Preparation Of Bismuth Telluride-based Thermoelectric Materials And Devices And Their Applications In Personal Thermal Management

As a kind of clean energy material,thermoelectric（TE）materials can realize the direct conversion of thermal energy and electric energy in different temperature intervals.Power generation and refrigeration through TE devices can improve energy efficiency.In recent years,with the development of flexible electronics and wearable technology,the application of TE materials and devices in the field of personal thermal management（PTM）is increasing.Compared with other PTM methods,wearable TE devices have the advantages of low requirements on the external environment,small size,less power consumption and no pollution.Among many TE materials,bismuth telluride-based materials have the best performance in the low temperature zone.However,there are still many problems in the development of bismuth telluride-based flexible TE materials and devices,such as:the existing flexible TE materials generally have low performance and poor practicability;Some flexible devices have poor wearable comfort and complicated preparation process,so it is difficult to realize product application.Therefore,it is urgent to develop high performance flexible bismuth telluride-based TE materials or make flexible design of traditional rigid materials with excellent performance,so as to realize their application in the wearable and PTM field.In order to solve the above problems,this paper intends to use the laser direct writing technology to prepare two-dimensional thin film materials based on bismuth telluride-based TE materials,so as to realize the preparation of low-cost and highly designable flexible TE materials and devices.By using the weaving technology,the TE block is combined with textiles to realize the flexible design of traditional rigid TE materials with excellent performance,and explore its application in PTM.The main contents include:（1）Bi₂Te₃ and Sb₂Te₃ nanosheets were synthesized by solvothermal method as matrix materials,and graphene oxide was introduced to prepare GO/Bi₂Te₃ and GO/Sb₂Te₃heterogeneous composite films by high-throughput scraping method.Based on laser direct writing technology,the patterned TE devices with various structures are constructed on the composite thin film platform.Among them,the reduction degree of GO was controlled by adjusting the temperature of laser direct writing,so as to regulate the TE properties of different regions of heterogeneous composite films.When the temperature difference is 30 K,the open circuit voltage range of the TE devices constructed based on different heterogeneous composite films is 6-10 m V.The TE devices prepared by this method have unique advantages in the aspects of design and miniaturization.（2）p-type Bi_0.5Sb_1.5Te₃ and n-type Bi₂Te_2.7Se_0.3 TE blocks with excellent TE properties were obtained by hot pressing method and used as energy transfer materials.Based on the woven process,a double-layer stretchable TE fabric with vertical heat transfer was prepared.In order to improve the TE conversion efficiency,the fabric surface is coated with liquid metal elastomer composite material with high thermal conductivity to dissipate heat.The experimental results show that the fabric can withstand more than 70%cyclic stretching.The TE fabric constructed by 6 pairs of p and n TE modules can produce an output voltage of about 25 m V and a maximum output power of about 320μW at a temperature gradient of 40 K.In terms of cooling performance,the TE fabric can produce A temperature difference of about 1.8℃at an input current of 0.5A,so it has great application potential in human thermal management.（3）Based on thermocouple temperature sensor,ECG acquisition sensor,bismuth telluride-based TE fabric,etc.,a wearable health monitoring and management system is prepared through the overall design of the system,which can realize real-time monitoring of heart rate and body temperature and PTM.Through several groups of experimental tests,it is proved that the system has good stability,accuracy and sensitivity in the aspect of physical signs monitoring,and can meet the needs of daily heart rate and temperature monitoring.In terms of temperature management,TE fabrics can provide real-time temperature management feedback for abnormal conditions based on sensor data.In practical application,it can provide a cooling effect of about1.8℃for the human body,so as to realize the adjustment of personal temperature.