High-aspect-ratio silver grids of solar cells prepared by direct writing

Abstract

Reducing the width of conductive silver wires, increasing the aspect ratio, improving the utilization rate of silver paste, and enhancing the uniformity of silver wires are key issues that need to be addressed in the manufacture of solar cells. This article explores the feasibility of using glass nozzles to directly write ultra-high viscosity silver paste containing micrometer-sized particles. By preparing a glass nozzle with a diameter of 45μm, conductive silver wires with an average width of about 43±2μm and an aspect ratio of up to 0.96 can be printed. After high-temperature sintering, the width of the silver wire is 32±2μm, the aspect ratio is 0.95, and the resistance of the finger line is 0.13 Ω/cm. In addition, the conductive silver paste is a Herschel–Bulkley (HB) non-Newtonian fluid. Combining the constitutive equation of the HB fluid, a mathematical model of the silver paste flow inside the nozzle is established. Therefore, the influence of characteristic parameters of the silver paste/nozzle on the printing process can be intuitively understood.