五甲川菁染料敏化SnO~2纳米结构多孔膜电极的光电化学研究

研究了五甲川菁敏化SnO~2纳米结构电极的光电化学行为。结合循环伏安曲线图及五甲川菁的光吸收阈值,初步确定五甲川菁染料电子基态和激发态能级位置。结果表明,五甲川菁染料电子激发态能级位置能与SnO~2纳米粒子导带边位置相匹配,因而使用该染料敏化可以显著地提高SnO~2纳米结构电极的光电流,使SnO~2纳米结构电极吸收波长红移至可见光区和近红外区,光电转换效率得到明显改善,IPCE值(单色光的转换效率)最高可达45.7%。     

Time-resolved photocurrent generation in a photoelectrochemical cell with phthalocyanine

The kinetics of photocurrent generated in the photoelectrochemical cell (PEC) with phthalocyanine (Pc) dyes in the microsecond time scale was discussed. The shape of the kinetics is rather complex and it was discussed in terms of molecular phenomena and electrochemical processes occurring after laser flash illumination. Time constants were calculated from the photocurrent decay curves and at least three time components were well recognized (rise in 0.40 micros, declining in 0.40-0.45 micros and secondary increase in about 2 micros). The shape of the kinetics was discussed in terms of dye singlet and triplet state participation in photocurrent generation and also in terms of creation of the Helmholtz-Goy double layer at the dye layer-semiconductor interface. The alteration in shape of the Helmholtz-Goy double layer in photoelectrochemical cell after laser pulse was also discussed.     

N,N′-对羧苄基吲哚三菁敏化纳米TiO2电极的研究

应用光电化学方法研究了N, N′-对羧苄基吲哚三菁（Cy5）染料敏化TiO2纳米晶电极的光电化学行为,优化了敏化的条件.结合Cy5的循环伏安曲线和光吸收阈值,初步确定Cy5电子基态和激发态能级位置.结果表明,Cy5电子激发态能级位置能与TiO2纳米粒子导带边位置相匹配,因而使用该染料敏化可以显著提高TiO2纳米晶的光电流,使TiO2纳米晶电极吸收波长由紫外光区红移至可见光区和近红外区,光电转换效率得到明显改善,在膜厚为6.5μm、敏化时间为6 h的条件下IPCE值（incident photo-to-electricity conversion efficiency）最高可达46.4％,总的光电转换效率η为1.70％.     

五甲川菁染料敏化SnO_2纳光结构多孔膜电极的光电化学研究

研究了五甲川菁敏化SnO_2纳米结构电极的光电化学行为.结合循环伏安曲线图及五甲川菁的光吸收阈值,初步确定五甲川菁染料电子基态和激发态能级位置.结果表明,五甲川菁染料电子激发态能级位置能与SnO_2纳米粒子导带边位置相匹配,因而使用该染料敏化可以显著地提高SnO_2纳米结构电极的光电流,使SnO_2纳米结构电极吸收波长红移至可见光区和近红外区,光电转换效率得到明显改善,IPCE值(单色光的转换效率)最高可达45.7％.     

Signature OH absorption spectrum from cluster models of solvation: a solvent-to-solute charge transfer state

Ab initio electronic structure theory calculations on cluster models support the characterization of the signature absorption spectrum of a solvated hydroxyl OH radical as a solvent-to-solute charge transfer state modulated by the hydrogen-bonding environment. Vertical excited states in OH(H2O)n clusters (n = 0-7, 16) calculated at the TDDFT level of theory (with companion calculations at the EOM-CCSD level of theory for n 相似文献   

五甲川菁染料的敏化作用及其在Gratzel型太阳能电池中的应用

采用新染料五甲川菁(Penta Methyl Cyanine)敏化TiO2纳米结构电极,UV-Vis吸收光谱和光电化学结果表明,使用该染料敏化使TiO2纳米结构电极吸收波长红移至可见光区和近红外区,可显著地提高TiO2纳米结构电极在可见光区的阳极光电流强度,明显改善光电转换效率.结合吸收光谱、电化学和光电化学结果初步讨论了敏化电极的光生电流的机理.     

石墨烯氧化物薄膜电极的光电化学特性

采用浸渍-提拉法制备了一系列石墨烯氧化物(GO)薄膜,并通过X射线衍射(XRD),扫描电镜(SEM),傅里叶变换红外光谱,紫外-可见吸收光谱和光电化学测量等技术对样品进行了表征.在GO电极上观察到阴极光电流,且光电流密度受薄膜的厚度影响.GO薄膜电极厚度为27nm时,光电流密度为0.25μA·cm-2.此外,GO电极的光电响应还受紫外光照影响,随着紫外光照时间的延长,阴极光电流逐渐减小.该工作提供了简便的通过控制薄膜厚度或紫外光照时间来控制GO薄膜半导体光电化学性能的方法.     

Nanostructured thin films of C60-aniline dyad clusters: electrodeposition, charge separation, and photoelectrochemistry

Clusters of C60-aniline dyads are deposited as thin films on nanostructured SnO2 electrodes under the influence of an electric field. At low applied DC voltage (<5 V) the clusters in toluene/acetonitrile (1:3) mixed solvent grow in size (from 160 nm to approximately 200 nm in diameter) while at higher voltages (>50 V) they are deposited on the electrode surface as thin films. The C60- aniline dyad cluster films when cast on nanostructured SnO2 films are photoelectrochemically active and generate photocurrent under visible light excitation. These nanostructured fullerene films are capable of delivering relatively large photocurrents (up to approximately 0.2 mA cm(-2), photoconversion efficiency of 3-4%) when employed as photoanodes in photoelectrochemical cells. Both luminescence and transient absorption studies confirm the formation of charge transfer product (C60 anion) following UV/Vis excitation of these films. Photo-induced charge separation in these dyad clusters is followed by the electron injection from C60-anion moiety into the SnO2 nanocrystallites. The oxidized counterpart is reduced by the redox couple present in the electrolyte, thus regenerating the dyad clusters. The feasibility of casting high surface area thin fullerene films on electrode surfaces has opened up new avenues to utilize dyad molecules of sensitizer bridge donor type in light energy conversion devices, such as solar cells.     

染料敏化太阳能电池的二氧化钛膜性能研究

以二氧化钛(TiO₂)纳米粉(P25)为原料,把它研磨成胶状,用涂敷法制得TiO₂纳米多孔膜,并组装成太阳能电池,用100W氙灯作为模拟太阳光,对电池进行光电性能测试.根据电池的短路电流(I_sc)、开路电压(V_oc)和填充因子(ff)等指标来反映电池的性能.研究表明,分散剂乙酰丙酮、OP乳化剂、研磨时间和热处理后的保温时间长短对TiO₂膜的性能均有很大的影响.其结果是,乙酰丙酮0.15mL、OP乳化剂0.10mL、研磨时间1h和保温时间0.5h时,TiO₂膜的光电性能较好,I_sc、V_oc和ff分别为8.85mA、567mV和0.445.并用XRD和比表面及孔隙分析仪对TiO₂膜进行了表征.     

Femtosecond to millisecond studies of electron transfer processes in a donor-(π-spacer)-acceptor series of organic dyes for solar cells interacting with titania nanoparticles and ordered nanotube array films

Time-resolved emission and absorption spectroscopy are used to study the photoinduced dynamics of forward and back electron transfer processes taking place between a recently synthesized series of donor-(π-spacer)-acceptor organic dyes and semiconductor films. Results are obtained for vertically oriented titania nanotube arrays (inner diameters 36 nm and 70 nm), standard titania nanoparticles (25 nm diameter) and, as a reference, alumina nanoparticle (13 nm diameter) films. The studied dyes contain a triphenylamine group as an electron donor, cyanoacrylic acid part as an electron acceptor, and differ by the substituents in a spacer group that causes a shift of its absorption spectra. Despite a red-shift of the dye absorption band resulting in an improved response to the solar spectrum, smaller electron injection rates and smaller extinction coefficients result in reduced dye sensitized solar cell (DSSC) conversion efficiencies. For the most efficient dye, TPC1, electron injection from the hot locally excited state to titania on a time scale of about 100 fs is suggested, while from the relaxed charge transfer state it proceeds in a non-exponential way with time constants from 1 ps to 50 ps. Our results imply that the latter process involves the trap states below the conduction band edge (or the sub-bandgap tail of the acceptor states), localized close to the dye radical cation, and is accompanied by fast electron recombination to the parent dye's ground state. This process should limit the efficiency of DSSCs made using these types of organic dyes. The residual, slower recombination can be described by a stretched exponential decay with a characteristic time of 0.5 μs and a dispersion parameter of 0.33. Both the electron injection and back electron transfer dynamics are similar in titania nanoparticles and nanotubes. Variations between the two film types are only found in the time resolved emission transients, which are explained in terms of the difference in local electric fields affecting the position of the emission bands.     

Two-photon absorption and effective broadband optical power limiting properties of a multi-branched chromophore containing 2,3-diarylquinoxalinyl moieties as the electron-pulling units

A novel multi-branched chromophore containing 2,3-diarylquinoxalinyl units as the electron-acceptors had been synthesized and its nonlinear optical properties were characterized in the femtosecond and nanosecond regime. The experimental results show that the studied fluorophore possesses strong and wide-dispersed two-photon absorption in near infrared (NIR) region. It is demonstrated that the incorporation of 2,3-disubstituted quinoxaline moieties as a part of π-conjugation in a dye molecule could be a useful approach toward large molecular two-photon absoptivities within the studied spectral region. Effective optical-power-attenuation behaviors in the nanosecond time domain of this compound were also investigated and the results indicate that such dye molecule can be a potential material as a broadband and quick-responsive optical limiter especially when against those laser lights with longer pulses.     

Infrared spectroscopy of niobium oxide cluster cations in a molecular beam: identifying the cluster structures

Infrared spectra of niobium oxide cluster cations are measured via IR multiple photon dissociation spectroscopy in the 400-1650 cm(-1) region. The cluster cations are obtained directly from a laser vaporization source and irradiated with the infrared light emitted by a free electron laser. For those oxide clusters that fragment after excitation, the IR spectra are recorded by measuring the cluster intensity changes as a function of the IR wavelength. The spectra of all examined oxide clusters exhibit two main absorption features that can be assigned to vibrations of terminal (Nb=O) or bridging (Nb-O-Nb) oxide groups. For selected clusters DFT calculations at the B3LYP/LACVP* level have been performed and the calculated vibrational spectra are compared to the experimental data to identify the gas phase structures of the clusters.     

菁类染料敏化的固态纳米TiO2光电化学电池

染料敏化TiO2光电化学电池具有较高的能量转换效率,价格仅为传统单晶硅太阳能电池的1／10,成为半导体光电化学领域的研究热点^[1-4]。但该类电池内的电解液可流动,造成电池密封困难,限制其实用化。针对这一问题,采用无机p-型半导体材料^[5,6]和高分子导体等电解液替代物组装固态光电化学电池成为该领域的新的研究方向^[7-9]。我们^[10]用凝胶网络高分子电解质组装成固态电池,取得了令人满意的结果。电池中原使用的敏化剂是顺二硫氰根－双（2,2′－联吡啶－4,4′－二羧酸）合钌（Ⅱ）(cis-bis)(thiocyanato)bis(2,2′-bipyridyl-4,4′-dicarboxylate)ruthenium(Ⅱ）,其价格昂贵,合成路线复杂。本文用自合成的、价格低廉的纯有机不对称菁类染料（Cyanine dye,以下简称为CD）敏化TiO2电极和基于聚氧乙烯（PEO）的凝胶网络高分子电解质组装成固态电池,并研究了所得固态电池的光电转换性能。     

Metal substitution in a Lindqvist polyoxometalate leads to improved photocatalytic performance

The photochemical properties of homo- and heterometallic molybdate-based Lindqvist polyoxometalate clusters are investigated in a comparative study and it is shown that vanadium substitution can be used as a facile synthetic tool to optimize the visible light absorption and photocatalytic activity of the cluster. The mono-vanadium substituted unit, [VMo(5)O(19)](3-) shows light absorption up to 480 nm whereas the light absorption of the molybdate analogue [Mo(6)O(19)](2-) is mainly in the UV region below 400 nm. The electronic absorption properties of both clusters are further investigated using TD-DFT calculations which show that vanadium incorporation leads to the formation of low-energy O → V LMCT transitions. In comparative photochemical dye decomposition test reactions under UV and Vis irradiation, a higher reactivity is observed for [VMo(5)O(19)](3-) together with turnover numbers of more than 1600. In addition it is shown that under anaerobic conditions, the photoreaction proceeds faster than in the presence of oxygen, suggesting that oxygen acts as a quencher in one of the photoredox steps.     

Quantum dot solar cells. Electrophoretic deposition of CdSe-C60 composite films and capture of photogenerated electrons with nC60 cluster shell

Encapsulation with a nC60 cluster shell facilitates capture of photogenerated electrons from CdSe quantum dots following visible light excitation. Electrophoretic deposition of CdSe-C60 composite clusters on optically transparent electrodes (OTE/SnO2) produce photoactive films that exhibit photoelectrochemical activity. The observed photoconversion efficiency (IPCE) of approximately 4% is significantly greater than those observed with CdSe or nC60 films.     

五甲川菁染料敏化p-NiO纳米结构电极的光电化学

研究了NiO纳米结构电极及五甲川菁染料敏化NiO纳米结构电极的光电化学行为。结果表明,NiO纳米结构电极在光照下产生阴极光电流,为p-型半导体,其禁带宽度为2.8eV,使用五甲川菁染料敏化可以显著地提高NiO纳米结构电极的阴极光电流,使NiO纳米结构电极吸收波长红移至可见光区,光电转换效率得到明显改善。研究了OTE/TiO~2/Ru(bpy)~2(SCN)~2和OTE/NiO/PMC作为光阳极和光阴极组成电池的电池特性,结果表明复合电池的光电压提高,但光电流的大小受光电流小的电极限制。     

Hydrogen bonding effects on the surface structure and photoelectrochemical properties of nanostructured SnO2 electrodes modified with porphyrin and fullerene composites

Hydrogen bonding effects on surface structure, photophysical properties, and photoelectrochemistry have been examined in a mixed film of porphyrin and fullerene composites with and without hydrogen bonding on indium tin oxide and nanostructured SnO2 electrodes. The nanostructured SnO2 electrodes modified with the mixed films of porphyrin and fullerene composites with hydrogen bonding exhibited efficient photocurrent generation compared to the reference systems without hydrogen bonding. Atomic force microscopy, infrared reflection absorption, and ultraviolet-visible absorption spectroscopies and time-resolved fluorescence lifetime and transient absorption spectroscopic measurements disclosed the relationship between the surface structure and photophysical and photoelectrochemical properties relating to the formation of hydrogen bonding between the porphyrins and/or the C60 moieties in the films on the electrode surface. These results show that hydrogen bonding is a highly promising methodology for the fabrication of donor and acceptor composites on nanostructured semiconducting electrodes, which exhibit high photoelectrochemical properties.     

Structure and optoelectronic properties of PbSe quantum dots /PVA. Does the polymer molecular weight matter?

Polyvinyl alcohol (PVA) with different molecular weights (8000, 14,000, and 132,000 g/mol) capped lead selenide (PbSe) quantum dots (QDs) are prepared. The nanocomposites are characterized by X‐ray diffraction (XRD) and transmission electron microscopy (TEM). XRD and TEM studies show that the particle size of PbSe QDs decrease with the increase in PVA molecular weight and/or PVA amount. This may be due to the increase in molecular weight inhibiting further growth of PbSe into the polymer matrix. Thermogravimetric analysis showed that the introduction of PbSe QDs into PVA decreases the crystallinity of the polymer. The optical absorption spectroscopy of prepared nanocomposites showed that the absorption peaks are strongly shifted to the lower wavelength (blue shift) from near infrared region to visible region by increasing the PVA molecular weight. The (I–V) characteristic curves of the PVA/PbSe nanocomposite films under illumination showed a photovoltaic cell‐like behavior. The results indicated that as the molecular weight of polymer increases, the conversion efficiency increases. Copyright © 2010 John Wiley & Sons, Ltd.     

Host-guest interactions in the supramolecular incorporation of fullerenes into tailored holes on porphyrin-modified gold nanoparticles in molecular photovoltaics

Novel gold nanoparticles modified with a mixed self-assembled monolayer of porphyrin alkanethiol and short-chain alkanethiol were prepared (first step) to examine the size and shape effects of surface holes (host) on porphyrin-modified gold nanoparticles. The porphyrin-modified gold nanoparticles with a size of about 10 nm incorporated C60 molecules (guest) into the large, bucket-shaped holes, leading to the formation of a supramolecular complex of porphyrin-C60 composites (second step). Large composite clusters with a size of 200-400 nm were grown from the supramolecular complex of porphyrin-C60 composites in mixed solvents (third step) and deposited electrophoretically onto nanostructured SnO2 electrodes (fourth step). Differences in the porphyrin:C60 ratio were found to affect the structures and photoelectrochemical properties of the composite clusters in mixed solvents as well as on the SnO2 electrodes. The photoelectrochemical performance of a photoelectrochemical device consisting of SnO2 electrodes modified with the porphyrin-C60 composites was enhanced relative to a reference system with small, wedged-shaped surface holes on the gold nanoparticle. Time-resolved transient absorption spectroscopy with fluorescence lifetime measurements suggest the occurrence of ultrafast electron transfer from the porphyrin excited singlet states to C60 or the formation of a partial charge-transfer state in the composite clusters of supramolecular complexes formed between porphyrin and C60 leading to efficient photocurrent generation in the system. Elucidation of the relationship between host-guest interactions and photoelectrochemical function in the present system will provide valuable information on the design of molecular devices and machines including molecular photovoltaics.     

Enhancement of Storage Capacity and Conversion Efficiency of Photoelectrochemical Cells: Effect of Dyes Adsorbed on Carbon Nano Tubes

We report here our studies on photoelectrochemical (PEC) cells where two commonly used photosensitive dyes, thionine and Rose Bengal were used as photosensitizers for conversion of light energy to electrical energy. The performance of the cells increased radically in presence of oxidized multiwalled carbon nano tubes (OMWCNTs) as reflected by the values of conversion efficiency (∼3.69%) and open circuit voltage (∼548.9 mV). To understand the role of OMWCNTs in enhancing the performance of the cells, the spectral study of dye–OMWCNT mixed systems were performed. The absorption spectra indicated more absorption of incident photons in presence of OMWCNT, whereas the infrared spectra suggested that the basic structure of dyes remained unaltered. The spectral studies implied that the dye molecules got adsorbed on OMWCNTs side walls causing efficient absorption of the incident light quanta. Moreover, insertion of planar lipid membrane (PLM) separating the two chambers of PEC cell could effectively counteract the recombination of photodissociated charges and thereby caused better storage capacity of the PEC cells with further increase in efficiency.