Inkjet printing of photopolymerizable small molecules for OLED applications

Abstract : The elaboration of organic light-emitting diodes (OLEDs) via a solution deposition process turns out to be a cheaper alternative to the vacuum evaporation technique. However the most popular spin-coating wet deposition process mainly used in the semiconductor industry is not applicable for large mother glass substrates used in display applications. The inkjet technology addresses this drawback and appears to be a good solution to produce on a large scale wet deposited OLEDs1. This process has been commonly used for polymer deposition and only a few examples2–4 have demonstrated the possibility of depositing small molecules in functional devices. Deposition of small molecules from inkjet printing is supposed to be easier than polymers because monomers do not show polydispersity and consequently the viscosity of the solution containing the monomers, the ink, is easily controllable in production. This work aims at fabricating OLEDs composed of inkjet-printed hole-transporting molecules and a new class of fluorescent molecules that have been further UV-photopolymerized right after deposition.