Controlled Synthesis of Spherical Silver Powder via Bromide-Ion Capping of Silver Facets in Molten-Salt Electrodeposition for Photovoltaic Silver Paste

Abstract

Abstract Spherical micro-nano silver powder plays a key role in heterojunction solar cells because it strongly affects electrode contact quality and ultimately device efficiency. However, conventional liquid-phase reduction usually relies on strong acids and organic reducing agents, while traditional electrodeposition often suffers from uncontrolled dendritic growth, which limits scalable and environmentally friendly production. In this work, we develop a nitrate molten-salt electrodeposition route for preparing spherical silver powder under mild and acid-free conditions. Bromide ions (Br–) are introduced as an inorganic capping agent to regulate the growth of silver crystals through facet-selective adsorption. The results show that Br– changes the growth behavior of Ag from dendritic anisotropic deposition to nearly isotropic spherical growth by modifying the interfacial growth kinetics of different crystal planes. Under the optimized conditions of 0.5 A cm–2 and 0.84 h, 15 g of silver powder with a uniform submicron size (D50 = 300 nm) can be obtained, with an energy consumption of only 0.0174 kWh. When applied to low-temperature silver paste for heterojunction solar cells, the as-prepared powder shows better conductivity and sintering behavior than commercial silver powder, leading to a 19.7% decrease in series resistance and an improvement in photoelectric conversion efficiency. This study provides a simple and green route for the controllable synthesis of high-performance spherical silver powder and demonstrates its potential for photovoltaic metallization applications.