Photopatterning of Polymer Emissive Layers for Micro-OLED Arrays via Thiol–Ene Photo-Cross-Linking Systems

The rapid advancement of near-eye display technologies has generated strong demand for high-resolution microdisplays. Organic light-emitting diodes (OLEDs), with their mature industrialization, lightweight nature, and compatibility with flexible substrates, represent an ideal platform for head-mounted high-resolution microdisplays. However, achieving high-resolution and precise patterning of organic light-emitting materials remains a significant challenge. Conventional patterning methods often destroy organic materials and are incapable of high-resolution patterning. Photochemical cross-linking provides a promising route for direct patterning of polymer semiconductors, while the application in the fabrication of micro-OLEDs has been rarely explored. To address the gaps in the existing research studies, a semiconducting photoresist was developed, and its effects on device performance were investigated in this work. The photoresist was obtained by blending the light-emitting polymer poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) with commercially available, low-cost cross-linking agents. An insoluble polymer network was thus formed through a UV-initiated thiol–ene addition reaction. High-resolution patterning of 2.6 μm dots and 5 μm lines is then achieved by using conventional photolithography methods. Ultimately, high-resolution micro-OLED arrays with a 5 μm pixel size and 3175 pixels per inch (PPI) were successfully demonstrated. This work provides a versatile and scalable approach for direct patterning of emissive layers (EMLs) in OLED devices.