Tetrabranched Photo-Crosslinker Enables Micrometer-Scale Patterning of Light-Emitting Super Yellow for High-Resolution OLEDs

Development of a simple and effective patterning method applicable to solution-processable organic luminophores over a large area is critical for the cost-effective production of organic light-emitting-diode (OLED) displays. Here, we demonstrate high-resolution patterning of light-emitting polymer active layers using a highly efficient photo-crosslinker (4Bx). The photo-crosslinker is structured in a tetrabranched geometry, wherein a photo-crosslinkable azide moiety is present at each of the four corners of the molecule, and each of these moieties can form a chemical bond with light-emitting polymer semiconductors under UV irradiation. Due to the high crosslinking efficiency of 4Bx, the use of an unprecedentedly small amount of 4Bx (0.1 wt %) allows fully crosslinking light-emitting Super Yellow polymers without degrading their photoluminescence and electroluminescence characteristics. Furthermore, precisely defined photo-crosslinked patterns of Super Yellow with feature sizes of 5 μm are formed by using p-xylene as the developing solvent that was carefully selected according to a Hansen solubility parameter analysis.