Preparation And Thermoelectric Properties Of PEDOT:PSS Flexible Fibers

With the increasing demand for new microelectronic devices and wearable electronic devices,the development of flexible thermoelectric materials which are widely available and easy processing,has become one of the hot topics in thermoelectric research.Conducting polymers,particularly poly(3,4-ethyl enedioxythiophene):poly(styrenesulfonate)(PEDOT:PSS),have been considered as highly promising flexible thermoelectric materials,owing to their unique advantages,including good solution processability,nontoxicity,high electrical conductivity,and low thermal conductivity.However,the thermoelectric properties and flexibility of the pristine PEDOT:PSS materials are poor and still far from meeting the requirements of wearable device applications.Further development of efficient and stretchable PEDOT:PSS thermoelectric materials is therefore particularly important.The thermoelectric properties of the conducting polymers show a strong dependence on their polymer chain conformations and chain stacking structures,and the strong spatial confinement effect from one-dimensional(1D)fiber configuration may induce arrangement of the polymer molecular chains.Based on this concept,1D PEDOT:PSS fibers were firstly developed to improve its thermoelectric performance by adjusting the arrangement order of molecular chains and conjugate stacking structure.In addition,considering that compounding conductive polymers with elastomeric materials is an effective way to improve their flexibility and stretchability,the high-performance,stretchable thermoelectric fibers were prepared by compounding PEDOT:PSS with waterborne polyurethane(WPU)elastomer.In this paper,one-dimensional structure was prepared to improve the order of PEDOT:PSS molecular chain,so as to improve the thermoelectric properties of PEDOT:PSS materials.At the same time,thermoelectric fibers were successfully prepared,which are expected to be widely used in the field of wearable electronic devices as energy supply components.The research content is as follows:1.The high-performance PEDOT:PSS thermoelectric fibers were continuously produced through a modified wet-spinning approach.After H2SO4 treatment,the PEDOT:PSS fiber showed an optimized power factor(PF)of 147.8 ?W·m-1K-2,with electrical conductivity of 4029.5 S cm-1 and Seebeck coefficient of 19.2 ?V K-1.To our best knowledge,this PF was 15 times that of a ?m-thick PEDOT:PSS film.In addition,the high degree of polymer chain alignment also endowed the PEDOT:PSS fibers with a high tensile strength of 389.5 MPa and a large breaking strain of 30.5%.Based on the specific one-dimensional structure of PEDOT:PSS fiber and its excellent thermoelectric properties along the fiber direction,a fiber-based wearable thermoelectric generator(TEG)can be prepared by sewing the fiber onto clothing.The TEG delivered an output power density of 0.323 ?W cm-2 at ?T=10 K.This work has successfully prepared high-performance organic thermoelectric fibers from the perspective of regulating the conformation and arrangement of molecular chains.2.PEDOT:PSS and WPU were physically mixed,and then the intrinsically stretchable thermoelectric fibers were prepared by a one-step wet spinning method.In the 1D composite thermoelectric fiber,the addition of WPU can synergistically enhance the thermoelectric properties and mechanical stretchabilities:During the wet-spinning process,based on the hydrogen bonding between PSS and WPU and the high elasticity of WPU,WPU could play a template effect for aligning and improving the chain packing order of the PEDOT:PSS segments upon mechanical stretching.Mechanical stretching during the wet-spinning process not only improves the alignment of the molecular chains in the fiber,but also improves the conjugated stacking configuration of PEDOT,which significantly improves the thermoelectric properties of the composite fiber;While after the fibers were completely dried,it still served as an elastomeric matrix endowing the composite thermoelectric fibers with good stretchability.The PEDOT:PSS/WPU composite fibers exhibited desirable wearable performance,including high power factor(26.1 ?W m-1 K-2),wide stretching range(>30%)and good stability under cyclic stretching.And their practical applications as stretchable temperature sensors and wearable TEGs based on body temperature were further demonstrated.In summary,the efficient and stretchable PEDOT:PSS thermoelectric fibers were successfully prepared,which provided theoretical bases and technical references for the development of high-performance flexible thermoelectric materials and was of great significance to promote the development of flexible electronic devices and wearable electronic devices.