NiCoSe4薄膜制备及其在染料敏化太阳能电池中的应用

作为染料敏化太阳能电池的关键构成部分,对电极一直是研究的重点,尤其是硒化物对电极.本文采用恒电位沉积-溶剂热-硒化过程制备出钴镍基硒化物薄膜,并直接作为染料敏化太阳能电池的对电极.物相、形貌以及表面元素价态等分析表明,在氟掺杂氧化锡(FTO)玻璃上可直接获得NiCoSe4薄膜,该薄膜是一种由纳米颗粒构成的片状多孔结构....     

溅射硒化物靶与金属单质靶制备Cu2 ZnSnSe4薄膜及电池的比较研究

采用磁控溅射SnSe-ZnSe-Cu硒化物靶和Sn-Zn-Cu金属单质靶的方法制备两种Cu2 ZnSnSe4(CZTSe)预制层,并将两种预制层采用相同的硒化工艺制备出CZTSe薄膜吸收层.分别采用XRD、Raman、SEM、EDS等分析了薄膜的晶体结构、相的纯度、表面及截面形貌和元素组分,结果发现采用硒化物靶制备的CZTSe吸收层薄膜更为平整致密且无明显孔洞.同时采用Hall测试和J-V测试对太阳电池薄膜的电学性质进行了表征,结果表明硒化物靶制备的CZTSe太阳电池的电流密度以及光电转化效率要高于金属单质靶,金属单质靶制备的CZTSe薄膜电池的开路电压为356 mV,短路电流密度为20.61 mA/cm2,光电转换效率为2.18;,而硒化物靶制备的CZTSe薄膜电池的开路电压为354 mV,短路电流密度为28.41 mA/cm2,光电转换效率为3.33;.     

多孔NixCoyS薄膜在染料敏化太阳能电池中的应用研究

为了进一步提高基于硫化镍钴电极的染料敏化太阳能电池光伏性能,将以自组装形成的二维聚苯乙烯光子晶体为模板,采用反向恒压电沉积技术制备一种具有多孔结构的硫化镍钴薄膜(NixCoyS-PC),并直接作为对电极应用于染料敏化太阳能电池中.对比测试结果发现,NixCoyS-PC电极展现出了比无多孔结构的硫化镍钴(NixCoyS-FTO)电极、铂电极更加优异的电催化性能,这是因为多孔结构有利于提高其电催化活性位点及氧化还原电对I-/I3-的扩散速率.因此,基于NixCoyS-PC电极的染料敏化太阳能电池展现出了较高的光电转换效率(5.80;),高于基于NixCoyS-FTO电极(5.43;)和铂电极(4.87;)的电池效率.     

多壁碳纳米管对电极染料敏化太阳能电池的性能研究

以SnO2/TiO2薄膜为光阳极,与以经酸化处理和与石墨复合的沉积在FTO导电基底的多壁碳纳米管(MWCNTs)薄膜为对电极,I-/I3-为电解液,组装成染料敏化太阳能电池.对电极通过循环伏安法(CV曲线)、电化学阻抗谱(EIS)及极化曲线法(Tafel曲线)进行电化学催化性能的表征,组装后的电池通过伏安特性曲线(J～V)进行光电性能分析,结果表明:酸化处理及与石墨复合有利于提高对电极的催化性能及电池光电性能.开路电压及短路电流密度分别可达0.53 V、4.67 mA/cm2,其中短路电流较未经过处理的MWCNTs对电极提高27.4;,同时讨论了对电极电化学性及电池光电性能增强的机制.     

黑磷-二硫化钼异质结光电流特性的研究

黑磷是一种近年来新兴的二维材料,具有可调控窄带隙及宽光吸收谱、高载流子迁移率等优异光电特性,可用于实现中红外波段高速光电探测器.但是黑磷样品在空气中的不稳定性也是制约其应用的主要因素.二硫化钼作为二维层状过渡金属硫属化物(TMDCs)中的典型代表,单层为直接带隙,双层及厚层为间接带隙,在可见光范围内有着较好的光电响应,但由于带隙范围的限制,在近红外的吸收较弱,几乎没有探测能力.基于此,本文通过构建二硫化钼在上,黑磷在下的垂直异质结构,通过硫化钼的保护作用实现了黑磷稳定性的提升,在空气环境中能够保持两个月之久;同时利用黑磷在近红外的吸收,增强了器件在近红外(940 nm)的响应.该异质结构对二维材料实现红外高性能的稳定探测有重要意义.     

高价态W掺杂对NiFe磷化物全分解水制氢催化活性影响的研究

近年来,通过光伏辅助电催化(PV-EC)分解水制备“绿氢”成为实现碳中和目标的关键。然而,普通电解水催化剂不能满足PV-EC系统中较高的太阳能到氢能(STH)转换效率的需求。因此,获取价格低廉、低反应过电势的电催化剂材料极为重要。本文选取具有高价态的过渡金属W作为掺杂源,采用一步电沉积方法制备出NiFeW三元金属磷化物。通过一系列的表征发现,NiFeW磷化物电催化剂表现出优异的析氢反应(HER)和析氧反应(OER)活性,且作为双功能电催化剂时,在10 mA/cm²电流密度下W掺杂后样品的过电势降低了51 mV。使用NiFeW磷化物作为双功能电催化剂和太阳能电池(a-Si∶H/a-SiGe∶H/a-SiGe∶H)作为驱动源,PV-EC器件实现了超过7%的理论STH转换效率,对推动太阳能分解水制氢装置的实际应用具有重要意义。     

High-k材料研究进展与存在的问题

随着集成电路的飞速发展,SiO2作为传统的栅介质将不能满足MOSFET器件高集成度的要求,需要一种新型High-k材料来代替传统的SiO2,这就要综合考虑以下几个方面问题:(1)介电常数和势垒高度;(2)热稳定性;(3)薄膜形态;(4)界面质量;(5)与Si基栅兼容;(6)工艺兼容性;(7)可靠性.本文综述了几类High-k栅介质材料的研究现状及存在的问题.目前任何一种有望替代SiO2的栅介质材料都不能完全满足上述几点要求.但是,科学工作者们已经发现了几种有希望的High-k候选材料.     

MI3(M=Bi,Sb,As)弹性和电子性质的第一性原理研究

采用基于密度泛函理论的第一性原理平面波赝势计算方法,对比研究了菱方结构MI3(M=Bi,Sb,As)的弹性和电子性质.结果表明:SbI3的生成焓最低,较BiI3、AsI3更易生成.这三种材料都体现了弹性各向异性特征.SbI3是偏延性材料,BiI3和AsI3是脆性材料.高压下AsI3更容易被压缩.德拜温度的大小关系依次为SbI3>BiI3>AsI3.MI3(M=Bi,Sb,As)都是间接带隙半导体,电子的局域程度较强.在费米能级附近,I-5p轨道电子和金属M-s轨道电子发生杂化,形成共价键.MI3(M=Bi,Sb,As)中的化学键是共价键和离子键的混合.     

微波辅助法制备氧化铜非酶葡萄糖传感器

采用微波辅助法制备了氧化铜(CuO)材料,其结晶度好,没有杂质,呈现片层堆叠而成的块状结构.以CuO材料修饰玻碳电极作为工作电极(CuO/GCE),饱和甘汞电极作为参比电极,铂丝电极作为对电极,在碱性条件下对葡萄糖溶液进行电化学性能检测.该传感器对520 nM到2.0 mM浓度范围内的葡萄糖溶液实现了优良的检测性能,灵敏度为2491.362μA·cm-2·mM-1,检测限为216 nM(S/N=3),在2 s内就可以完成反应.丙烯酸等物质对传感器的影响可以忽略,具有良好的抗干扰性.     

水溶性高质量二维材料纳米片的制备及其表征

近几年来,二维(2D)材料的研究,已成为纳米科学最令人兴奋的领域之一.其中液相分离具有层状结构的块体材料来制备二维材料的方法成为研究热点.相比于化学气相沉积(CVD)等自下而上的制备方法,通过块体层状材料的剥离制备二维材料及其分散液的方法具有低成本、可大规模生产的优势.在这里主要研究以液相剥离(LPE)的方法制备石墨烯(graphene)、六方氮化硼(h-BN)和四种过渡金属硫属化物(TMDs)溶液,这种水溶性的二维材料具有绿色环保、成本低等优点.使用拉曼光谱(Raman),原子力显微镜(AFM),扫描电子显微镜(SEM)等仪器对研制的层状纳米片的物质组分、表面结构等进行表征,通过紫外(UV)吸收光谱估算出不同离心转速下的浓度,最后通过电化学工作站的循环伏安法(cyclic voltammetry)测出用于MoS2纳米片电解质门控的离子液体体电容,分析可见制得的二维材料纳米片平均尺寸在400 nm左右,离子溶液的体电容为1.21 F/cm3,该体电容是研究电子器件性能的关键性参数.上述表征结果对基于水溶性二维材料纳米片的电子器件研究有着重要的科学与应用价值.     

Graphene/Polyaniline Nanocomposite Multilayer Counter Electrode by Inserted Polyaniline of Dye-Sensitized Solar Cells

Polyaniline (PANI) conducting polymer and graphene are preferred counter electrode (CE) materials for dye-sensitized solar cells (DSSC). Graphene/PANI nanocomposite multilayer CE is created through the insertion of a PANI layer. It has been demonstrated as a platinum-free counter electrode for cost-efficient DSSCs. Here, graphene/PANI nanocomposite and PANI were synthesized by electro-polymerization from a solution containing aniline monomers and graphene. Graphene/PANI nanocomposite multilayer CE showed improved electrical conductivity, interface charge transfer rate, and catalytic activity on I₃^? reduction compared with the Pt CE. The high electro-catalytic ability of graphene/PANI nanocomposite multilayer CE was demonstrated by cyclic voltammetry and electrochemical impedance spectroscopy.     

Crystal structure of non-stoichiometric copper selenides studied by neutron scattering and X-ray diffraction

Structural characteristics of non-stoichiometric copper selenides were studied by the elastic neutron and X-ray scattering techniques. Rietveld analysis was used to refine the structure of the high-temperature β-phase of the Cu_1.75Se, Cu_1.78Se, and Cu_1.83Se samples. The homogeneity ranges of the cubic phase were determined. The modification of the crystal structure accompanying the β-α phase transition was studied for Cu_1.75Se and Cu_1.98Se compounds within the 443-10 K temperature range. It was shown that the phase transition is accompanied by distortions of the fcc lattice and the ordering of copper ions.     

双向有序Ti3C2Tx/rGO复合气凝胶的制备及其电化学性能的研究

近年来,二维材料MXene因其优异的电化学性能引起了人们的关注,被广泛应用于电化学储能领域。然而,在组装电极过程中,MXene纳米片往往会产生严重的自堆积效应从而大幅限制了其电化学性能。设计三维结构的气凝胶是解决MXene自堆积问题同时开发高性能MXene基超级电容器电极材料的关键。本文利用氧化石墨烯(GO)改善了Ti₃C₂T_x气凝胶的力学强度,并通过双向冷铸和冷冻干燥、温和还原的方法制备了具有双向有序结构的Ti₃C₂T_x/rGO复合气凝胶(A-TGA)。A-TGA具有较好的力学性能和导电性,因此可直接作为超级电容器的电极材料。同时,双向有序的独特结构为电解质离子提供了无阻碍的传输通道,大幅提升了气凝胶的电化学性能。A-TGA在电流密度为1 A·g^-1时的比电容为370 F·g^-1,在100 mV·s^-1扫速下经过5 000次循环后,电容保持率高达94%,表现出优异的循环稳定性。     

Three-dimensional Bi2Se3 nanopattern films self-assembled with ultrathin nanosheets on the surface of Se nanotubes

Regular three-dimensional (3D) rose-like Bi₂Se₃ nanopattern film is fabricated through a simple chemical route. This nanopattern film is self-assembled with ultrathin Bi₂Se₃ nanosheets having thicknesses of less than 8 nm. The Bi₂Se₃ nanosheets were formed on the surface of Se nanotubes, and the Se nanotubes were used as both the Se resource and the substrate to support the growth of the Bi₂Se₃ nanopattern film. Since several length scales are involved in this confined 3D structure, which are developed at different time, during the formation of the micro-structure, a careful control of these length scales is expected to provide new opportunities for engineering the boundary scattering of phonons of different wavelengths and developing new thermoelectric materials with novel properties.     

负极材料Li4Ti5O12的制备与性能研究

利用纳米二氧化钛(P25)粉为钛源,Li2CO3为锂源,采用固相法及高能球磨法制备亚微米级尖晶石Li4Ti5O12.将Li4Ti5O12与碳纳米管(CNTs)制备成复合电极作为工作电极与锂片组成电池进行电化学性能测试.通过SEM,XRD等表征材料形貌、结构及粒径分布,通过充放电测试表征其电化学性能.结果表明,在800℃合成温度及8h合成时间制备条件下可以得到小尺寸且颗粒均匀的亚微米晶体Li4Ti5O12,且合成的产物电化学性能最佳.在800℃及8h合成条件下,产物首次充放电容量分别为188.0 mAh/g和189.1 mAh/g,首次充放效率为99.4％,且具有良好的可逆性.     

Janus型二维磁电材料CrXX’(X/X’=S,Se,Te)第一性原理研究

自石墨烯被发现以来,各种具有新奇特性的二维材料受到了越来越多的关注。Janus型二维材料具有不对称的表面特性,这种特殊的结构往往具有独特的电学、磁学与光学性质,使其成为近年来材料科学领域研究的热点。本文搭建了Janus型结构CrXX’(X/X’=S,Se,Te)(CrSSe, CrSTe, CrSeTe),研究了体系的电学、磁学、光学性质,并探究了双轴应变对其电学、磁学、光学性质的影响。结果表明,CrSSe、CrSTe与CrSeTe均呈现金属性,都是电子的优良导体,三种体系的电子结构对外加应变具有很好的鲁棒性。CrXX’(X/X’=S,Se,Te)具有本征铁磁性,并且通过施加双轴应变可对其磁矩进行调控。此外,三种体系均具有较高的居里温度,特别是CrSTe的居里温度可达310 K。CrXX’(X/X’=S,Se,Te)还具有优异的可见光与紫外光吸收性能,应变可对其光吸收系数进行调控,并且压应变与拉应变可分别使其吸收谱线向短波与长波方向移动。本文的工作为进一步研究二维Janus单层CrXX’(X/X’=S,Se,Te)在新型室温自旋电子器件领域的应用提供了理论支持。     

Ti3C2Tx MXene制备及在超级电容器中的应用研究进展

二维材料(2D)MXenes因其具有高比表面积、高导电率、可溶液加工等特性,作为超级电容器电极材料受到广泛关注。本文中总结了基于HF和氟化盐的刻蚀、基于碱的刻蚀、电化学刻蚀、路易斯酸熔融盐刻蚀等几种Ti₃C₂T_x MXene的制备方法,综述了真空辅助过滤、阳离子自组装、逐层组装工艺、印刷工艺、组装MXene气凝胶和水凝胶等Ti₃C₂T_xMXene基电极材料的组装策略及其在超级电容器的应用。研究表明,不同制备方法和电极组装策略将会影响电极材料的结构和电化学性能。对Ti₃C₂T_x MXene的制备方法和电极组装策略进行了对比总结,指出了研究中存在的问题,并展望了MXene今后的研究方向。     

Electrode effects on the electrical properties of chalcogenide films

The effect of Al, Ag and Cr metal electrodes on the electrical properties of CeSeTe films was studied. The relative ease of the diffusion of metallic atoms and the accompanied tendency to nucleation leads to irreversible changes of the film resistivity while annealing. The recrystallization temperature of the chalcogenide film depends strongly on the type of the metal electrode. The observed increase in the values of resistivity after annealing, was interpreted on the basis of charged dangling bond theory.     

Self-selecting vapour growth of bulk crystals – Principles and applicability

A method of self-selecting vapour growth (SSVG) for bulk binary and multernary crystals of semiconducting materials is reviewed comprehensively for the first time. Although it has been developed over three decades, the method is less well known – even though it is physically distinct from the more widely used ‘Piper–Polich’ and ‘Markov–Davydov’ vapour transport bulk growth methods. The means by which growth takes place on a polycrystalline source to form a crystal free from the walls is described. Modelling and empirical observations have been used to establish the characteristics of the almost isothermal temperature fields that drive the transport in SSVG. It is demonstrated that precise control of thermal radiation is a fundamental requirement for tailoring the temperature distribution—a fact that has been used well in the design of horizontal tube furnace growth rigs. Achievements in the growth of useful PbS, PbSe, PbTe, CdTe and ZnTe compound crystals are described. The SSVG method has proved to be particularly well suited to the growth of solid solutions, and the results of growth experiments, and of compositional and structural analysis, are presented for Pb(Se,S), (Pb,Sn)Se, (Pb,Sn)Te, (Pb,Ge)Te, Cd(Te,Se), Cd(Te,S) and (Cd,Zn)Te. The excellent compositional uniformity delivered is attributed to entropy driven mixing in the low thermal gradients present in SSVG.

To date, most SSVG has been done at the <50 g level for research or small scale production use. Prospects for scaling up the growth are considered, there being no barriers identified in principle. However, there is a limitation in that the shape of the grown crystals is not accurately controlled at present. To overcome this, and to offer an alternative method of scaling up, the use of vertical tube systems is explored. A significant additional advantage of the vertical configuration is that it allows for continuous recycling of the source/crystal mass so as to continuously self-refine the increasingly uniform – and crystalline – product. Achievements to date in growing II–VI and IV–VI crystals are described for prototype vertical SSVG systems. Finally, future prospects for the SSVG method in terms of further developments to the method, and the specific materials that will benefit from it are highlighted.