Preparation of electronic pastes for high-precision screen printing: action mechanisms and synergistic effects of different polymer binders

Abstract

With the continuous advancement of Tunnel Oxide Passivated Contact (TOPCon) solar cell technology, increasingly stringent demands are being placed on the printing precision of electronic pastes. Polymer binders, as critical components of electronic pastes, play a pivotal role in regulating viscosity, enhancing rheological properties, and improving printability. However, the specific action mechanisms by which polymer binders within electronic pastes, as well as the synergistic effects among different polymers, remain insufficiently explored. The effects of various polymer binders on the rheological and printing properties of organic carriers and electronic pastes were systematically investigated. The optimal concentration of polymer binders was determined by the viscosity of organic carriers and the wettability of silicon wafers. The flow behavior and rheological properties of organic carriers and electronic pastes were evaluated using the Ostwald-de Waele power-law model and the Herschel-Bulkley model, respectively. Additionally, screen printing was employed to evaluate the action mechanisms of polymer binders in electronic pastes. High quality electronic pastes (Ag-PSE and Ag-PSC) with excellent rheology properties and printability were successfully developed through the matching and combination of polymers. The optimized electronic pastes exhibited suitable viscosity, high pseudoplasticity, and excellent structural recovery. When utilized as TOPCon front fine grid pastes, the electrode grid lines produced via screen printing and sintering demonstrated high aspect ratios (0.4308 and 0.4324), narrow line widths (only 23.22 μm and 24.45 μm) and low resistivity (2.52 × 10^–6 Ω cm and 2.54 × 10^–6 Ω cm).