氧化铟/聚(3,4-乙烯二氧噻吩)复合材料的微结构及其热电性能研究

通过化学氧化合成的方法将纳米In_2O_3复合到聚(3,4-乙烯二氧噻吩)(PEDOT)中得到In_2O_3/PEDOT复合材料.利用X射线衍射、红外光谱、电子显微镜及正电子湮没等方法对复合材料的微观结构进行了系统研究,同时对材料的热学和电学性能进行了表征.结果表明,当In_2O_3的含量在22 wt%以下时,In_2O_3能很好地分散到PEDOT基体中.热电性能测试则显示In_2O_3/PEDOT复合材料的导电率随In_2O_3含量增加明显增大.纯PEDOT的电导率仅为7.5 S/m,而含12.3 wt%In_2O_3的复合材料的电导率达到25.75 S/m.该复合材料相应的功率因子(68.8×10~(-4)μW/m·K~2)相对于纯的PEDOT(14.5×10~(-4)μW/m·K~2)提高了近4倍.另外,复合材料的热导率相对于纯PEDOT也有所降低.最终复合材料的热电优值由0.015×10~(-4)提高到了0.073×10~(-4).结果表明,In_2O_3/PEDOT复合材料的热电性能相对于纯PEDOT的热电性能得到了比较明显的提高.     

Enhanced thermoelectric properties of PEDOT/PSS/Te composite films treated with H<Subscript>2</Subscript>SO<Subscript>4</Subscript>

Firstly, tellurium (Te) nanorods with a high Seebeck coefficient have been integrated into a conducting polymer PEDOT/PSS to form PEDOT/PSS/Te composite films. The Seebeck coefficient of the PEDOT/PSS/Te (90 wt.%) composite films is ~191 μV/K, which is about 13 times greater than that of pristine PEDOT/PSS. Then, H₂SO₄ treatment has been used to further tune the thermoelectric properties of the composite films by adjusting the doping level and increasing the carrier concentration. After the acid treatment, the electrical conductivity of the composite films has increased from 0.22 to 1613 S/cm due to the removal of insulating PSS and the structural rearrangement of PEDOT. An optimized power factor of 42.1 μW/mK² has been obtained at room temperature for a PEDOT/PSS/Te (80 wt.%) sample, which is about ten times larger than that of the untreated PEDOT/PSS/Te composite film.     

Capacitance properties of poly(3,4-ethylenedioxythiophene)/carbon nanotubes composites

The electrochemical properties of composites prepared from an electrically conducting polymer poly(3,4-ethylenedioxythiophene), i.e. PEDOT and multiwalled carbon nanotubes (CNTs) have been investigated for supercapacitor application. The novel composite material was prepared by chemical or electrochemical polymerization of EDOT directly on the nanotubes or from a homogenous mixture of PEDOT and CNTs. Acetylene black (AB) has been also used as a composite component in order to evaluate whether nanotubes are giving improved properties or not. Electrodes prepared from such composites were used in supercapacitors operating in acidic (1 M H₂SO₄), alkaline (6M KOH) and organic (1 M TEABF₄ in AN) electrolytic solutions. The capacitance values were estimated by galvanostatic, voltammetry and impedance spectroscopy techniques with two- or three-electrode cell configuration. Due to the open mesoporous network of nanotubes, the easily accessible electrode/electrolyte interface allows quick charge propagation in the composite material and an efficient reversible storage of energy in PEDOT during subsequent charging/discharging cycles. The composites with AB supply quite good capacitance results, however, nanotubes as electrode component gave definitively a more homogenous dispersion of PEDOT that should give a better charge propagation. The values of capacitance for PEDOT/carbon composites ranged from 60 to 160 F/g and such material has a good cycling performance with a high stability in all the electrolytes. Organic medium is especially interesting because of higher energy stored. Another quite important advantage of this composite is its significant volumetric energy because of the high density of PEDOT.     

Graphene for Thermoelectric Applications: Prospects and Challenges

Thermoelectric power generators require high-efficiency thermoelectric materials to transform waste heat into usable electrical energy. An efficient thermoelectric material should have high Seebeck coefficient and excellent electrical conductivity as well as low thermal conductivity. Graphene, the first truly 2D nanomaterial, exhibits unique properties which suit it for use in thermoelectric power generators, but its application in thermoelectrics is limited by the high thermal conductivity and low Seebeck coefficient resulting from its gapless spectrum. However, with the possibility of modification of graphene's band structure to enhance Seebeck coefficient and the reduction of its thermal conductivity, it is an exciting prospect for application in thermoelectric power generation. This article examines the electronic, optical, thermal, and thermoelectric properties of graphene systems. The factors that contribute to these material properties in graphene systems like charge carriers scattering mechanisms are discussed. A salient aspect of this article is a synergistic perspective on the reduction of thermal conductivity and improvement of Seebeck coefficient of graphene for a higher thermoelectric energy conversion efficiency. In this regard, the effect of graphene nanostructuring and doping, forming of structural defects, as well as graphene integration into a polymer matrix on its thermal conductivity and Seebeck coefficient is elucidated.     

Research status and performance optimization of medium-temperature thermoelectric material SnTe

Thermoelectric materials have the ability to directly convert heat into electricity, which have been extensively studied for decades to solve global energy shortages and environmental problems. As a medium temperature (400-800 K) thermoelectric material, SnTe has attracted extensive attention as a promising substitute for PbTe due to its non-toxic characteristics. In this paper, the research status of SnTe thermoelectric materials is reviewed, and the strategies to improve its performance are summarized and discussed in terms of electrical and thermal transport properties. This comprehensive discussion will provides guidance and inspiration for the research on SnTe.     

Enhanced thermoelectric performance of PEDOT: PSS films via ionic liquid post-treatment

Thermoelectric(TE)energy harvesting can effectively convert waste heat into electricity,which is a crucial technology to solve energy concerns.As a promising candidate for energy conversion,poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)(PEDOT:PSS)has gained significant attention owing to its easy doping,high transparency,and solution processability.However,the TE performance of PEDOT:PSS still needs to be further enhanced.Herein,different approaches have been applied for tuning the TE properties:(i)direct dipping PEDOT:PSS thin films in ionic liquid;(ii)post-treatment of the films with concentrated sulfuric acid(H₂SO₄),and then dipping in ionic liquid.Besides,the same bis(trifluoromethanesulfonyl)amide(TFSI)anion and different cation salts,including 1-ethyl-3-methylimidazolium(EMIM+)and lithium(Li+),are selected to study the influence of varying cation types on the TE properties of PEDOT:PSS.The Seebeck coefficient and electrical conductivity of the PEDOT:PSS film treated with H2SO4EMIM:TFSI increase simultaneously,and the resulting maximum power factor is 46.7μW·m^-1·K^-2,which may be attributed to the ionic liquid facilitating the rearrangement of the molecular chain of PEDOT.The work provides a reference for the development of organic films with high TE properties.     

基于石墨烯/PEDOT：PSS叠层薄膜的柔性OLED器件

石墨烯具有独特的电学性能、优异的机械延展性和良好的化学稳定性,是制备高性能导电薄膜的理想材料,但是当前石墨烯的高电阻率限制了它的实际应用。本文采用喷涂方法制备了石墨烯/聚（3,4-亚乙二氧基噻吩）-聚（苯乙烯磺酸）（PEDOT：PSS）复合导电薄膜,对复合薄膜的表面形貌与光电性能进行了研究。PEDOT：PSS的引入不仅降低了石墨烯薄膜的表面电阻,同时还平滑了薄膜表面。在此基础上,成功制备了柔性黄光有机电致发光器件,器件在12 V时达到效率最大值0.9 cd/A。器件在曲率半径为10 mm时弯曲了100次后,发光亮度并无明显变化。该复合薄膜可实际应用于柔性有机电致发光显示器件。     

Stanene: A Promising Material for New Electronic and Spintronic Applications

The attractive mechanical and electronic properties of freestanding graphene has led to the exploration of two‐dimensional (2D) materials which can be integrated with contemporary electronics. As a 2D analog of graphene, stanene has become a hopeful candidate for 2D films due to its excellent quantum effects, superconductivity, and thermoelectric properties. Focusing on the promising 2D elemental material stanene, the fundamental electronic properties and experimental preparation of this material are reviewed. The prospects of utilizing the ability to manipulate the electronic properties of stanene for nanoelectronic and optoelectronic applications are determined.     

PEDOT as an alignment layer and electrode in AFLC devices

PEDOT [Poly (3, 4-ethylenedioxythiophene) poly (styrenesulfonate)] is a material typically used organic light emission displays (OLEDs) manufactured as a conductor, or rather, as a hole injector. In this paper, three different issues have been studied: the use of rubbed PEDOT as alignment layer, the resistivity of the applied PEDOT layers, i.e., its potential as a replacement of ITO electrodes, and the induction of asymmetry in the electro-optical response of liquid crystal cells by assembling the display with dissimilar coated aligning surfaces — PEDOT on one side and buffed nylon on the counter electrode     

Roughness influence on the sheet resistance of the PEDOT:PSS printed on paper

The use of paper as a platform to manufacture organic electronic devices, electronic paper, has expanding potential for many applications because of several properties offered. In this work, we show a study of PEDOT:PSS printed by inkjet on bond paper, vegetal paper and sheets of PET. The relation between the surface density of the deposited material, morphology and resistivity was investigated for samples printed with a commercial Hewlett-Packard(HP)^® printer and Microsoft Word^® software. The amount of material deposited, i.e. surface density, was controlled using the print number in the same position and changing the gray scale used in the image formation. Changing the surface density of printed PEDOT:PSS, it is possible to produce a continuous film permeating the papers fibers. Sheet resistances obtained, when 7.0 mg cm⁻² of PEDOT:PSS were deposited on the surfaces, were: (a) 413.2 kΩ/Sq for bond paper, (b) 5.6 kΩ/Sq for vegetable paper and (c) 2.3 kΩ/Sq for PET. The exponential dependence of sheet resistance with the surface density of printed material allows us to evaluate the strong influence of substrate roughness on PEDOT:PSS conductivity and to predict, for each one, conditions to minimize it.     

Strategies for optimizing the thermoelectricity of PbTe alloys

The thermoelectric materials have been considered as a potential candidate for the new power generation technology based on their reversible heat and electricity conversion.Lead telluride(Pb Te) is regarded as an excellent mid-temperature thermoelectric material due to its suitable intrinsic thermoelectric properties.So tremendous efforts have been done to improve the thermoelectric performance of Pb Te,and figures of merit,z_T 2.0,have been reported.Main strategies for optimizing the thermoelectric performance have been focused as the main line of this review.The band engineering and phonon scattering engineering as two main effective strategies are systemically summarized here.The band engineering,like band convergence,resonant levels,and band flatting have been addressed in improving the power factor.Additionally,phonon scattering engineerings,such as atomic-scale,nano-scale,meso-scale,and multi-scale phonon scatterings have been applied to reduce the thermal conductivity.Besides,some successful synergistic effects based on band engineerings and phonon scatterings are illustrated as a simultaneous way to optimize both the power factor and thermal conductivity.Summarizing the above three main parts,we point out that the synergistic effects should be effectively exploited,and these may further boost the thermoelectric performance of Pb Te alloys and can be extended to other thermoelectric materials.     

Thermoelectric properties of porous silicon

We have studied the thermoelectric properties of porous silicon, a nanostructured, yet single-crystalline form of silicon. Using electrochemical etching, liquid-phase doping, and high-temperature passivation, we show that porous Si can be fabricated such that it has thermoelectric properties superior to bulk Si, for both n- and p-type doping. Hall measurements reveal that the charge carrier mobility is reduced compared to the bulk material which presently limits the increase in thermoelectric efficiency.     

Facile fabrication of highly flexible,porous PEDOT: PSS/SWCNTs films for thermoelectric applications

High-performance organic composite thermoelectric(TE)materials are considered as a promising alternative for harvesting heat energy.Herein,composite films of poly(3,4-ethyienedioxythiophene):poly(styrene sulfonate)/single-walled carbon nanotubes(PEDOT:PSS/SWCNTs)were fabricated by utilizing a convenient solution mixing method.Thereafter,the as-prepared hybrid films were treated using sulfuric acid(H₂SO₄)to further optimize the TE performance.Film morphological studies revealed that the sulfuric acid treated PEDOT:PSS/SWCNTs composite samples all possessed porous structures.Due to the successful fabrication of highly conductive networks,the porous nano-architecture also exhibited much more excellent TE properties when compared with the dense structure of the pristine samples.For the post-treated sample,a high power factor of 156.43μW·m^-1·K^-2can be achieved by adjusting the content of CNTs,which is approximately 3 orders of magnitude higher than that of the corresponding untreated samples(0.23μW·m^-1·K^-2).Besides,the obtained films also showed excellent mechanical flexibility,owing to the porous nanostructure and the strong p–p interactions between the two components.This work indicates that the H₂SO₄ treatment could be a promising strategy for fabricating highly-flexible and porous PEDOT:PSS/SWCNTs films with high TE performances.     

Predicting the Potential Performance in P-Type SnS Crystals via Utilizing the Weighted Mobility and Quality Factor

The figure of merit ZT is the direct embodiment of thermoelectric performance for a given material. However,as an indicator of performance improvement, the only ZT value is not good enough to identify its outstanding inherent properties, which are highly sought in thermoelectric community. Here, we utilize one powerful parameter to reveal the outstanding properties of a given material. The weighted mobility is used to estimate the carrier transports of p-type SnS crystals, including the differences in doping level, carrier scattering and electronic band structure. We analyze the difference in carrier scattering mechanism for different crystal forms with the same doping level, then evaluate and confirm the temperature-dependent evolution of electronic band structures in SnS. Finally, we calculate the quality factor B based on the weighted mobility, and establish the relationship between ZT and B to further predict the potential performance in p-type SnS crystals with low cost and earth abundance, which can be realized through taking advantage of the inherent material property, thus improving Bfactor to achieve optimal thermoelectric level.     

Chemical synthesis and characterization of poly(3,4-ethylenedioxythiophene)/tungsten composite materials in the presence of ionic liquids

Poly(3,4-ethylenedioxythiophene)/tungsten (PEDOT/W) composites were prepared by an in situ chemical oxidative polymerization of 3,4-ethylenedioxythiophene in different ionic liquids; 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF₄), 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF₆), 1-butyl- 3-methylimidazolium bis(trifluoromethylsulfonyl) imide (BMIMTFSI), and 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl) imide (BMPTFSI). These polymer/metal hybrids (PEDOT/W) were subsequently characterized for their structural, crystalline, thermal and morphological properties by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The significant enhancement in properties can be attributed to the nanoscale particle size and uniform size distribution of PEDOT/W and the synergistic effect between the inorganic nano-W and organic PEDOT material.     

硒化亚铜薄膜热电性能研究进展

热电材料可以实现热能和电能的相互转换,它是一种环境友好的功能性材料.当前,热电材料的热电转换效率低,这严重制约了热电器件的大规模应用,因此寻找更加优异热电性能的新材料或提高传统热电材料的热电性能成为热电研究的主题.与块状材料相比,薄膜具有二维的宏观性质和一维的纳米结构特性,方便研究材料的物理机制与性能的关系,还适用于制备可穿戴电子设备.本文总结了Cu₂Se薄膜5种不同的制备方法,包括电化学沉积、热蒸发、旋涂、溅射以及脉冲激光沉积.另外,结合典型事例,总结了薄膜的表征手段,并从Cu₂Se的电导率、塞贝克系数和热导率等参数出发,讨论了各个参数对热电性能的影响机制.最后介绍了Cu₂Se薄膜热电的热门应用方向.     

Effect of dimethyl sulfoxide on the electrical properties of PEDOT:PSS/n-Si heterojunction diodes

Effect of dimethyl sulfoxide (DMSO) on the electrical properties of PEDOT:PSS/n-Si heterojunction diodes has been studied. Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) was deposited on n-type Si wafer using facile process of spin coating. The DMSO content was varied from 0 to 8 vol%. Electrical characterization of these heterojunction diodes as performed using both current–voltage (I–V) and capacitance–voltage (C–V) measurements. All diodes showed rectifying behavior. AFM measurement revealed that the surface became more rough after the DMSO treatment of PEDOT:PSS films. The RMS values were found in the range of 4–6 nm. The resistivity of the PEDOT:PSS films decreased with increase in temperature. The addition of DMSO into PEDOT:PSS solution results in a decrease in resistivity of films by approximately two orders of magnitude. PEDOT:PSS films showed high transmission more than 85% in the entire visible region. Raman spectroscopy indicated effect of the DMSO treatment on the chemical structure of PEDOT chains, suggesting a conformational change of PEDOT chain in the film. An optimal value of DMSO was obtained with 5 vol% content, and it showed the best PEDOT:PSS films properties and good quality heterojunction diodes characteristics with ideality factor of 2.4 and barrier height 0.80 eV.     

Electrochemical elaboration of adherent poly(3,4-ethylene-dioxythiophene) films and hybride nanowires on nickel

In the line of elaboration of conducting polymer on oxidizable metal, electropolymerization of 3,4-ethylene-dioxythiophene (PEDOT) was performed in ammonium oxalate aqueous solution on nickel. The advantageous effect of the oxalate ions on the electropolymerization process as well as on the physical characteristics of the resulting polymer film has been evidenced. Among these properties, adhesion has been drastically improved. Hybride nanowires nickel/PEDOT have been elaborated to highlight the nickel-PEDOT adhesion. The protective effect of the PEDOT film against corrosion in NaCl is nevertheless very slight.     

Effect of porosity on the thermoelectric efficiency of PbTe

The effect of electron and phonon scattering on nanometer-sized pores on the thermoelectric properties of lead telluride has been studied theoretically. Estimations show that the thermoelectric efficiency can increase by 20–25% at room temperature and by 5–10% at 600 K at the optimal pore size of several nanometers and the porosity of ~10%. An analysis shows that the increase in the thermoelectric efficiency due to additional scattering in the porous material is related to the decrease in the thermal conductivity of the lattice and the increase in the thermoelectric coefficient due to the change in the energy dependence of the relaxation time. To estimate the multiple scattering at high pore concentration, the lattice thermal conductivity by the molecular-dynamics method and the electron free paths in a coherent potential approximation were calculated. It is shown that the inclusion of the multiple scattering slightly influences the thermoelectric properties at noted sizes and pore concentrations.     

Energy band and charge-carrier engineering in skutterudite thermoelectric materials

The binary CoSb₃ skutterudite thermoelectric material has high thermal conductivity due to the covalent bond between Co and Sb, and the thermoelectric figure of merit, ZT, is very low. The thermal conductivity of CoSb₃ materials can be significantly reduced through phonon engineering, such as low-dimensional structure, the introduction of nano second phases, nanointerfaces or nanopores, which greatly improves their ZT values. The phonon engineering can optimize significantly the thermal transport properties of CoSb₃-based materials. However, the improvement of the electronic transport properties is not obvious, or even worse. Energy band and charge-carrier engineering can significantly improve the electronic transport properties of CoSb₃-based materials while optimizing the thermal transport properties. Therefore, the decoupling of thermal and electronic transport properties of CoSb₃-based materials can be realized by energy band and charge-carrier engineering. This review summarizes some methods of optimizing synergistically the electronic and thermal transport properties of CoSb₃ materials through the energy band and charge-carrier engineering strategies. Energy band engineering strategies include band convergence or resonant energy levels caused by doping/filling. The charge-carrier engineering strategy includes the optimization of carrier concentration and mobility caused by doping/filling, forming modulation doped structures or introducing nano second phase. These strategies are effective means to improve performance of thermoelectric materials and provide new research ideas of development of high-efficiency thermoelectric materials.