Thermoelectric Performance Optimization And Application Of PEDOT:PSS

Thermoelectric materials are functional materials that convert thermal and electrical energy through internal carrier transport.With the development of flexible wearable devices and microelectronic devices,organic thermoelectric materials with flexibility have become a hot research topic in the field of thermoelectrics.However,the low Seebeck coefficient of organic thermoelectric materials leads to a much lower thermoelectric performance than that of inorganic semiconductor thermoelectric materials,which makes the research and development of organic thermoelectric materials face new opportunities and challenges.In this paper,the performance of PEDOT:PSS with high electrical conductivity is optimized using a post-treatment and compounding process to achieve better flexibility and thermoelectric properties.Firstly,PEDOT:PSS thermoelectric films were prepared by the drop-casting method in this research,and post-processed with formamide(CH3NO),concentrated sulphuric acid(H2SO4)and sodium borohydride(NaBH4)successively,resulting in a Seebeck coefficient of 28 μV/K,conductivity of 1725.5 S/cm and power factor of 135.3 μW/m·K2 at room temperature.It is shown from the testing that the increase in power factor of the composite films was due to the selective removal of the PSS insulating phase,as well as the enhanced crystallinity of the PEDOT and the π-π interaction between the PEDOT chains,resulting in a higher carrier concentration.After modifying its oxidation level by NaBH4,the optimal power factor was observed.The polyimide was then applied as a flexible substrate of the film,whose power generation voltage and current could be achieved as 16.21 mV and 90 μA with an external 87 Ω resistor.Total power of 0.73 μW with a power density of 83.14 μW/cm2 was shown when 15 samples were connected in series at a temperature difference of 39℃.Secondly,polyacrylamide hydrogels(PAM)were prepared using acrylamide,ammonium persulfate and N,-N’methylenebisacrylamide,which was combined with PEDOT:PSS to create PAM/PEDOT:PSS composites.Comparison of the thermoelectric properties of the composite films with different PAM contents shows that the ionic conductivity of the composite decreases and the Seebeck coefficient increases as the PAM content increases,with a maximum power factor of 72.3 μW/m·K2 achieved at 85 wt%PAM.The PAM/PEDOT:PSS sample testing revealed a maximum open circuit voltage of 0.47 V at a temperature difference of 39℃.When connected to the same load as its internal resistance(50 kΩ),it generated a current of 4.7 μA and a power of 1.1 μW,with a power density of 11.2μW/cm2.The material demonstrated good thermal stability,which could continuously operate for 1.5 hours at 185℃.Finally,given the difficulties in obtaining a cold source for thermoelectric materials,this study innovatively adopted a radiation cooling film(PMRC),characterizing no external energy consumption and sustainable cooling,as the cold side of the thermoelectric material,which is of practical importance in terms of increasing the temperature difference and the electrical output.Post-treated PEDOT:PSS was selected as the power generation module that uses the temperature difference between human body temperature and the environment as a source of power to supply the watch.The experimental results show that the maximum output power and the corresponding power density of the thermoelectric devices are increased by 27.2%after combining with PMRC,and the power density is increased from 83.14μW/cm2 to 105.8 μW/cm2,which verifies the feasibility of its application.