Formation of efficient dye-sensitized solar cells by introducing an interfacial layer of long-range ordered mesoporous TiO2 thin film

Long-range ordered cubic mesoporous TiO 2 films with 300 nm thickness were fabricated on fluorine-doped tin oxide (FTO) substrate by evaporation-induced self-assembly (EISA) process using F127 as a structure-directing agent. The prepared mesoporous TiO 2 film (Meso-TiO 2) was applied as an interfacial layer between the nanocrystalline TiO 2 film (NC-TiO 2) and the FTO electrode in the dye-sensitized solar cell (DSSC). The introduction of Meso-TiO 2 increased J sc from 12.3 to 14.5 mA/cm (2), and V oc by 55 mV, whereas there was no appreciable change in the fill factor (FF). As a result, the photovoltaic conversion efficiency ( eta) was improved by 30.0% from 5.77% to 7.48%. Notably, introduction of Meso-TiO 2 increased the transmittance of visible light through the FTO glass by 23% as a result of its excellent antireflective role. Thus the increased transmittance was a key factor in enhancing the photovoltaic conversion efficiency. In addition, the presence of interfacial Meso-TiO 2 provided excellent adhesion between the FTO and main TiO 2 layer, and suppressed the back-transport reaction by blocking direct contact between the electrolyte and FTO electrode.     

Electrophoretic deposition of mesoporous TiO2 nanoparticles consisting of primary anatase nanocrystallites on a plastic substrate for flexible dye-sensitized solar cells

A film of mesoporous TiO(2) nanoparticles (MTNs) consisting of anatase nanocrystallites was electrophoretically deposited and compressed on a plastic substrate for the corresponding DSSC that gave an excellent conversion efficiency (η) of 5.25% under illumination of 100 mW cm(-2).     

The preparation of highly flexible mesoporous TiC/CNF film for flexible dye-sensitized solar cells

Journal of Solid State Electrochemistry - The flexible TiC/carbon nanofiber (TiC/C NF) film was prepared by electrospinning, stabilization, and carbonization. All the obtained TiC/CNFs had rough...     

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.     

Graft copolymer directed synthesis of micron-thick organized mesoporous TiO2 films for solid-state dye-sensitized solar cells

Micron thick, well-organized mesoporous TiO(2) films with high porosity and good connectivity were synthesized by templating an amphiphilic graft copolymer for solid-state dye-sensitized solar cells.     

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.     

Hierarchical TiO(2) flowers built from TiO(2) nanotubes for efficient Pt-free based flexible dye-sensitized solar cells

A novel hierarchical TiO(2) flower consisting of anatase TiO(2) nanotubes on a Ti foil substrate has been prepared via a mild hydrothermal reaction of TiO(2) nanoparticles/Ti foil. The photovoltaic performance of DSSC based on hierarchical TiO(2) flowers/Ti (7.2%) is much higher than that of TiO(2) nanoparticle/Ti (6.63%) because of its superior light scattering ability and fast electron transport. Moreover, full flexible DSSC based on the novel hierarchical TiO(2) flowers/Ti foil photoelectrode and electrodeposited poly(3,4-ethylenedioxythiophene) (PEDOT) on indium tin oxide-coated poly(ethylene terephthalate) (ITO-PET) counter electrode shows a significant power conversion efficiency of 6.26%, accompanying a short-circuit current density of 11.96 mA cm(-2), an open-circuit voltage of 761 mV and a fill factor of 0.69.     

Facile synthesis of thick ordered mesoporous TiO2 film for dye-sensitized solar cell use

Crack-free thick ordered mesoporous TiO₂ films with excellent optical quality have been synthesized by combination of “Doctor Blade” technique and a two-step evaporation induced self-assembly (EISA) method. By employing the as-synthesized mesoporous film with the thickness of 7 μm as the photoanode in dye-sensitized solar cell (DSC), a solar conversion efficiency of 6.53% has been obtained at 30 mW cm⁻² light intensity.     

Efficient dye-sensitized solar cells based on surfactant-mediated TiO2 nanostructures

Journal of Solid State Electrochemistry - Dye-sensitized solar cells (DSSCs) based on TiO2 nanostructures have attracted much attention due to their high photoconversion efficiency. Here, we report...     

Activation energy of electron transport in dye-sensitized TiO2 solar cells

Various characteristics of dye-sensitized nanostructured TiO2 solar cells, such as electron transport and electron lifetime, were studied in detail using monochromatic illumination conditions. The electron transport was found to be a thermally activated process with activation energies in the range of 0.10-0.15 eV for light intensities that varied 2 orders of magnitude. Electron lifetimes were determined using a new method and found to be significantly larger (>1 s) than previously determined. An average potential was determined for electrons in the nanostructured TiO2 under illumination in short-circuit conditions. This potential is about 0.2 V lower than the open-circuit potential at the same light intensity. The electron transport time varies exponentially with the internal potential at short-circuit conditions, indicating that the gradient in the electrochemical potential is the driving force for electron transport in the nanostructured TiO2 film. The applicability of the conventionally used trapping/detrapping model is critically analyzed. Although experimental results can be fitted using a trapping/detrapping model with an exponential distribution of traps, the distribution parameters differ significantly between different types of experiment. Furthermore, the experimental activation energies for electron transport are smaller than those expected in a trapping/detrapping model.     

Microwave processing of TiO2 blocking layers for dye-sensitized solar cells

The microwave heat treatment of blocking layers for dye-sensitized solar cells has been investigated. It has been found that the solar cell efficiencies achieved with microwave heating were considerably higher than those achieved with conventional heating at low temperatures (100°C). This was attributed to microwave heating providing better sintering of the blocking layer and better interfacial contact between the substrate and the TiO₂ layers. These results are promising with regard to the application of microwave heating to the production of dye-sensitized solar cells on flexible polymer substrates.     

TiO2/SnO2复合空心球在染料敏化太阳能电池中的应用

采用模板辅助法制备了SnO2/TiO2复合空心球,样品直径为1.5~4.0μm,比表面积达到了92.9 m^2·g^-1,复合空心球表现出优越的光散射性能.以这种复合空心球作为染料敏化太阳能电池的光阳极,电池的光电转换效率可达到7.72%,高于SnO2微米球(2.70%)和TiO2微米球(6.26%).此外,以锐钛矿型TiO2纳米晶作为底层,SnO2/TiO2复合空心球作为光散射层制备的双层结构光阳极,电池光电转换效率进一步提升至8.43%.     

Rutile TiO2 nano-branched arrays on FTO for dye-sensitized solar cells

Hierarchical TiO(2) nanostructures would be desirable for preparing dye-sensitized solar cells because of their large amount of dye adsorption and superior light harvesting efficiency, as well as efficient charge separation and transport properties. In this study, rutile TiO(2) nano-branched arrays grown directly on transparent conductive glass (FTO) were prepared by a facile two-step wet chemical synthesis process, using a simple aqueous chemical growth method involving immersing the TiO(2) nanorod arrays in an aqueous TiCl(4) solution as seeds, which were prepared by a hydrothermal method. The dye-sensitized solar cells based on the TiO(2) nano-branched arrays which were only about 3 μm in length show a short-circuit current intensity of 10.05 mA cm(-2) and a light-to-electricity conversion efficiency of 3.75%, which is nearly three times as high as that of bare nanorod arrays, due to the preferable nanostructure, which not only retains the efficient charge separation and transport properties of the nanorod arrays, but also can improve the amount of dye adsorption due to the increased specific surface area from the nanobranches.     

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％．     

Hierarchical twin-scale inverse opal TiO2 electrodes for dye-sensitized solar cells

We describe the preparation of three-dimensional hierarchical twin-scale inverse opal (ts-IO) electrodes for dye-sensitized solar cells (DSSCs). The ts-IO TiO(2) structure was obtained from a template fabricated via the assembly of mesoscale colloidal particles (40-80 nm in diameter) in the confined geometry of a macroporous IO structure. The photovoltaic properties of ts-IO electrodes were optimized by varying the layer thickness or the size of mesopores in the mesoscale colloidal assembly. Electron transport was investigated using impedance spectroscopy. The result showed that due to the competing effects of recombination and dye adsorption, the maximum efficiency was observed at an electrode thickness of 12 μm. The electrodes of smaller mesopores diameters yielded the higher photocurrent density due to the decrease in the electron transport resistance at the TiO(2)/dye interface. A maximum efficiency of 6.90% was obtained using an electrode 12 μm thick and a mesopore diameter of 35 nm.     

TiO2 derived by titanate route from electrospun nanostructures for high-performance dye-sensitized solar cells

We report the use of highly porous, dense, and anisotropic TiO(2) derived from electrospun TiO(2)-SiO(2) nanostructures through titanate route in dye-sensitized solar cells. The titanate-derived TiO(2) of high surface areas exhibited superior photovoltaic parameters (efficiency > 7%) in comparison to the respective electrospun TiO(2) nanomaterials and commercially available P-25.     

TiO2 nanotubes in dye-sensitized solar cells: Higher efficiencies by well-defined tube tops

Aligned self-organized TiO₂ nanotubes of 15–20 µm length proved to be very promising for application in dye-sensitized solar cells. Conventional anodic nanotube layers usually show an irregular structure (nanograss) or a thin nucleation layer at the top of the nanotube array. In the present paper, we demonstrate that by a simple photoresist based method, well-defined and open TiO₂ nanotube tops can be obtained which significantly enhances their performance when used in DSSCs. In fact, the layers show the highest reported solar energy conversion efficiency up to now for a pristine (particle-free) nanotube layer.     

Addition of TiO2 nanowires in different polymorphs for dye-sensitized solar cells

TiO₂ (B) and TiO₂ anatase nanowires were prepared at 150 °C for 120 h by a hydrothermal method followed by calcination in air at 400 °C for 2 h and at 700 °C for 2 h for TiO₂ (B) and TiO₂ anatase, respectively. Although dye-sensitized solar cells (DSC) with fully nanowire electrodes showed a rather low light-to-electricity conversion efficiency of 1.33 % for TiO₂ (B) and 2.42% for TiO₂ anatase, 10 wt % nanowire-dispersed electrodes in a P-25 TiO₂-nanoparticle matrix demonstrated improved efficiency of 6.17 % for TiO₂ (B) and 6.53% for TiO₂ anatase, these exceeding that of pure P-25 electrodes in this work (η=5.59%). The dominant mechanisms of the improvement at 10 wt% for the two different polymorphs are thought to be different, i.e., a light-scattering and film-thickness increment for the TiO₂ (B) system, whereas there is an improved conduction path through the matrix for the TiO₂ anatase system.      

Incorporation of functionalized single-wall carbon nanotubes in dye-sensitized TiO2 solar cells

Effects of incorporation of acid-treated single-wall carbon nanotubes (a-SWCNs) in TiO(2) film and of anchorage of dye-linked, a-SWCNs (hereafter dye-SWCNs) to the TiO(2)/electrolyte interface on photocurrent-voltage characteristics of dye-sensitized solar cells were studied. Compared with an unmodified cell, the modified cell with the a-SWCNs in TiO(2) film showed a 25% increase in short-circuit photocurrent (J(sc)). The J(sc) increase is correlated with improved connectivity between the a-SWCNs and the TiO(2) particles and with enhanced light scattering by TiO(2) clusters formed in the presence of the a-SWCNs. In the case of anchoring dye-SWCNs to the TiO(2)/electrolyte interface, the open-circuit voltage (V(oc)) increased by as much as 0.1 V, possibly due to the basicity of the TiO(2) surface from NH groups of ethylenediamine moieties of the anchored dye-SWCNs.