Fully Inkjet‐Printed Microlens‐Integrated Color Conversion Layer for Full‐Color Micro‐LED Displays: Improved Angular Light Extraction and Long‐Term Stability

ABSTRACT

Quantum dot (QD) color conversion enables full‐color micro light‐emitting diode (micro‐LED) displays, but QD color conversion layers (CCLs) suffer from low efficiency due partly to total internal reflection (TIR). In this study, we improved the angular light‐extraction characteristics by optimizing the geometry of a microlens‐integrated CCL (MI‐CCL), in which the microlens array was printed using an acrylic‐based monomer resin. The relationship between light extraction and microlens geometry was investigated through ray tracing simulations and photoluminescence (PL) intensity measurements at viewing angles ranging from 0° to 80°. Consequently, the red QD MI‐CCL maintained 95.7% of its PL intensity at 80° relative to its value at 0°, compared with 73.0% for the QD CCL without an MLA. Furthermore, the microlens layer served as a buffer layer during atomic layer deposition (ALD), protecting the underlying QD layer. Depositing Al ₂ O ₃ over the microlens buffer layer improved the long‐term stability of the MI‐CCL, which maintained 97.2% of its initial luminance after 2400 h, compared with 56% for the sample encapsulated with Al ₂ O ₃ alone. Finally, blue, red, and green MI‐CCL arrays were separately integrated onto blue micro‐LED arrays, demonstrating their applicability to full‐color micro‐LED displays. This integrated design effectively addresses optical loss and encapsulation‐related degradation simultaneously.