Organic vapor-jet printing with reduced heat transfer for flexible organic electronics

Abstract

Organic vapor-jet printing (OVJP) is a promising organic thin-film deposition method that combines the advantages of field-proven vacuum thermal evaporation techniques for small molecules and mask-free, on-demand printing technologies. However, the excessive heat transfer from the OVJP nozzle to a substrate prevents use of plastic substrates, which typically have low glass transition temperature. Hence, this study aims at reducing the radiative heat transfer to an underlying medium and broadening the use of OVJP even to temperature-sensitive cases, especially to high-resolution flexible organic electronic device fabrication. To this end, we adopt low-emissivity coating on the nozzle by electrochemically plating gold on the surface. As a result, we have dropped the thermal radiation to one third of the radiation from the conventional stainless-steel-based nozzle, while maintaining temperature conditions and the substrate-to-nozzle distance. Using the low-emissivity coated nozzle, we have succeeded in fabricating a flexible tactile sensor array and a flexible organic light-emitting diode on polyimide and polyethylene terephthalate substrates. The reduction of heat transfer to the substrate has allowed plastic substrates to be used in OVJP, demonstrating a possibility for OVJP as a promising low-cost fabrication techniques for flexible devices.