High-Resolution Patterning Technologies for Intrinsically Stretchable Light-Emitting Devices

Abstract

Light-emitting devices with unconventional form factors—such as flexible and stretchable—are essential components for next-generation displays, enabling seamless integration onto complex, non- developable surfaces. These deformable optoelectronic systems are particularly well suited for applications such as wearable health monitoring system that acquire precise biosignals and wirelessly transmit data to cloud-based diagnostic platforms and immediately visualize to user, or for integration into human-interactive robotics. Conventional stretchability strategies based on geometric engineering—such as wrinkling, buckling, or serpentine interconnects—have enabled limited deformability but remain constrained by stress concentrations at rigid-soft interfaces, reduced pixel density, and compromised fill factors under strain. In contrast, intrinsically stretchable light-emitting devices, composed entirely of mechanically compliant materials, offer uniform strain distribution and mechanical robustness without sacrificing structural simplicity. Simultaneously, high-resolution patterning is another critical requirement for next-generation displays, particularly as higher pixel densities are demanded for smaller, deformable form factors typical of wearable systems. Additionally, when considering the demand for reliable, high-throughput fabrication compatible with scalable manufacturing, it becomes essential to develop a high-resolution patterning strategy. In the first part of this work, an intrinsically stretchable high-resolution multifunctional display was developed, combining simple device architecture with robust mechanical stability. By employing a transfer-printed phosphor-elastomer composite, synesthesia displays capable of simultaneously generating synchronized light and sound were realized. The device exhibits high stretchability of 120%, operating reliably under both static and dynamic deformation without acoustic distortion. Based on this technique, emissive layer (EML) patterning was conducted, realizing high-resolution mosaic image consisting of a 300 µm dot pattern and obtained multicolor stretchable display. This design exemplifies a compact, multifunctional interface for next-generation human–machine interaction. The second part presents a strategy for fabricating highly efficient, ultrahigh-definition quantum dot (QD)-based light emitting diodes (QLEDs). Despite the unique advantages of QDs, including high photoluminescence quantum yield, wide color range and high color purity, conventional patterning methods fall short in achieving both high definition and device efficiency. To overcome this limitation, double-layer transfer printing of QD/ZnO film was developed using surface-engineered viscoelastic stamps, enabling pixelated RGB patterns at 2,565 pixels per inch (PPI) and monochrome patterns up to ~20,526 PPI. The method minimizes leakage currents via dense packing of QDs and ZnO nanoparticles, achieving an external quantum efficiency of 23.3%. The technique was further extended to fabricate highly efficient ultrathin wearable QLEDs, establishing a scalable route toward ultrahigh-resolution, full-color QD displays. The final part demonstrates intrinsically stretchable QLEDs incorporating a ternary nanocomposite EML composed of colloidal QDs, an elastomeric matrix, and a charge transport polymer. This architecture maintains a consistent interparticle spacing under 50% tensile strain, ensuring mechanical durability and electrical reliability. The polymer-rich bottom region facilitates efficient hole injection, resulting in devices with a turn-on voltage of 3.2 V and peak luminance of 15,170 cd m−2 at 6.2 V, without brightness degradation under strain. Moreover, these materials were used to construct stretchable full-color passive-matrix QLED arrays. Collectively, this dissertation presents a comprehensive framework encompassing intrinsically stretchable device architecture, high-resolution patterning techniques, and optimized interfacial charge transport design. These advancements establish a comprehensive and versatile framework for high- performance, deformable light-emitting systems with broad applicability in wearable electronics, soft robotics, and interactive display technologies. This dissertation is based on research work that has been previously published in peer-reviewed journals. The contents have been adapted with minor modifications to comply with the requirements of the dissertation format. The detailed list of publications is as follows: Chapter 2 is based on the article: Stretchable High‐Resolution User‐Interactive Synesthesia Displays for Visual–Acoustic Encryption. Advanced Functional Materials 33, 2302473 (2023). Chapter 3 is based on the article: Highly efficient printed quantum dot light-emitting diodes through ultrahigh-definition double-layer transfer printing. Nature Photonics 18, 1105–1112 (2024). Chapter 4 is based on the article: Intrinsically stretchable quantum dot light-emitting diodes. Nature Electronics 7, 365–374 (2024). Minor edits, including reformatting, language revision, and the removal of journal-specific sections such as abstracts and reference lists, have been applied to the published works for integration into this dissertation. Full citations are provided within the relevant chapters to acknowledge the original sources.