Study On Synthesis And Thermoelectric Properties Of Thiophene Thermoelectric Materials

Thermoelectric material is a new type of functional material that can convert the thermal energy generated by the temperature difference of waste heat into electrical energy.The development and research of new thermoelectric materials to achieve sustainable development has gradually become the focus of researchers.Inorganic thermoelectric materials have made excellent research progress as the most mature branch in the field of thermoelectric materials research.In recent years,organic thermoelectric materials have become a new research hotspot in the field of thermoelectric research due to their ultra-low thermal conductivity,non-toxic environmental protection,and low prices of raw materials.In order to solve the problem of low conductivity of organic thermoelectric materials,this article designs and synthesizes thiophene conjugated polymer organic thermoelectric materials with a narrow band gap,and through acidification or FeCl₃doping post-processing methods,the electrical conductivity is greatly improved,and the thermoelectric performance of the material is significantly improved.Finally,we further selected a conjugated polymer with a high Seebeck coefficient and single-walled carbon nanotubes(SWCNT)to further explore ways and mechanisms to greatly improve thermoelectric performance,the specific research contents are as follows:(1)The thiophene conjugated polymers PCPDT-C and PCPDT-T were synthesized by Suzuki coupling reaction,and the product structure was confirmed by¹HNMR and XPS.The intrinsic optical band gaps of PCPDT-C and PCPDT-T were tested by UV-Vis and voltammetry cycles.Then the method of hydrochloric acid acidification and FeCl₃doping is used to improve the thermoelectric properties of the material,and the thermoelectric properties of the material are adjusted by adjusting the acidification concentration,film annealing time and temperature.The results show that the conductivity of the conjugated polymer film after acidification with hydrochloric acid and FeCl₃doping has been significantly improved,and the highest PCPDT-C reached1.56 S/cm(20?).Under variable temperature conditions,with the increase of temperature,the polymer molecular chain movement will be intensified,which will destroy the regularity between polymer molecules,reduce the?-?conjugate stacking effect between molecules,and thus reduce the carrier mobility,the conductivity decreases and the Seebeck coefficient increases.PCPDT-C reached the maximum power factor of 1.26?Wm^-1K^-2at 95?after acidification with hydrochloric acid.This indicates that hydrochloric acid acidification and FeCl₃doping have a significant effect on improving the thermoelectric properties of thiophene organic thermoelectric materials.(2)Compounding the high-Seebeck coefficient conjugated polymer PCPDT-C obtained after doping treatment with highly conductive inorganic material single-walled carbon nanotubes(SWCNT),after compounding,the electrical conductivity of the material has been further improved significantly,reaching a maximum of 1172 S/cm.Under the conditions of variable temperature and normal temperature,as the SWCNT mass fraction increases,the electrical conductivity of the composite increases first and then decreases.When the SWCNT mass fraction is40%,PCPDT-C(FeCl₃)/SWCNT composite material achieves a maximum power factor of 32.8?Wm^-1K^-2at 95°C,this shows that the thermoelectric properties of the prepared materials have the potential for commercial application.