Jiwoong Yang

Daegu Gyeongbuk Institute of Science and Technology | DGIST · Department of Energy Science and Engineering

The synthesis of nanoparticles with particular compositions and structures can lead to nanoparticles with notable physicochemical properties, thus promoting their use in various applications. In this area of nanoscience, the focus is shifting from size- and shape-uniform single-component nanoparticles to multicomponent nanoparticles with enhanced p...

Nanoclusters are important prenucleation intermediates for colloidal nanocrystal synthesis. In addition, they exhibit many intriguing properties originating from their extremely small size lying between molecules and typical nanocrystals. However, synthetic control of multicomponent semiconductor nanoclusters remains a daunting goal. Here, we repor...

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...

Elucidating the water-induced degradation mechanism of quantum-sized semiconductor nanocrystals is an important prerequisite for their practical application because they are vulnerable to moisture compared to their bulk counterparts. In-situ liquid-phase transmission electron microscopy is a desired method for studying nanocrystal degradation, and...

A universal approach for enhancing water affinity in polymer photocatalysts by covalently attaching hydrophilic photocrosslinkers to polymer chains is presented. A series of bisdiazirine photocrosslinkers, each comprising bisdiazirine photophores linked by various aliphatic (CL‐R) or ethylene glycol‐based bridge chains (CL‐TEG), is designed to prev...

Recent advances in skin-attachable electronics have attracted substantial interest because of their potential in various fields such as robotics, healthcare, and wearable technology. Among various electroluminescent (EL) devices, quantum dot light-emitting diodes (QLEDs) are promising for next-generation displays due to their superior color purity,...

Photoelectrochemical (PEC) water splitting, recognized for its potential in producing solar hydrogen through clean and sustainable methods, has gained considerable interest, particularly with the utilization of semiconductor nanocrystal quantum dots (QDs). This minireview focuses on recent advances in PEC hydrogen production using I-III-VI semicond...

Stretchable displays that can change their shape and size under strain could be used to create displays with unconventional form factors. However, intrinsically stretchable light-emitting devices have poor luminous performance, such as low brightness. Here we show that intrinsically stretchable quantum dot light-emitting diodes (QLEDs) can be made...

Understanding the mechanism underlying the formation of quantum‐sized semiconductor nanocrystals is crucial for controlling their synthesis for a wide array of applications. However, most studies of 2D CdSe nanocrystals have relied predominantly on ex situ analyses, obscuring key intermediate stages and raising fundamental questions regarding their...

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 effici...

Silver nanowires (NWs) are promising materials for flexible electronics, such as electronic skins due to their excellent electrical, thermal, and mechanical properties. Achieving precise patterning of Ag NWs is essential for the successful integration and miniaturization of the electronic device system, but the high aspect ratio (AR) of NWs and the...

Effective passivation of grain boundaries in perovskite solar cells is essential for achieving high device performance and stability. However, traditional polymer‐based passivation strategies can introduce challenges, including increased series resistance, disruption of charge transport, and insufficient passivation coverage. In this study, a novel...

The flexible type of displays, which can alter their shape freely (e.g., bendable or foldable displays) according to situational demands, is under an intense spotlight due to applications in human‐friendly mobile electronics. Among various types of light‐emitting diodes (LEDs), meanwhile, perovskite‐based LEDs (PeLEDs) have garnered particular atte...

Heavy‐metal‐free ternary Cu–In–Se quantum dots (CISe QDs) are promising for solar fuel production because of their low toxicity, tunable band gap, and high light absorption coefficient. Although defects significantly affect the photophysical properties of QDs, the influence on photoelectrochemical hydrogen production is not well understood. Herein,...

Photoelectrochemical (PEC) hydrogen production is an emerging technology that uses renewable solar light aimed to establish a sustainable carbon‐neutral society. The barriers to commercialization are low efficiency and high cost. To date, researchers have focused on materials and systems. However, recent studies have been conducted to utilize therm...

The Cover Feature shows the strategies to improve the photoelectrochemical hydrogen evolution of quantum dot (QD)‐based semiconductors (yellow balls) by applying a co‐catalyst (buried grey balls) or a passivation layer (blue layers) as shown in the left electrode. The co‐catalyst facilitates the charge‐transfer kinetics by providing active sites fo...

Crystal structures determine material properties, suggesting that crystal phase transformations have the potential for application in a variety of systems and devices. Phase transitions are more likely to occur in smaller crystals; however, in quantum‐sized semiconductor nanocrystals, the microscopic mechanisms by which phase transitions occur are...

Compositional engineering of CsPbBr3 perovskite nanocrystals (PNCs) via Zn(II)-doping is an effective way to passivate the defect states, and improve the stability, photoluminescence (PL) efficiency, and reduce the inherent lead-toxicity...

Solar‐driven photoelectrochemical (PEC) hydrogen production is one potential pathway to establish a carbon‐neutral society. Nowadays, quantum dots (QDs)‐sensitized semiconductors have emerged as promising materials for PEC hydrogen production due to their tunable bandgap by size or morphology control, displaying excellent optical and electrical pro...

High-resolution semiconductor nanocrystal quantum dot (QD) patterns are required for applications in display devices. For this, the dry transfer printing of QDs is promising because it does not degrade the inherent properties of QDs. However, the effect of the surface ligands on this process remains poorly understood, despite its importance. Herein...

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, w...

Semiconductor nanocrystal quantum dots (QDs) are promising materials for solar energy conversion because of their bandgap tunability, high absorption coefficient, and improved hot-carrier generation. CuInSe2 (CISe)-based QDs have attracted attention because of their low toxicity and wide light-absorption range, spanning visible to near-infrared lig...

Colloidal quantum dots (QDs) are promising materials for the next-generation displays, because of their excellent optical properties such as color tuneability, bright emissions, and extremely high color purity. For the practical applications of QD-displays, it is important to develop high-resolution QD printing methods that produce QD pixel arrays....

Heterogeneous catalysts comprising noble metals and magnetic materials allow a straightforward separation from a reaction using an external magnet and are recovered easily. In this study, we synthesized magnetic Fe3O4-Pdn hybrid heterogeneous catalysts via a rapid one-pot aqueous-phase method. The synthesized Fe3O4-Pd NPs dispersed well with small...

Stretchable displays have recently received increasing attention as input and/or output interfaces for next-generation human-friendly electronic systems. Stretchable electroluminescent (EL) devices are a core component of stretchable displays, and they can be classified into two types, structurally stretchable EL devices and intrinsically stretchab...

Nanocapsules are hollow nanoscale shells that have applications in drug delivery, batteries, self-healing materials, and as model systems for naturally occurring shell geometries. In many applications, nanocapsules are designed to release their cargo as they buckle and collapse, but the details of this transient buckling process have not been direc...

Flexible light-emitting devices that can transform from two-dimensional to three-dimensional (3D) forms could be of use in the development of next-generation displays. Various approaches for converting two-dimensional structures into 3D architectures have been explored, including origami methods that rely on folding along lines in which a structure...

Over the last several decades, colloidal quantum dots (QDs) have been widely studied because of their unique optical and electronical properties such as band gap tunability, extremely high color purity, and efficient light absorption and emission. Consequently, they have been regarded as promising materials for next-generation optoelectronic device...

Colloidal quantum dots (QDs) exhibit unique characteristics such as facile color tunability, pure color emission with extremely narrow bandwidths, high luminescence efficiency, and high photostability. In addition, quantum dot light-emitting diodes (QLEDs) feature bright electroluminescence, low turn-on voltage, and ultrathin form factor, making th...

Liquid cell transmission electron microscopy (TEM) enables the direct observation of dynamic physical and chemical processes in liquids at the Liquid cell transmission electron microscopy (TEM) enables the direct observation of dynamic physical and chemical processes in liquids at the nanoscale. Quantitative investigations into reactions with fast...

The fundamental bandgap Eg of a semiconductor—often determined by means of optical spectroscopy—represents its characteristic fingerprint and changes distinctively with temperature. Here, we demonstrate that in magic sized II-VI clusters containing only 26 atoms, a pronounced weakening of the bonds occurs upon optical excitation, which results in a...

Doping is one of the key technologies in modern semiconductor science and industry. However, the synthetic control of doped nanocrystals is difficult to achieve. Here, we report the facile synthesis of manganese (II) doped ZnSe nanocrystals with controlled dimensionality. A strong Lewis acid-base reaction using air-stable and environmentally friend...

Liquid Pockets Encapsulated in MoS2 Liquid Cells - Volume 25 Supplement - Jiwoong Yang, Moon Kee Choi, Peter Ercius, Haimei Zheng

The formation of inorganic nanoparticles has been understood based on the classical crystallization theory described by a burst of nucleation, where surface energy is known to play a critical role, and diffusion-controlled growth process. However, this nucleation and growth model may not be universally applicable to the entire nanoparticle systems...

Two dimensional (2D) materials have found various applications because of their unique physical properties. For example, graphene has been used as the electron transparent membrane for liquid cell transmission electron microscopy (TEM) due to its high mechanical strength and flexibility, single-atom thickness, chemical inertness, etc. Here, we repo...

Rational design and synthesis of transition metal sulfide complex nanostructures are significant for achieving desired materials properties for a variety of applications. Herein, we synthesized nickel sulfide (NiS) nanostructures using laser irradiation in an aqueous solution and under the ambient condition. Crystalline nanostructures with high pha...

Nonclassical features of crystallization in solution have been recently identified both experimentally and theoretically. In particular, an amorphous-phase-mediated pathway is found in various crystallization systems as an important route, different from the classical nucleation and growth model. Here, we utilize high-resolution in situ transmissio...

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-gen...

Magic-sized clusters represent materials with unique properties at the border between molecules and solids, and provide important insights into the nanocrystal formation process. However, synthesis, doping, and especially structural characterization become more and more challenging with decreasing cluster size. Herein, we report the successful intr...

Recent advances in graphene liquid cells for in situ transmission electron microscopy (TEM) have opened many opportunities for the study of materials transformations and chemical reactions in liquids with high spatial resolution. However, the behavior of thin liquids encapsulated in a graphene liquid cell has not been fully understood. Here, we rep...

Heteroatom‐doped carbon nanomaterials with high surface area and tunable microporosity are important but they generally require difficult and multistep syntheses. Herein, a simple and straightforward strategy is introduced that involves a wrap‐bake‐sublime approach to synthesize microporosity controlled and heteroatom codoped carbon nanocages. A zi...

In article number 1703114, Mansoo Choi, Min Jae Ko, Yung‐Eun Sung and co‐workers report mesoscopic and perovskite solar cells employing CoN nanofilms for regeneration of light absorbers. Room‐temperature vapor‐deposited CoN successfully replaces costly Pt in dye‐sensitized solar cells and leads to highly efficient energy conversion in inverted pero...

Organic/inorganic hybrid solar cells, typically mesoscopic and perovskite solar cells, are regarded as promising candidates to replace conventional silicon or thin film photovoltaics. There have been intensive investigations on the development of advanced materials for improved power conversion efficiencies, however, economical feasibilities and re...

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-...

In article number 1700217, Taeghwan Hyeon, Dae-Hyeong Kim, and co-workers present an ultrathin quantum-dot light-emitting diode display that can visualize different types of information retrieved from wearable electronics with high brightness and low operation voltage. The integrated system reliably monitors temperature and changes in body motion,...

An ultrathin skin-attachable display is a critical component for an information output port in next-generation wearable electronics. In this regard, quantum dot (QD) light-emitting diodes (QLEDs) offer unique and attractive characteristics for future displays, including high color purity with narrow bandwidths, high electroluminescence (EL) brightn...

Two-dimensional (2D) composite materials have gained much interest, and their synthesis and characterization have been intensively investigated to fully exploit the new functionalities and realize their potential applications. Among the various approaches to preparing heterostructures based on 2D materials, the process of self-organization between...

Flexible and stretchable optoelectronic devices can be potentially applied in displays, biosensors, biomedicine, robotics, and energy generation. The use of nanomaterials with superior optical properties such as quantum dots (QDs) is important in the realization of wearable displays and biomedical devices, but specific structural design as well as...

There is an urgent need to develop metal-free, low cost, durable, and highly efficient catalysts for industrially important oxygen evolution reactions. Inspired by natural geodes, unique melamine nanogeodes are successfully synthesized using hydrothermal process. Sulfur-modified graphitic carbon nitride (S-modified g-CN x ) electrocatalysts are obt...

Transparent electrodes have been widely used for various electronics and optoelectronics, including flexible ones. Many nanomaterial-based electrodes, in particular 1D and 2D nanomaterials, have been proposed as next-generation transparent and flexible electrodes. However, their transparency, conductivity, large-area uniformity, and sometimes cost...

Large-scale colloidal synthesis and integration of uniform-sized molybdenum disulfide (MoS2 ) nanosheets for a flexible resistive random access memory (RRAM) array is presented. RRAM using MoS2 nanosheets shows a ≈10 000 times higher on/off ratio than that based on exfoliated MoS2 . The good uniformity of the MoS2 nanosheets allows wafer-scale syst...

Magic-sized semiconductor clusters represent an exciting class of materials located at the boundary between quantum dots and molecules. It is expected that replacing single atoms of the host crystal with individual dopants in a one-by-one fashion can lead to unique modifications of the material properties. Here, we demonstrate the dependence of the...

Colloidal nanocrystals have been intensively studied over the past three decades due to their unique properties that originate, in large part, from their nanometer-scale sizes. For applications in electronic and optoelectronic devices, colloidal nanoparticles are generally employed as assembled nanocrystal solids, rather than as individual particle...

Copper-indium-selenide (CISe) quantum dots (QDs) are a promising alternative to the toxic cadmium- and lead-chalcogenide QDs generally used in photovoltaics due to their low toxicity, narrow band gap, and high absorption coefficient. Here, we demonstrate that the photovoltaic performance of CISe QD-sensitized solar cells (QDSCs) can be greatly enha...

Doping semiconductor nanocrystals with magnetic transition-metal ions has attracted fundamental interest to obtain a nanoscale dilute magnetic semiconductor, which has unique spin exchange interaction between magnetic spin and exciton. So far, the study on the doped semiconductor NCs has usually been conducted with NCs with larger than 2 nm because...

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 devic...

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 multidirect...

We present a new synthetic process of near infrared (NIR)-absorbing copper-indium-selenide (CISe) quantum dots (QDs) and their applications to efficient and completely heavy-metal-free QD-sensitized solar cells (QDSCs). Lewis acid-base reaction of metal iodides and selenocarbamate enabled us to produce chalcopyrite-structured CISe QDs with controll...

The shape-controlled synthesis of colloidal semiconductor nanocrystals has attracted a lot of interest because of their shape-dependent physical and chemical properties. With the growing understanding of the shape evolution, several successful syntheses of two-dimensional (2D) nanocrystals have been reported. In this review, we focus on the recent...

The impact of quantum confinement on the exchange interaction between charge carriers and magnetic dopants in semiconductor nanomaterials has been controversially discussed for more than a decade. We developed manganese-doped CdSe quantum well nanoribbons with a strong quantum confinement perpendicular to the c-axis, showing distinct heavy hole and...

The dimension-controlled synthesis of CdS nanocrystals in the strong quantum confinement regime is reported. Zero-, one-, and two-dimensional CdS nanocrystals are selectively synthesized via low-temperature reactions using alkylamines as surface-capping ligands. The shape of the nanocrystals is controlled systematically by using different amines an...