高效金属双卟啉染料的计算设计及其敏化TiO2半导体复合体系的理论研究

基于广泛的密度泛函理论计算,理论上设计并表征了一类新型的金属双卟啉染料.这些新型的卟啉染料具有很强的光捕获能力,且其低激态表现出优良的电荷分离性质.通过对这类染料体系的结构修饰,如包含不同金属的共轭大环(卟啉环或咔咯环)的取代,可以很容易地调控它们的光电子性质.计算表明,这类金属双卟啉染料的电子性质能很好地匹配不同的氧化还原电对,在染料太阳能敏化电池研究中具有好的应用前景.基于第一性原理计算,预测了金属双卟啉染料敏化TiO2体系的电子结构性质,讨论了可能的直接和间接电子注入机制,其间接电子注入时间约20 fs,电子注入过程非常快.     

对电极性能对染料敏化太阳电池动力学过程的影响

借助电化学阻抗谱(EIS)和强度调制光电流谱(IMPS)/强度调制光电压谱(IMVS)技术, 采用不同纳米TiO₂多孔薄膜对电极研究了染料敏化太阳电池(DSC)内部2个主要电荷输运过程的内在联系, 并探讨了载Pt材料对DSC界面动力学过程及电池宏观性能的影响机理. 借助等效电路模型分析了基于不同对电极材料电池的填充因子变化原因. 结果表明, 对电极材料的电极电荷交换过程制约光阳极膜内电子传输, 进而影响电池光伏性能; 同时对电极催化反应速率主要与催化剂活性、 载Pt材料电导率和催化反应面积有关.     

纳米级包覆层厚度对染料敏化太阳电池中电子注入效率和电子寿命的影响

选取氧化钐作为包覆材料, 采用浸渍法对已烧结好的纳米TiO₂多孔薄膜电极进行修饰, 并将其应用于染料敏化太阳电池中, 研究了纳米级氧化钐包覆层厚度及均匀性对染料敏化太阳电池中电子注入效率和电子复合过程的影响和作用机制. 结果表明, 包覆层厚度对电子注入效率和电子复合具有明显影响, 且电子注入效率和电子寿命随包覆层厚度的增加而呈现相反的变化趋势, 包覆层厚度在0.4 nm以内, 电池性能最好.     

给电子基团对吲哚染料电子结构和吸收光谱的影响

利用密度泛函理论(DFT)和含时密度泛函理论(TD-DFT), 分别基于B3LYP和PBE1PBE方法研究了一系列含有不同给电子基团的吲哚染料分子(ID1-ID3)的电子结构和吸收光谱性质. 重点比较了不同电子给体对染料的分子结构、吸收光谱以及其在电池中的光伏性能的影响. 结果表明从ID1、ID2到ID3, 随着电子给体中苯环数目的增加, 吲哚分子上的共轭效应逐渐增大, 导致吲哚分子最高占据分子轨道-最低未占据分子轨道(HOMO-LUMO)之间的能隙变窄, 分子的吸收光谱发生红移. 染料分子的吸收光谱和LUMO能级分别影响染料的吸光效率和光电转化过程中电子的注入过程, 从而使其二者成为决定电池光伏性能的重要参数. 综合考虑上述两个参数对电池性能的贡献, 通过理论研究证实, 在ID1-ID3系列染料中, ID3具有较长的吸收谱带、较大的分子消光系数和合适的LUMO能级, 从而表现出最为优越的光伏性能, 这与实验得出的结论很好地吻合.     

锌掺杂对TiO2染料敏化电池光阳极中电荷俘获态分布及电子复合过程的影响

基于瞬态光电压和瞬态光电流技术研究了锌掺杂的TiO2染料敏化太阳能电池中电子复合及传输的动力学行为.通过实验获得了不同阳极掺杂条件下的电子复合时间常数与电子收集时间常数,考察了锌掺杂对电池阳极材料导带能级和电子俘获态的影响.研究结果表明,锌的掺杂在提高TiO2导带能级的同时延长了俘获态电子的复合时间常数,从而大大提高了电池的开路电压.     

π桥中不同吸电子基团对三苯胺-氰基丙烯酸类染料敏化太阳能电池性能影响的理论研究

采用密度泛函理论和含时密度泛函理论计算了染料的紫外-可见吸收光谱、电子注入驱动力、半导体导带能级移动量以及染料与碘的相互作用能等一系列评价电池性能的理论参数,以解释在π桥上引入不同吸电子基团导致三苯胺-氰基丙烯酸基染料敏化太阳能电池光电转换效率降低的原因.结果表明,在染料π桥上引入吸电子基团虽可以在一定程度上改善吸收光谱,但同时也引入了额外的与电解质中碘相互作用的位点,加快了与电解质之间的复合速率,影响了电子注入驱动力,最终导致电池光电转换效率降低.因此,在设计高效光敏染料时除了考虑吸收光谱外,也应考虑染料与电解质之间的复合以及电子注入驱动力这2个影响电池性能的关键因素.     

新型D-π-A类敏化太阳电池染料及其应用

功能性有机染料在染料敏化太阳能电池领域具有重要的应用前景,电子给体、π共轭桥和电子受体（D-π-A）结构的染料是其中重要的组成类型.本文主要依据三苯胺和吲哚啉等取代苯胺为电子给体染料的结构设计,并结合本课题组的相关工作,综述了2008年以来此类D-π-A光敏染料的光电转换性能的研究进展.     

氧气氛烧结电极对染料敏化太阳电池微观性能影响机理研究

为了改善染料敏化太阳电池内电子的传输复合过程, 研究者尝试不同方法制备或改性TiO₂薄膜. 不同烧结气氛可以改变TiO₂薄膜的表面特性, 是一种有效的方法并被广泛研究. 采用两步烧结法制备氧气氛烧结TiO₂电极并应用于染料敏化太阳电池:第一步将电极在空气或氧气氛中510℃保温30 min以清除TiO₂薄膜中有机物; 第二步将电极进一步在氮气氛中510℃保温10 min以移除电极表面吸附的多余氧原子. 通过与空气烧结电池宏观性能及微观性能的对比, 细致研究了氧气氛烧结电极表面特性对染料敏化太阳电池传输复合微观动力学过程的影响机制. TiO₂薄膜表面特性及带边移动、电子传输复合过程的表征分别借助XPS能谱仪和强度调制光电流谱(IMPS)/强度调制光电压谱(IMVS)等探测技术完成. 结果表明, 氧气烧结电极Ti³⁺复合中心减少, 使电池内部电子复合得到有效抑制. 同时, 氧气烧结电极染料吸附量增加且导带边正移, 使得光生电子浓度升高, 膜内电子传输过程加快. 最终, 氧气烧结电极有效改善了电池光吸收效率、电子收集效率以及注入效率, 使电池效率由6.90%提升至7.53%.     

二氢吲哚类染料用于染料敏化太阳能电池光敏剂的比较

采用密度泛函理论(DFT)和含时密度泛函理论(TD-DFT)对四种二氢吲哚染料进行研究, 从中筛选出相对优秀的染料敏化太阳能电池光敏剂. 对前线分子轨道的计算表明, 二氢吲哚染料的前线分子轨道结构非常有利于染料激发态向TiO2电极的电子注入. 对真空中的紫外和可见光吸收光谱的计算表明, 二氢吲哚染料的吸收光谱与太阳辐射光谱匹配较好. 对染料分子的能级计算表明, 二氢吲哚染料的能级结构比较适合于I-/I-3作电解液的TiO2纳米晶太阳能电池的光敏剂. 二氢吲哚染料最低未占据分子轨道(LUMO) 能级均比TiO2晶体导带边能级高, 能够保证激发态染料分子高效地向TiO2电极转移电子. 二氢吲哚染料最高占据分子轨道(HOMO)的能级比I-/I-3能级低, 保证了失去电子的染料分子能够顺利地从电解液中得到电子. 与实验数据比较, 得出在提高染料敏化太阳能电池转换效率方面, 对染料的关键要求是LUMO能级的位置. 染料分子的稳定性是染料敏化太阳能电池使用寿命的关键因素. 通过对化学键键长的比较表明, 二氢吲哚染料的分子稳定性基本相同. 对计算结果的分析表明, 二氢吲哚染料1(ID1)的LUMO能级最高, 分子稳定性最好, 在酒精溶液中的吸收光谱与太阳辐射光谱匹配很好, 在同类染料中是较好的染料敏化太阳能电池光敏剂.     

具有推拉电子结构卟啉染料的合成及其在染料敏化太阳能电池中的应用

将N,N’-二-(9,9’-二己基芴)胺作为电子供体引入具有推拉电子结构的卟啉染料中,设计合成了2个新的染料敏化太阳能电池(DSSCs)敏化剂WP-1和WP-2。利用核磁共振氢谱和高分辨质谱对染料结构进行了表征。测试了染料的紫外-可见吸收光谱。将其应用于染料敏化太阳能电池中,在模拟太阳光(100×10-3W/cm2)照射下,染料WP-1和WP-2敏化电池的能量转换效率分别达到了4.01%和7.07%。WP-2敏化的电池封装后经自然光照射500 h后,光电效率仍能维持在初始效率的98%以上。说明N,N’-二-(9,9’-二己基芴)胺作为电子供体,很适合推拉电子结构的卟啉染料。不仅丰富了用于卟啉染料的电子供体的种类,也为进一步将二芴胺衍生物引入到卟啉染料中的研究奠定了基础。     

染料敏化太阳电池中TiO2/染料/电解质界面的修饰

染料敏化太阳电池(DSC)作为新型太阳电池自问世以来受到了广泛关注, 其系统内部的接触界面尤其是TiO₂/染料/电解质界面一直是该领域的研究热点. 光敏染料的吸附以及电子的注入、传输和复合都发生在该界面, 其界面性质对DSC性能具有很大影响. 对染料敏化太阳电池中TiO₂/染料/电解质界面进行修饰可以有效抑制染料聚集和电子复合, 提高电子的注入效率与传输速率; 同时, 对TiO₂导带边的位置及染料吸附等也产生一定的影响, 最终提高电池的光电转换效率和稳定性. 本文主要从不同的修饰途径详细评述了TiO₂/染料/电解质界面修饰方法及机理研究进展,包括TiO₂光阳极的修饰改性、染料溶液中共吸附剂的引入和多种染料共敏化处理以及电解质中不同功能添加剂的应用. 指出了这些修饰方法目前存在的主要问题, 并对未来的发展方向进行了展望.     

有机染料敏化剂分子设计新进展

综述了应用于染料敏化太阳能电池的多吡啶钌配合物、胺类染料、卟啉和酞菁类染料分子设计方面影响其光电转化效率的因素研究及新进展.     

Photoinduced electron transport process in electrochemical cell I. Phenomenological description

The process of electron transport plays an essential role in the fundamental phenomena of life like photosynthesis, respiration and vision as well as in photoelectronic devices. However, the molecular mechanisms of the electron way and factors governing the transport rate in such systems are still unclear. Several groups have reported theoretical approaches for searching the mechanisms by using statistical mechanics, coherent dynamics and quantum mechanics. The current density vector inside the semiconducting layer is determined. In this paper we consider the problem of transport of electron promoted in the electrochemical cell constructed of two electrodes with the dye molecules immersed in. We describe the process of electron promotion by refractive light wave on the vacuum–semiconductor boundary as well as on the semiconducting electrode and the dye molecule layer in terms of extended phenomenological electrodynamics formalism. The results of our theoretical model show that such a theoretical approach will give more information on the mechanism of electron transport and will give insight in the determination of some electric features of materials.     

Dye Bonding to TiO(2): In Situ Attenuated Total Reflection Infrared Spectroscopy Study, Simulations, and Correlation with Dye-Sensitized Solar Cell Characteristics

Processing dye-sensitized solar cells gains more and more importance as interest in industrial applications grows daily. For large-scale processing and optimizing manufacturing in terms of environmental acceptability as well as time and material saving, a detailed knowledge of certain process steps is crucial. In this paper we concentrate on the sensitizing step of production, i.e., the anchoring of the dye molecules onto the TiO(2) semiconductor. A vacuum-tight attentuated total reflection infrared (ATR-IR) flow-through cell was developed, thus allowing measurements using a vacuum spectrometer to monitor infiltration of dye molecules into the porous TiO(2) film in situ at high sensitivity. In particular, the influence of the anchor and backbone of perylene dye molecules as well as the influence of solvents on the adsorption process was investigated. The experiments clearly show that an anhydride group reacts much slower than an acid group. A significantly lower amount of anhydride dye can be adsorbed on the films. Ex situ transmission experiments furthermore indicate that the availability of OH groups on the TiO(2) surface may limit dye adsorption. Also the backbone and base frame of the dye can influence the adsorption time drastically. Electrical cell characteristics correlate with the amount of adsorbed dye molecules determined by in situ ATR-IR measurements. The latter is also sensitive toward the diffusion of the dye through the porous layer. To gain a deeper understanding of the interplay between diffusion and adsorption, simulations were performed that allowed us to extract diffusion and adsorption constants. Again it was demonstrated that the anchoring group has a strong effect on the adsorption rate. The influence of the solvent was also studied, and it was found that both adsorption and desorption are affected by the solvent. Protic polar solvents are able to remove bound dye molecules, which is a possible pathway of cell degradation. Most importantly, the analysis shows the potential of this approach for the evaluation of molecules or additives concerning their characteristics important for cell processing.     

β-cyclodextrin as the vehicle for forming ratiometric mercury ion sensor usable in aqueous media, biological fluids, and live cells

The selective and sensitive detection methods for toxic transition-metal ions, which are rapid, facile, and applicable to the environmental and biological milieus, are of great importance. In this study, we designed a β-CD-based ratiometric sensor for detecting mercury ions in aqueous media, some biological fluids, and live cells. In this sensing platform, the thiocarbamido-containing probe dye was covalently linked onto the hydrophilic β-CD rim, which is conducive to complexing with metal ion, while the donor dye was anchored inside hydrophobic β-CD cavity via the adamantyl moiety, which is good for avoiding self-aggregation and enhancing the quantum yield of the donor dye. Upon associating with mercury ion, the probe dye undergoes ring-opening process and serves as the energy acceptor and constitutes the FRET system with the donor dye; by this way ratiometric detection of mercury ion in water can be realized with the detection limit of 10 nM. The cyclodextrin plays a crucial role for the sensing system; it not only accommodates both the donor dye and the probe dye which can form FRET system upon addition of Hg(2+) but also makes the sensor water-soluble and cell membrane permeable. This nontoxic sensing platform can be used for mercury ion detection in aqueous medium, biological fluids, and live cells (L929 and Hela). We also found that, upon being taken up by L929 cells, the sensor exhibited no cytotoxicity, and the cell proliferation was not affected.     

Photovoltaic and spectral properties of tetraphenyloporphyrin and metallotetraphenyloporphyrin dyes

Spectroscopical properties and photocurrent (or photovoltage) of tetraphenyloporphyrins and metallotetraphenyloporphyrins in nematic liquid crystal have been studied. Photoelectric response has been measured in an electrochemical cell made of the semitransparent semiconducting and golden electrodes with porphyrin dyes embedded in liquid crystal. Fluorescence, time-resolved luminescence in microsecond time scale and photoacoustic spectra have also been measured. The competition between radiative, non-radiative processes and charge transfer is discussed. It has been shown that effectivity of porphyrins for photocurrent generation depends on the presence/absence of central metal in the macrocycle of porphyrin skeleton and the kind of metal. The schematic model of the contributions of the dye molecule and semiconducting electrode in the electron transfer process is shown.     

激子的分裂与高效太阳能电池

能将单重态激子分裂为两个三重态激子的化合物,可作为一种新型的敏化剂,较大程度地提高太阳能电池的光-电转换能力.本文扼要地介绍了激子分裂的基本要点和发展状况,并对研究这一现象的实验方法和分裂机制等进行了讨论.在实验方法部分,叙述了通过稳态与瞬态延迟光谱的测定,可对体系中单重态的分裂和三重态重合,进而对激子的分裂进行研究,此外,还对激子的偶合、能级间的能量关系,以及环境效应等作了介绍.文章还对激子分裂过程的可能机制和如何选择这类敏化剂分子的一些基本准则,给予了讨论和说明.     

染料敏化纳米太阳能电池

本文介绍了染料敏化纳米太阳能电池的结构和原理,对纳米TiO₂膜、敏化染料、空穴传输材料的研究进展进行了综述.     

Photoacoustic investigations on the photostability of Coumarin 540-doped PMMA

In this paper, we present a laser-induced photoacoustic study on the photostability of laser dye Coumarin 540 doped in PMMA matrix and modified by the incorporation of low-molecular weight additives. The dependence of photostability of the dye on various experimental conditions, such as nature of solvents, incident optical power and dye concentration, is investigated in detail. The activation rates for the bleaching process are calculated for different concentrations and they suggest the possibility of two distinct mechanisms responsible for photodegradation. Further, analysis of the data confirms the linear dependence of photodegradation on the intensity of incident radiation. The role of different externally influencing parameters, such as wavelength and modulation frequency of incident radiation, is also discussed.     

多吡啶钌染料和有机染料共染色的钴基敏化太阳电池

具有低费米能级的外球电子媒介体的开发带来了染料敏化太阳电池性能的重大进展.针对这种快复合器件,通过精细的调控二氧化钛表面的染料包覆层结构来有效抑制界面电荷复合是目前该领域的一个重要研究主题.在本文中,利用高吸收系数的多吡啶钌染料与具有三维立体结构的有机给受体染料对二氧化钛薄膜进行共染色.基于邻菲罗啉钴氧化还原电对,相对于纯钌基染料染色的器件,瞬态吸收与瞬态光电压衰减测试表明具有三维立体结构的有机染料的引入不仅提高了电子注入效率,还同时减慢了二氧化钛中的电子与氧化态染料及电解质中的电子受体之间的复合反应速率,使器件开路电压从808 mV提升到883 mV.这种界面光活性层微结构变化诱导的电子注入效率的改善和电荷复合的减慢还过补偿了因薄膜光吸收减弱带来的不利影响,获得了更大的光电流输出,在模拟AM1.5太阳光辐照条件下器件功率转换效率从8.5%提升到10.3%.