A Study on Improving Color Uniformity of Flexible OLEDs through Pixel-Define Layer Optimization in Inkjet Printing

Organic light-emitting diodes (OLEDs) are increasingly being developed as high-resolution, large-area displays where chromaticity and color uniformity are critical performance parameters. This study investigates the effect of ink solution volume and solid content on the color uniformity of the emissive layer and device performance by controlling the pixel define layer (PDL) surface energy through hydrophobic silane-treated SiO2 nanospheres. Therefore, the particle size of the SiO2 nanospheres was modulated by varying the TEOS volume to optimize the PDL surface energy. The optimized PDL structure enabled uniform film formation of the thin emissive layer. In addition, a theoretical model was developed to compute ink volume based on contact angle, aligning closely with experimental results. These results offer a foundation for improving color uniformity and vividness in next-generation high-quality OLED displays.