finger widths introduce printability challenges and increased series resistance. Hybrid and core-shell pastes, such as Cu-core/Ag-shell configurations, mitigate Cu’s oxidation and diffusion risks at low temperatures but face limitations in high-temperature processes (>750°C) required for TOPCon and IBC cells. To address this, Ag-doped Ni pastes (4% Ag) demonstrate a breakthrough, achieving power conversion efficiencies comparable to traditional Ag contacts while slashing Ag usage to <0.5 mg/Wp. In parallel, Cu-only pastes are explored for their ultra-low cost and high conductivity, yet require advanced barrier layers (e.g., Ni, Ti) to suppress Cu diffusion into silicon during high-temperature firing. Recent optimizations in rapid thermal annealing processes enable Cu paste stability at industrial scales, achieving efficiencies of ~22.5%. Meanwhile, Al-only pastes, while limited by higher contact resistance, show promise for rear-side metallization if used with Al/(boron doped)Si or Al/Ge alloy mixtures.

Keywords: Si solar cells; BC technology; Ag-free contacts; TOPCon

Biography:
Veysel Unsur is a Professor and Head of Metallization and Back-Contact (BC) Technologies at ODTÜ-GÜNAM, the largest photovoltaic research institute in Turkiye, spanning the full value chain from materials science to PV systems. He holds a B.Sc. in Physics and a Ph.D. in Electrical and Computer Engineering from the University of North Carolina.

Dr. Unsur’s research focuses on solar cell metallization, alternative contact materials, and advanced back-contact device architectures and designs. He leads and contributes to major international collaborations, including EU Horizon, CETP, and m-ERA.NET initiatives, as well as large-scale national R&D projects, bridging fundamental research with industrial innovation.