少铅钙钛矿CH3NH3SrxPb(1-x)I3的合成及其在全固态薄膜太阳能电池中的应用

近年来, 有机-无机杂化铅卤化物钙钛矿太阳能电池(PSCs)得到了迅猛发展, 其最高光电转换效率已经达到19.3%. 该类型太阳能电池使用的钙钛矿型吸光材料为含Pb的有机-无机杂化铅卤钙钛矿, 从长远来看,Pb的毒性将制约其大规模应用. 本文从减少吸光材料中Pb的含量出发, 尝试用Sr 部分取代Pb制备一系列少铅钙钛矿CH₃NH₃Sr_xPb_(1-x)I₃, 并将其应用于钙钛矿太阳能电池进行光电性能的研究. 研究结果表明, 相比于全Pb 钙钛矿(CH₃NH₃PbI₃)材料, Sr 取代量为30% (x=0.3)时, 所形成的CH₃NH₃Sr_0.3Pb_0.7I₃光谱吸收大范围增强,但基于此材料制备的电池器件性能明显下降.     

二维钙钛矿光伏器件

有机-无机杂化卤化物钙钛矿太阳能电池(perovskite solar cells, PSCs)由于其成本低廉、制备工艺简单、光电转换率高等优点引起了越来越多的关注,在下一代半导体光伏技术中显示出巨大的发展潜力。然而PSCs器件在商业化生产应用之前,必须解决某些关键问题,例如器件在湿度、光照和过热条件下缺乏稳定性,性能会急剧衰退。层状二维(two-dimensional, 2D)钙钛矿由于其优异的环境稳定性而受到研究人员的广泛关注。通过引入不同种类的疏水性大体积有机铵阳离子可以在钙钛矿体内形成稳定的2D结构。然而,由于绝缘有机间隔阳离子的存在,使其电荷输运能力受阻并影响光电转换性能。本文根据不同种类2D钙钛矿光伏器件的发展进程,总结了影响2D钙钛矿结构和性能的关键问题,如晶体垂直取向设计、量子阱调控和有机层间隔阳离子替换工程等。最后对2D PSCs的未来发展进行展望。     

钙钛矿基近红外光电探测器

近年来,具有ABX₃晶体结构的金属卤化物钙钛矿材料因其可调带隙、高吸收系数、长载流子传输距离等光电学特性而在光电探测领域表现出良好应用前景,尤其是基于纯Sn或者Sn/Pb混合阳离子制备的杂化钙钛矿在760～1050nm范围的近红外光电响应性能非常优异,展现出高灵敏度、低暗电流和高探测率等多方面优势。为进一步拓宽钙钛矿的近红外以及红外响应波长范围,研究人员探索了将有机材料、晶体硅/锗、Ⅲ-Ⅴ族化合物、Ⅳ-Ⅵ族化合物、上转换荧光材料等作为互补光吸收层与钙钛矿结合制备异质结来构筑出宽谱响应的近红外光电探测器。基于以上研究,本文总结了当前拓宽钙钛矿光电探测器的光谱范围的有效途径。同时,对钙钛矿材料的近红外光电探测器的未来发展前景作出了展望。     

PbO-PbI2复合物膜转化的CH3NH3PbI3钙钛矿薄膜及其光电特性

有机-无机卤化物钙钛矿是一类优异的光电材料. 在过去四年内, 基于有机-无机卤化物钙钛矿的光电器件实现了超过15%的光电转换效率. 而有机-无机卤化物钙钛矿材料的可控制备是保证其在光电器件中应用的基础. 本文采用新的沉积方法在玻璃衬底表面制备了一种典型的有机-无机卤化物钙钛矿CH₃NH₃PbI₃薄膜. 其制备过程是: 采用超声辅助的连续离子吸附与反应法在玻璃衬底表面沉积PbO-PbI₂复合物膜, 之后与CH3NH3I蒸汽在110 ℃环境下反应, 将PbO-PbI₂复合物膜转化成CH₃NH₃PbI₃钙钛矿薄膜. 对CH₃NH₃PbI₃薄膜的微观结构, 结晶性及其光电性能等进行了表征. 结果表明, CH₃NH₃PbI₃薄膜呈晶态, 具有典型的钙钛矿晶体结构. 薄膜表面形貌均匀, 晶粒尺寸超过400 nm. 在可见光范围, CH₃NH₃PbI₃薄膜透过率低于10%, 能带宽度为1.58eV. 电学性能研究表明CH₃NH₃PbI₃薄膜表面电阻率高达1000 MΩ. 高表面电阻率表明CH₃NH₃PbI₃薄膜具有一定的介电性能, 其介电常数(ε_r)在100 Hz时达到155. 本研究提出了一种制备高质量CH₃NH₃PbI₃钙钛矿薄膜的新方法, 所得CH₃NH₃PbI₃薄膜可望在光、电及光电器件中得到应用.     

金属卤化物钙钛矿光电材料和器件

2009年ABX₃钙钛矿晶型的甲胺铅卤CH₃NH₃PbX₃(X=I、Br、Cl)钙钛矿材料首次应用于太阳能电池,但初始报道效率低、稳定性差。2012年后,可溶液法制备的钙钛矿太阳能电池凭借其吸光系数高、激子结合能低等优点,迅速表现出低成本和高效率的突出优势,并在光电器件等交叉领域具有很强的应用潜力。因此,钙钛矿太阳能电池被Science杂志评为2013年度国际十大科技进展,是化学和材料领域特别是光伏领域新兴的变革性技术之一。钙钛矿太阳能电池材料与器件的发展一直面临大面积、高效率、稳定性和环境友好性等挑战,对应的是钙钛矿晶体可控生长、缺陷钝化、器件优化材料稳定性和铅毒性等科学问题。     

全无机卤化铅钙钛矿的结构、热力学稳定性和电子性质

有机-无机杂化卤化铅钙钛矿因具有独特的电子和光学特性,已经成为光电领域最有前途的材料。但是,有机-无机钙钛矿材料及器件稳定性差,限制了其实际应用。与杂化钙钛矿相比,全无机卤化物钙钛矿CsPbX₃(X=Cl,Br,I)显示出更强的热稳定性。全无机卤化物钙钛矿CsPbX₃具有多个晶型,在不同的温度下呈不同相结构。目前,关于CsPbX₃的结构和物理性质仍存在争议。本文我们针对三个晶相α-,β-和γ-CsPbX₃的结构,热力学稳定性和电子性质进行了全面的理论研究。第一性原理计算表明,从高温α相到低温β相,然后再到γ相的相变伴随着PbX₆八面体的畸变。零温形成能计算表明,γ相最稳定,这与实验中γ相为低温稳定相的结论一致。电子性质计算表明,所有CsPbX₃钙钛矿都表现出直接带隙性质,并且带隙值从α相到β相再到γ相逐渐增加。这是由于相变发生时,Pb-X成键强度逐渐减弱,使价带顶能量降低,进而带隙增加。在所有相中,α相结构中较强的Pb-X相互作用,导致了较强的带边色散,使其具有较小的载流子有效质量。     

SnO2表面卤化提高钙钛矿太阳能电池光伏性能

钙钛矿太阳能电池(PSCs)成为近几年来迅速发展的新型太阳能电池,其中将SnO₂纳米粒子层用作电子传输层(ETL)的钙钛矿太阳能电池器件得到了广泛的关注。SnO₂有着更低的制备温度,使其具备应用于柔性器件的潜力,但与钙钛矿层能级不匹配等问题限制着其发展。而在界面处加入钝化层,尤其是表面卤化的方法或可解决这一问题。本文综合研究了SnO₂表面卤化对钙钛矿太阳能电池光伏性能的影响,选用四丁基氯化铵(TBAC)、四丁基溴化铵(TBAB)和四丁基碘化铵(TBAI)三种钝化材料对SnO₂表面进行钝化处理,并对钝化材料溶液进行了浓度梯度研究。通过材料形貌、结构和光学性能表征以及电池器件性能测试分析等方法,证明了SnO₂表面卤化可提高钙钛矿层的质量和PSCs光伏性能,并从器件内部电荷传输动力学等角度解释了器件性能改善的原因。为进一步说明其性能改善的机理,采用基于密度泛函理论(DFT)的第一性原理计算方法对材料表面性质进行了深入研究,从能量、结构、电荷密度、态密度、功函数等角度解释了表面卤化提高SnO₂/钙钛矿界面处电子传输特性的原因。实验和理论计算均表明TBAC对于SnO₂具有较好的钝化效果,并随着溶液浓度的提升钝化作用越明显。SnO₂表面卤化作用的深入研究不仅对提高电池器件性能具有实际意义,还能够帮助理解太阳能电池界面现象,为界面改性提供新的研究思路。     

钙钛矿材料组分调控策略及其光电器件性能研究进展

近年来，钙钛矿太阳电池的光电转换效率取得了爆发式增长，这与电池中钙钛矿薄膜的制备工艺和材料组分密切相关.关于钙钛矿薄膜的制备方法，相关的研究报道及综述较多，然而钙钛矿材料组分调控方面的研究梳理工作相对缺乏.本综述总结了近年来不同组分体系钙钛矿材料的研究进展，包括有机无机铅卤钙钛矿、全无机铅卤钙钛矿、少铅钙钛矿以及无铅钙钛矿.重点介绍了不同体系中具有代表性的材料组分及其对器件性能的影响，旨在梳理通过组分调控提高钙钛矿电池的效率及稳定性的研究思路，最终实现商业化应用.     

基于易升华添加剂辅助合成纯相富铯(CH(NH2)2)xCs1−xPbI3 钙钛矿

钙钛矿材料化学组分是决定钙钛矿太阳能电池效率和稳定性的关键,纯无机钙钛矿CsPbI₃具有相对较好的热稳定性和光稳定性,但由于Cs⁺具有较小的离子半径而导致无机钙钛矿相不稳定。最近研究发现富铯FA_xCs_1?xPbI₃钙钛矿具有相对稳定的相结构,且可以很大程度上保持无机钙钛矿材料的热稳定性和光照稳定性,是一种非常具有前景的钙钛矿材料体系。目前这种富铯的FA_xCs_1?xPbI₃材料合成是通过引入过量有机组分FAI实现的,其中FAI一方面充当钙钛矿的掺杂剂,另一方面过量的FAI充当添加剂。由于其具有较高的升华温度,后续需要较高的温度使过量的FAI升华,实际上这在实验上很难实现对FAI升华量的精确控制。本文重点研究具有低升华温度的胺类,如碘甲胺(MAI)、碘化二甲胺(DMAI)、碘化乙胺(EAI)、碘化胺(NH₄I)和醋酸甲脒(FAAC),作为添加剂制备富铯FA_xCs_1?xPbI₃钙钛矿材料体系的可行性,这一方面可以有效降低钙钛矿薄膜的热处理温度;另一方面可拓宽的制备纯相钙钛矿成分的窗口期,这对大面积制备纯相富铯FA_xCs_1?xPbI₃钙钛矿薄膜尤为重要。结果表明MAI和DMAI可以作为合成FA_xCs_1?xPbI₃钙钛矿材料的有效添加剂,其与PbI2间较强的作用力可以促进Cs₄PbI₆的形成并有效抑制δ-CsPbI₃副产物的生成。合适的升华温度可以使薄膜在保持钙钛矿相结构的同时在较低温度升华去除过量的添加剂,最终实现在相对温和的条件下制备纯相富铯FA_xCs_1?xPbI₃钙钛矿材料。     

溶液法制备有机太阳电池阳极界面修饰层MoO3

在全溶液低温制备高效、稳定有机光伏器件过程中,合理选择制备器件界面修饰材料的方法至关重要,它已成为近期有机光伏领域的重点研究内容之一。合理的界面材料能降低界面的势垒高度,减少器件的串联电阻。溶液法制备三氧化钼（MoO₃）阳极界面缓冲层能有效地改善有机太阳电池阳极界面收集和载流子传输的效率,从而提高太阳电池能量转换效率,同时也提高太阳电池的稳定性。本文综述了近年来溶液法制备有机太阳电池阳极界面修饰层MoO₃的研究进展,介绍了阳极界面修饰层MoO₃的各种制备方法与原理,阐述了基于溶液法制备界面修饰层MoO₃薄膜的研究现状与存在问题,以期为全溶液法制备高效稳定有机太阳电池的研究提供有价值的参考。     

丙烯酸酯无皂乳液稳定性研究

研究了亲水性单体ＡＡ和引发剂Ｋ２Ｓ２Ｏ８用量对三元共聚物（ＭＭＡ／ＢＡ／ＡＡ）无皂乳液（ｐＨ＝８）的电解质稳定性、冻融稳定性和机械稳定性的影响。当乳液电解质稳定性最好时存在ＡＡ和Ｋ２Ｓ２Ｏ８用量最佳值,而乳液的机械稳定性则随ＡＡ和Ｋ２Ｓ２Ｏ８用量增大而迅速提高。乳液中加入丙酮可以改善其稳定性。     

A convenient tool for studying the stability of proteins and nucleic acids

The aim of this work is to discuss the thermodynamic properties, obtained by differential scanning calorimetry (DSC), of the thermal transition of proteins and nucleic acids and to analyze these data using statistical thermodynamic relations. The denaturation of the ordered, specific structures of biological macromolecules is a cooperative process and in many cases the macromolecules undergo a two-state transition. Differential scanning calorimetry, giving direct thermodynamic information, has proved to be very useful in clarifying the energetics of macromolecule transitions and in characterizing their thermal stability. Here, various examples are discussed: i) the equilibrium thermal denaturation of ribonuclease A, a model for the use of DSC by following the temperature-unfolding of the proteins, a monomolecular transition; ii) the equilibrium thermal dissociation of a DNA double helix in two strands, an example of how DSC is used to follow a bimolecular process; iii) an example of the use of DSC for studying the melting of unimolecular and tetramolecular DNA quadruple-helices.     

Phase‐Stable CsPbI3 Nanocrystals: The Reaction Temperature Matters

High temperature colloidal synthesis for obtaining thermal, colloidal and phase‐stable CsPbI₃ nanocrystals with near‐unity quantum yield is reported. While standard perovskite synthesis reactions were carried out at 160 °C (below 200 °C), increase of another ≈100 °C enabled the alkylammonium ions to passivate the surface firmly and prevented the nanocrystals from phase transformation. This did not require any inert atmosphere storage, use of heteroatoms, specially designed ligands, or the ice cooling protocol. Either at high temperature in reaction flask or in the crude mixture or purified dispersed solution; these nanocrystals were observed stable and retained the original emission. Different spectroscopic analyses were carried out and details of the surface binding of alkyl ammonium ligands in place of surface Cs in the crystal lattice were investigated. As CsPbI₃ is one of the most demanding optical materials, bringing stability by proper surface functionalization without use of secondary additives would indeed help in wide spreading of their applications.     

The effect of the hydration degree on the hydrothermal and thermo-oxidative stability of some collageneous matrices

The methods of the thermal analysis (TG, DTG and DTA) were used in order to investigate the effect of the hydration degree on the thermal behaviour of some collageneous matrices. It was pointed out that the degradation of hydrated collagen in the temperature range 20-400°C occurs through two successive processes accompanied by mass losses. The first process, consisting in the collagen dehydration, is endothermic and takes place in the temperature range ≈25 - ≈125°C. The second process is exothermic and consists in the decomposition and/or thermo-oxidation of dry collagen. The thermal parameters of both processes depend on the hydration degree of collagen. The observed dependencies show that the hydrothermal and thermo-oxidative stability of collagen are strongly correlated with its water content. This revised version was published online in July 2006 with corrections to the Cover Date.     

烧结Nd-Fe-B磁体的环境稳定性研究进展

结合本研究室的最新研究成果,综述了烧结Nd-Fe-B磁体的环境稳定性的影响因素及研究进展,包括:磁体的温度稳定性、高温及电化学稳定性、时间稳定性和力学稳定性等,阐明改善磁体环境稳定性的重要性和迫切性。还对磁体服役过程的长时间稳定性与其他环境稳定性之间相互关系进行了探讨,通过对服役环境的分析,提出当前研究中存在的主要问题,并展望其未来的潜在的发展趋势。     

Excellent blue fluorescent trispirobifluorenes: synthesis, optical properties and thermal behaviors

Tetraiodotrispirobifluorene (1) was synthesized through cyclization of 2,7-diiodofluorene with pentaerythrityl tetrabromide under base condition. Subsequent treatment of 1 with arylboronic acid or arylacetylene under Pd-catalyzed coupling condition led to corresponding tetraaryl trispirobifluorenes (3–8). These trispirobifluorene derivatives exhibited bright-violet to blue photoluminescence (PL) with excellent quantum efficiencies and showed high thermal stabilities. ‘Green-emission tail’ could not be detected for those tetraaryl substituted trispirobifluorenes (3–8) annealed both in N₂ and in air.     

The lateral electric force on an off-axis sphere in a circular cylinder

The electrophoretic velocity of a sphere within a liquid-filled circular cylinder in a direction parallel to the cylinder axis has been studied by Yariv and Brenner (Phys. Fluids 2002, 14, 3354–3357; SIAM J. Appl. Math. 2003, 64, 423–441). We use their analyses of the electric field in order to determine the electrical force on the sphere along the cylinder radius (i.e., perpendicular to its axis) when either the radius of the sphere is small compared to that of the cylinder, or when the radius of the sphere is only slightly smaller than that of the cylinder. In both cases the force acts towards the centreline of the cylinder, and hence this force tends to stabilize electrophoresis of the sphere along the cylinder axis.     

Fluorene-bridged polyphenylquinoxalines with high solubility and good thermal stability: Synthesis and properties

<正>A novel fluorene-bridged tetraketone monomer,9,9-bis[(4-benzilyloxy)phenyl]fluorene(FLTK) was synthesized and characterized.The tetraketone was polymerized with various aromatic tetraamines to afford a series of polyphenylquinoxalines(PPQs).The obtained polymers were found to be soluble in common organic solvents such as N-methyl-2-pyrrolidone(NMP),chloroform and m-cresol.Flexible and tough PPQ films obtained by spin-casting their NMP solutions exhibited tensile strengths higher than 60 MPa.The films also demonstrated good thermal stability up to 500℃in nitrogen and glass transition temperatures higher than 280℃.In addition,the PPQ films exhibited good hydrolytic stability. High surface and volume resistivity retentions were achieved for the films after immersion or boiling in water for 24 h.     

SAPO－34分子筛的热稳定性及水热稳定性

利用高温Ｘ射线衍射技术，结合差热分析，对ＳＡＰＯ－３４分子筛烧除模板剂及随后吸附－脱附水的过程进行了研究．发现模板剂烧除的强放热效应不会导致分子筛骨架结构的破坏，活化后的分子筛中吸附－脱附水，其Ｘ射线衍射强度可逆地减弱与恢复．高温（８００℃）长时间焙烧及水蒸气处理考察结果表明，ＳＡＰＯ－３４分子筛具有优异的热稳定性和良好的水热稳定性．８００℃条件下连续焙烧３００ｈ，ＳＡＰＯ－３４的结晶度仍大于８０％，但同温度下长时间水热处理将导致ＳＡＰＯ－３４向无定形转变，并伴有硅原子向晶体表面迁移     

Thermal and hydrothermal stabilities of the alkali-treated HZSM-5 zeolites

HZSM-5 zeolites with the micro-mesopore hierarchical porosity have been prepared by the post-synthesis of alkali-treatment, and their thermal and hydrothermal stabilities were studied using DTA, XRD, and NH3-TPD characterization techniques. Compared to the unmodified zeolite, the thermal and hydrothermal stabilities of the alkali-treated ZSM-5 zeolites were slightly deteriorated because of the introduction of mesopores caused by the desilication. Nevertheless, the alkali-treated zeolite framework could be maintained until the temperature increased to 1175 ℃.