Large area processing and printing of conducting copper structures for use in (opto)electronics (Conference Presentation)

Most current electronics manufacturing technologies utilise subtractive processing that is expensive, wasteful and energy intensive. Printed electronics is revolutionising the electronics industry by enabling additive processing that significantly reduces expense, waste and energy consumption. The EU-funded PLASMAS project demonstrates the capability of printed electronics based on novel nanoparticle Cu inks with favourable cost to performance ratios, through development of large area printed circuit boards and printed logic as well as OLED and OPV elements with printed Cu nanoparticle electrodes. However, a number of challenges need to be overcome when printing these metal nanoparticle inks – the typical feature height of printed structures of several 100 nm tend to exhibit a rough surface, which can lead to shorts in the device after subsequent overcoating of the organic active layer materials. Furthermore, the sintering temperature of the nanoparticle inks needs to be low (< 130 °C) in order to allow deposition and curing on transparent flexible substrates such as PET. We therefore present the process development of solution-processed electrodes based on inkjet-printed Cu grids, by embedding the inkjet-printed metal grids to yield ITO-free optoelectronic devices. Secondly, we present roll-to-roll inkjet-printed RFID antennas based on Cu inks. Finally, we demonstrate a truly low-temperature sintering route for a Cu nanoparticle ink by using a reducing atmosphere of formic acid, yielding stable highly conducting layers. The results of the project highlight overall parameters for solution processing and implementation of novel metal nanoparticle materials and architectures in printed electronics.