Preparation And Performance Investigation On Flexible Thermoelectric Devices Based On Carbon Nanocomposites

Carbon nanomaterials like carbon nanotubes and graphene generally have excellent mechanical properties,high electrical conductivity,good flexibility and light weight.Metal chalcogenides with special topological properties and band structures,such as Bi₂Te₃ and Sb₂Te₃,usually have a high Seebeck coefficient and conductivity,which are almost the best inorganic semiconductor alloy materials with excellent thermoelectric properties at room temperature.In this project,by studying the above thermoelectric nanomaterials,carbon nanotubes and two-dimensional nanoalloys were composited into flexible films as flexible thermoelectric device unit with lateral temperature difference.The polyurethane sponge skeleton was coated with reduced graphene oxide?rGO?to prepare a flexible graphene aerogel with the three-dimensional network structure,which was used for the flexible thermoelectric device unit with longitudinal temperature difference.Therefore,flexible thermoelectric power generation devices with two temperature gradient conduction directions of“planar direction”and“thickness direction”were respectively designed and fabricated.The detailed contents show as below:Two-dimensional Bi₂Te₃ and Sb₂Te₃ nanosheets were synthesized by solvothermal method,and combined with aminated carbon nanotubes and single wall carbon nanotubes respectively to prepare n-type Bi₂Te₃-MWCNTs and p-type Sb₂Te₃-SWCNTs composite films by flitering and sintering.The maximum power factor of the n-and p-type composite films was 58.7?W/mK² and 27.4?W/mK².Two kinds of p-n type flexible planar thermoelectric power generation devices were designed and fabricated.The waste heat of a flexible gallium arsenide photovoltaic cell under illumination was converted into output voltage via the thermoelectric power generation device.A p-type rGO aerogel with three-dimensional network skeleton structure was prepared by impregnation method and chemical reduction method.Reduction degree of graphene oxide by hydroiodic acid and ascorbic acid hydrothermal fluid was studied.The effects of high and low skeletal density,reducing reagents and compression set on rGO aerogel block resistance and thermoelectric properties were investigated.Two kinds of flexible thermoelectric power generation devices with longitudinal temperature difference were fabricated by p-type aerogel combining n-type foamed nickel,and their thermoelectric properties and mechanical stability were studied.The first device had an output voltage of 4.3 mV at a longitudinal temperature difference of 15 K.The second device with higher compressive strength?178 MPa?had an output voltage of 12 mV at a longitudinal temperature difference of70 K,and was able to generate voltage of 5.2 mV by utilizing the waste heat of the flexible solar cell during illumination.