Joon Sang Kang

Improving the thermal management of small-scale devices requires developing materials with high thermal conductivities. The semiconductor boron arsenide (BAs) is an attractive target because of ab initio calculation indicating that single crystals have an ultrahigh thermal conductivity. We synthesized BAs single crystals without detectable defects and measured a room-temperature thermal conductivity of 1300 watts per meter-kelvin. Our spectroscopy study, in conjunction with atomistic theory, rev

Heat dissipation is an increasingly critical technological challenge in modern electronics and photonics as devices continue to shrink to the nanoscale. To address this challenge, high thermal conductivity materials that can efficiently dissipate heat from hot spots and improve device performance are urgently needed. Boron phosphide is a unique high thermal conductivity and refractory material with exceptional chemical inertness, hardness, and high thermal stability, which holds high promises fo

Two-dimensional van der Waals materials have shown novel fundamental properties and promise for wide applications. Here, we report for the first time an experimental demonstration of the in situ characterization and highly reversible control of the anisotropic thermal conductivity of black phosphorus. We develop a novel platform based on lithium ion batteries that integrates ultrafast optical spectroscopy and electrochemical control to investigate the interactions between lithium ions and the la

A solid‐state thermoelectric device is attractive for diverse technological areas such as cooling, power generation and waste heat recovery with unique advantages of quiet operation, zero hazardous emissions, and long lifetime. With the rapid growth of flexible electronics and miniature sensors, the low‐cost flexible thermoelectric energy harvester is highly desired as a potential power supply. Herein, a flexible thermoelectric copper selenide (Cu 2 Se) thin film, consisting of earth‐abundant el

Two-dimensional (2D) van der Waals material tin selenide (SnSe) has recently attracted intensive interest due to its exceptional thermoelectric performance. However, the thermal properties and phonon transport mechanisms in its single-crystal form remain elusive. Here, we measured high-quality SnSe single crystals using nanoscale thermometry based on ultrafast optical spectroscopy and found that its intrinsic thermal conductivity is highly anisotropic in different crystallographic directions. To

To achieve successful real-time detection of airborne pathogenic microorganisms, the problem must be considered in terms of their physical size and biological characteristics. We developed an airborne microorganism detection chip to realize the detection of microorganisms, ensuring compactness, sensitivity, cost-efficiency, and portability, using three key components: an inertial impaction system, a cartridge-type impaction plate, and a mini-fluorescent microscope. The inertial impaction system

Although a cascade impactor is widely used for bioaerosol sampling and separation, the conventional system has some shortcomings when it is applied for the portable device. In the present study, a microscale cascade impactor system was developed using a soft lithography process to provide good portability and cost efficiency. The system described here included three impaction stages, and a rectangular-shaped jet nozzle was employed with a 0.5 L/min airflow rate. The collection efficiency of each

n-Doping the fullerene-based interlayer in perovskite solar cells enhances heat dissipation and charge extraction by improving thermal/electrical conductivity, and energy level alignment, which boosts photovoltaic performance and stability.

A continuous high-throughput aerosol-based method for fabrication of antimicrobial air filters using natural antimicrobial nanoparticles was developed. We used the nebulization and electrospray methods for deposition of nanosized antimicrobial substances on pristine filter media. The roll-to-roll process was introduced for high-throughput fabrication of antimicrobial filters, and electrospray generation and dispersion equipment were used for high performance. The present method covers a filter a

The thermal chiral anomaly is a new mechanism for thermal transport that occurs in Weyl semimetals (WSM). It is attributed to the generation and annihilation of energy at Weyl points of opposite chirality. The effect was observed in the Bi1-xSbx alloy system, at x=11% and 15%, which are topological insulators at zero field and driven into an ideal WSM phase by an external field. Given that the experimental uncertainty on x is of the order of 1%, any systematic study of the effect over a wider ra

Weyl semimetals are bulk solids in which chiral anomalies, i.e., negative magnetoelectric and magnetothermal resistances, exist as a result of the chiral properties of the Weyl fermions. The thermal chiral anomaly has potential in devices that actively control heat fluxes; these would be an early application of topological properties, realized after the materials are optimized. Here, we optimized the band structure of ${\mathrm{Bi}}_{1\ensuremath{-}x}{\mathrm{Sb}}_{x}$ alloys in the topological