Preparation Of N-type Organic Thermoelectric Materials Based On Single-walled Carbon Nanotubes And Organic Small Molecules

Enhancement in the efficiency of energy use is urgent,particularly with the background of fossil energy exhaustion,since the heat generated in industrial productions and daily lives is mostly dissipated and wasted.Thermoelectric(TE)materials can realize direct energy conversion between electricity and heat,being very attractive in harvesting low-quality or waste heat.Recently,organic/inorganic composite TE materials with mechanical flexibility,low thermal conductivity,low cost,and no moving parts or bulk fluids compared to their inorganic counterparts have gained great attention.In the past several years,great progresses have been made for p-type TE composites.In sharp contrast,n-type organic/inorganic TE composites still remain a great challenge.The research work of this paper focuses on the preparation of n-type composite thermoelectric materials based on single-walled carbon nanotubes and organic small molecules,including the following three parts:1?SWCNT / DETA composites were prepared by blending SWCNT with organic small molecule DETA by solution blending,and then a high performance n-type composite thermoelectric material was obtained by re-reduction with CaH2.The Seebeck coefficient and conductivity of the material are-41.0 ± 1.5 ?V K-1,160 ± 10 S cm-1 respectively.The microstructures and contens of the composites were characterized by scanning electron microscopy(SEM)and absorption spectroscopy(FTIR),and the mechanism of single-walled carbon nanotubes(SWCNT)transition from p-type conductivity to n-type conductivity was explained for material doping.Finally,we tested the thermoelectric device with excellent performance based on this material.After testing,the thermoelectric device with 14 p-n structures could generate 62 mV open circuit voltage and 649 nW output power under the temperature gradient of 55 K.2?We designed and synthesized organic conductive small molecule perylene dimide(PDINE)and naphthalene diimide(NDINE),and SWCNT / PDINE and SWCNT / NDINE nanocomposites with n-type properties were prepared.The higher conductivity and the Seebeck coefficient make the material exhibit a very high PF value(135 ± 14 ? m m-1 K-2),one of the highest performance in the current n-type organic thermoelectric materials.Then we used the material to form five p-n junctions of thermoelectric devices,tested,the device at a temperature gradient of 50 K,showing a large output power of 3.3 ?W.At the same time,we also used the thermo gravimetric analysis to test the thermal stability of the composites.Compared with other organic thermoelectric materials,this n-type organic thermoelectric composite material has high temperature resistance(? 200 ?),greatly expanding the material application temperature range.3?The SWCNT / PMMA composite hydrogel thermocell material based on the redox reaction is simple to prepare,which not only avoids the inconvenience caused by the use of liquid electrolyte in the thermocell,but also provides better mechanical properties due to the enhanced effect of SWCNT.At the same time,SWCNT brings the network structure permeation filter effect,surface polarization and so on to promote the migration of Sn2 + / Sn4 + redox transfer,which makes the thermalcell material showing a large Seebeck coefficient(1200 ?V K-1)and conductivity(0.11 S cm-1).