Structural Analysis And Optimization Of Cu₂Se Based Thermoelectric Devices

Based on the potential application prospect of Cu2 Se material in thermal power generation and waste heat energy utilization,aiming at the shortcomings of expensive commercial powder and complex forming process,this paper prepared low-cost Cu2 Se powder by high temperature melting method,and successfully prepared bulk sample by microwave sintering(WS)rapid synthesis process,and studied the effect of microstructure of the material on its thermoelectric properties.Based on the feasibility analysis of different Cu2Se-based thermoelectric structures,a new Cu2Se-based multi-layer single-arm structure was explored,and the thermoelectric performance of the structure was optimized by multi-objective genetic optimization algorithm.The conclusions are as follows:(1)The main components of the synthesized Cu2 Se powder samples are α-Cu2Se(orhombic system)and β-Cu1.8Se(cubic system),while the commercial powder as the control group only has α phase.The Cu2 Se samples prepared in this paper all have micropores,and the diameter of micropores increases with the increase of WS holding time,and the diameter difference between micropores decreases with the increase of WS holding time.The thermal conductivity of Cu2 Se samples at high temperature decreased significantly compared with that at room temperature.Seebeck coefficient,resistivity,power factor,and ZT value(thermoelectric value)increase with increasing temperature.The microstructure of the material has a significant effect on the thermoelectric properties.The electric transmission performance and ZT value increase with the increase of crystal size,the relative density increases with the increase of the original Se particle size,and the material porosity decreases with the increase of the Se particle size.The decrease of the number of micropores in the material improves the effective mass of the material carriers,but the decrease of the number of micropores also leads to the decrease of the carrier concentration.At 500℃,the ZT value of Cu2 Se samples prepared by synthetic powder in this paper is up to 0.67,which is similar to the ZT value of Cu2 Se samples prepared by commercial powder.It is easier to synthesize Cu2 Se crystals with single lattice structure when the stoichiometric ratio of powder synthesis is 2.1:1.The content of Cu element can effectively regulate the phase,carrier concentration and thermal conductivity of Cu2 Se synthesis.(2)The results of thermoelectric coupling analysis for different structures of Cu2Se-based thermoelectric devices show that when the temperature difference is 500℃,the maximum output power and maximum conversion efficiency of single-arm thermoelectric devices are0.145 W and 5.2%,respectively.For multi-arm thermoelectric structure,the maximum power output and maximum conversion efficiency of single-arm module are increased by 65% and4.155 W respectively.The thermoelectric conversion efficiency of multilayer chip thermoelectric structure is low,the highest is only 2.27%,but the output working current of this structure is increased by 21.45 A,26.8 times compared with the traditional single-arm thermoelectric module,and the output power is increased by 0.535 W,3.69 times compared with the traditional single-arm thermoelectric structure.The multi-objective genetic algorithm was used to optimize the thermoelectric performance of different structures of the device.When the temperature difference was 500℃,the maximum conversion efficiency of the series Cu2 Se single-arm module was improved by 8.5% and the maximum output power was improved by10.23% compared with the original conversion efficiency.For multi-layer chip Cu2 Se singlearm structure,the maximum conversion efficiency and the maximum output power after optimization are improved by 63.44% and 63.24% respectively,and the comprehensive performance is improved significantly.