A Dye-sensitized Nanocrystalline Solid State Photovoltaic Cell

A new type of dye-sensitized nanocrystalline solid state photovoltaic cell based on the wide band gap n-TiO2/p-CuI heterojunction was fabricated. Tetra-carboxyphenyl porphyrine (TPP-(COOH)(4)), squarylium cyanine derivative (SQ-(CH2),(SO3Py+)-Py-.) and ruthenium bipyridyl complex (RuL2(NCS)(2)) were used as photosensitizers. Larger photocurrents and photovoltages were shown in the cell sensitized by ruthenium bipyridyl complex and can be further increased by intercalation of a TiO2 thin underlayer.

Titania Nanostructures for Dye-sensitized Solar Cells

Titania is one kind of important materials, which has been extensively investigated because of its unique electronic and optical properties. Research efforts have largely focused on the optimization of the dye,but recently the titania nanostructures electrode itself has attracted more attention. It has been shown that particle size, shape, crystallinity, surface morphology, and chemistry of the TiO_2 material are key parameters which should be controlled for optimized performance of the solar cell. Titania can be found in different shape of nanostructures including mesoporous, nanotube, nanowire, and nanorod structures. The present article reviews the structural, synthesis, electronic, and optical properties of TiO_2 nanostructures for dye sensitized solar cells.

Composite Electrode SnO_2/TiO_2 for Dye-Sensitized Solar Cells

Composite nanoporous electrode SnO2/TiO2 was fabricated for the dye sensitized solar cell (DSSC) with N3 (Cis-Ru). After introducing of TiO2, the open-circuit photovoltage (Voc) was higher than that of the pure SnO2 electrode, while short-circuit photocurrent (Isc) was varied with the ratio of the TiO2. Appropriate content of the TiO2 can be beneficial to the efficiency of the solar cell, and it gives negative impact on the composite electrode when the content of TiO2 is higher.

New tetrazole-based organic dyes for dye-sensitized solar cells

A series of new metal-free organic dyes that contain donors with triphenylamine or its derivatives and tetrazole-based acceptors were synthesized and characterized by photophysical, electrochemical, and the- oretical computational methods. They were applied in nanocrystalline TiO2 solar cells （DSSCs）. It is found that the introduction of diphenylamine units as antennas in the as-synthesized dyes could improve photo- voltaic performance compared with phenothiazine and carbazole units as antennas in DSSCs. The dye with （2H-tetrazol-5-yl） acrylonitrile electron acceptor also displayed the highest solar-to-electrical energy conver- sion efficiency.

Optical and Electrical Properties of Sensitized Polyaniline by Electrochemical Polymerization

To sensitize polyaniline with dyes by electrochemical polymerization, HClO 4 is employed as the dopant and oxidant, and the polyaniline with different sensitive properties is synthesized. The effect of sensitized emeraldine salt on the absorption spectrum is discussed in details. The maximum conductivity of sensitized films reaches 1.22 S/cm, and investigation on dye sensitizing of the polymer reveals that C.I. Direct Blue 71, C.I. Direct Blue 84, C.I. Direct Black 19 and CuPc-(COOH) 4 may enhance the photoconductivity of polyaniline greatly.

Fabrication and Fluorescence Study of Sensitizing Dye/TiO_2 Films

Fluorescence spectra of the sensitizing dye/ TiO2 bilayer films were studied. Charge-transfer complexes were formed in the above bilayer.

Self-assembled structure of cyanine dyes: J-aggregates characteristics on optical information storing microcrystals

Dye sensitization is a fundamental function for solar cell and silver halide (AgX) microcrystal to increase the optoelectronic conversion efficiency. In this paper, the spectral properties and self-assembled structure of three types of cyanine dyes, adsorbed both on (100) surface of 0.4 μm AgBr cubic crystal and (111) surface of 1.8 μm AgBr tabular crystal, were studied with combination of spectroscopy and atomic force microscopy (AFM) technique. Rectangular aggregation structure is formed on the crystal faces of (100) and (111) for both anionic and cationic dyes, while herringbone-stacking structure is formed by anionic-cationic dye, and a J-band spectrum is correspondingly detected. The photoelectron property of dye-sensitized samples was also investigated with microwave absorption and dielectric spectrum detection technology. After excited by a 355 nm fast-pulse laser, the photoelectron decay process of anionic-cationic dye sensitized sample is the fastest. This indicates that the affection of anionic-cationic dye aggregates to the photoelectron decay is the biggest, and the sensitization is more efficient.

PHOTOPOLYMERIZATION OF MMA INITIATED BY CYANINE DYE AND HEXAARYLBIIMIDAZ0LE

The photoinitiating system composed of 1-ethyl-3'-methylthiacyanine bro-mide (C-I), 2-chlorohexaarylbiimidazole (o-Cl-HABI) and 3-mercapto-4-methyl-4H-1, 2, 4-triazole (MTA), which act as sensitizer, initiator and hydrogen-donor respectively, can beused to initiate the polymerization of methyl methacrylate (MMA). The kinetic study wascarried out in trichloromathane solution at 30℃ by using dilatometry. The relation be-tween the polymerization rate and the concentrations of C-I, o-Cl-HABI, MTA and MMAwas studied.

Geometry, Electronic Structure, and Related Properties of Dye Sensitizer： 3,4-bis[1- （carboxymethyl）-3-indolyl]- 1 H-pyrrole-2,5-dione

The geometry, electronic structure, polarizability and hyperpolarizability of dye sensitizer 3,4-bis[1-（carboxymethyl）-3-indolyl]-1H-pyrrole-2,5-dione （BIMCOOH） were studied using density functional theory （DFT） with hybrid functional B3LYP, and the electronic absorption spectra were investigated using semi-empirical quantum chemical method ZINDO-1 and time-dependent DFT （TDDFT）. The results of natural bond orbital suggest that the natural charges of the dione, indole, and acetic groups are about 0.15e, -0.29e, and 0.44e, respectively. The calculated isotropic polarizability, polarizability anisotropy invariant and hyperpolarizability are 305.4, 188.3, and 1155.4 a.u., respectively. The electronic absorption spectral features in visible and near-UV region were assigned to the π→π^＊ transition due to the qualitative agreement between the experiment and the TDDFT calculations, and the transitions of the excited states 9-11 related to photoinduced intramolecular charge transfer processes. The analysis of electronic structure and UV-Vis absorption indicates that the indole groups primarily contributed sensitization of photo-to-currency conversion processes, and the interracial electron transfer between semiconductor TiO2 electrode and dye sensitizer BIMCOOH are electron injection processes from excited states of the dyes to the semiconductor conduction band.

Density Functional Theory Study on Organic Dye Sensitizers Containing Bis-dimethylfluorenyl Amino Benzofuran

The geometries, electronic structures, polarizabilities and hyperpolarizabilities, as well as the UV-Vis spectra of the two organic dye sensitizers containing bis-dimethylfluorenyl amino benzofuran were studied via density functional theory （DFT） and time-dependent DFT. The features of electronic absorption spectra were assigned on account of the agreement between the experiment and the calculations. The absorption bands in visible region are related to photoinduced electron transfer processes, and the dimethylfluorenyl amino benzo[b]furan groups are major chromophore that contributed to the sensitization of photo-to-current conversion. The role of vinylene group in geometry, electronic structure and spectra property is analyzed according to the comparative study of the dyes.

Characteristics of Polyaniline/Si Heterojunction Solar Cell By Electrochemical Dye Sensitization

Using the electrochemical polymerization dye sensitization(ECDS) method, polyaniline(PAn), which is used as top region material in solar cells, is sensitized with direct blue dye(DS), and sensitized Al grid/DS-PAn/n-Si/Al heterojunction solar cells is prepared by ECDS. Influences of the ECDS on the absorption spectrum and the junction characteristics of the solar cell were discussed, and the output characteristics were measured. The results show that the absorption spectrum of the sensitized PAn films is much wider and stronger in Vis-range; the diode quality factor is about 6.3 and the height of latent barrier potential of p-n junction is 0.89eV; the short-circuit current and the conversion efficiency of sensitized DS-PAn/Si heterojunction solar cells are greatly improved, which the short-circuit current can increase 6 times, the fill factor is 57% and the efficiency can reach 1.42% under the illumination of 37.2W/m^2, respectively.

Preparation of Y^(3+)-doped Bi-_(2)MoO_(6) nanosheets for improved visible-light photocatalytic activity: Increased specific surface area, oxygen vacancy formation and efficient carrier separation

Although Bi_(2)Mo O_(6)(BMO) has recently received extensive attention, its visible-light photocatalytic activity remains poor due to its limited photoresponse range and low charge separation efficiency. In this work, a series of visible-light-driven Y^(3+)-doped BMO(Y-BMO) photocatalysts were synthesized via a hydrothermal method. Degradation experiments on Rhodamine B and Congo red organic pollutants revealed that the optimal degradation rates of Y-BMO were 4.3 and 5.3 times those of pure BMO, respectively. The degradation efficiency of Y-BMO did not significantly decrease after four cycle experiments. As a result of Y^(3+)doping, the crystal structure of BMO changed from a thick layer structure to a thin flower-like structure with an increased specific surface area. X-ray photoelectron spectroscopy showed the presence of highintensity peaks for the O 1s orbital at 531.01 and 530.06 eV, confirming the formation of oxygen vacancies in Y-BMO. Photoluminescence(PL) and electrochemical impedance spectroscopy measurements revealed that the PL intensity and interface resistances of composites decreased significantly, indicating reduced electron–hole pair recombination. This work provides an effective way to prepare high-efficiency Bibased photocatalysts by doping rare earth metal ions for improved photocatalytic performance.

Coumarin derivative dye sensitized NaYGdF4:Yb,Er nanoparticles with enhanced NIR Ⅱ luminescence for bio-vascular imaging

Lanthanide-doped biocompatible nanoparticles have promising applications in near-infrared second region imaging due to their high chemical stability,enhanced photostability and sharp emission bandwidth.However,the weak light absorption capacity limits the application of rare-earth nanoparticles(RENPs) for bioimaging.We prepared a coumarin-derived dye sensitized NaYGdF4:Yb,Er nanoparticle probe,in which the organic dye enhances photon absorption through the sensitization process,improving the luminescence efficiency of the rare earth particles near 1000 and 1500 nm.In addition,good water solubility and stability of the probe are imparted by coating the particles with amphiphilic polymers distearoyl phosphatidylethanolamine-polyethylene glycol(DSPE-PEG) and polyacrylic acid.This composite probe with good biocompatibility and NIR Ⅱ luminescence properties can be used for vascular imaging,providing a tool for the detection of hematologic-related diseases.

Double-layered TiO_(2) cavity/nanoparticle photoelectrodes for efficient dye-sensitized solar cells

TiO_(2) nanoparticles(NPs)in the size of-25 nm,namely P25,are very common material as the electron collecting layer in dye-sensitized solar cells(DSsCs).However,the light-scattering improvement of TiO2 NP photoelectrodes is stll a challenge.Here,we built TiO2 cavities on the top of the TiO2 NP layer by using carbonaceous microspheres as the template,forming the TiO_(2) cavity/nanoparticle(C/NP)photoelectrode for the application in DSSCs.The cavity amount in the TiO_(2) C/NP photoelectrode was controlled by adjusting the weight ratio of carbonaceous microspheres.SEM results confirm the successful formation of the double-layered TiO_(2) C/NP electrode.J-V tests show that the optimized TiO_(2) C/NP electrode prepared with 25 wt.%carbonaceous microspheres contributes to remarkable improvement of the short-circuit current density(Jsc)and the power conversion efficiency(PcE).The best photovoltaic performance solar cell with the PCE of 9.08%is achieved with the optimized TiO_(2) C/NP photoelectrode,which is over 98% higher than that of the TiO_(2) NP photoelectrode.Further investigations of UV-vis DRS,IPCE,OCVD,and EIS demonstrate that the competition between light scattering effect and charges recombination in this TiO_(2) C/NP photoelectrode is responsiblefor the PCE enhancement.

Solar cells based on doubly concerted companion dyes with the efficiencies modulated by inserting an ethynyl group at different positions

To develop efficient sensitizers for dye-sensitized solar cells(DSSCs),we recently reported doubly concerted companion(DCC)dye XW83 with a wrapped porphyrin sub-dye unit linked to an organic sub-dye unit through a flexible chain,which exhibits panchromatic absorption and excellent anti-aggregation ability.To further improve the absorption,we herein report XW87 and XW88 by inserting an ethynyl group into the organic sub-dye unit of XW83 near the donor and acceptor,respectively.For the corresponding organic dyes Z3 and Z4,the introduced ethynyl group improves their absorption,but induces aggravated charge recombination,leading to lowered power conversion efficiencies(PCEs).Similar to the organic dyes,the introduced ethynyl group improves the absorption of DCC dyes XW87 and XW88 as well.In addition,the ethynyl group near the acceptor of the organic sub-dye unit can be well protected by the long wrapping chains from the porphyrin unit.As a result,XW88 affords the highest JSC(21.84 mA/cm^(2)),V_(OC)(782 mV)and PCE(12.2%)among the DCC dyes.These results provide an effective method for developing efficient DSSC dyes by inserting an ethynyl group at a suitable position of a DCC dye.

Noble-metal-free dye-sensitized selective oxidation of methane to methanol with green light(550 nm)

Developing low-energy input route for conversion of methane(CH_(4))to value-added methanol(CH_(3)OH)at room temperature is important in environment and industry.Bonding in electron donor-acceptor hybrid can potentially promote charge transfer and photocatalytic efficiency of CH_(4) conversion.Herein,bonding in electron donor rhodamine B(RhB)-acceptor(TiO_(2))hybrid(RhB/TiO_(2))significantly promotes the selectivity of photocatalytic oxidation of CH4 to CH3OH and utilization of visible light(low-energy photons)at ambient condition.Even under green light irradiation(λ=550 nm),the noble-metal-free RhB/TiO_(2) hybrid synthesized presents enhanced oxidation of CH4 to CH_(3)OH with a generation rate of 143µmol·g^(−1)·h^(−1) and selectivity of 94%.This work demonstrates the possibility and feasibility of noble-metal-free catalysts for activating CH4 under visible light at room temperature.

Photocatalytic degradation of rhodamine B by dye-sensitized TiO_2 under visible-light irradiation

Perylene tetracarboxylic diimide (PTCDI),widely used in organic photovoltaic devices,is an n-type semiconductor with strong absorption in the visible-light spectrum.There has been almost no study of the PTCDI-sensitized TiO2 composite used to photocatalytically degrade pollutants.In this study,PTCDIand copper phthalocyanine tetrasulfonic acid (CuPcTs)-sensitized TiO2 composites were prepared using a hydrothermal method.The morphologies and structures of the two composites were characterized by X-ray diffraction,transmission electron microscopy,ultraviolet-visible spectroscopy,and fluorescence spectroscopy.The visible-light photocatalytic activities of the composites were evaluated using the degradation of rhodamine B as a model reaction.Results showed that dye-sensitized TiO2 samples had a wider absorption spectrum range and higher visiblelight photocatalytic activity compared to TiO2 samples.The double dye-sensitized (or co-sensitized) TiO2 composite with efficient electron collection exhibited higher photocatalytic activity than did the single dye-sensitized TiO2 composite.The electron transfer processes of single and double dye-sensitized TiO2 composites were illustrated according to band theory.

Effect of Mie resonance on photocatalytic hydrogen evolution over dye-sensitized hollow C-TiO_(2) nanoshells under visible light irradiation

Light utilization is one of the key factors for the improvement of photocatalytic perfo rmance.He rein,we design C-TiO_(2) hollow nanoshells with strong Mie resonance for enhanced photocatalytic hydrogen evolution in a dye-sensitized system under visible light irradiation(λ≥420 nm).By tuning the inner diameters of hollow nanoshells,the Mie resonance in hollow nanoshells is adjusted for better excitation of dye molecules,which thus greatly enhances the light utilization in visible light region.This work shows the potential of Mie resonance in nanoshells can be an alternative strategy to increase the light utilization for photocatalysis.

Printing photovoltaics by electrospray

Solution processible photovoltaics(PV)are poised to play an important role in scalable manufacturing of low-cost solar cells.Electrospray is uniquely suited for fabricating PVs due to its several desirable characteristics of an ideal manufacturing process such as compatibility with roll-to-roll production processes,tunability and uniformity of droplet size,capability of operating at atmospheric pressure,and negligible material waste and nano structures.This review begins with an introduction of the fundamentals and unique properties of electrospray.We put emphasis on the evaporation time and residence time that jointly affect the deposition outcome.Then we review the efforts of electrospray printing polymer solar cells,perovskite solar cells,and dye sensitized solar cells.Collectively,these results demonstrate the advantages of electrospray for solution processed PV.Electrospray has also exhibited the capability of producing uniform films as well as nanostructured and even multiscale films.So far,the electrospray has been found to improve active layer morphology,and create devices with efficiencies comparable with that of spin-coating.Finally,we discuss challenges and research opportunities that enable electrospray to become a mainstream technique for industrial scale production.

Analysis on dye-sensitized solar cells based on Fe-doped TiO_2 by intensity-modulated photocurrent spectroscopy and Mott-Schottky

The pure TiO2 and Fe salts [Fe（C2O4）3,5H2O]-doped TiO2 electrodes were prepared by the hydrothermal method. The pure TiO2 or Fe-doped TiO2 slurry was coated onto the fluorine-doped tin oxide glass substrate by the Doctor Blade method and then sintered at 450 ℃. The Mott-Schottks, plot indicates that the fiat band potential of TiO2 was shifted positively after Fe-doped TiO2. The positive shift of the fiat band potential improves the driving force of injected electrons from the LUMO of the dye to the conduction band of TiO2. This study shows that photovoltaic efficiency increased by 22.9% from 6.07% to 7.46% compared to pure TiO2, and the fill factors increased from 0.53 to 0.63.