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The structural and electronic properties of well-known 4,4′-(4-(5-(2,2-dicyanovinyl)thiophen-2-yl)phenylazanediyl)dibenzoic acid ( O2) and its hypothetical dyes O3- O7 were investigated by computational techniques. The absorption properties were probed. By replacing the 2-methylidenepropanedinitrile acceptor with 1,3-diethyl-5-methylene-2-thioxo-dihydropyrimidine-4,6(1 H,5 H)-dione, the molecular orbital energy levels were well tuned. The modified dyes meet the basic requirements of both -Δ Ginj and -Δ Greg being over 0.2 eV for an efficient hole injection and dye regeneration, respectively. All the designed p-type dyes O3- O7 have smaller energy gap and significant red shift in absorption spectra than that of the reference O2. Finally, our results suggested that O3- O7 have larger light-harvesting efficiencies (LHE) in the visible spectral regions of 400 nm to 700 nm than O2. Among all the dyes, O5 is expected to have an excellent performance as a p-type sensitized dye in solar cells due to its great LHE and sufficient hole injection efficiency. [ABSTRACT FROM AUTHOR]

A Photoanode in dye sensitized solar cell is responsible for photoabsorption and conduction of the generated electrons for which TiO 2 is a highly employed material due to its non-toxic nature and low cost. This study reports a convenient and facile method to prepare un-doped and magnesium (Mg) doped TiO 2 thin films using Aerosol assisted Chemical Vapor deposition on Indium doped Tin oxide substrates. The as prepared films were subjected to morphological and structural characterizations as well as the optical absorption, band gap and surface area measurements of films. The studies indicated that Mg substituted Ti in the TiO 2 lattice and formed new energy levels which decreased the band gap of the doped films. Moreover, increasing the concentration of Mg shifted the optical absorption of the films from ultra-violet region to the visible region. The IV measurements of the DSSCs fabricated using 2 mol% Mg doped TiO 2 film, N719 dye, I − /I 3 − redox electrolyte and platinum sputtered on ITO counter electrode, revealed approximately twofold increase in overall efficiency of DSSCs as compared to undoped TiO 2 based DSSC. The increase in V oc and J sc , as well as the efficiency of 6.1%, is an indication that 2 mol% Mg doped TiO 2 film is a potential candidate as a photoanode material in DSSC. [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]

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]

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]

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]

Based on a prototype sensitizer W2, we designed triarylamine-based p-type sensitizers W2-1 to W2-7 that contain modified π-spacers (π'), a π-spacer and two anchors. For W2-1 to W2-4, instead of 2,1,3-benzothiadiazole in W2, thieno[3,4-b]-1,4-dioxin, thiophene, thieno[3,4-c][1,2,5]thiadizole, thiazolo[5,4-d]thiazole are π' and thiophene as π-spacer. For W2-5 to W2-8, π' and π are same, with 2,1,3-benzothiadiazole, thieno[3,4-b]-1,4-dioxin, thieno[3,4-c][1,2,5]thiadiazo, thiazolo[5,4-d]thiazole, respectively, as the π'-spacers. Structure optimization, electronic level and absorption characters were calculated with density functional theory (DFT) and time-dependent DFT (TDDFT) at the CAM-B3LYP/6-311G (d,p). The solvent effect was involved using a polarized continuum model in chloroform. The results showed that the highest occupied molecular orbital and the lowest unoccupied molecular orbital guarantee sufficient hole injection (lower than -0.2 eV), and dye regeneration (lower than -0.2 eV). W2-4 has higher light-harvesting efficiency (LHE) (0.994) and larger overlap with the visible light from 400 nm to 600 nm. Finally, the results suggest that the driving force of hole injection, dye regeneration and charge recombination (ΔGinj, ΔGreg and ΔGCR) of W2-4 are the best, with more negative ΔGinj (-4.33), ΔGreg (-1.74) and more positive ΔGCR (1.92). Replacing 2,1,3-benzothiadiazole with thiazolo[5,4-d]thiazole as π'-spacers is a effective way to improve the performance of the dyes. An introduction of thiazolo[5,4-d]thiazole group can improve the absorption ability and hinder charge recombination.Absorption spectra of p-type D-π-A sensitizers with modified π-spacers [ABSTRACT FROM AUTHOR]