Hun Lee

Daytime radiative coolers are used to pump excess heat from a target object into a cold exterior space without energy consumption. Radiative coolers have become attractive cooling options. In this study, a daytime radiative cooler was designed to have a selective emissive property of electromagnetic waves in the atmospheric transparency window of 8-13 μm and preserve low solar absorption for enhancing radiative cooling performance. The proposed daytime radiative cooler has a simple multilayer st

Abstract Transparency is an important characteristic in practical applications of radiative cooling, but the transmitted sunlight trapped in an inner space is generally the main cause of the increasing temperature. A transparent radiative cooler that can lower a temperature during the daytime by transmitting visible light, reflecting near‐infrared (NIR) light, and radiating thermal energy through the atmospheric window is proposed. In contrast to transparent selective emitters that transmit most

This work reports the fabrication of superhydrophobic and oleophobic surfaces with an overhang structure by reverse nanoimprint lithography. An overhang structure is difficult to fabricate by conventional lithography; however, it was conveniently formed by reverse imprint lithography, employed in conjunction with reactive ion etching. The obtained overhang structure was coated with a fluoroalkylsilane monolayer to reduce its surface energy. Further, four different types of nanopatterns were sepa

Printable metalenses composed of a silicon nanocomposite are developed to overcome the manufacturing limitations of conventional metalenses. The nanocomposite is synthesized by dispersing silicon nanoparticles in a thermally printable resin, which not only achieves a high refractive index for high-efficiency metalenses but also printing compatibility for inexpensive manufacturing of metalenses. The synthesized nanocomposite exhibits high refractive index >2.2 in the near-infrared regime, and onl

Passive daytime radiative cooling, which is a process that removes excess heat to cold space as an infinite heat sink, is an emerging technology for applications that require thermal control. Among the different structures of radiative coolers, multilayer- and photonic-structured radiative coolers that are composed of inorganic layers still need to be simple to fabricate. Herein, we describe the fabrication of a nanoparticle-mixture-based radiative cooler that exhibits highly selective infrared

Abstract A single-step printable platform for ultraviolet (UV) metasurfaces is introduced to overcome both the scarcity of low-loss UV materials and manufacturing limitations of high cost and low throughput. By dispersing zirconium dioxide (ZrO 2 ) nanoparticles in a UV-curable resin, ZrO 2 nanoparticle-embedded-resin (nano-PER) is developed as a printable material which has a high refractive index and low extinction coefficient from near-UV to deep-UV. In ZrO 2 nano-PER, the UV-curable resin en

We present an amorphous Si anode deposited on a Cu nanopillar current collector, fabricated using a thermal roll-to-roll process followed by electroformation and LPCVD, for application in high-rate Li-ion batteries. Cu nanopillar current collectors with diameters of 250 and 500 nm were patterned periodically with 1 μm pitch and 2 μm height to optimize the diameters of the pillars for better electrochemical performance. Void spaces between Cu nanopillars allowed not only greater effective control

III–V nitride semiconductors have great potential for optoelectronic and electronic devices due to their wide direct band gaps. Because GaN is chemically very stable, dry etching techniques must be established in order to fabricate devices. In this work, we report the reactive ion etching (RIE) of GaN using CHF3/Ar and C2ClF5/Ar plasmas. GaN films on (001) GaAs were grown by electron cyclotron resonance (ECR) plasma associated molecular beam epitaxy (MBE) and the films showed (0001)hex orientati

In this study, multifunctional light-emitting and passive radiative cooling (LEPC) materials and devices are designed by embedding chemically designed perovskite nanocrystals (NCs) into the radiative polymer layer. Lead halide perovskite NCs are chosen as the light-emitting material, owing to their high photon radiation rate and low phonon generation. To integrate the perovskite NCs into the radiative polymer layers, a surface passivation is achieved by coating the NCs with silica. The silica sh