Heon 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

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

Passive daytime radiative cooling provides cooling without energy input. This method is eco-friendly, which is beneficial, considering the increasing problems of global warming and urban heat islands. A poly(vinylidene fluoride) (PVDF) and polyurethane acrylate (PUA) matte white coating was prepared via photo-initiated free-radical polymerization. The porous polymeric coating without a metal-reflective layer exhibited an average emissivity of 0.9333 in the atmospheric window and an average solar

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

Daytime radiative cooling serving as a method to pump heat from objects on Earth to cold outer space is an attractive cooling option that does not require any energy input. Among radiative cooler structures, the multilayer- or photonic-structured radiative cooler, composed of inorganic materials, remains one of the most complicated structures to fabricate. In this study, transparent sapphire-substrate-based radiative coolers comprising a simple structure and selective emitter-like optical charac

By combining nanoimprint lithography technique and a two-step lift-off process, a Si nanotube array is fabricated and applied as a light absorber for n-Si/PEDOT:PSS hybrid solar cells. The light is effectively trapped within the nanotubes and the device reveals a Jsc of 29.9 mA · cm(-2) and a power conversion efficiency of 10.03%, which is an enhancement of 13.4% compared to the cell having the best-known Si architecture of nanocones as a light absorber to date.

Passive daytime radiative cooling (PDRC) devices have enabled subambient cooling of terrestrial objects without any energy input, offering great potential to future clean energy technology. Among various PDRC structures, random dielectric particles in a polymer matrix or paint-like coatings have displayed powerful radiative cooling performances with excellent scalability and easy fabrication. While modeling and analyzing such a system is nontrivial to enhance the cooling effect and engineer the

In this work, a tandem grating solar absorber is proposed, which can be easily fabricated on a wafer scale and is thermally stable up to 800 K. The base of the solar thermal absorber consists of a tungsten substrate, SiO 2 spacer, and 2D tungsten nanohole array filled with SiO 2 . On top of the base structure, a 2D tungsten nanodisc array is coated with an additional SiO 2 spacer, forming the tandem grating structure. The outside area of the nanodisc array is also filled with SiO 2 ; thus, the p

A cross-point-type phase-change random access memory (PRAM) cell without an access transistor is successfully fabricated with the In/sub 2/Se/sub 3/ resistor, which has much higher electrical resistivity than conventionally used Ge/sub 2/Sb/sub 2/Te/sub 5/ and of which electrical resistivity can be varied by the factor of 10/sup 5/ related with the degree of crystallization. Thus, the switching power can be delivered more effectively due to its higher electrical resistivity and device failure re