Films For Dye-sensitized Solar Cells Research Articles

The performance of dye-sensitized solar cells using different carbon materials as counter electrodes

Counter electrode films for dye-sensitized solar cells (DSSCs) were prepared by screen printing using graphite, activated carbon, carbon black and carbon nanotubes (CNTs) as raw materials. The effects of pore structure, BET surface area and the sheet resistance of the as-prepared counter electrode films on the performance of DSSCs were investigated. Results show that the conductivity of the raw materials is not the crucial factor for the performance of the DSSCs. The performance of the DSSC is not directly improved by increasing the BET surface area of the raw materials. It is also related to the pore size distribution of carbon materials, the particle shape and their alignment. The DSSCs assembled using CNT film counter electrodes with a BET surface area of 31.2 m 2 g −1 show the largest photoelectric conversion efficiency of 5.87%.

Directly Determine an Additive-Induced Shift in Quasi-Fermi Level of TiO2 Films in Dye-Sensitized Solar Cells

The shifts in quasi-Fermi level (QFL) of TiO2 films affected by additives are directly measured using three-electrode dye-sensitized solar cells (DSCs). The difference in QFL of TiO2 under short circuit and open circuit are also analyzed. It is found that the QFL difference between the electrolyte side of the TiO2 film and the equilibrium redox potential, as well as the QFL difference between the two sides of the TiO2 film shift to higher potential owing to the addition of TBP to the electrolyte. The shift values are influenced by the cations present in the electrolyte. These directly determined changes in QFL in TiO2 films both under open circuit and short circuit may provide valuable information for studying DSC operation mechanisms such as the dynamics of charge separation and charge recombination processes.

Directly Determine an Additive-Induced Shift in Quasi-Fermi Level of TiO2Films in Dye-Sensitized Solar Cells

Directly Determine an Additive-Induced Shift in Quasi-Fermi Level of TiO₂Films in Dye-Sensitized Solar Cells

The blocking effect of charge recombination by sputtered and acid-treated ZnO thin film in dye-sensitized solar cells

► ZnO film was fabricated by the sputter deposition using Zn target without O 2 gas. ► Zn film was acid-treated for the sufficient oxidization. ► ZnO layer was used as the compact layer for the prevention of charge recombination. Compact layer preventing the charge recombination has much attention in studies on efficiency enhancement of dye-sensitized solar cells (DSCs). Especially, the charge recombination at the interface between transparent conductive oxide (TCO) and an electrolyte plays an important role due to bad contact of TCO/TiO 2 interface. Although TiO 2 has been widely adopted as a source of the compact layer, ZnO compact layer was investigated in this study because of its unique properties. ZnO thin film was deposited by Zn sputtering without O 2 gas in particular. For the sufficient oxidization of Zn film, the acid treatment was introduced and the thickness of the compact layer was controlled. As a result, the overall performance was much increased from 6.20% to 7.81% by the acid treatment and the thickness control of the compact layer.

Promoting Effect of Graphene on Dye-Sensitized Solar Cells

In this paper, a simple approach without a prereduction of graphene oxide was exploited to prepare a graphene-doped TiO2 film for dye-sensitized solar cells (DSSCs). The performance measurement of the DSSCs showed that the incorporation of graphene could increase the short-circuit current density and power conversion efficiency by 52.4 and 55.3%, respectively. Furthermore, it was demonstrated that the performance enhancement was due to the promoting effect of graphene on electron transfer instead of the increase of dye loading in TiO2/graphene composite films. However, graphene can also absorb solar light, which could lead to the decrease of light harvest of dye molecules and thus a negative effect on the power conversion efficiency of DSSCs. Furthermore, graphene might decrease the actual dye loading on TiO2 in a TiO2/graphene film, which can also make a negative contribution to the conversion efficiency. As a result, the promoting effect of graphene is strongly dependent on its content; namely, the efficiency of DSSCs increases to the maximum value and then decreases with increasing graphene content in TiO2/graphene composites.

Preparation and study of microstructures, optical properties and oscillator parameters of titanium (IV) oxide (TiO2) film

In this study, Titanium (IV) Oxide (TiO2) film has been prepared and characterized by X-ray diffraction (XRD). The XRD pattern of TiO2 film of anatase phase exhibit very sharp peaks at 25° and 47.85°. According to Scherrer’s formula the grain size of anatase (101) phase TiO2 nananoparticle is 38.5 nm. The optical properties and constants of TiO2 film of thickness (4 μm) have been investigated at room temperature. The transmittance, reflectance and absorbance spectra are measured in the wavelength range (340–900 nm). Optical constants of TiO2 film are derived from the transmission spectra and the refractive index dispersion of the film. The oscillator energy, E0 dispersion energy, Ed, the static refractive index, n0, and other parameters have been determined by the single oscillator Wemple-DiDomenico method. This film can be used in the form of thin film in dye-sensitized solar cells.

Poly(vinyl chloride)-g-poly(2-(dimethylamino)ethyl methacrylate) graft copolymers templated synthesis of mesoporous TiO2 thin films for dye-sensitized solar cells

A poly(vinyl chloride) (PVC) main chain was grafted with poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) containing a quaternary amine group using atom transfer radical polymerization. The successful synthesis of a PVC-g-PDMAEMA graft copolymer was confirmed by Fourier transform infrared, nuclear magnetic resonance, thermogravimetric analysis, and transmission electron microscopy. The PVC-g-PDMAEMA graft copolymer was used as a structure-directing agent (SDA) for the fabrication of a mesoporous thin film containing a titanium dioxide (TiO2) layer. To control the porosity of the resultant inorganic layer, the ratio of SDA to TTIP as well as the concentration of the sol–gel was varied. The structure and porosity of the mesoporous film were characterized by XRD and SEM analysis. The mesoporous TiO2 film fabricated on the FTO surface was used as a photoanode for the dye-sensitized solar cell (DSSC). DSSC performance was the greatest when using TiO2 film with a higher porosity and lower interfacial resistance. The highest energy conversion efficiency reached 3.2 % at 100 mW/cm2, which was one of the highest reported values for a quasi-solid-state DSSC with 600-nm-thick TiO2 film.

Influence of Polyethylene Glycol on the Morphology of Electrodeposited ZnO Films for Dye-Sensitized Solar Cells

Polyethylene glycol (PEG) was used as an additive for the electrodeposition of ZnO films from Zn(NO3)2. The presence of PEG in the bath resulted in a more open morphology and an increase of the active surface area of the ZnO films, and thermogravimetric analysis showed that a small amount of PEG was incorporated in the films. As a consequence of the improved film morphology, dye-sensitized solar cells prepared with galvanostatically deposited ZO films showed a higher conversion efficiency.

Modified multistep electrophoretic deposition of TiO2 nanoparticles to prepare high quality thin films for dye-sensitized solar cell

In this study, a modified procedure is introduced which consists of multistep process for improving the structure of mesoporous TiO2 films. The films were prepared by electrophoretic deposition (EPD) on FTO (F-SnO2 coated glass). It is shown that high quality TiO2 film can be produced by multistep EPD method. The effect of EPD time on the thickness and density of the films have been investigated. The performance of dye-sensitized solar cells (DSSCs) that were fabricated by improved layer are tested under AM 1.5 simulated sunlight. Finally, the structure and effective parameters of DSSCs that were fabricated by one step and multistep EPD are investigated precisely, using electrochemical impedance spectroscopy.

Effect of hydroxyl group attachment on TiO2 films for dye-sensitized solar cells

The effect of hydroxyl group attachment on the nanocrystalline TiO2 photoelectrodes for the performance of dye-sensitized solar cells (DSSCs) was investigated. The photoelectrodes were prepared using commercial TiO2 nanoparticles (Degussa P25). Hydroxyl groups were attached to the TiO2 film using hydrogen peroxide by thermal treatment method and the OH-attached sample was compared with the untreated one. The FTIR spectra evidenced the presence of hydroxyl groups attached to the TiO2 nanoparticles. Thermogravimetric analysis showed that the sample treated with hydrogen peroxide was attached with higher weight percentage of hydroxyl groups. The photovoltaic characteristics of the as-prepared DSSCs were measured by an electrochemical analyzer under the standard AM 1.5 illumination of 100mW/cm2 light source. The hydroxyl groups attached sample showed an enhanced performance of DSSC than that of the blank P25 film. It shows that higher amount of dye was adsorbed due to the surface hydroxyl groups on the H2O2-treated samples. Electrochemical impedance spectroscopy (EIS) measurement indicated that the electron lifetime for the H2O2-treated sample was longer than that of the untreated sample. The higher dye loading due to the attached hydroxyl groups on the sample was confirmed using UV–vis measurement.

Enhanced Electron Lifetime on Nitrogen-Doped TiO<SUB>2</SUB> Films for Dye-Sensitized Solar Cells

Nitrogen-doped TiO2 crystallites were prepared via the hydrolysis of TiCl4 using an ammonia medium in an aqueous solution for DSSC photoelectrodes. The optimized photoelectrode for the DSSC was prepared with 9.4 nm sized N-doped TiO2 crystal (BET; 200 m2/g), which provides a relatively high short circuit current and energy conversion efficiency in the DSSC. The photovoltaic performance of the N-doped TiO2 electrode was confirmed using incident photon-to-current efficient spectra, impedance analyses, and Bode-phase plots which proved that the N-doped TiO2 electrode has a significantly enhanced electron lifetime compared with that of the P25 electrode.

Progress on TiO<SUB>2</SUB>-based Nanomaterials and Its Utilization in the Clean En-ergy Technology

TiO2 nanomaterials are the research hotspots among recent nanotechnologies, and those are demon- strated having the crucial application prospects in the solar light photocatalytic splitting water into hydrogen, the photocatalytic reduction of CO2, as well as dye-sensitized solar cells. This article mainly reviewed recent research trends of TiO2-based nanomaterials, the existing problems, and the advances in the clean energy utilization. Espe- cially, the hot research issues such as non-metallic element doping, high energy facets exposed titania, and compact film for dye-sensitized solar cells, were commented and prospected.

표면형상 변화에 따른 염료감응 태양전지의 전기화학적 특성

We use UV(ultraviolet)-<TEX>$O_3$</TEX> treatment to increase the surface area and porosity of <TEX>$TiO_2$</TEX> films in dye-sensitized solar cells (DSSCs). After the UV-<TEX>$O_3$</TEX> treatment, surface area and porosity of the <TEX>$TiO_2$</TEX> films were increased, the increased porosity lead to amount of dye loading and solar conversion efficiency was improved. Field emission scanning electron microscopy images clearly showed that the nanocrystalline porosity of films were increased by UV-<TEX>$O_3$</TEX> treatment. The Brunauer, Emmett, and Teller surface area of the <TEX>$TiO_2$</TEX> films were increased from <TEX>$0.71cm^2/g$</TEX> to <TEX>$1.31cm^2/g$</TEX> by using UV-<TEX>$O_3$</TEX> treatment for 20 min. Also, UV-<TEX>$O_3$</TEX> treatment of <TEX>$TiO_2$</TEX> films significantly enhanced their solar conversion efficiency. The efficiency of the films without treatment was 4.9%, and was increased to 5.6% by UV-<TEX>$O_3$</TEX> treatment for 20 min. Therefore the process enhanced the solar conversion efficiency of DSSCs, and can be used to develop high sensitivity DSSCs.

Multi-functional photoanode films using mesoporous TiO2 aggregate structure for efficient dye sensitized solar cells

We present here the photovoltaic performance of dye sensitized solar cells (DSCs) using sub-micron sized mesoporous TiO2 aggregates which incorporate built-in multi-functional properties such as high dye uptake, efficient light scattering and enhanced charge collection. The DSC prepared with these mesoporous anatase TiO2 aggregates as photoanode with no additional scattering layer exhibits an enhanced conversion efficiency of 9.00% at 1 sun and 10.84% at 0.16 sun illumination. The properties of the photoanode film in DSCs were analyzed by surface area, diffuse reflectance, intensity modulated photocurrent/voltage spectroscopy (IMPS/IMVS) and electrochemical impedance spectroscopy (EIS) measurements in order to gain knowledge of the decisive factors contributing to such high power conversion efficiency. The present study reveals that the mesoporous aggregate offers large internal surface area and high light scattering with its unique structure. Due to the high crystallinity and compact packing of primary nanocrystallites forming the aggregate structure of mesoporous TiO2, the electron diffusion length is substantially long reflecting a lower number of electrons trapped at the grain boundaries. A good compromise of electron transport time and extended life time in mesoporous aggregate films compared to their non-aggregate counterparts leads to efficient charge collection and higher power conversion efficiency.

Effect of binder molecular weight on morphology of TiO2 films prepared by tape casting and their photovoltaic performance

Titanium(IV) oxide in the form of anatase has proven to be the best choice for photoanodic material in dye-sensitized solar cells (DSCs). The aim of the work was to study the influence of binder molecular weight on the morphology of deposited films, and consequently, DSC parameters. For this study, five different TiO2 tape casting slips were prepared from commercially available nanoanatase powder and polyethylene glycol (PEG) as a binder. The process of drying and sintering was carefully designed, so that the organic template was slowly decomposed, leaving favorable crack-free, porous structure. It was found that there is an optimal region of binder molecular weight for obtaining homogeneous, nonagglomerated and porous microstructure which is a necessary condition for application of TiO2 films in DSCs.

酸化チタン中空粒子膜の電気化学的作製と色素増感太陽電池への応用

酸化チタン中空粒子膜の電気化学的作製と色素増感太陽電池への応用

Enhanced photovoltaic properties of TiO2 film prepared by polycondensation in sol reaction

A TiO2 film of dye-sensitized solar cells was fabricated using a TiO2 sol prepared from titanium isopropoxide as a starting material. The effect of polycondensation time and temperature on physical and chemical properties of TiO2 film shows that the crystallinity, particle size, roughness, and surface area of TiO2 film can be successfully controlled by adjusting the polycondensation time and temperature in the synthesis process of the TiO2 sol. Adsorption properties (adsorption equilibrium, isosteric enthalpies of adsorption, and adsorption energy distributions) of N719 dye molecules on the prepared TiO2 film revealed that the short circuit current (Isc) and overall conversion efficiency (ηeff) are highly dependent on the crystallite size and the N719 dye adsorption properties. The TiO2 film has a pure anatase phase, high surface area including pore volume, and large anatase crystallite size and is capable of enhancing the photovoltaic performance. The energy conversion efficiency of the dye sensitized solar cells is highly dependent on the physical and chemical properties of TiO2 films.

Structure and Electron-Conducting Ability of TiO2 Films from Electrophoretic Deposition and Paste-Coating for Dye-Sensitized Solar Cells

An electrophoretic deposition (EPD) method, consisting of repetitive short-term depositions with intermediate drying, was developed to prepare nanocrystalline TiO2 films for dye-sensitized solar cells (DSSCs). After calcination, the EPD TiO2 films exhibited a more compact TiO2 network than films derived from the conventional paste-coating (PC) method. X-ray absorption fine structure spectroscopic analysis showed that the EPD films had a higher density of defect states than the PC films because of the higher number of interparticle necking regions created in the EPD films. However, the DSSCs assembled with the EPD films outperformed those with the PC films by 20% in photocurrent and 15% in solar energy conversion efficiency. Intensity-modulated photocurrent spectroscopic analysis showed that the EPD films had a shorter electron transit time than the PC films. Under one-sun illumination on the cells at open-circuit, impedance analysis showed that the EPD films had a constant charge collection efficiency of 95% for thicknesses ranging from 4 to 13 μm, whereas the efficiency of the PC films was not greater than 90% and showed a decreasing trend with increasing film thickness. Concerning the porosity dependence of the electron transport dynamics, the electron diffusivity had much weaker dependence than one would expect from the percolation model with hard spheres. This may result from the fact that interparticle necking causes greater lattice distortion for more compact TiO2 films. The present study demonstrates that an optimized EPD process can construct a nanocrystalline TiO2 architecture with a minimized void fraction to shorten the electron traveling distance and to effectively collect photogenerated charges, even for films with large thicknesses.

Nanostructured TiO2 Films for Dye-Sensitized Solar Cells Prepared by the Sol–Gel Method

TiO2 films were prepared on glass substrates using the sol-gel process for a dye-sensitized solar cell application. The TiO2 sol was prepared using hydrolysis/polycondensation. Titanium (IV) Tetra Isopropoxide (TTIP) was used as precursor and Nitric acid (HNO3) was used as a catalyst for the peptization. The crystal structure and morphology of the prepared materials were characterized by XRD, and an SEM. The observations confirmed the nanocrystalline nature of the TiO2. The reaction parameters, such as the catalyst concentrations, the calcination time, and the calcination temperature were varied during the synthesis in order to achieve nanosize TiO2 particles. The prepared TiO2 particles were coated onto FTO glass using a screen printing technique. The prepared TiO2 films were characterized by UV-vis. The TiO2 particles calcinated at low temperatures showed an anatase phase they grew into a rutile phase when the calcination temperature increased. The size and structure of the TiO2 particles were adjusted to specific surface areas. It was found that the conversion efficiency of the DSSC was highly affected by the properties of the TiO2 particles.

Poly(vinyl chloride)-graft-poly(N-vinyl caprolactam) graft copolymer: synthesis and use as template for porous TiO2 thin films in dye-sensitized solar cells

Poly(N-vinyl caprolactam) (PNVCL) side chains were grafted to a poly(vinyl chloride) (PVC) backbone via atom transfer radical polymerization. The synthesized PVC-g-PNVCL graft copolymer was templated for the preparation of porous TiO2 thin films, which involved a sol–gel reaction and calcination process. The interaction of the carbonyl groups in the PVC-g-PNVCL with the titania was revealed by FT-IR spectroscopy. X-ray diffraction and transmission electron microscopy analysis showed the formation of porous TiO2 thin films with the anatase phase. A series of porous TiO2 thin films with different pore sizes and porosities was prepared by varying the solution compositions and were used as photoelectrodes in dye-sensitized solar cells (DSSC) with a polymer electrolyte. The DSSC performed best when using the TiO2 film with higher porosity, lower interfacial resistance, and longer electron life time. The highest energy conversion efficiency, photovoltage (V oc), photocurrent density (J sc), and fill factor (FF) were 1.2%, 0.68 V, 3.2 mA/cm2, and 0.57 at 100 mW/cm2, respectively, for the quasi-solid state DSSC with a 730-nm-thick TiO2 film.