The Thermoelectric Performances Of Poly(3,4-ethylenedioxythiophene):Poly(Styrenesulfonate) By Second-treatment Through Acids Or Alkalies

There increasing works on exploring and using the new energy materials have been ding recently, for the problem about pollution and the limitation of energy sources. Thermoelectric (TE) material is a kind of "green" and functional material employed in power generation and refrigeration, can directly achieve the conversion of electrical energy and thermal energy taking advantage of industrial waste heat and renewable energy, have good energy saving and environmental benefits. Compared with the traditional inorganic TE materials, the organic conducting polymers (CPs) as novel TE materials have been paid much attention because of that they have attractive features for use including their potential low cost due to abundance of carbon resources, easy processing into versatile forms, low thermal conductivity and good environmental stability. Among numerous CPs, poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate)(PEDOT:PSS) will be a promising candidate for organic TE materials owing to high electrical conductivity, low thermal conductivity, good environmental stability, and their unique "metallic and non-metallic" performance. Consequently, it is greatly significant to investigate the TE performances of PEDOT:PSS. This dissertation mainly detected and discussed the TE performance of PEDOT:PSS composite films by second-treatment through acids and alkalies.1. The free-standing PEDOT:PSS/OA films have been prepared for the thermoelectric performance research with the oxalic acid solutions with different concentration (from0.1M to1M) treated the on the140℃hot plant. After treated with oxalic acid solutions, the free-standing PEDOT:PSS films showed high electrical conductivity and stable Seebeck coefficient. The electrical conductivity can be reached to392.8S cm-1after treated with0.8M oxalic acid solutions. Moreover, its power factor was up to9.7μWm-1K-2at room temperature.2. PEDOT:PSS doped with urea, obtained a serious PEDOT:PSS/urea composite films with different content of urea. The highest electrical conductivity of these films is about63.1S cm-1at room temperature, and the Seebeck coefficient was been enhanced simultaneously, it increased from14.47μVK-1to20.7μK-1. The result about SEM showed that the thermoelectric properties enhanced mainly due to the surface of the composite films became smoother and the relationship between thermoelectric properties and the structure and arrangement of the molecules.3. Different contents of urea and Dimethyl sulfoxide (DMSO) were doped PEDOT:PSS aqueous solution simultaneously. TE performance of these free-standing PEDOT:PSS composite films was observed. The results indicated that the electrical conductivity could be enhanced from8.16to over400S cm-1and the maximum Seebeck coefficient reached a value of18.81μV K-1at room temperature. The power factor of the PEDOT:PSS composite films reaches up to8.81μWm-1K-2. The dimensionless Figureure-of-merit (ZT) of these films was estimated and the high value could be reached to2.48×10-2at room temperature.4. PEDOT:PSS aqueous solution with different pH values were obtained through dropping different kinds of acids and alkalis and casted to the free-standing films, for the research on TE performance of PEDOT:PSS films effected by pH value. oxalic acid solution, HC1solution, ethylenediamine (EDA), NaOH solution, and NH4OH were selected for getting PEDOT:PSS aqueous solution with different pH values. The results of this work showed that the acids can enhance the TE performance of the PEDOT:PSS, and the alkalies treatment can enhcance Seebeck coefficient about4times and decreace the electric conductivity about1-3orders of magnitude.5. The composite PEDOT:PSS/[1R-(-)-Camphorsulfonic acid] and PEDOT:PSS/[(±)-10-Camphorsulfonic Acid] solution prepared through added different contents1R-(-)-Camphorsulfonic acid (L-CSA) and (±)-10-Camphor-sulfonic Acid (DL-CSA) into PEDOT:PSS aqueous solution respectively. The TE performance of these composite PEDOT:PSS/L-CSA and PEDOT:PSS/DL-CSA films obtained in different annealing methods were studied. The result showed that there was no obvious difference effect on TE performance by annealing in different condition, however, in the same annealing condition, L-CSA played a better role on enhancing the TE performance than DL-CSA.6. Different concentrations L-CSA and DL-CSA solutions were chosen to second-treated the pre-prepared pristine PEDOT:PSS, respectively. The TE performance has been researched on these obtained films. In the room temperature, the electrical conductivity enhanced for three orders of magnitude after the treatment by L-CSA and DL-CSA solution without the dropping the Seececk coefficient. The electrical conductivity reached up417.1S cm-1and644.7S cm-1by the L-CSA and DL-CSA solution treatment. And the highest power factor was21.1μWm-1K-2.The study of the thermol performance of the PEDOT:PSS as well as its excellent stability suggest PEDOT:PSS will be one of the excellent candidate with good prospect and potential materials in the TE hemisphere.