Performance Study Of Thermoelectric Devices Based On Three Coupled Quantum Dots And Multi-level Quantum Dots

In this thesis,the thermodynamic performance characteristics and optimal analysis of the three-coupled quantum dots with four-terminal structure heat engine,the three-terminal heat engine and refrigerator based on the resonant tunneling multi-level quantum dots.In the steady-state case,we derive the expressions for the performance parameters of system through the master equation theory and Landauer equation theory,and then the parameters are optimized reasonably to improve the performance of thermoelectric devices.The main contents of this thesis are as follows:In chapter 1,we mainly introduce the development of thermoelectric devices,finite-time thermodynamics theory,linear response and Onsager reciprocity.In chapter 2,We establish a model of the four terminal thermoelectric heat engine based on three coupled quantum dots,which consists of left/right electron reservoir,two thermal reservoirs and three coupled quantum dots.Based on the master equation theory,we derive the expressions of the current and heat flow between the three quantum dots and the corresponding reservoir,and we define the efficiency of the heat engine.The working range of the device is plotted by the data obtained from numerical simulation.Finally,the parameters are optimized to achieve the maximum power output of the heat engine.In chapter 3,we establish a three-terminal heat engine model based on the resonant tunneling of multi-level quantum dots.With the help of Landauer formula,the general expressions for the charge and heat currents,the power output and efficiency are derived.In the linear response regime an explicit analytic expressions for the charge and heat currents,the maximum power output and the corresponding efficiency is presented.Next,the performance characteristics and optimization performance of the heat engine in the nonlinear response region are studied by numerical calculation.Finally,the influence of the main parameters,including the asymmetry factor,the energy-level spacing,the energy difference,the number of discrete energy levels,the bias voltage,and the temperature difference on the optimal performance of the heat engine is analyzed in detail.By choosing appropriate parameters,the heat engine can work in the optimal working range.In chapter 4,on the basis of the three-terminal multi-level quantum dot heat engine model,another three-terminal refrigerator based on the resonant tunneling of multi-level quantum dots is designed.In the weak coupling strength region,by drawing the characteristic curve,we found that only when N(28)1,the refrigerator can reach the Carnot COP.Then we optimized the performance of the refrigerator.Finally,the cooling rate and COP of the refrigerator in strong/weak coupling strength regime are discussed and compared.In chapter 5,we summarize the main work of this thesis,discuss the shortcomings in the work,and make suggestions for improvement.