Thermodynamic Performance of Three-Terminal Hybrid Quantum Dot Thermoelectric Devices

We propose four different models of three-terminal quantum dot thermoelectric devices. From general thermodynamic laws, we examine the rew;rsible efficiencies of the four different models. Based on the master equation, the expressions for the efficiency and power output are derived and the corresponding working regions are determined. Moreover, we particularly analyze the performance of a three-terminal hybrid quantum dot refrigerator. The performance characteristic curves and the optimal performance parameters are obtained. Finally, we discuss the influence of the nonradiative effects on the optimal performance parameters in detail.

A Three-Terminal Quantum Well Heat Engine with Heat Leakage

We propose a model for a three-terminal quantum well heat engine with heat leakage. According to the Landauer formula, the expressions for the charge current, the heat current, the power output and the efficiency are derived in the linear-response regime. The curves of the power output and the efficiency versus the positions of energy levels and the bias voltage are plotted by numerical calculation. Moreover, we obtain the maximum power output and the corresponding efficiency, and analyze the influence of the heat leakage factor, the positions of energy levels and the bias voltage on these performance parameters.

Optimal Performance Analysis of a Three-Terminal Thermoelectric Refrigerator with Ideal Tunneling Quantum Dots

The model of a three-terminal thermoelectric refrigerator with ideal tunneling quantum dots is established. It consists of a cavity connected to two quantum dots embedded between two electron reservoirs at different temperatures and chemical potentials. According to the Landauer formula the expressions for the heat current, the cooling rate and the coefficient of performance （COP） are derived analytically. The performance characteristic curves of the cooling rate versus the coefficient of performance are plotted with numerical calculation. The optimal regions of the cooling rate and the COP are determined. Moreover, we optimize the cooling rate and the COP with respect to the position of energy level of the right quantum dot, respectively. The influence of the width of energy level and the temperature ratio on performance of the three-terminal thermoelectric refrigerator is analyzed. Lastly, when the width of energy level is small enough, the optimal performance of the refrigerator is discussed in detail.

Entropies of the Y-Junction Type Nanostructures

Recent research on nanostructures has demonstrated their importance and application in a variety of fields.Nanostructures are used directly or indirectly in drug delivery systems,medicine and pharmaceuticals,biological sensors,photodetectors,transistors,optical and electronic devices,and so on.The discovery of carbon nanotubes with Y-shaped junctions is motivated by the development of future advanced electronic devices.Because of their interactionwithY-junctions,electronic switches,amplifiers,and three-terminal transistors are of particular interest.Entropy is a concept that determines the uncertainty of a system or network.Entropy concepts are also used in biology,chemistry,and applied mathematics.Based on the requirements,entropy in the form of a graph can be classified into several types.In 1955,graph-based entropy was introduced.One of the types of entropy is edgeweighted entropy.We examined the abstract form of Y-shaped junctions in this study.Some edge-weight-based entropy formulas for the generic view of Y-shaped junctions were created,and some edge-weighted and topological index-based concepts for Y-shaped junctions were discussed in the present paper.

Performance optimization of three-terminal energy selective electron generators

The energy selective electron device works among electron reservoirs with different temperatures and chemical potentials.Electrons obey the Fermi-Dirac distribution,and with the help of resonant filters,a part of electrons with specific energy levels can tunnel among reservoirs and provide current to an external circuit.Herein,an irreversible three-terminal energy selective electron generator model is proposed.Using statistical mechanics and finite-time-thermodynamics,analytical expressions of power and efficiency are derived,and the optimal performance of the device is investigated.Results show that the central energy level difference of filters,the chemical potential difference of low-temperature reservoirs,the interval of mean-central-energy-level of filters and the mean-chemical-potential of low-temperature reservoirs can be optimized to maximize power and efficiency.On the basis of power and efficiency analyses,performance characteristics under different objective functions,including efficient power and ecological function,are discussed and the corresponding optimal performance regions are obtained.The relationship between the entropy generation rate and the efficiency is investigated,and it is shown that the minimum-entropy-generation-state does not coincide with the maximum-efficiency-state.

Estimating zero-sequence impedance of three-terminal transmission line and Thevenin impedance using relay measurement data

Current and voltage waveforms recorded by intelligent electronic devices(IEDs)are more useful than just performing post-fault analysis.The objective of this paper is to present techniques to estimate the zero-sequence line impedance of all sections of a three-terminal line and the Thevenin equivalent impedance of the transmission network upstream from the monitoring location using protective relay data collected during short-circuit ground fault events.Protective relaying data from all three terminals may not be always available.Furthermore,the data from each terminal may be unsynchronized and collected at different sampling rates with dissimilar fault time instants.Hence,this paper presents approaches which use unsynchronized measurement data from all the terminals as well as data from only two terminals to estimate the zero-sequence line impedance of all the sections of a three-terminal line.An algorithm to calculate positive-,negative-and zero-sequence Thevenin impedance of the upstream transmission network has also been presented in this paper.The efficacy of the proposed algorithms are demonstrated using a test case.The magnitude error percentage in determining the zero-sequence impedance was less than 1%in the test case presented.

Recirculation of Parallel-Connected Planetary Gear Trains

Recirculation is expected to be identified for its possibility to dramatically decrease the efficiency of planetary gear trains(PGTs).However,it exhibits an unexplained connection with the structure,making it challenging to identify without tedious computation through tooth and speed ratios,thus complicating the design process.This study employs a generic model utilizing the mechanical balance principle and reveals the fundamental laws of the previously unexplained connection for parallel-connected ring-sun-type PGTs.Two necessary and sufficient conditions,torque and structure,were proven for multi-stage and two-stage PGTs without recirculation,respectively.This shows that the structure,specifically whether the links are central gears or carriers,and the connections between them directly impact the recirculation of these PGTs.A geometric model representing the structure and kinematics was developed to visualize the power flow.Thus,the recirculation of parallel-connected ring-sun-type PGTs can be predicted without calculations.Our results provide the underlying insights to understanding recirculation from the structural connection viewpoint,thereby contributing to the conceptual design phase where the task is to select the kinematic structure and the gear size is unknown.

Modified Bogoliubov-de Gennes treatment for Majorana conductances in three-terminal transports

We consider a two-lead(three-terminal) setup of non-local transport through Majorana zero modes(MZMs) and construct a Majorana master equation(which is also valid for small bias voltages). We first present representative results of current and then show that only a modified Bogoliubov-de Gennes(Bd G) treatment can consistently recover the same results. Based on the interplay of the two approaches, we reveal the existence of non-vanishing channels of teleportation and crossed Andreev reflections even at the limit ∈;→ 0(zero coupling energy of the MZMs), which leads to new predictions for the height of the zero-bias-peak of the local conductance and the ∈;-scaling behavior of the teleportation conductance, for verification by experiments.

Characterization of Nanometer-Spaced Few-Layer Graphene Electrodes

We study graphene electrodes that can be used for contacting single molecules. The nanometer-scale gap is made by feedback controlled electroburning in few-layer graphene sheets. We analyze the time stability, and the influence of the temperature and gate voltage on the current flowing through the empty gaps. The electrodes are stable at room temper- ature for long periods of time. We show statistics of the relation between the initial resistance of the few-layer graphe- ne flakes and the final size of the gaps. We find that thicker flakes are more suitable for the fabrication of the elec-trodes.

Band-tailored van der Waals heterostructure for multilevel memory and artificial synapse

Two-dimensional(2D)van der Waals heterostructure(vdWH)-based floating gate devices show great potential for next-generation nonvolatile and multilevel data storage memory.However,high program voltage induced substantial energy consumption,which is one of the primary concerns,hinders their applications in lowenergy-consumption artificial synapses for neuromorphic computing.In this study,we demonstrate a three-terminal floating gate device based on the vdWH of tin disulfide(SnS2),hexagonal boron nitride(h-BN),and few-layer graphene.The large electron affinity of SnS2 facilitates a significant reduction in the program voltage of the device by lowering the hole-injection barrier across h-BN.Our floating gate device,as a nonvolatile multilevel electronic memory,exhibits large on/off current ratio(105),good retention(over 104 s),and robust endurance(over 1000 cycles).Moreover,it can function as an artificial synapse to emulate basic synaptic functions.Further,low energy consumption down to7 picojoule(pJ)can be achieved owing to the small program voltage.High linearity(<1)and conductance ratio(80)in long-term potentiation and depression(LTP/LTD)further contribute to the high pattern recognition accuracy(90%)in artificial neural network simulation.The proposed device with attentive band engineering can promote the future development of energy-efficient memory and neuromorphic devices.

Three‐terminal perovskite/integratedbackcontactsilicon tandem solar cells under low light intensity conditions

The current climate and energy crisis urgently needs solar cells with efficiencies above the 29% single junction efficiency bottleneck.Silicon/perovskite tandem solar cells are a solution,which is attracting much attention.While silicon/perovskite tandem cells in 2-terminal and 4-terminal configurations are well documented,the three-terminal concept is still in its infancy.It has significant advantages under low light intensities as opposed to concentrated sunlight,which is the critical factor in designing tandem solar cells for low-cost terrestrial applications.This study pre-sents novel studies of the sub-cell performance of the first three-terminal perovskite/silicon selective band offset barrier tandem solar cells fabricated in an ongoing research project.This study focuses on short circuit current and operating voltages of the subcells under light intensities of one sun and below.Lifetime studies show that the perovskite bulk carrier lifetime is insensitive to illumination,while the silicon cell's lifetime decreases with decreasing light intensity.The combination of perovskite and silicon in the 3T perovskite-silicon tandem therefore reduces the sensitivity of V_(OC) to light intensity and maintains a relatively higher V_(OC) down to low light intensities,whereas silicon single-junction cells show a marked decrease.This technological advantage is proposed as a novel advantage of three-terminal perovkite/silicon solar cells for low light intensities of one sun or less.