Extensive enhancement in power conversion efficiency of dye-sensitized solar cell by using Mo-doped TiO2 photoanode

Journal of Solid State Electrochemistry - In this work, we have synthesized Mo-doped TiO2 nanoparticles by sol–gel method and used them as photoanode in dye-sensitized solar cells (DSSCs). Mo...     

静电喷雾法制备高效染料敏化太阳能电池的二氧化钛光阳极

TiO2光阳极膜是染料敏化太阳能电池（DSSC）的核心部件之一,它对电池的光电转换效率起决定性作用．TiO2电极一般采用刮涂法和丝网印刷法制备．近3年,通过静电喷雾制备光阳极的方法得到国内外学者的关注．静电喷雾制备光阳极会受到多种因素的影响,如电压、流速、悬浮液浓度、喷雾距离以及喷雾时间等．但这些因素对成膜和DSSC器件性能的影响却没有得到全面的研究或者报道．本文使用静电喷雾法制备了多孔TiO2纳米膜,并研究了以其为电极的电池器件特性．经过超声充分分散的稳定TiO2乙醇悬浮液在高电压下喷雾到导电玻璃上成膜．通过改变电喷雾距离,得到了具有不同形貌的TiO：光阳极膜,并解释了其形成的机理及其对电池性能的影响．研究还表明,光阳极膜的TiC14处理能够很好地改善电池性能．通过优化,基于流速为0．8mL／h、电喷雾距离和时间分别为2．2cm和8min条件下制备的光阳极,结合TiC14处理,组装的电池在模拟太阳光源AM1．5G下光电转化效率达6．24％．     

A strategy to increase the efficiency of the dye-sensitized TiO2 solar cells operated by photoexcitation of dye-to-TiO2 charge-transfer bands

Dye-sensitized nanoporous TiO2 solar cells (DSSCs) can be classified into two types, namely, Type-I and Type-II. Type-I DSSCs are the DSSCs in which electrons are injected from the adsorbed dyes by photoexcitation of the dyes followed by electron injection from the excited dyes to TiO2 (pathway A). Type-II DSSCs are the DSSCs in which electrons are injected not only by pathway A but also by direct one-step electron injection from the dyes to TiO2 by photoexcitation of the dye-to-TiO2 charge-transfer (DTCT) bands (pathway B). The DSSCs employing catechol (Cat) or its derivatives as the sensitizers have been the typical examples of Type-II DSSCs. However, their solar energy-to-electricity conversion efficiencies (eta) have never exceeded 0.7%, and the external quantum efficiencies (EQE) at the absorption maximums of the DTCT bands have never exceeded 10%. We found that the attachment of electron-donating compounds such as (pyridin-4-yl)vinyl and (quinolin-4-yl)vinyl, respectively, to Cat (designated as Cat-v-P and Cat-v-Q, respectively) leads to 2- and 2.7-fold increases, respectively, in eta, driven by large increases in short circuit current (Jsc). The EQE increased from 8.5 to 30% at 400 nm upon changing from Cat to Cat-v-P, at which only the DTCT band absorbs. In the case of the Cat-v-Q-sensitized DSSC, even the eta obtained by exciting only the DTCT band was higher than 1%. Interestingly, the illumination of only the DTCT band resulted in the increase of fill factor from 62.6% to 72.3%. This paper provides for the first time an insight into the strategy to increase the eta values of Type-II DSSCs.     

Spatial arrangement of carbon nanotubes in TiO2 photoelectrodes to enhance the efficiency of dye-sensitized solar cells

Three electrode structures with different spatial arrangements of carbon nanotubes (CNTs) in the mesoporous TiO(2) layer were employed in dye-sensitized solar cells to study the effect of surface states at the interface formed by the incorporation of CNTs. It was found that the decay of open circuit voltage (V(oc)) was significantly minimized by avoiding the direct contact of nanotubes to the conducting substrate by introducing a thin buffer layer of TiO(2) while maintaining the superior electron collection efficiency from the incorporation of nanotubes.     

Highly-ordered dye-sensitized TiO2 nanotube arrays film used for improving photoelectrochemical electrodes

Thin titanium oxide nanotube arrays (TNAs) films were synthesized by anodization of titanium foil in an aqueous dimethyl sulfoxide solution using a platinum foil counter electrode.TNAs up to 6.8 μm in length,120 nm in inner pore diameter,and 20 nm in wall thickness were obtained by 40 V potentials anodization for 24 h.Their microstructures and surface morphologies were characterized by XRD,TEM,SAED and UV-vis spectroscopy.The photoelectrochemical properties of as-prepared unsensitized and dye-sensitized TNAs electrodes were examined under simulated solar light (AM 1.5,100 mW/cm2) illumination.The results showed that the photocurrent of the dye-sensitized TNAs electrodes reached 6.9 mA/cm2,which was 6 times more than that of the dye-sensitized TiO2 nanoparticles (TNPs) electrodes.It implied that the electron transport process and the charge recombination suppression within TNAs electrodes were much more favorable in comparison with that in the TNPs electrodes.Electrodes applying such kind of titania nanotubes will have a potential to further enhance the efficiencies of TNAs-based dye-sensitized solar cells.     

Nb doping of TiO2 nanotubes for an enhanced efficiency of dye-sensitized solar cells

Nb-doped TiO(2) nanotube (with C(Nb) < 1 wt%) layers were successfully fabricated by self-ordered electrochemical anodization of Ti-Nb alloys. When used in dye-sensitized solar cells the efficiency enhanced by up to 30% compared to non-doped TiO(2) nanotubes. IMVS measurements indicate the beneficial effect to be due to lower recombination losses.     

Control of dark current in photoelectrochemical (TiO2/I--I3-)) and dye-sensitized solar cells

The ruthenium complex bis-tetrabutylammonium cis-dithiocyanato-N,N'-bis-2,2'-bipyridine-4-carboxylic acid, 4'-carboxylate ruthenium(II), N-719, was found to block the dark current of dye sensitized solar cells (DSC), based on mesoporous TiO2 films deposited on a F-doped tin oxide electrode and the effect was compared to surface treatment by TiCl4 and the introduction of a compact TiO2 blocking layer.     

Solar energy conversion by dye-sensitized photovoltaic cells

The quality of human life depends to a large degree on the availability of energy. This is threatened unless renewable energy resources can be developed in the near future. Chemistry is expected to make important contributions to identify environmentally friendly solutions of the energy problem. One attractive strategy discussed in this Forum Article is the development of solar cells that are based on the sensitization of mesoscopic oxide films by dyes or quantum dots. These systems have already reached conversion efficiencies exceeding 11%. The underlying fundamental processes of light harvesting by the sensitizer, heterogeneous electron transfer from the electronically excited chromophore into the conduction band of the semiconductor oxide, and percolative migration of the injected electrons through the mesoporous film to the collector electrode will be described below in detail. A number of research topics will also be discussed, and the examples for the first outdoor application of such solar cells will be provided.     

Scattering spherical voids in nanocrystalline TiO2- enhancement of efficiency in dye-sensitized solar cells

Spherical voids as light scattering centers in nanocrystalline TiO2 films were realized with polystyrene particles of diameter 400 nm, thus enhancing the photovoltaic performance by 25% on large areas, as well as providing an indication that these films can be used with electrolytes of higher viscosity.     

Preparation of dye-sensitized solar cells using template free TiO2 nanotube arrays for enhanced power conversion

Journal of Sol-Gel Science and Technology - By using the vertically aligned ZnO nanorod arrays (NRAs), TiO2 nanoparticles attached ZnO nanorods (TiO2@ZnO) and TiO2 nanotube arrays (NTAs) were...     

Sponge-like TiO2 layers for dye-sensitized solar cells

A titanium oxide layer used in a dye-sensitized solar cell (DSSC) has to meet two opponent properties to enable high conversion efficiency: a large surface area (for high dye loading) and good connection between TiO₂ grains (for efficient extraction of electrons toward the front contact). In order to meet a trade-off between these criteria a preparation method for TiO₂ paste formulation based on Pechini sol–gel method and commercial nanocrystalline TiO₂ powder has been developed. A series of TiO₂ pastes with different molar ratios between titanium isopropoxide, citric acid and ethylene glycol (1:X:4X) in the paste have been examined. The structure and morphology as well as cross-cut tests of deposited and sintered TiO₂ layers have been analyzed. Results reveal that the paste with X = 8 exhibits the best properties, resulting in an overall conversion efficiency of DSSC under standard test conditions (100 mW/cm², 25 °C, AM 1.5G) up to 6.6% for ionic liquid based electrolyte.     

Anisotropic TiO2 nanomaterials in dye-sensitized solar cells

The review presented below summarizes the up-to-date research efforts in using one-dimensional TiO(2) nanomaterials in dye-sensitized solar cells. A brief account of the methods of synthesis of the anisotropic nanomaterials as well as their photovoltaic performance in DSCs was summarily presented. The usefulness of the materials as scattering layer in DSCs was also surveyed.     

A convenient route to high area, nanoparticulate TiO2 photoelectrodes suitable for high-efficiency energy conversion in dye-sensitized solar cells

Ethanol-soluble amphiphilic TiO(2) nanoparticles (NPs) of average diameter ～9 nm were synthesized, and an α-terpineol-based TiO(2) paste was readily prepared from them in comparatively few steps. When used for fabrication of photoelectrodes for dye-sensitized solar cells (DSSCs), the paste yielded highly transparent films and possessing greater-than-typical, thickness-normalized surface areas. These film properties enabled the corresponding DSSCs to produce high photocurrent densities (17.7 mA cm(-2)) and a comparatively high overall light-to-electrical energy conversion efficiency (9.6%) when deployed with the well-known ruthenium-based molecular dye, N719. These efficiencies are about ～1.4 times greater than those obtained from DSSCs containing photoelectrodes derived from a standard commercial source of TiO(2) paste.     

Partially nanowire-structured TiO2 electrode for dye-sensitized solar cells

Partially nanowire-structured TiO₂ was prepared by a hydrothermal processing followed by calcination in air. The hydrogen titanate powder as-synthesized was calcined at 300 °C for 4 h to obtain the partially nanowire-structured TiO₂. A dye-sensitized solar cell (DSC) with a film thickness of 5.6 μm, fabricated using the partially nanowire-structured TiO₂ showed better performance than using a fully nanowire-structured TiO₂ or a conventional equi-axed TiO₂ nanopowder. The short-circuit current density (J_SC), the open-circuit voltage (V_OC), the fill factor (FF) and the overall efficiency (η) are 11.9 mA/cm², 0.754 V, 0.673 and 6.01 %, respectively. The effects of one-dimensional nanostructure and electron expressway concept are discussed.     

Novel unsymmetrically pi-elongated porphyrin for dye-sensitized TiO2 cells

A novel naphthyl-fused zinc porphyrin carboxylic acid has been synthesized and employed successfully in a dye-sensitized TiO2 solar cell, with a power conversion efficiency of 4.1%, which is improved by 50% relative to the unfused porphyrin reference cell.     

Synthesis and photonic band calculations of NCP face-centered cubic photonic crystals of TiO2 hollow spheres

With the help of self-assembly, thermal sintering, selective etching techniques and sol-gel process, the non-close packed (ncp) face-centered cubic (fcc) photonic crystals of titanium dioxide (TiO2) hollow spheres connected by TiO2 cylindrical tubes have been fabricated using silica template. The photonic bandgap calculations indicate that the ncp structure of TiO2 hollow spheres was easier to open the pseudogaps than close packed system at the lowest energy.     

三苯胺类染料敏化太阳能电池能量转化效率的全息定量构效关系研究

研究构建了三苯胺类化合物分子结构与相应染料敏化太阳能电池能量转化效率(PCE)之间的全息定量构效关系(HQSAR)模型。当fragment distinction、fragment size、hologram length和principal components分别为“C、DA”、“4-7”、“199”和“6”时,可以获得最优HQSAR模型。采用外部测试集验证和留一交叉验证对所建立模型进行检验,外部测试集验证中CCC和 Q2F3分别为0.933和0.892,留一交叉验证中其q2cv和r2分别为0.791和0.902,表明所建立模型具有较好的拟合效果和预测能力。通过所建立HQSAR模型的分子贡献图可知,环戊并二噻吩基团的存在有利于提高PCE值,长烷基链的存在可能降低PCE值。