Seungjun Chung

Softening of thermoelectric generators facilitates conformal contact with arbitrary-shaped heat sources, which offers an opportunity to realize self-powered wearable applications. However, existing wearable thermoelectric devices inevitably exhibit reduced thermoelectric conversion efficiency due to the parasitic heat loss in high-thermal-impedance polymer substrates and poor thermal contact arising from rigid interconnects. Here, we propose compliant thermoelectric generators with intrinsically

Drop-on-demand inkjet printing is one of the most attractive techniques from a manufacturing perspective due to the possibility of fabrication from a digital layout at ambient conditions, thus leading to great opportunities for the realization of low-cost and flexible thin-film devices. Over the past decades, a variety of inkjet-printed applications including thin-film transistors (TFTs), radio-frequency identification devices, sensors, and displays have been explored. In particular, many resear

The interface engineering of two-dimensional (2D) transition-metal dichalcogenides (TMDs) has been regarded as a promising strategy to modulate their outstanding electrical and optoelectronic properties because of their inherent 2D nature and large surface-to-volume ratio. In particular, introducing organic molecules and polymers directly onto the surface of TMDs has been explored to passivate the surface defects or achieve better interfacial properties with neighboring surfaces efficiently, thu

We report high performance and stable inkjet-printed stretchable silver electrodes on wave structured elastomeric substrates. Highly conductive silver electrodes were deposited directly on a ultraviolet ozone treated polydimethylsiloxane (PDMS) substrates having vertical wavy structures. Adhesion between printed silver lines and PDMS surface has been enhanced by intentionally roughened PDMS surface with wire-electro discharge machined aluminum mold. During slow (16.7 μm/s) stretching test, resis

Two-dimensional (2D) transition-metal dichalcogenides (TMDCs) have gained considerable attention as an emerging semiconductor due to their promising atomically thin film characteristics with good field-effect mobility and a tunable band gap energy. However, their electronic applications have been generally realized with conventional inorganic electrodes and dielectrics implemented using conventional photolithography or transferring processes that are not compatible with large-area and flexible d

Abstract Although 2D molybdenum disulfide (MoS 2 ) has gained much attention due to its unique electrical and optical properties, the limited electrical contact to 2D semiconductors still impedes the realization of high‐performance 2D MoS 2 ‐based devices. In this regard, many studies have been conducted to improve the carrier‐injection properties by inserting functional paths, such as graphene or hexagonal boron nitride, between the electrodes and 2D semiconductors. The reported strategies, how

As two-dimensional (2D) transition metal dichalcogenides electronic devices are scaled down to the sub-micrometer regime, the active layers of these materials are exposed to high lateral electric fields, resulting in electrical breakdown. In this regard, understanding the intrinsic nature in layer-stacked 2D semiconducting materials under high lateral electric fields is necessary for the reliable applications of their field-effect transistors. Here, we explore the electrical breakdown phenomena

We report the electrical properties of synthesized large-area monolayer molybdenum disulfide (MoS2) field-effect transistors (FETs) with low-cost inkjet-printed Ag electrodes. The monolayer MoS2 film was grown by a chemical vapor deposition (CVD) method, and the top-contact Ag source/drain electrodes (S/D) were deposited onto the films using a low-cost drop-on-demand inkjet-printing process without any masks and surface treatments. The electrical characteristics of FETs were comparable to those

High-performance all-inkjet-printed organic inverters are fabricated on flexible substrates. By introducing end-functionalized polystyrene on both surfaces of inkjet-printed source/drain Ag electrodes and poly(4-vinylphenol) dielectrics, organic-compatible and hydroxyl-free interfaces between those layers and 6,13-bis(triisopropylsilylethynyl)pentacene drastically reduce the interfacial trap and contact resistance. The resulting organic inverters show a full up-down switching performance and a h

and lays the foundation for two-dimensional materials-based transparent phototransistors.

Abstract Flexible thermoelectrics that enable conformal contact with heat sources of arbitrary shape are indispensable for self‐powered wearable electronics. Scalable integration of flexible thermoelectric (TE) materials into functional devices has improved over the past few years, however, the practical applications of flexible TE materials are still hindered by low performance. Herein, highly aligned carbon‐nanotube yarns (CNTYs) are proposed, combined with selective doping via picoliter scale

The era of miniaturized and customized electronics requires scalable energy storage devices with versatile shapes. From the perspective of manufacturing, direct ink writing (DIW)-based 3D printing has attracted unprecedented interest, paving the way to demonstrate micro-batteries with design freedom and outstanding performance. Despite demands for all-printed Li-ion batteries with maskless processing, most of the efforts have been dedicated to developing printable active electrodes or building t

Abstract Compliant thermoelectric generators (TEGs) can fully exploit their energy conversion efficiency by establishing conformal interfaces on arbitrarily shaped 3D heat sources. Although additive manufacturing processes allow scalable fabrication with flexibility and customizability, most printable TEGs are fabricated as planar‐type devices that harvest heat only in the in‐plane direction. Herein, 3D‐compliant TEGs fabricated solely using direct ink writing, which enables thermal‐transfer opt

Solution-based metal oxide semiconductors (MOSs) have emerged, with their potential for low-cost and low-temperature processability preserving their intrinsic properties of high optical transparency and high carrier mobility. In particular, MOS field-effect transistors (FETs) using the spray pyrolysis technique have drawn huge attention with the electrical performances compatible with those of vacuum-based FETs. However, further intensive investigations are still desirable, associated with the p