TiO2 nanotubes infiltrated with nanoparticles for dye sensitized solar cells

We present a detailed study of the infiltration of titanium dioxide (TiO(2)) nanotubes (NTs) with TiO(2) nanoparticles (NPs) for dye sensitized solar cells (DSSCs). The aim is to combine the merits of the NP's high dye loading and high light harvesting capability with the NT's straight carrier transport path and high electron collection efficiency to improve the DSSC performance. On infiltrating NTs with TiCl(4) solution followed by hydrothermal synthesis, 10 nm size NPs were observed to form a conformal and dense layer on the NT walls. Compared with the bare NT structure, dye loading of this mixed NT and NP structure is more than doubled. The overall photon conversion efficiencies of the fabricated DSSCs are improved by 152%, 107%, and 49% for 8, 13, and 20 μm long NTs, respectively. Electron transport and recombination parameters were extracted based on electrochemical impedance spectroscopy measurements. Although a slight reduction of electron lifetime was observed in the mixed structures due to enhanced recombination with a larger surface area, the diffusion length is still significantly longer than the NT length used, suggesting that most electrons are collected. In addition to dye loading and hence photocurrent increment, the photovoltage and filling factor were also improved in the mixed structure due to a low serial resistance, leading to the enhancement of the overall efficiency.     

Enhanced performance of TiO2 nanoparticle and aerogel composite electrode for dye sensitized solar cell

To evaluate the effects of specific surface area to the photocurrent conversion efficiency of dye-sensitized solar cell (DSC), we adopted TiO2 aerogel (TA)/nanoparticle (TP) composite as a photoelectrode. We prepared three types of photoelectrodes, TPs, TAs, and TATPs (1:1 TAs and TPs composite photoelectrode). The performance of TATP composite electrode was compared with that of TP and TAs. TATPs showed the improved cell efficiency, more than 0.5%, compared with a reference TPs below 15 micrometer thickness. Although the introduction of TAs increases the specific surface area for the dye adsorption, DSC composed of only TAs does not show the best efficiency result due to the crack generation. In conclusion, to produce the best photocurrent conversion efficiency, the high specific surface area of TiO2 photoelectrode for high dye adsorption should be balanced with proper control of the good electron transfer path.     

Preparation of ultrathin TiO2 single-crystal nanowires for high performance dye sensitized solar cells

Ultrathin TiO₂ anatase nanowires (NWs) were successfully prepared via a rapid and facile hydrothermal route. Consequently, the TiO₂ NWs and TiO₂ nanoparticles (NPs) composites electrodes were prepared with different weight ratios (25, 50 and 100 %) for a dye sensitized solar cell, and the photoelectrical performance has been systematically studied. It is observed that although the amount of absorption dye decreases, the composite solar cells exhibit a higher power conversion efficiency compared to either pure TiO₂ NP or NW solar cells by rationally tuning the weight ratios. The behavior was attributed to a combination of the rapid carrier transport in NW framework and the high dye loading on P25 surface.     

TiO2 thin film encapsulated ZnO nanorod and nanoflower dye sensitized solar cells

The performance of dye-sensitized solar cells based on ZnO nanorods and nanoflowers coated with thin shells of TiO₂ thin film prepared by sol–gel deposition are described. It is found that shells act as insulating barriers that improve cell open-circuit voltage and short-circuit current density. The superior performance of the ZnO–TiO₂ core–shell cells is a result of a radial electron transport within each ZnO nanorods and nanoflowers that decreases the rate of recombination and percolation of the electron in these devices.     

Tuning the dye aerosol impaction and TiO2 nanoparticle stacking structures for High-Efficiency Dye-Sensitized solar cells

The rapid manufacturing of high-efficiency dye-sensitized solar cells (DSSCs) is limited by the slow dye adsorption on TiO₂ nanoparticles (NPs)-accumulated photoelectrode using conventional dip-coating process. Therefore, we aim to accelerate the adsorption of dyes that are attached on TiO₂ NPs by employing an aerosol impactor. Herein the aerosolized dyes are designed to get deposited rapidly on the TiO₂ NPs-accumulated photoelectrode. In addition, to effectively trap the irradiated sunlight in DSSCs, we assemble the photoelectrodes incorporated with bilayered TiO₂ thin films comprising small TiO₂ NPs-based underlayer and large TiO₂ NPs-based overlayer as dye-supporting and light-scattering mediums, respectively. Furthermore, the effects of dye aerosol impaction and TiO₂ stacking structures on the efficiency of DSSCs are examined. The power conversion efficiency (PCE) of DSSCs comprising a N719 dye-supporting layer treated with dip-coating process was determined as ～ 5.67%; however, when the bilayered TiO₂ thin films with an optimized thickness ratio of light-scattering overlayer and dye-supporting underlayer were coated with N719 dyes using dye aerosol impactor, the resulting PCE increased to ～ 7.46%. This suggests that the photovoltaic characteristics of DSSCs can be enhanced considerably using the effective TiO₂ NP stacking structures coated with rapid, uniform, and strong aerosol dye adsorption throughout the TiO₂-based photoelectrodes.     

Highly efficient solar cells using TiO(2) nanotube arrays sensitized with a donor-antenna dye

Donor antenna dyes provide an exciting route to improving the efficiency of dye sensitized solar cells owing to their high molar extinction coefficients and the effective spatial separation of charges in the charge-separated state, which decelerates the recombination of photogenerated charges. Vertically oriented TiO(2) nanotube arrays provide an optimal material architecture for photoelectrochemical devices because of their large internal surface area, lower recombination losses, and vectorial charge transport along the nanotube axis. In this study, the results obtained by sensitizing TiO(2) nanotube arrays with the donor antenna dye Ru-TPA-NCS are presented. Solar cells fabricated using an antenna dye-sensitized array of 14.4 microm long TiO(2) nanotubes on Ti foil subjected to AM 1.5 one sun illumination in the backside geometry exhibited an overall conversion efficiency of 6.1%. An efficiency of 4.1% was obtained in the frontside illumination geometry using a 1 microm long array of transparent TiO(2) nanotubes subjected to a TiCl(4) treatment and then sensitized with the Ru-TPA-NCS dye. Open circuit voltage decay measurements give insight into the recombination behavior in antenna-dye sensitized nanotube photoelectrodes, demonstrating outstanding properties likely due to a reduction in the influence of the surface traps and reduced electron transfer from TiO(2) to ions in solution.     

Current trends in materials for dye sensitized solar cells

Here, we intend to review those patents related with the technology of dye sensitized solar cells. In particular we discuss patents and papers that enable metal oxide layer to be more controllable and feasible for applications, and new and innovative dyes, sensitizers and electrolytes with promising features. Finally various methods were reviewed for fabricating semiconductor layers and complete DSSC devices focusing on the mass production of photovoltaic cells.     

Versatile preparation method for mesoporous TiO2 electrodes suitable for solid-state dye sensitized photocells

Nano-structured TiO₂ electrodes, suitable for dye sensitized solid-state solar cells were prepared by a new simple spraying technique (SPT). Physical properties of these electrodes were compared with the electrodes prepared by the ‘doctor blade’ technique (typical sliding method, DB). Dye sensitized solid-state solar cells, comprising of CuI as the hole conductor, were fabricated with these electrodes and enhanced photo responses were obtained with SPT electrodes. The effects of additives, either to the spray solution or to the hole conductor on the photoresponses of the above devices were also studied. The cells fabricated with SPT electrodes containing Al(BuⁱO)₃ showed ∼ 2.4% efficiency and addition of 1-ethyl-3-methyl imidazolium thiocyanate into CuI layer further enhanced the efficiency up to 2.75% under the irradiance of 100 mW cm⁻² (AM 1.5).     

Room temperature synthesis of rutile TiO2 hierarchical nanoneedle flower morphology for dye sensitized solar cell

Rutile TiO2 nanoneedle flowers (representing concurrent nano-micro hierarchical morphology) with high shape anisotropy ratio are synthesized at room temperature by using a simple and efficient one step electrochemical process of anodic dissolution. This process employs highly acidic bath of perchloric acid (pH <2) and a large current density on the surface of Titanium foil to form nanostructures. The diameter and length of rutile TiO2 nanoneedle is approximately 8 nm and 100 nm respectively (aspect ratio >10). Dye sensitized solar cell (DSSC) configured using such rutile TiO2 flowers is shown to exhibit IPCE of 30% and power conversion efficiency of approximately 3.6%.     

ZnO纳米四脚状阵列电极染料敏化太阳能电池

采用化学气相沉积(CVD)法制备了不同尺寸的四脚状纳米ZnO和ZnO纳米棒。采用X射线粉末衍射(XRD)、扫描电子显微镜(SEM)对纳米ZnO的晶型结构和形貌进行表征,研究结果表明CVD法制备的四脚状纳米ZnO具有三维空间结构,其最小平均臂宽约为70nm,臂长约300nm,制备的纳米棒直径约为84nm,长约2μm,且都为六方纤锌矿晶型结构。将ZnO纳米四脚状及纳米棒利用滚涂法在FTO导电玻璃上形成ZnO光阳极,经N719染料敏化后组装成染料敏化太阳能电池,光电性能结果表明,染料敏化小尺寸的四脚状纳米ZnO太阳能电池光电转换效率(η=1.88%)高于染料敏化大尺寸的四脚状纳米ZnO太阳能电池光电转换效率(η=1.18%),远高于染料敏化ZnO纳米棒太阳能电池的光电转换效率(η=0.7%)。     

New trends for solar cell development and recent progress of dye sensitized solar cells

This article reviews the new concepts and new trends of solar cell development. To increase the photoelectric conversion efficiency, reduce the cost, and for application in a much broader field, thin film solar cell, flexible solar cell, and tandem solar cell have become important subjects to be studied. As the representative of the solar cells of the third generation, the progress and challenges of dye sensitized solar cell was also reviewed.     

New trends for solar cell development and recent progress of dye sensitized solar cells

This article reviews the new concepts and new trends of solar cell development. To increase the photoelectric conversion efficiency, reduce the cost, and for application in a much broader field, thin film solar cell, flexible solar cell, and tandem solar cell have become important subjects to be studied. As the representative of the solar cells of the third generation, the progress and challenges of dye sensitized solar cell was also reviewed.     

CdS quantum dot sensitized nanocrystalline Gd-doped TiO2 thin films for photoelectrochemical solar cells

CdS quantum dot sensitized Gd-doped TiO₂ nanocrystalline thin films have been prepared by chemical method. X-ray diffraction analysis reveals that TiO₂ and Gd-doped TiO₂ nanocrystalline thin films are of anatase phase. The absorption spectra revealed that the absorption edge of CdS quantum dot sensitized Gd-doped TiO₂ thin films shifted towards longer wavelength side (red shift) when compared to that of CdS quantum dot sensitized TiO₂ films. CdS quantum dots with a size of 5 nm have been deposited onto Gd-doped TiO₂ film surface by successive ionic layer adsorption and reaction method and the assembly of CdS quantum dot with Gd-doped TiO₂ has been used as photo-electrode in quantum dot sensitized solar cells. CdS quantum dot sensitized Gd-doped TiO₂ based solar cell exhibited a power conversion efficiency of 1.18 %, which is higher than that of CdS quantum dot sensitized TiO₂ (0.91 %).     

Hydrothermal synthesis of titanate nanoparticle/carbon nanotube hybridized material for dye sensitized solar cell application

With the hydrothermal treatment, titanate nanostructure with distinctively different morphology and surface characteristics was successfully synthesized from commercial rutile titania powder dispersed in accommodating media which were deionized water or NaOH solution. Hybridized materials of titanate nanoparticles and carbon nanotubes (CNT) were also synthesized by the hydrothermal treatment process. Intrinsic interaction of titanate nanoparticles and CNTs could be confirmed by spectroscopic analysis. The synthesized titanate nanoparticle/CNT hybridized material was then employed for fabricating a working electrode of dye-sensitized solar cells (DSSC). Based on experimental results, DSSC fabricated from the hybridized titanate nanoparticles and carbon nanotubes could provide the highest photoconversion efficiency of approximately 3.92%.     

Chemical synthesis of CdS onto TiO2 nanorods for quantum dot sensitized solar cells

A quantum dot sensitized solar cell (QDSSC) is fabricated using hydrothermally grown TiO₂ nanorods and successive ionic layer adsorption and reaction (SILAR) deposited CdS. Surface morphology of the TiO₂ films coated with different SILAR cycles of CdS is examined by Scanning Electron Microscopy which revealed aggregated CdS QDs coverage grow on increasing onto the TiO₂ nanorods with respect to cycle number. Under AM 1.5G illumination, we found the TiO₂/CdS QDSSC photoelectrode shows a power conversion efficiency of 1.75%, in an aqueous polysulfide electrolyte with short-circuit photocurrent density of 4.04 mA/cm² which is higher than that of a bare TiO₂ nanorods array.     

Facile hydrothermal synthesis of graphene-ZnSe electro-catalytic electrodes for dye sensitized solar cells

A ZnSe-graphene nanocomposites was prepared using by a facile hydrothermal method followed fabrication serials film counterelectrode (CEs) by the doctor-blade method. Transmission electron microscopy (TEM) results show that ZnSe nanoparticles are uniformly implanted on the graphene film. The improved performance compared to the pristine ZnSe is attributed to the increased number of active catalytic sites of ZnSe/rGO and highly conducting path of graphene. The comprehensive ZnSe/rGO synthesis process is a simple and scalable process which can easily adapt for large scale electro-catalytic film fabrication for several other electro-chemical energy harvesting and storage applications.     

Hydrothermal synthesis of 1D TiO2 nanostructures for dye sensitized solar cells

Mono-dimensional titanium oxide nanostructures (multi-walled nanotubes and nanorods) were synthesized by the hydrothermal method and applied to the construction of dye sensitized solar cells (DSCs). First, nanotubes (TiNTs) and nanotubes loaded with titanium oxide nanoparticles (TiNT/NPs) were synthesized with specific surface areas of 253 m²/g and 304 m²/g, respectively. After that, thermal treatment of the nanotubes at 500 °C resulted in their transformation into the corresponding anatase nanorods (TiNT-Δ and TiNT/NPs-Δ samples). X-ray diffraction and Raman spectroscopy data indicated that titanium oxide in the pristine TiNT and TiNT/NP samples was converted into anatase phase TiO₂ during the heating. Additionally, specific surface areas and water adsorption capacities decreased after the heat treatment due to the sample agglomeration and the collapse of the inner nanotube channels. DSCs were fabricated with the nanotube TiNT and TiNT/NP samples and with the anatase nanorod TiNT-Δ and TiNT/NPs-Δ samples as well. The highest power conversion efficiency of η = 3.12% was obtained for the TiNT sample, despite its lower specific surface compared with the corresponding nanoparticle-loaded sample (TiNT/NP).     

Structural and optical properties of Eu2O3 coated TiO2 nanoparticles and their application for dye sensitized solar cell

Specialized applications of dye sensitized solar cells (DSSCs) have attracted much attention as an economical substitute to first and second generation solar cells. Surface modification of TiO₂ nanoparticles with high band gap Eu₂O₃ coating has been carried out by chemical precipitation arrested solvothermal method. The characterizations have been done through X-ray diffraction, transmission electron microscopy, diffuse UV–visible, and photoluminescence spectroscopy. Scanning electron microscopy results reveal an increase in surface roughness in case of Eu₂O₃/TiO₂ electrode, which leads to enhancement in the dye loading capability. The synthesized nanoparticles have been employed for the fabrication of DSSCs. Effect of Eu₂O₃ coating on their performance has been studied. Eu₂O₃/TiO₂ electrode provides better surface area for the dye adsorption, which slows down the electron–hole recombination, and thus, improves the DSSC performance. The photocurrent density–voltage (J–V) characteristics reveal that the efficiency of DSSCs fabricated from Eu₂O₃/TiO₂ nanoparticles is 52 % higher than that from bare TiO₂ nanoparticles.