Research On The Thermoelectric Properties And Refrigeration Applications Of Semiconductor Thermoelectric Materials

The lack of energy and waste heat pollution is a very sticky problem in present world.It is urgent to find new solutions.It provides new ideas for solving energy and thermal pollution to utilize the Seebeck Effect and the Peltier Effect for thermoelectric power generation and thermoelectric refrigeration.The development,optimization and application of thermoelectric materials have become an important subject in the new energy materials research field.In this paper,the thermoelectric properties of materials and devices are researched from two aspects:on the one hand,the thin film thermoelectric devices were prepared to research the thin film of thermoelectric materials and regulate their thermoelectric properties;on the other hand,the miniaturization of thermoelectric refrigeration applications was researched.In the research on thermoelectric thin film materials,Poly?3,4-ethylenedioxythiophene??PEDOT?thin films were prepared to research the effects of electrode and acid solution treatment on their thermoelectric properties;polycrystalline CH₃NH₃PbI₃ thin film devices were prepared,then a physical method of photoexcitation was used to adjust and improve the thermoelectric properties,so as to enhance its electrical conductivity and Seebeck coefficient simultaneously.In the resrarch on miniaturization of thermoelectric refrigeration application,the influence of different P-N pairs,different number of cascade layers and miniaturization on the refrigeration performance of semiconductor thermoelectric cooler were measured and analyzed,and guidance and suggestions for the optimal economic application of refrigeration were provided.Finally,the most suitable thermoelectric cooler was selected for the optimized application design and research of the semiconductor refrigerator,and the temperature-adjustable high-precision semiconductor Thermostatic refrigeration system was fabricated by combining the single-chip technology.More findings about our research are listed as followed:?1?In the research on thermoelectric thin film materials,PEDOT thin films and devices were prepared,and it was found that the electrode and the film thickness have a significant influence on the thermoelectric properties of the PEDOT thin film device.The Seebeck coefficient could exceed 120?V.K^-1 in Al?hot?/PEDOT:PSS/Au?cold?device,and the electrical conductivity was the largest in Au?hot?/PEDOT:PSS/Au?cold?device with the condition of 150?,a temperature difference of 8?and thickness of 2?m.In the study of the effect of acid treatment on PEDOT thermoelectric performance,the PEDOT thin film device formed by twice acid treatments before and after the film formation,had electrical conductivity of 1643.04 S.cm^-1,which was about1000 times higher than that without acid treatments,and also had a high Seebeck coefficient of 13.6618 mV.K^-1,and finally a power factor of 30.6665 nW.m.K^-2 was obtained.?2?In the research on thermoelectric thin film materials,organic-inorganic CH₃NH₃PbI₃ thin film device was also prepared,and the electrical conductivity was increased from 7.8×10^-6 S.m^-1 in the dark to 4×10^-5 S.m^-1 in illumination conditions by photoexcitation.Simultaneously,the Seebeck coefficient was also increased from 26?V.K^-1 to-17 mV.K^-1 with increasing light intensity from 0 to 100%.The Power Factor?PF?value of 11.51 nW.m.K^-2 in the illumination condition was further bigger than the PF of 5.27×10^-6 nW.m.K^-2 in the dark condition.?3?In the research on the influence of different P-N pairs on the refrigeration performance of single-stage thermoelectric cooler,at a same current value,the thermoelectric cooler with more P-N pairs had relatively lower cold end temperature,larger refrigeration temperature difference and refrigeration capacity,and lower refrigeration efficiency.With the increase of current,the cold side temperature of the thermoelectric cooler decreased and the cooling temperature difference increased,and finally both reached saturation.The refrigeration capacity and refrigeration efficiency increased first and then decreased with the increase of current,so there were maximum refrigerating capacity and refrigerating efficiency.When the current approached the limit value,the cooling efficiency was closed to zero.In the research on the refrigeration performance of multistage thermoelectric cooler with different cascade layers,at a same current value,the multistage thermoelectric cooler with larger cascade layers had relatively lower the cold end temperature,larger the refrigeration temperature difference,but smaller refrigeration capacity and refrigeration efficiency.The thermoelectric cooler with very micro size?2.3×2.3 mm²?had very small refrigeration capacity,which required better radiator on the hot side in their applications,so its refrigeration temperature difference was relatively small.?4?Based on the above research results on the refrigeration performance of thermoelectric cooler,two secondary thermoelectric were used to design a semiconductor refrigerator with a capacity of 6 L,which were installed symmetrically and connected in parallel,with water-cooled radiator at the hot end and fan absorbing heat at the cold end to accelerate heat transfer.The experimental results showed that the semiconductor refrigeration refrigerator composed of the above conditions had the best refrigeration performance,which could generate a refrigeration temperature difference of 37.1?under the power of 60W.Compared with the original refrigeration condition.the power was reduced by 29W,but the refrigeration temperature difference was increased by 13.6?,which greatly improved the refrigeration performance of the semiconductor refrigerator.Finally,a high-precision semiconductor thermostatic refrigeration system with intelligent temperature regulation was manufactured,which combined with the single-chip technology,control circuit and program.In the refrigeration system,the temperature in the thermotank was accurate to±1?,with a controllable temperature.