Direct Optical Lithography Using Diazirine Cross-Linker for Quantum Dot Light Emitting Diodes and Enhancing Photoluminescence Quantum Yield through Post-treatment
Namji Lee, Donghyun Choi, Keum‐Jin Ko, Hae-Sik Kim, Jeong Hwan Yu, Jong‐Soo Lee
Abstract
The precise patterning of colloidal quantum dots (QDs) is essential for fabricating high-resolution subpixels in optoelectronic devices, including quantum dot light-emitting diodes (QLEDs). However, conventional photolithographic methods using photoresists often result in QD swelling, pattern distortion, and degradation of the optical properties. To overcome these limitations, we propose a direct optical lithography (DOL) approach without a photoresist, utilizing 4-(3-trifluoromethyl)-3H-diazirin-3-yl)benzoic acid (TDBA) as a carbene cross-linker. This method enables the formation of high-resolution QD patterns with feature sizes as small as ∼2 μm while preserving their optical properties. Furthermore, postpatterning thiol–ene treatment using pentaerythritol tetrakis(3-mercaptopropionate) (PETMP) significantly enhances the photoluminescence quantum yield (PLQY), achieving increase compared to pristine QDs. As a proof of concept, we demonstrate red-emitting cross-linked QLEDs with a maximum external quantum efficiency ( EQE max ) of 10.3%. Additionally, semitransparent QLEDs incorporating red, green, and blue QDs were fabricated to demonstrate the applicability of this approach for the next generation display applications. Our strategy provides a scalable, high-performance patterning technique with broad potential for advanced optoelectronic devices.