Evaluation of commercial pure conductive copper pastes by screen printing for a-Si:H/c-Si heterojunction solar cells
G. Rodrigues Lopes, J. Jourdan, Stéphane Bastide, Wilfried Favre
Abstract
This paper investigates the feasibility of using commercial copper (Cu) pastes as an alternative to silver (Ag)-based pastes in the metallization of silicon heterojunction (SHJ) solar cells. While SHJ technology has emerged as a promising option for high-efficiency solar cells, the reliance on Ag presents significant challenges due to its scarcity and cost. This study identifies that the tested cells printed using Cu pastes demonstrate inferior overall performance compared to full Ag and Ag/Cu pastes. To understand the underlying causes of this performance disparity, a series of experiments were conducted. Notably, no degradation in cell performance associated with Cu-induced defects in silicon was found, even after annealing at 200 °C extended to 40 min. The contact resistivity of the commercial Cu pastes was found to be comparable to that of Ag pastes, with even better performance under certain annealing conditions. However, the higher resistance (R line ) of the Cu lines remained a critical issue. Microscopic analysis revealed a significantly smaller cross-sectional area for the analyzed Cu lines printed through the same screen openings, although this alone did not fully explain the observed differences in R line . Annealing under Ar (a low/no oxidation condition) allowed to reduce by 60 % one Cu paste R line , staying insufficient to compete with reference Ag-based pastes but emphasizing the influence of oxidation. These preliminary findings address the challenges associated with replacing Ag contacts with Cu by screen printing in the metallization of SHJ solar cells.