Moon Kee Choi

Deformable full-colour light-emitting diodes with ultrafine pixels are essential for wearable electronics, which requires the conformal integration on curvilinear surface as well as retina-like high-definition displays. However, there are remaining challenges in terms of polychromatic configuration, electroluminescence efficiency and/or multidirectional deformability. Here we present ultra-thin, wearable colloidal quantum dot light-emitting diode arrays utilizing the intaglio transfer printing t

Abstract In the future electronics, all device components will be connected wirelessly to displays that serve as information input and/or output ports. There is a growing demand of flexible and wearable displays, therefore, for information input/output of the next-generation consumer electronics. Among many kinds of light-emitting devices for these next-generation displays, quantum dot light-emitting diodes (QLEDs) exhibit unique advantages, such as wide color gamut, high color purity, high brig

Abstract Displaying information on transparent screens offers new opportunities in next‐generation electronics, such as augmented reality devices, smart surgical glasses, and smart windows. Outstanding luminance and transparency are essential for such “see‐through” displays to show vivid images over clear background view. Here transparent quantum dot light‐emitting diodes (Tr‐QLEDs) are reported with high brightness (bottom: ≈43 000 cd m −2 , top: ≈30 000 cd m −2 , total: ≈73 000 cd m −2 at 9 V)

Biomimetic miniaturized suction cups (mSCs) are designed for the patient friendly, dry adhesives of smart medical skin. Both strong van der Waals force and induced negative pressure by the ultrasoft mSCs facilitate tight skin coupling without discomfort or irritations, improve sensitivities of the embedded stretchable electronics for continuous vital sign monitoring, and enable multiple drug reloading without loss of the adhesion. As a service to our authors and readers, this journal provides su

Graphene has been highlighted as a platform material in transparent electronics and optoelectronics, including flexible and stretchable ones, due to its unique properties such as optical transparency, mechanical softness, ultrathin thickness, and high carrier mobility. Despite huge research efforts for graphene‐based electronic/optoelectronic devices, there are remaining challenges in terms of their seamless integration, such as the high‐quality contact formation, precise alignment of micrometer

Optoelectronic devices with unconventional form factors, such as flexible and stretchable light-emitting or photoresponsive devices, are core elements for the next-generation human-centric optoelectronics. For instance, these deformable devices can be utilized as closely fitted wearable sensors to acquire precise biosignals that are subsequently uploaded to the cloud for immediate examination and diagnosis, and also can be used for vision systems for human-interactive robotics. Their inception w

High-definition red/green/blue (RGB) pixels and deformable form factors are essential for the next-generation advanced displays. Here, we present ultrahigh-resolution full-color perovskite nanocrystal (PeNC) patterning for ultrathin wearable displays. Double-layer transfer printing of the PeNC and organic charge transport layers is developed, which prevents internal cracking of the PeNC film during the transfer printing process. This results in RGB pixelated PeNC patterns of 2550 pixels per inch

Metal halide perovskites have emerged as promising light-emitting materials for next-generation displays owing to their remarkable material characteristics including broad color tunability, pure color emission with remarkably narrow bandwidths, high quantum yield, and solution processability. Despite recent advances have pushed the luminance efficiency of monochromic perovskite light-emitting diodes (PeLEDs) to their theoretical limits, their current fabrication using the spin-coating process po

Synaptic photodetectors exhibit photon-triggered synaptic plasticity, which thus can improve the image recognition rate by enhancing the image contrast. However, still, the visualization and recognition of invisible ultraviolet (UV) patterns are challenging, owing to intense background noise. Here, inspired by all-or-none potentiation of synapse, we develop an integrated device of synaptic phototransistors (SPTrs) and quantum dot light-emitting diodes (QLEDs), facilitating noise reduction and vi

Hydrogels are widely implemented as key materials in various biomedical applications owing to their soft, flexible, hydrophilic, and quasi-solid nature. Recently, however, new material properties over those of bare hydrogels have been sought for novel applications. Accordingly, hydrogel nanocomposites, i.e., hydrogels converged with nanomaterials, have been proposed for the functional transformation of conventional hydrogels. The incorporation of suitable nanomaterials into the hydrogel matrix a

Mechanically deformable photodetectors (PDs) are key device components for wearable health monitoring systems based on photoplethysmography (PPG). Achieving high detectivity, fast response time, and an ultrathin form factor in the PD is highly needed for next-generation wearable PPG systems. Self-powered operation without a bulky power-supply unit is also beneficial for point-of-care application. Here, we propose ultrathin self-powered PDs using heavy-metal-free Cu–In–Se quantum dots (QDs), whic

We present a simple method of utilizing anodized aluminum oxide (AAO) as a reproducible template for fabricating high-aspect-ratio uniformly bent polymeric nanopillars that can be used as a physical adhesive. It is shown how to achieve straight high-aspect-ratio nanopillars with concepts of the work of adhesion and lateral collapse between polymer pillars without serious damage to the master template. With the support of manufacturing polymeric nanopillars from the reusable AAO, a simple route t

Recently, highly conductive polymer nanocomposites, particularly soft polymer nanocomposites, have received extensive attention as promising material candidates for wearable devices. Compared with the cases of the wearable devices based on conventional rigid electronic materials, the wearable devices based on polymer nanocomposites exhibit excellent conformal contacts with the skin due to the soft mechanical properties of these nanocomposites; therefore, soft polymeric nanocomposites can be appl