Critical look at the atmospheric Cu fire-through dielectric metallization for cost-effective and high efficiency silicon solar cells

TL;DR

This paper presents Laser-Enhanced Contact Optimization (LECO) as a scalable method to improve copper-silicide interface stability in silicon solar cells, reducing resistance and enhancing efficiency without using silver.

Contribution

The study introduces LECO for localized nano-scale Joule heating to form stable Cu3Si interfaces, addressing copper diffusivity and electromigration issues in solar cell metallization.

Findings

LECO induces stable Cu3Si formation confirmed by STEM.

LECO reduces series resistance by a factor of 3.

LECO improves chemical resistance and interface cleanliness.

Abstract

The formation of stable copper-silicide (Cu3Si) interfaces is crucial for cost-effective, high-efficiency solar cells. However, copper's diffusivity and electromigration issues pose challenges for contact stability. This study employs Laser-Enhanced Contact Optimization (LECO) to induce localized nano-scale Joule heating at the Cu-Si interface in phosphorus-doped p-PERC solar cells. High-resolution STEM and bright field analyses confirm stable Cu3Si formation in LECO-treated samples, with significantly reduced material segregation compared to nonLECO samples. SEM and post-etch EDS mapping demonstrate improved chemical resistance and interface cleanliness. Electrically, LECO treatmenet reduces series resistance by a factor 3, enhancing fill factor and efficiency while preserving diode quality. These results highlight LECO as a scalable method for reliable, silver-free solar cell metallization.