Against the backdrop of persistently high silver price, silver paste further intensifies cost pressure on crystalline silicon and tandem solar cells. There is an urgent need to develop low-silver or silver-free conductive pastes with reduced cost to achieve the dual objectives of cost reduction and efficiency enhancement in solar cells. Among the available strategies, replacing silver powder with silver-coated copper powder currently represents one of the most effective cost-reduction approaches for conductive pastes. Silver-coated copper paste not only delivers electrical performance comparable to that of conventional silver paste but also substantially lowers material cost due to its reduced silver content. Moreover, it demonstrates superior resistance to continuous oxidation and enhanced long-term reliability. Consequently, it has emerged as a key material for the metallization of both crystalline silicon and tandem solar cells.

Silver-coated copper powder typically comprises spherical microparticles with the particle size ranging from 1.0 to 7.0 μm and exhibits high packing porosity. Therefore, achieving optimal conductivity requires the incorporation of submicron silver powder to improve particle packing density and nano-silver powder to facilitate low-temperature sintering. However, driven by the industry-wide trend toward silver reduction, identifying viable alternatives to nano-silver powder is critically important for further cost-effective optimization of paste performance. Conductive nano-oxide powders possess high surface energy, high electrical conductivity, high melting and boiling points, and low shrinkage, rendering them promising candidates to replace the nano-silver powder. Nano-antimony tin oxide (ATO) powder, as a representative n-type semiconductor material, shares the same semiconductor type as the window layer in SHJ (silicon heterojunction) or tandem solar cells. It readily forms ohmic contacts when interfaced with either silver-coated copper powder or silver powder and exhibits low resistivity. Compared with costly nano-silver powder, its cost-effectiveness is particularly pronounced.

This study aims to enhance the sintering behavior and conductivity of low-temperature silver-coated copper paste through the addition of high-surface-energy nano-ATO powder. Using SHJ solar cells as the test platform, the application effects and underlying mechanisms are systematically investigated. The impact of nano-ATO is evaluated with respect to the paste’s thermodynamic properties, rheological behavior, electrical performance, and corresponding solar cell performance. The main findings are as follows:

1) When the ATO content is \leqslant 1.5%, it effectively lowers the volatilization temperature of solvents during the curing process, minimizes solvent residue, and thereby promotes both powder sintering and resin curing.

2) As the ATO content increases, key rheological properties of the paste-including thixotropy, yield stress, and elastic modulus are enhanced. The static paste structure is reinforced, which helps suppress sagging and enables the printing of narrower, more stable line widths.

3) The bulk resistivity of the paste initially decreases and subsequently increases with rising ATO content, whereas the contact resistivity between the electrode and the substrate continues to decline as ATO content increases.

4) ATO powder reduces the accumulation of organic resin at the contact interface, thereby improving the open-circuit voltage. Additionally, it facilitates the formation of finer grid lines, which enhances the short-circuit current. The series resistance of the solar cell first decreases and then increases with increasing ATO content.

Driven by the synergistic effects of these factors, the efficiency of the SHJ solar cell peaks at an ATO addition of 1% (mass fraction), achieving a relative improvement of 0.485% compared with that of the conventional solar cell prepared with silver paste. This demonstrates that an optimal amount of nano-ATO powder can effectively enhance the overall conductivity of the paste, thereby significantly improving the comprehensive performance of the solar cell.