Research On Thermoelectric Properties Of Organic/Inorganic Hybrid Materials And Devices

Nowadays,due to the growing global energy crisis and greenhouse effect,thermoelectricity,as a kind of green and clean energy,has attracted more and more attention.By utilizing the advantages of both organic and inorganic materials,the organic/inorganic hybrid materials have made continuous breakthroughs in thermoelectrics in recent years.The deep understanding of the relationships between the structure,interface and property based on organic/inorganic hybrid materials and devices is indispensable to effectively promote the heat-electricity conversion efficiency and realize the ultimate commercialization.This dissertation focuses on the thermoelectric study of organic/inorganic hybrid materials and devices.Tuning the thermoelectric properties of organic/inorganic hybrid thin-film devices through surface polarization can give experimental and theoretical supports to solve the coupling between Seebeck coefficient,electrical conductivity,and thermal conductivity,while the researches and developments of new organic/inorganic hybrid materials with good thermoelectric performance provide experimental basis for further study of new material,device and its application with high efficiency.Firstly,the effect of doping,surface polarization and interfacial modification on the thermoelectric properties were studied in the hybrid thin-film devices based on a typical P-type organic semiconductor.Secondly,the surface polarization and interface dipoles were investigated by varying the dielectric oxide layer in N-type hybrid thin-film devices.The thermoelectric properties,structures and surface defects of a new organic/inorganic hybrid perovskite material were explored.A new N-type of organic/inorganic hybrid materials with high conductivity has been prepared,then the relationship between the material structure and thermoelectric properties were analyzed.The research contents could be summarized four parts as listed below:?1?The effect of doping,surface polarization and interfacial modification on the thermoelectric properties were investigated in the hybrid thin-film devices based on P-type conducting polymer P3 HT.The doping of PbS quantum dots can influence the carrier concentration and charge mobility in hybrid thin-film devices,leading to an enhancedelectrical conductivity but decreased Seebeck coefficient.Besides the effect on carrier concentration,the surface polarization enhanced by MoO₃ dielectric layer can also function as a new driving force to develop the Seebeck effect in the P3HT-based hybrid devices,which leads to the simultaneously enhanced electrical conductivity and Seebeck coefficient,contributing to the much better thermoelectric performance in hybrid devices.The interfacial modification induced by LiF layer would reduce the potential barrier at the electrode interface and can improve the electrical conductivity.?2?In N-type hybrid thin-film devices based small molecules C₆₀,the surface polarization and interface dipole were investigated by varying the dielectric oxide layer?TiOx?ZnO?NiO?.In hybrid devices with TiOx and ZnO layer,the surface polarization and thermally-dependent interface dipoles functions in the same direction and enhance the electrons diffusion,promoting N-type Seebeck effect in hybrid devices.However,the surface polarization and thermally-dependent interface dipoles generate the contrary influence on the electrons diffusion in NiO/C₆₀ hybrid devices,leading to the P-type to N-type transition of Seebeck coefficient.The carrier concentration and density of states would increase as temperature rises,while the surface polarization would be enhanced due to the electron-phonon coupling,leading to different Seebeck effect in different hybrid devices.?3?In the organic/inorganic hybrid CH₃NH₃PbBr₃ perovskite single crystal prepared from solution growth method,the effect of light,surface defects and other factors on the semiconducting and thermoelectric properties were investigated by Seebeck effect and photoluminescence measurements.The observed negative-to-positive Seebeck coefficient in dark condition is due to the coexist N-type and P-type defects in CH₃NH₃PbBr₃ and the negative Seebeck coefficient can be attributed to the N-type defects near the surface of CH₃NH₃PbBr₃ single crystal.CH₃NH3_PbBr₃ behaves as a P-type semiconductor under light since the defects have been filled by the photo-generated carriers.The ultra-low thermal conductivity of CH₃NH₃PbBr₃ is ascribed to the unique structure of organic/inorganic hybrid perovskite.?4?A new N-type organic/inorganic hybrid C₆H₄NH₂CuBr₂I have been papered from solution method and the Seebeck effect influenced by self-doping and polarization was alsoinvestigated.The high conductivity of C₆H₄NH₂CuBr₂I film can be attributed to self-doping effect caused by CuI,while the relatively large Seebeck coefficient is due to the unique structure and polarization property.The organic/inorganic hybrid C₆H₄NH₂CuBr₂I presents extremely high power factor up to 1740 ?W/mK²,suggesting a promising N-type thermoelectric material for power generator.