Solvent-free fabrication of functional flexible organic devices via organic vapor-jet printing (OVJP)

Abstract

Organic vapor-jet printing (OVJP) is a solvent-free organic thin-film printing method in which organic vapor is entrained into a heated inert carrier gas stream and jetted on a cooled substrate through a nozzle.1,2) Aspects such as easy scalability, mask-free printing, and high material utilization efficiency make OVJP particularly attractive for fabrication of large-area devices or integrated circuits at low cost. Despite such advantages, however, the applications of OVJPs have been limited mostly to rigid substrates due to the large amount of heat transfer from the heated nozzle head. For this reason, it has been highly challenging to use OVJP to fabricate flexible electronic devices, which are the areas organic electronics are considered to have significant advantages over competing technologies. In this research, we present a simple but very effective methodology that can significantly reduce the heat transfer to substrates in OVJP, thus demonstrating the feasibility of fabricating organic devices, in an additive manner, on flexible substrates via OVJP. We have focused on maintaining all other properties other than the heat transfer flux, such as heating conditions and printing resolution. To this end, low-emissivity (low-ε) coating has been adopted on the surface of the OVJP nozzle; in this way, the surface emissivity of the OVJP nozzle has been greatly reduced without altering key deposition conditions. Joint theoretical and experimental studies both indicate a significant decrease in substrate temperature when the proposed low-ε nozzle is used. (Fig. 1) We demonstrate a flexible sensor array to show the feasibility of the proposed approach for solvent-free fabrication of functional flexible organic devices via OVJPs.