Preparation And Thermoelectric Properties Of PEDOT:PSS-Based Flexible Nanocomposite Films And Devices

With the rapid development of economy and the continuous growth of world population,global energy shortage and low energy utilization have gradually become an important factor for restricting social and economic development.Thermoelectric(TE)materials,as a kind of functional green material,can directly convert thermal energy into electric energy or verse vice.Therefore,TE materials have attracted more and more attention.TE devices made from TE materials(TE power generation and TE refrigeration devices)have a series of advantages,such as light weight,small size,no pollution,no noise,long operating lifetime,no moving parts,etc.Therefore,they have remarkable research values and application prospects.Due to the high cost,complex preparation process,and environmental pollution of inorganic TE materials,researchers gradually focus on conducting polymer TE materials with advantages of light weight,abundant sources,easy synthesis and processing,good flexibility and high efficiency.As one of the most widely studied conducting polymer TE materials,poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate)(PEDOT:PSS),has good filmforming property,outstanding environmental stability,high conductivity,and low thermal conductivity,which has attracted more and more researchers' attention.However,so far the TE properties of conducting polymers are still much lower than that of the inorganic TE materials.Preparation of inorganic/conducting polymer composites using inorganic TE materials as fillers is an effective way to improve the TE properties of conducting polymers.Based on this concept,the composites were prepared by using graphene,Bi-Te based alloy nanosheets,Sn Se nanosheets and single-walled carbon nanotubes(SWCNTs)as fillers,and PEDOT: PSS as matrix materials,respectively.And then thermoelectric generations(TEGs)were fabricated using the as-prepared corresponding composites.The main work in this thesis is as follows:(1)Graphene/PEDOT:PSS composite TE films with 2wt% graphene were prepared by a vacuum filtration method and the effects of adding graphene on the composition,microstructure,and TE properties of the composite films were studied.A power factor of 29.3 ?W/m K2 was obtained for the composite films at 380 K.The maximum output power of 30.85 n W was achieved at a temperature difference of 55.9 K for the 5-unit TEGs(each unit is 2.5 cm × 0.5 cm)fabricated by using the as-prepared composite film strips.(2)Bi-Te based alloy nanosheets were prepared by a lithium ion hydrothermal intercalation-exfoliation method.Bi-Te based alloy nanosheet/PEDOT:PSS composite TE films were prepared by a vacuum filtration method and the effects of the content of Bi-Te based alloy nanosheets on the composition,microstructure and TE properties of the composites films were studied.A power factor of 58.9 ?W/m K2 was obtained for the composite films with 10 wt% BiTe based alloy nanosheets at 380 K.The maximum output power of 16.9 n W was achieved at a temperature difference of 47.2 K for the 5-unit TEGs fabricated by using the as-prepared composite film strips(each unit is 2.5 cm × 0.5 cm).The composite films were post-treated by ethylene glycol(EG)and dimethyl sulfoxide(DMSO)solution.The maximum power factors of the composite films treated by EG and DMSO are 63.1 ?W/m K2 and 72.0 ?W/m K2 at 380 K,respectively.(3)Sn Se nanosheets were prepared by a lithium ion hydrothermal intercalation-exfoliation method.Free-standing SWCNT/Sn Se nanosheet/PEDOT:PSS composite TE films were prepared by a vacuum filtration method and the effects of different SWCNTs contents on the composition,microstructure and TE properties of the composite were studied.A power factor of 109.9 ?W/m K2 was obtained at 380 K for the composite films with 60 wt% SWCNTs.The maximum output power of 1161.9 n W was achieved at a temperature difference of 74.4 K for the 8-unit TEGs fabricated by using the as-prepared composite film strips(each unit is 2.5 cm × 0.4 cm).