Efficient flexible dye-sensitized solar cells from rear illumination based on different morphologies of titanium dioxide photoanode

The TiO_(2) with nanoparticles(NPs),nanowires(NWs),nanorods(NRs)and nanotubes(NTs)structures were prepared by using a in-situ hydrothermal technique,and then proposed as a photoanode for flexible dye-sensitized solar cell(FDSSC).The influences of the morphology of TiO_(2) on the photovoltaic performances of FDSSCs were investigated.Under rear illumination of 100 mW·cm^(−2),the power conversion efficiencies of FDSSCs achieved 6.96%,7.36%,7.65%,and 7.83%with the TiO_(2) photoanodes of NPs,NWs,NRs,and NTs and PEDOT counter electrode.The FDSSCs based on TiO_(2) NRs and NTs photoanodes have higher short circuit current densities and power conversion efficiencies than that of the others.The enhanced power conversion efficiency is responsible for their nanotubes and rod-shaped ordered structures,which are more beneficial to transmission of electron and hole in semiconductor compared to the TiO_(2) nanoparticles and nanowires disordered structure.

Synthesis and Characterization of Novel Schiff Base for Enhanced Dye-Sensitized Solar Cell Photo-Response Mechanism

The efficient photo-response mechanism is one of the key factors in the commercialization of dye-sensitized solar cells in a bid to satisfy renewable energy demands. Progress in green technology has put solar energy on the front burner as a provider of clean and affordable energy for a sustainable society. We report the synthesis of a novel Schiff base with optical transparency in the visible and near IR region of the solar spectrum that can find application in the DSSCs photo-response mechanism. The synthesized crystal exhibited features that could handle some of the shortcomings of dye-sensitized solar cells which include wide band solar spectrum absorption and capability for swift charge transfer within the photoelectrodes. The synthesized Schiff base was characterized using x-ray diffractometer, UV/Visible spectrometer, Frontier transmission infrared spectrometer and conductometer. XRD data revealed the grown crystal to have an average crystallite size of 2.08 nm with average microstrain value of about 269.43. The FT-IR recorded transmission wave ѵ (CO) at 1207.7 cm−1 while dominant wave occurred at ѵ1654.9 and ѵ1592.3 cm−1 relating to ѵ (CN) stretching and ѵ (NH) bending respectively were observed. The IR spectrum revealed the bonding species and a probable molecular structure of 2,6-bis(benzyloxy)pyridine. The UV/Visible spectra convoluted to maximum peak within the near IR region suggesting that 2,6-bis(benzyloxy)pyridine can absorb both the visible and near IR region while its electrical conductivity was determined to be 4.58 µS/cm. The obtained result of the present study revealed promising characteristics of a photosensitizer that can find application in the photo-response mechanism of DSSCs.

Influence of Triarylamine and Indoline as Donor on Photovoltaic Performance of Dye-Sensitized Solar Cells Employing Cobalt Redox Shuttle

Two organic dyes XSS1 and XS52 derivated from triarylamine and indoline are synthesized for dye-sensitized solar ceils （DSCs） employing cobalt and iodine redox shuttles. The effects of dye structure upon the photophysical, electro-chemical characteristics and cell perfor- mance are investigated. XS51 with four hexyloxyl groups on triarylamine performs better steric hindrance and an improvement of photovoltage. X852 provides higher short-circuit photocurrent density due to the strong electron-donating capability of indoline unit. The results from the redox electrolyte on cell performances indicate that the synthesized dyes are more suitable for tris（1,10-phenanthroline）cobalt（II/III） redox couple than I-/I3- redox couple in assembling DSCs. Application of X852 in the cobalt electrolyte yields a DSC with an overall power conversion efficiency of 6.58% under AM 1.5 （100 mW/cm2） irradiation.

Dye-sensitized TiO2@SBA-15 composites: Preparation and their application in photocatalytic desulfurization

Photocatalytic oxidation desulfurization has become a research hotspot in recent years because of mild reaction conditions, less energy consumption and high selectivity. In this paper, TiO2 was loaded onto SBA-15 molecular sieves and sensitized with organic dyes(2, 9-dichloroquinacridone, DCQ) to extend its spectral response range from ultraviolet light to visible light. The catalyst DCQ-X%TiO2@SBA-15 was characterized by BET measurements, X-ray diffraction, Fourier transform infrared spectroscopy and Ultraviolet-visible diffuse reflection spectra, and then it was applied for photocatalytic oxidation desulfurization of gasoline. The effects of different catalytic systems, TiO2 concentration, catalyst dosage, and different model sulfur compounds on catalytic desulfurization performance were investigated. Experimental results show that DCQ-TiO2@SBA-15 has a better performance than the unsensitized TiO2@SBA-15, and the desulfurization rate can reach up to 96.1% in a reaction time of 90 min.

Novel micro-ring structured ZnO photoelectrode for dye-sensitized solar cell

The micro-ring like structured zinc oxide(ZnO) film was deposited on SnO_2: F coated glass substrate by sol-gel dip-coating technique with 1.0 g polyethylene glycol(PEG) content. The surface morphology of micro-ring structured ZnO film has been confirmed by the scanning electron microscope. This ZnO film is used to fabricate the solar cell with the help of ruthenium based dye and carbon counter electrode. The photoelectric and incident photon-to-current conversion efficiency was 1.17% and 48.4%, respectively. The DSC results have been compared with ZnO films prepared without PEG contents.

Dye-sensitized Solar Cells with Higher J_(sc) by Using Polyvinylidene Fluoride Membrane Counter Electrodes

A flexible counter electrode(CE) for dye-sensitized solar cells(DSCs) has been fabricated using a micro-porous polyvinylidene fluoride membrane as support media and sputtered Pt as the catalytic material.Non-conventional structure DSCs have been developed by the fabricated CEs. The Pt metal was sputtered onto one surface of the membrane as the catalytic material. DSCs were assembled by attaching the Ti O2 electrode to the membrane surface without Pt coating. The membrane was with cylindrical pore geometry. It served not only as a substrate for the CE but also as a spacer for the DSC. The fabricated DSC with the flexible membrane CE showed higher photocurrent density than the conventional sandwich devices based on chemically deposited Pt/FTO glass, achieving a photovoltaic conversion efficiency of 4.43%. The results provides useful information in investigation and development of stable, low-cost, simple-design, flexible and lightweight DSCs.

Recent Progress of Counter Electrodes in Nanocrystalline Dye-sensitized Solar Cells

Dye-sensitized solar cell （DSC） consists a combination of several different materials： photoanodes with nanoparticulated semiconductors, sensitizers, electrolytes and counter electrodes （CEs）. Each materials performs specific task for the conversion of solar energy into electricity. The main function of CE is to transfer electrons to the redox electrolyte and regenerate iodide ion. The work of CE is mainly focused on the studies of the kinetic performance and stability of the traditional CEs to improve the overall efficiency of DSC, seeking novel design concepts or new materials. In this review, the development and research progress of different CE materials and their electrochemical performance, and the problems are discussed.

Preparation and performance of dye-sensitized solar cells based on ZnO-modified TiO_2 electrodes

The ZnO-modified TiO2 electrode was prepared by adding Zn（CH3COO）2·2H2O to the TiO2 colloid during the sol-gel production process, and was used in dye-sensitized solar cells （DSCs）. The open circuit voltage （Voc） and fill factor （if） of the cells were improved sig- nificantly. The performances of the ZnO-modified TiO2 electrode such as dark current, transient photocurrent, impedance, absorption spectra, and fiat band potential （Vfb） were investigated. It is found that the interface charge recombination impedance increases and Vfb shifts about 200 mV toward the cathodic potential. The effect mechanism of ZnO modification on the performance of DSCs may be that ZnO occupies the surface states of the TiO2 film.

Influence of TiCl_4 treatment on performance of dye-sensitized solar cell assembled with nano-TiO_2 coating deposited by vacuum cold spraying

Titanium tetrachloride (TiCl4) treatment was employed to TiO2 coating deposited on fluoride-doped tin oxide (FTO) conducting glass and indium oxide doped tin oxide (ITO) conducting glass, respectively. The nano-crystalline TiO2 coating was deposited using a composite powder composed of polyethylene glycol (PEG) and 25 nm TiO2 particles by vacuum cold spraying (VCS) process. A commercial N-719 dye was used to adsorb on the surface of TiO2 coating to prepare TiO2 electrode, which was applied to assemble dye-sensitized solar cell (DSC). The cell performance was measured under simulated solar light at an intensity of 100 mW·cm-2. Results show that with an FTO substrate the DSC composed of a VCS TiO2 electrode untreated by TiCl4 gives a short-circuit current density of 13.1 mA·cm-2 and an open circuit voltage of 0.60 V corresponding to an overall conversion efficiency of 4.4%. It is found that after TiCl4 treatment to the VCS TiO2 electrode with an FTO substrate, the short circuit current density of the cell increases by 31%, the open-circuit voltage increases by 60 mV and a higher conversion yield of 6.5% was obtained. However, when an ITO substrate is used to deposit TiO2 coating by VCS, after TiCl4 treatment, the conversion efficiency of the assembled cell reduces slightly due to corrosion of the conducting layer on the ITO glass by TiCl4.

Well-aligned Ni Pt alloy counter electrodes for high-efficiency dye-sensitized solar cell applications

Development of cost-effective and robust counter electrodes(CEs) is a persistent objective for highefficiency dye-sensitized solar cells(DSSCs). To achieve this goal, we present here the hydrothermal synthesis of well-aligned Ni Pt alloy CEs, which is templated by ZnO nanowires and nanosheets. The preliminary results demonstrate that Ni Pt alloy electrodes are featured by increased charge-transfer processes and electrocatalytic activity in comparison with expensive Pt CE, yielding power conversion efficiencies of 8.29% and 7.41% in corresponding DSSCs with Ni Pt nanowire and nanosheet alloy CEs, respectively. Additionally, the Ni Pt alloy CEs also display extraordinary dissolution-resistant ability when suffering longterm utilization in liquid-junction DSSCs.

DYE-SENSITIZED PHOTOPOLYMERIZATION OF METHYL METHACRYLATE INITIATED BY COUMARIN DYE/IODONIUM SALT SYSTEM

The photosensitive initiating system composed of 7-diethylamino-3-(2'-benzimidazolyl)coumarin dye (DEDC) and diphenyliodonium hexafluorophosphate (DIHP) which act as the sensitizer and the initiator respectively, can be used to initiate the polymerization of methyl methacrylate (MMA). The results showed that when exposed to visible light, coumarin dye/iodonium salt undergoes quick electron transfer from DEDC to DIHP and free radicals are produced. The visible light photoinduced reaction between DEDC and DIHP is mainly through the excited singlet state of DEDC and thus it is a little sensitive to O-2. The influence of concentration of DEDC, DIHP and MMA on the rate of photopolymerization of MMA was also investigated.

Dye-Sensitized Solar Cells Based on ZnO Films

In order to improve the performance of the dye-sensitized solar cells based on ZnO films, ZnO nanoparticles of different sizes were prepared by two methods. Some surfactants were added into the particles to form three types of ZnO pastes. Electrodes of various thickness applied to dye-sensitized solar cell were prepared starting from each of those pastes by the screen-printing method. The performance of dye-sensitized solar cells was optimized via both the selected particle size and film thickness. The reason of the inefficiency was explained by the infrared and ultraviolet- visible absorption spectra.

A Bi-layer Composite Film Based on TiO_2 Hollow Spheres, P25,and Multi-walled Carbon Nanotubes for Efficient Photoanode of Dye-sensitized Solar Cell

A bi-layer photoanode for dye-sensitized solar cell(DSSC) was fabricated, in which TiO_2 hollow spheres(THSs) were designed as a scattering layer and P25/multi-walled carbon nanotubes(MWNTs) as an under-layer. The THSs were synthesized by a sacrifice template method and showed good light scattering ability as an over-layer of the photoanode. MWNTs were mixed with P25 to form an under-layer of the photoanode to improve the electron transmission ability of the photoanode. The power conversion efficiency of this kind of DSSC with bi-layer was enhanced to 5.13 %,which is 14.25 % higher than that of pure P25 DSSC.Graphical Abstract A bi-layer composite photoanode based on P25/MWNTs-THSs with improved light scattering and electron transmission, which will provide a new insight into fabrication and structure design of highly efficient dyesensitized solar cells.

A new D–D–π–A dye for efficient dye-sensitized solar cells

New metal-free organic dye sensitizers containing mono-triphenylamine or bis-triphenylamine as the electron donor, a thiophene as the π-conjugated system, and a cyanoacrylic acid moiety as the electron acceptor were synthesized. The optical and electrochemical properties of the dyes were investigated,and their performance as sensitizers in solar cells was evaluated. Dye-sensitized solar cells based on dye containing bis-triphenylamine as the electron donor produced a photon-to-current conversion efficiency of 6.06%（Jsc = 14.21 m A/cm;, Voc = 0.62 V, ff = 0.69） under 100 m W/cm;simulated AM 1.5 G solar irradiation（100 m W/cm;）.

Towards Improvement of Photovoltaic Performance of Aqueous Dye-sensitized Solar Cells by Tungsten-doped Mesoporous Nanobeads TiO_2 Working Electrode

Tungsten doped(W-doped) TiO_2 mesoporous nanobeads, possessing high surface area and superior scattering effect, were used for photoanode preparation. The W-doping would induce a positive shift of the TiO_2 conduction band, and enhance the driving force for electron injection and collection efficiencies. The electrochemical impedance spectra indicated a retarded charge recombination and increased electron diffusion length after W-doping. By fine-tuning the W-doping concentration to 0.25%, aqueous DSCs produced a significant improved the open circuit voltage of 712 mV and a short circuit current of 7.05 mA·cm^(-2), leading to an overall increased power conversion efficiency of 3.40% at 1 000 W·m^(-2) simulated irradiation, which is roughly 25% enhancement compared to that without W-doping photoanode.

Recent advances in cobalt-, nickel-, and iron-based chalcogen compounds as counter electrodes in dye-sensitized solar cells

The electroactive materials used in the counter electrode(CE)are of great concern as they influence the photovoltaic performances of dye-sensitized solar cells.The main functions of CE materials are collecting electrons from the external circuit and transferring them to the electrolyte and realizing the catalytic reduction of the redox species(I3^– or Co^3+)present in the electrolyte.The research hotspot of CE materials is seeking functional materials that display high efficiency,low cost,and good electrochemical stability and can substitute the benchmark platinum electrode.Chalcogen compounds of cobalt,nickel,and iron have been widely applied as CE materials and exhibit excellent electrocatalytic performances owing to their unique electrical properties,similar energies of adsorption of I atoms as platinum,excellent catalytic activities,and good chemical stabilities.In this review,we trace the developments and performances of chalcogen compounds of iron,cobalt,and nickel as CE materials and present the latest research directions for improving the electrocatalytic performances.We then highlight the optimization strategies for further improving their performances,such as fabrication of architectures,regulation of the components,synthesis of composites containing carbon materials,and elemental doping.

New strategy to incorporate nano-particle sized water oxidation catalyst into dye-sensitized photoelectrochemical cell for water splitting

In order to develop a new strategy to deposit nano-particle sized water oxidation catalyst based on earth abundant element to the photoanode in a photoelectrochemical cell for water splitting, Co;O;as water oxidation catalyst was prepared and subsequently modified by 3-aminopropyltriethoxysilane. The amino functionalized Co;O;catalyst was carefully characterized and then integrated to the ruthenium dye sensitized photoelectrode through fast Schiff base reaction. Cyclic voltammetry experiments in the dark confirmed that the modified Co;O;catalyst was still active toward water oxidation, which could be initiated by oxidation of the ruthenium photosensitizer. Under visible light irradiation, incorporation of the modified Co;O;catalyst resulted in dramatic enhancement of the transient photocurrent density for the photoanode, which was 8 times higher than that of without Co;O;catalyst.

Effect of imidazole based polymer blend electrolytes for dye-sensitized solar cells in energy harvesting window glass applications

The exploration of polymer electrolyte in the field of dye sensitized solar cell(DSSC) can contribute to increase the invention of renewable energy applications. In the present work, the influence of imidazole on the poly(vinylidene fluoride)(PVDF)–poly(methyl methacrylate)(PMMA)–Ethylene carbonate(EC)–KI–I2 polymer blend electrolytes has been evaluated. The different weight percentages of imidazole added into polymer blend electrolytes have been prepared by solution casting. The prepared films were characterized by Fourier transform infrared spectroscopy(FTIR), X-ray diffraction(XRD), thermogravimetric analysis(TGA), UV–visible spectra, photoluminescence spectra and impedance spectroscopy. The surface roughness texture of the film was analyzed by atomic force microscopy(AFM). The ionic conductivity of the optimized polymer blend electrolyte was determined by impedance measurement, which is 1.95 × 10-3 S·cm-1 at room temperature. The polymer electrolyte containing 40 wt% of imidazole content exhibits the highest photo-conversion efficiency of 3.04%under the illumination of 100 m W·cm-2. Moreover, a considerable enhancement in the stability of the DSSC device was demonstrated.

Low platinum loading PtNPs/graphene composite catalyst with high electrocatalytic activity for dye-sensitized solar cells

Platinum nanoparticles （PtNPs）/graphene composite materials are synthesized by a controlled chemical reduction of H2PtC16 on graphene sheets. The electrocatalytic activity of a PtNPs/graphene composite counter electrode for a dye-sensitized solar cell （DSSC） is investigated. The results demonstrate that the PtNPs/graphene composite has high electrocatalytic activity for the dye-sensitized solar cell. The cell employing PtNPs （1.6 wt%）/graphene counter electrode reaches an conversion efficiency （η） of 3.89% upon the excitation of 100 mW/cm2 AM 1.5 white light, which is comparable to that of the cell with a Pt-film counter electrode （7 = 3.76%）. It suggests that one can use only 14% Pt content of the conventional Pt-film counter electrode to obtain a comparable conversion efficiency. It may be possible to obtain a high performance DSSC using the PtNPs/graphene composite with a very low Pt content as a counter electrode due to its simplicity, low cost, and large scalability.

Gel electrolytes containing several kinds of particles used in quasi-solid-state dye-sensitized solar cells

Composite gel electrolytes containing several kinds of particles used as the quasi-solid-state electrolytes in dye-sensitized solar cells(DSSCs)were reported.Mesoporous particles(MCM-41)with unique structures composed of ordered nanochannels were served as a new kind of gelator for quasi-solid-state electrolytes.MCM-41,hydrophobic fumed silica Aerosil R972 and TiO_(2)nanopatricles P25 were dispersed into gel electrolytes respectively.The solar energy-to-electricity conversion efficiency of these cells is 4.65%,6.85%and 5.05%respectively under 30 mW·cm^(-2)illumination.The preparation methods and the particles sizes exert an influence on the performance of corresponding solar cells.Owing to unique pore structures and high specific BET surface area,mesoporous silica MCM-41 was expected to have the potential to afford conducting nanochannels for redox couple diffusion.