Juying Xiao

Bio: Juying Xiao is an academic researcher from Xiamen University. The author has contributed to research in topics: Photovoltaic system & Maxwell's demon. The author has an hindex of 3, co-authored 6 publications receiving 13 citations.

Intermediate-band-assisted near-field thermophotovoltaic devices with InAs, GaSb, and Si based absorbers

Abstract: A new scheme of near-field thermophotovoltaic devices is proposed by introducing the intermediate-band absorber. The two-step excitation via the intermediate band provides a large photogenerated current density and maintains a high voltage output for the thermal-electric conversion. Energy dissipation processes in devices are analyzed by using the detailed balance model. Results show that the powers and efficiencies of thermophotovoltaic devices with intermediate bands in appropriate positions are clearly larger than those of the conventional counterparts. Based on the optical properties observed in experiments, three types of absorber materials are compared, which indicates that InAs with low energy bandgap is more suitable as a high-temperature material for photon absorptions than GaSb and Si. Comparing the performance of our model with experiments, we show that the InAs based thermophotovoltaic device allows the enhancement of efficiency over a range of gap sizes. The proposed model may open a new field in the application of thermophotovoltaic devices.

Nonequilibrium free energy and information flow of a double quantum-dot system with Coulomb coupling*

Abstract: We build a double quantum-dot system with Coulomb coupling and aim at studying the connections among the entropy production, free energy, and information flow. By utilizing the concepts in stochastic thermodynamics and graph theory analysis, the Clausius and nonequilibrium free energy inequalities are built to interpret the local second law of thermodynamics for subsystems. A fundamental set of cycle fluxes and affinities is identified to decompose the two inequalities by using Schnakenberg's network theory. The results show that the thermodynamic irreversibility has the energy-related and information-related contributions. A global cycle associated with the feedback-induced information flow would pump electrons against the bias voltage, which implements a Maxwell Demon.

The Maximum Efficiency and Parametric Optimum Selection of a Solar-Driven Thermionic-Photovoltaic Integrated Device

Abstract: A neoteric model of the solar-driven integrated device mainly composed of a thermionic generator (TIG) with a graphene-based anode and a thermophotovoltaic cell is presented, where the major irreversible losses inside and outside the system are considered. The analytical expressions for the power output and efficiency of two subsystems and the integrated device are derived. The temperatures of the emitter and collector are determined through heat balance equations. The effects of the voltage outputs of the generator and cell, area ratio of the absorber to the emitter, bandgap energy of the cell, and solar concentration factor on the systemic performance are evaluated. Several main parameters are optimized and parametric selection criteria are provided. The maximum efficiencies of the integrated device operated at different conditions are calculated. For example, under 1000 solar concentration, the efficiency of the integrated device attains 45.23%, which is obviously higher than that of a single solar-driven TIG (STIG) or other existing hybrid systems with a traditional TIG. It is found that replacing metallic anode by graphene anode and integrating a photovoltaic cell into the STIG largely enhance the conversion efficiency of solar energy.

Nonequilibrium free energy and information flow of a double quantum-dot system with Coulomb coupling

Abstract: We build a double quantum-dot system with Coulomb coupling and aim at studying the connections among the entropy production, free energy, and information flow. By utilizing the concepts in stochastic thermodynamics and graph theory analysis, the Clausius and nonequilibrium free energy inequalities are built to interpret the local second law of thermodynamics for subsystems. A fundamental set of cycle fluxes and affinities is identified to decompose the two inequalities by using Schnakenberg's network theory. The results show that the thermodynamic irreversibility has the energy-related and information-related contributions. A global cycle associated with the feedback-induced information flow would pump electrons against the bias voltage, which implements a Maxwell Demon.

Hyperbolic metamaterial-based near-field thermophotovoltaic system for hundreds of nanometer vacuum gap = 하이퍼볼릭 메타물질 기반의 근접장 열광전지 장치

Abstract: Artificially designed hyperbolic metamaterial (HMM) possesses extraordinary electromagnetic features different from those of naturally existing materials. In particular, the dispersion relation of waves existing inside the HMM is hyperbolic rather than elliptical; thus, waves that are evanescent in isotropic media become propagating in the HMM. This characteristic of HMMs opens a novel way to spectrally control the near-field thermal radiation in which evanescent waves in the vacuum gap play a critical role. In this paper, we theoretically investigate the performance of a near-field thermophotovoltaic (TPV) energy conversion system in which a W/SiO2-multilayer-based HMM serves as the emitter at 1000 K and InAs works as the TPV cell at 300 K. By carefully designing the thickness of constituent materials of the HMM emitter, the electric power of the near-field TPV devices can be increased by about 6 times at 100-nm vacuum gap as compared to the case of the plain W emitter. Alternatively, in regards to the electric power generation, HMM emitter at experimentally achievable 100-nm vacuum gap performs equivalently to the plain W emitter at 18-nm vacuum gap. We show that the enhancement mechanism of the HMM emitter is due to the coupled surface plasmon modes at multiple metal-dielectric interfaces inside the HMM emitter. With the minority carrier transport model, the optimal p-n junction depth of the TPV cell has also been determined at various vacuum gaps.

Sub-diffractional, volume-confined polaritons in a natural hyperbolic material: hexagonal boron nitride

Abstract: Strongly anisotropic media, where the principal components of the dielectric tensor have opposite signs, are called hyperbolic. Such materials exhibit unique nanophotonic properties enabled by the highly directional propagation of slow-light modes localized at deeply sub-diffractional length scales. While artificial hyperbolic metamaterials have been demonstrated, they suffer from high plasmonic losses and require complex nanofabrication, which in turn induces size-dependent limitations on optical confinement. The low-loss, mid-infrared, natural hyperbolic material hexagonal boron nitride is an attractive alternative. Here we report on three-dimensionally confined 'hyperbolic polaritons' in boron nitride nanocones that support four series (up to the seventh order) modes in two spectral bands. The resonant modes obey the predicted aspect ratio dependence and exhibit high-quality factors (Q up to 283) in the strong confinement regime (up to λ/86). These observations assert hexagonal boron nitride as a promising platform for studying novel regimes of light-matter interactions and nanophotonic device engineering.

Nanophotonic Color Routing

Abstract: Recent advances in low-dimensional materials and nanofabrication technologies have stimulated many breakthroughs in the field of nanophotonics such as metamaterials and plasmonics that provide efficient ways of light manipulation at a subwavelength scale. The representative structure-induced spectral engineering techniques have demonstrated superior design of freedom compared with natural materials such as pigment/dye. In particular, the emerging spectral routing scheme enables extraordinary light manipulation in both frequency-domain and spatial-domain with high-efficiency utilization of the full spectrum, which is critically important for various applications and may open up entirely new operating paradigms. In this review, a comparative introduction on the operating mechanisms of spectral routing and spectral filtering schemes is given and recent progress on various color nanorouters based on metasurfaces, plasmonics, dielectric antennas is reviewed with a focus on the potential application in high-resolution imaging. With a thorough analysis and discussion on the advanced properties and drawbacks of various techniques, this report is expected to provide an overview and vision for the future development and application of nanophotonic color (spectral) routing techniques.