Optimization of microstructure in high-silver content conductive inks via solvent volatilization modulation for application in flexible electronics

Abstract

Flexible printed electronics represent a swift, efficient, and cost-effective technique for depositing metallic conductive materials onto flexible substrates, particularly with the pivotal advancement of functional conductive inks. Metal–organic decomposition conductive inks have garnered substantial interest owing to their straightforward synthesis, convenient storage, and low processing temperatures. However, during low-temperature heating, these inks frequently encounter issues such as fast pyrolysis and gas escape, leading to numerous defects in the microstructure of silver films. Moreover, low silver content results in a high volumetric shrinkage rate, negatively impacting electrical conductivity. To address these limitations, this study synthesized four distinct silver precursors and conducted an in-depth analysis of their chemical compositions, thermal behaviors, and microscopic morphologies. Conductive inks were developed with a high silver content using silver citrate as the silver source with gradient thermal volatilization and low-temperature reduction properties. The impact of solvents and complexing agents on the performance of ink formulations was then examined. Furthermore, the evolution of the inks' microstructure was investigated during thermal decomposition along with the influence of the microscopic morphology on electrical conductivity. Finally, the thermal decomposition mechanism was elucidated in detail. By introducing organic solvents with varying boiling points, the intensity of thermal decomposition was effectively reduced, thereby minimizing the appearance of surface defects such as bubble holes and sintering marks. This strategy significantly enhanced the density of the silver film, reduced its surface roughness, and improved its electrical conductivity.