Chemistry of solid metal-based inks and pastes for printed electronics – A review

Printed electronics, PE, is one of the fastest growing technologies in the world; it allows the construction of electronic devices in low-cost flexible substrates by printing techniques (e.g., screen, gravure, offset, flexography and inkjet printing) traditionally used in several industries (e.g., graphics arts, textiles, polymers). In PE, ink pigments are replaced by metallic particles or precursors that impart the electrical conductivity to the resultant printed patterns. This work reviews the available solid metal formulations used for conductive inks and pastes, focusing on both metallic particles and polymeric components. The influence and technical requirements of most commonly used printing techniques, along with the post-processing treatments to reach the aim performance in the resultant inks has been addressed. Considering that PE is an emerging profitable field with novel applications in radio frequency identification (RFID) tags, thin-film transistors (TFT), light-emitting diodes (LED), transparent conductive electrodes (TCE) and organic solar cells (OSC), among others, it is crucial to know how printed formulations work and how they can be molded to fulfill the applications requirements. In this review, apart from metallic solid particles that has been widely reviewed in the past, the chemistry of polymer matrices has been focused in order to elucidate its important role in resultant inks performance. Novel outstanding formulations, such as reactive or metal-organic-decomposition (MOD) inks, have been presented.The authors gratefully acknowledge the financial support of the NORTE 2020 project TSSIPRO (Technologies for Sustainable and Smart Innovative Products, NORTE-01-0145-FEDER-000015) and the COMPETE project iFACTORY: Novas Capacidades de Industrializac¸ ão (POCI-01-0247-FEDER-002814)