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Overview
A key challenge for building a sustainable and decarbonized world is to transform our existing energy systems. Meanwhile, significant progress has been made in both understanding the energy flow at the material level, and tailoring material structures through various synthetic methods. The convergence of these two paths offer new opportunities to manipulate the flow of energy, such as light, electrons, heat or chemical energy. We aim to exploit such fundamental energy transport process within materials, and use them to develop energy-efficient devices/systems to accelerate the clean energy transition.
Advanced materials synthesis
We aim to develop and utilize a variety of techniques to create nanostructure materials with designed composition, shape and size. The materials synthesis is guided by fundamental mechanisms of how microscopic energy carriers move and interact within the material. This allows us to create materials with specific energy transport properties, including photonic, thermal, electronic and electrochemical properties. We exploit these properties for a range of applications, including energy harvesting, microelectronics, decarbonization, and sustainability.
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Relevant publications:
1. Jiawei Zhou et al., Angle-selective thermal emitter for directional radiative cooling, Joule 7, 12 2830-2844, 2023
2. Jiawei Zhou et al., Heat conductor-insulator transition in electrochemically controlled hybrid superlattices, Nano Letters 22, 5443, 2022
First-principles modeling
We develop a set of density functional theory (DFT)-based computational techniques to understand how energy moves in materials at an atomistic level. These techniques offer us a magnifier to look into the energy transport process, allowing us to better understand the key temporal/spatial dimensional scales that impact the transport properties. Further, as ab initio methods, these techniques can be used to predict the properties of unseen materials. Combined with material synthesis, this helps us to discover new compounds with unique energy transport properties.
Relevant publications:
1. Jiawei Zhou et al., Mobility enhancement in heavily doped semiconductors via electron cloaking, Nature Communications 13, 2482, 2022
2. Jiawei Zhou et al., Large thermoelectric power factor from crystal symmetry-protected non-bonding orbital in half-Heuslers, Nature Communications 9, 1721, 2018
3. Te-Huan Liu*, Jiawei Zhou* et al., First-principles mode-by-mode analysis for electron-phonon scattering channels and mean free path spectra in GaAs, Physical Review B 95, 075206, 2017
4. Jiawei Zhou et al., First-principles calculations of thermal, electrical, and thermoelectric transport properties of semiconductors, Semiconductor Science and Technology 31, 043001, 2016 (Invited Review)
Energy conversion
Conversion of energy with different types (for example, light-to-electrical, electrical-to-thermal, etc.) are fundamental to how we build the clean energy infrastructure. We are particularly interested in the role of microscopic energy carriers in such dynamic processes. The goal is to understand and potentially design energy transport pathways that enhance the efficiency. Our recent examples include solid-state cooling using semiconductor materials, photo-excited carriers' interactions with phonons, and light-induced molecular water evaporation.
Relevant publications:
1. Yaodong Tu, Jiawei Zhou et al., Plausible photomolecular effect leading to water evaporation exceeding thermal limit, Proceedings of National Academy of Sciences 120, e2312751120, 2023
2. Jiawei Zhou et al., Large thermoelectric power factor from crystal symmetry-protected non-bonding orbital in half-Heuslers, Nature Communications 9, 1721, 2018
3. Te-Huan Liu*, Jiawei Zhou* et al., Electron mean-free-path filtering in Dirac material for improved thermoelectric performance, Proceedings of National Academy of Sciences 115, 879, 2018
4. Jiawei Zhou et al., Ab initio optimization of phonon drag effect for lower-temperature thermoelectric energy conversion, Proceedings of National Academy of Sciences 112, 14777, 2015
Thermal engineering
Over half of the global energy demands are supplied in the form of heat, which contributes to about 40% of global CO2 emission. Effectively storing, transporting and utilizing heat is critical to the overall efficiency of our energy system. Material design together with microscopic energy transport understandings offer new opportunities to manage heat. We aim to explore the extremes in heat transport, and create unique heat transfer pathways at a scalable scale. Our recent examples include heat conducting polymers/hydrogels, extremely heat-insulating vacuum array materials, and direction-selective thermal emitters. These projects have important implications for a range of applications, including building energy saving, industrial manufacturing, microelectronics cooling and heat management in energy storage devices.
Relevant publications:
1. Jiawei Zhou et al., Angle-selective thermal emitter for directional radiative cooling, Joule 7, 12 2830-2844, 2023
2. Jiawei Zhou et al., Vacuum insulation arrays as damage-resilient thermal superinsulation materials for energy saving, Joule 6, 2358, 2022
3. Xin Qian*, Jiawei Zhou* et al., Phonon-engineered extreme thermal conductivity materials, Nature Materials 20, 1188, 2021 (Invited Review)
4. Jiawei Zhou et al., Dynamic intermolecular interactions through hydrogen bonding of water promote heat conduction in hydrogels, Materials Horizons 7, 2936, 2020
5. Zhiwei Ding*, Jiawei Zhou* et al., Phonon hydrodynamic heat conduction and Knudsen minimum in graphite, Nano Letters 18, 638, 2018
Transport characterization tools
Discovering materials with unique energy transport properties require characterization tools that measure the transport properties. We are particularly interested in developing characterization techniques for studying the energy transport process at the microscopic level, obtaining information that is otherwise unavailable through traditional measurement methods. One such technique is using ultrafast optical pulses as both the driving force and the measuring probe (for example, transient reflectance and transient grating method). This allows us to study various properties (electron diffusivity, thermal diffusivity, elasticity, etc.) simultaneously, as well as the interaction among different energy carriers, all at the same spot on a sample. We are also interested in developing techniques that help to rapidly screen materials, obtaining their transport properties within seconds instead of minutes or hours as in traditional methods.
Relevant publications:
1. Jiawei Zhou et al., Heat conductor-insulator transition in electrochemically controlled hybrid superlattices, Nano Letters 22, 5443, 2022
2. Jiawei Zhou et al., Direct observation of large electron-phonon interaction effect on phonon heat transport, Nature Communications 11, 6040, 2020
3. Jiawei Zhou et al., Dynamic intermolecular interactions through hydrogen bonding of water promote heat conduction in hydrogels, Materials Horizons 7, 2936, 2020
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