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This paper presents a simple, low cost method of synthesizing TiO2 nanoparticles by sol-gel method, where titanium isopropoxide is used as a starting material. Further, same TiO2 is used to sensitize 2-cyano-3- (4-(7-(5-(4- (diphenylamino) phenyl)-4- octylthiophen-2-yl) benzo[c] [1, 2, 5] thiadiazol-4- yl)phenyl) acrylic acid (RK-1 dye) and Di-tetrabutylammonium cis-bis (isothiocyanato) bis (2,2'-bipyridyl- 4,4'-dicarboxylato) ruthenium(II) (N-719 dye) for light harvesting applications. Anatase structure and average particle size of 7.3 nm were confirmed from XRD pattern. From SEM, it was noticed that particles were of varying size and shape and aggregation with clear porosity. FTIR spectra reveal Ti-O bond corresponding to 483 cm - 1 and from UV-Vis absorption, energy band gap was found to be 3.2 eV. Photocurrent density (J) - photovoltage (V) characteristic of DSSC of different thicknesses of TiO2 were obtained, it was observed that optimum solar energy to electricity conversion efficiency (η) for RK-1 dye and N- 719 dye 4.08 % and 5.12 % with TiO2 thickness of 5.4 pm and 8.6 ym respectively under AM 1.5 irradiation (1000 W/m2) conditions. [ABSTRACT FROM AUTHOR]

Pt/Pd hollow nanofibers were obtained by sputtering a Pt/Pd alloy (80/20 wt%) onto polymer nanofibers (used as sacrificial template) and were used as counter-electrodes (CEs) in dye-sensitized solar cells (DSSCs). We demonstrate that optimization of nanofiber density and Pt/Pd sputtering thickness can increase the short circuit current density and consequently lead to a ∼15% enhancement in power conversion efficiency (PCE), when compared to the commonly used flat Pt/Pd CEs with the same thickness. The processes that contribute to such PCE improvement are: (i) increased surface area provided by the high aspect ratio hollow nanofibers and (ii) improved electro-catalytic performance, as validated by electrochemical impedance spectroscopy (EIS) measurements. The latter showed a two-fold decrease in the charge-transfer resistance of the nanostructured-CE, compared to the flat CE. The contribution of the Pt/Pd hollow nanofiber to light scattering was negligible as shown by reflectance measurements. These results suggest a simple and straightforward strategy to increase PCE in DSSCs, to minimize the use of precious metals used in this kind of devices and, more generally, to tailor the CE structure in photoelectrochemical systems to boost their functional properties, thanks to the advantages afforded by this complex morphology. [ABSTRACT FROM AUTHOR]

In this work we investigate electrolyte degradation mechanisms in a Dye Sensitized Solar Cell (DSSC), when stressed under forced reverse bias (RB) conditions. During the stress test, we observe a gradual and visually evident cluster shaped browning of platinised counter-electrode in contact with electrolyte solution; Raman spectroscopy confirms that the observed phenomena is due to formation of polyiodide ions and reveals an arose marked fluorescence background, stemming from new chemical species induced by RB stress test. Raman and fluorescence measurements on RB stressed model electrolyte solutions reveal that photoluminescence emission is mainly related to degradation mechanisms involving the I − /I 3 - redox couple. In fact, due to the RB stress, the redox couple is unbalanced and the formation of various associated structures between 1-methyl-3-propyl imidazolium iodide (PMII) ions is favored. This can be detected by observing the Red Edge Effect (REE) in fluorescence emission spectra of stressed solutions. Thus, polyiodides formation in RB stressed DSSCs could be added to the several depletion channels of triiodide anions and should be taken into account in designing new stable and efficient electrolytes. [ABSTRACT FROM AUTHOR]

Highlights: [•] A colloidal TiO2 ink assists the low temperature manufacturing of photoanodes. [•] The ink key component is a TiO2 colloid stabilized with 3,6,9-trioxadecanoic acid. [•] 3,6,9-Trioxadecanoic acid was linked to titania colloid through labile hydrogen bonds. [•] The optimized ink has a simple composition, high stability and homogeneity. [•] DSSCs had a 5.6% efficiency after a soft thermal treatment (140°C). [ABSTRACT FROM AUTHOR]

Due to their low cost, facile fabrication, and high-power conversion efficiency (PCE), dye-sensitized solar cells (DSSCs) have attracted much attention. Ruthenium (Ru) complex dyes and organic solvent-based electrolytes are typically used in high-efficiency DSSCs. However, Ru dyes are expensive and require a complex synthesis process. Organic solvents are toxic, environmentally hazardous, and explosive, and can cause leakage problems due to their low surface tension. This review summarizes and discusses previous works to replace them with natural dyes and water-based electrolytes to fabricate low-cost, safe, biocompatible, and environmentally friendly DSSCs. Although the performance of "eco-friendly DSSCs" remains less than 1%, continuous efforts to improve the PCE can accelerate the development of more practical devices, such as designing novel redox couples and photosensitizers, interfacial engineering of photoanodes and electrolytes, and biomimetic approaches inspired by natural systems. [ABSTRACT FROM AUTHOR]

Abstract: We report the improvement of the operational stability of dye-sensitized solar cells (DSSCs) by incorporating multi-wall carbon nanotubes (MWCNTs) in conventional nanostructured semiconducting TiO2 photoanodes. DSSCs were prepared by adding various concentrations of MWCNTs (up to 1.0% wt.) to TiO2 anatase nanoparticles. Optimization of MWCNT concentration leads to photoconversion efficiency as high as 4.1% as opposed to 3.7% for pure TiO2 photoanodes. The performance of the solar cells was measured for 10 consecutive days of continuous ambient light exposure. MWCNT addition results in the decrease of efficiency from 4.1% to 3.7%, while a decrease from 3.7% to 2.4% was recorded in pure TiO2 photoanodes. These results are encouraging toward the commercial exploitation of DSSCs. [Copyright &y& Elsevier]

Abstract: We report the preparation of nanoporous TiO2 electrode modified with an insulating material—BaCO3 and used as electrode for quasi solid state dye sensitized solar cells (DSSCs), with a benzothiadiazole-based dye (BTDR2) as sensitizer and PEDOT:PSS coated FTO as counter electrode. We found that the BaCO3 modification significantly increases the dye adsorption, resulting from the fact that the surface of BaCO3 is more basic than TiO2. The performance of the DSSCs with and without BaCO3 modified TiO2 electrodes were analyzed by cyclic voltammograms, optical absorption spectra, current–voltage characteristics in dark and under illumination and electrochemical impedance spectra. The photovoltaic performance has been significantly improved for the BaCO3 modified electrode as compared to bare TiO2 electrode having the same other components in the DSSCs. The value of the overall power conversion efficiency (η) improves from 2.42% to 4.38% under illumination intensity, when BaCO3 modified electrode is used instead of bare TiO2 electrode. The improvement in η has been attributed to the increased dye adsorption, reduction in recombination rate and enhancement in the electron lifetime when the modified TiO2 electrode is used. [Copyright &y& Elsevier]

• Designed and synthesized six new metal-free 2-cyanoacetanilide based organic dyes (SA1-6) for DSSC application. • All the dyes possess the thermodynamic requirements to be used as DSSCs. • The dyes SA4-6 bearing pyridine moiety showed better efficiency than that of dyes SA1-3 with nitro group. • SA1 co-sensitized with HD-2 displayed the best efficiency (η) of (8.02%) with increasing in both V OC (0.68 V) and J SC (20.33 mA/cm2). The design, synthesis and photovoltaic performance of metal-free 2-cyanoacetanilide based organic dyes, SA1-6 have been reported as sensitizers / co-sensitizers in dye sensitized solar cells (DSSCs). All dyes possess the thermodynamic requirements to be applied in DSSCs. The DFT and TD-DFT calculations were completed using Guassian09 package software. The obtained results showed appropriate charge separation between the ground state oxidation potential (GSOP) and excited state oxidation potential (ESOP) levels of the dyes. In addition, there was a good a greement between the theoretical and experimental data. Over co-sensitization, SA1-6 exhibited better efficiency than the main sensitizer HD-2. Among the dyes we synthesized, SA1 displayed improved PCE of 8.02 % with increasing in both V OC value of 0.682 V and J SC value of 20.33 mA/cm2, whereas the DSSC fabricated with dye HD-2 alone showed PCE of 7.49 % with J SC of 19.01 mA/cm2 and V OC of 0.63 V. Finally, Electrochemical impedance spectroscopy measurements, beside electron lifetimes of SA1-6 and HD-2 , were obtained and are in good agreements with the experimental photovoltaic parameters. [ABSTRACT FROM AUTHOR]

Dye-sensitized solar cells (DSSCs) are a promising third-generation photovoltaic cell technology whose advantages are low-cost fabrication, reduced energy payback time, better performance under diffuse light conditions and flexibility. Typically DSSCs employ toxic dyes such as metal-based porphyrins requiring complex synthesis. In contrast, natural pigments are environmentally and economically superior to synthetic dyes. However, narrow absorption spectra of natural pigments result in low efficiencies of the solar cells. Hence, co-sensitizing pigments with complementary absorption spectra, which increases the absorption band, is an attractive pathway to enhance the efficiency. In this paper, we report the performance of betanin-chlorophyll co-sensitized solar cell using betanin (λmax = 535 nm) and chlorophyll-a (λmax = 435 nm, 668 nm), natural pigments having complementary absorption spectra. Density functional theory simulations were performed to verify that the lowest unoccupied molecular orbital and the highest occupied molecular orbital levels of the dye molecules, are aligned appropriately with that of TiO2 and the redox electrolyte, respectively, which is necessary for optimal device performance. Electrochemical impedance spectroscopic studies were performed to determine parameters corresponding to the charge transfer processes in the dye solar cells. Individual and co-sensitized solar cells were fabricated and the co-sensitized solar cell demonstrated a higher efficiency of 0.601% compared to efficiencies of 0.562% and 0.047% shown by betanin and chlorophyll solar cells, respectively. [ABSTRACT FROM AUTHOR]