Organic Dyes Containing Pyrenylamine‐Based Cascade Donor Systems with Different Aromatic π Linkers for Dye‐Sensitized Solar Cells: Optical,Electrochemical, and Device Characteristics

New organic dyes containing pyrenylamine donors in a cascade arrangement and cyanoacrylic acid acceptors have been synthesized and characterized by optical, electrochemical, and theoretical studies. The dyes inherit a D ‐π¹‐D ‐π²‐A (D=donor, A=acceptor) molecular architecture where the π linkers π¹ are changed from phenyl to biphenyl and fluorene, whereas the π linker π² that connects the donor fragment with the acceptor is a phenyl unit. The conjugation pathway linking the two donor segments has been found to play a major role in the optical and electrochemical properties. Shorter π linkers such as phenyl groups facilitate the donor–acceptor interaction while the nonplanar biphenyl spacer decreases the electronic communication between the donors and enhances the oxidation propensity of the corresponding dye. All the dyes display an intense longer wavelength electronic transition,which is attributable to the amine‐to‐cyanoacrylic acid charge transfer. The extinction coefficient of this peak grows dramatically on increasing the conjugation pathway length between the two donor segments. The dyes were used as sensitizers in nanocrystalline TiO₂‐based dye‐sensitized solar cells (DSSCs) and the cascade donor system contributed to the enhancement in the device efficiency due to favorable absorption and redox properties.     

Efficient NIR‐Light Emission from Solid‐State Complexes of Boron Difluoride with 2′‐Hydroxychalcone Derivatives

This article describes a series of nine complexes of boron difluoride with 2′‐hydroxychacone derivatives. These dyes were synthesized very simply and exhibited intense NIR emission in the solid state. Complexation with boron was shown to impart very strong donor–acceptor character into the excited state of these dyes, which further shifted their emission towards the NIR region (up to 855 nm for dye 5 b , which contained the strongly donating triphenylamine group). Strikingly, these optical features were obtained for crystalline solids, which are characterized by high molecular order and tight packing, two features that are conventionally believed to be detrimental to luminescence in organic crystals. Remarkably, the emission of light from the π‐stacked molecules did not occur at the expense of the emission quantum yield. Indeed, in the case of pyrene‐containing dye 4 , for example, a fluorescence quantum yield of about 15 % with a fluorescence emission maximum at 755 nm were obtained in the solid state. Moreover, dye 3 a and acetonaphthone‐based compounds 1 b , 2 b , and 3 b showed no evidence of degradation as solutions in CH₂Cl₂ that contained EtOH. In particular, solutions of brightly fluorescent compound 3 a (brightness: ε×Φ_f=45 000 M ^?1 cm^?1) could be stored for long periods without any detectable changes in its optical properties. All together, these new dyes possess a set of very interesting properties that make them promising solid‐state NIR fluorophores for applications in materials science.     

High efficiency ultra-deep dyeing of cotton via mercerization and cationization

A potentially environmentally responsible dyeing procedure for ultra-deep shades on cotton was developed using a cationization method in combination with mercerization. The effects of both treatments on dyeing performance and colorfastness properties of cotton fabrics dyed with reactive dyes were analyzed individually and in combination. Both mercerization and cationization have been proved to be effective in increasing the depth of shade on cotton. The colorfastness properties, except colorfastness to wet crocking, of mercerized–cationized cotton fabrics dyed without salt were much better than untreated cotton dyed using a conventional dyeing procedure. Unlike untreated cotton fabrics, the concentration of Na₂CO₃ in the dyeing process of mercerized–cationized cotton fabrics was lowered from 20 to 5 g/L without compromising dye fixation and colorfastness properties. With low concentrations of dyes and Na₂CO₃ and no electrolyte in the dye bath effluent, the dyeing procedure of mercerized–cationized cotton fabrics for ultra-deep shades is potentially a more environmentally benign method than conventional dyeing with reactive dyes.     

5-Phenyl-iminostilbene based organic dyes for efficient dye-sensitized solar cells

Four new 5-phenyl-iminostilbene dyes (ISB-3–6) containing electron-withdrawing benzo-[c][1,2,5]thiadiazole have been designed and synthesized for use as DSSCs. Their absorption properties and electrochemical and photovoltaic performances have been investigated systematically. Among these dyes, DSSCs based on a dye containing benzo-[c][1,2,5]thiadiazole and benzene moieties (ISB-4) showed the best performance: a short-circuit photocurrent density (J_sc) of 13.69 mA cm⁻², an open-circuit photovoltage (V_oc) of 722 mV, and a fill factor (FF) of 0.71, which corresponds to a power conversion efficiency (PCE) of 6.71%, under optimized conditions. Additionally, long-term stability of the ISB-4 based DSSCs with ionic-liquid electrolytes was demonstrated under 1000 h of light soaking, the photovoltaic performance is up to 5.75%. The results suggest that 5-phenyl-iminostilbene containing dyes are promising candidates for application in DSSCs.     

Pyrenoimidazole‐Based Deep‐Blue‐Emitting Materials: Optical,Electrochemical, and Electroluminescent Characteristics

A series of pyrenoimidazoles that contained various functional chromophores, such as anthracene, pyrene, triphenylamine, carbazole, and fluorene, were synthesized and characterized by optical, electrochemical, and theoretical studies. The absorption spectra of the dyes are dominated by electronic transitions that arise from the pyrenoimidazole core and the additional chromophore. All of the dyes exhibited blue‐light photoluminescence with moderate‐to‐high quantum efficiencies. They also displayed high thermal stability and their thermal‐decomposition temperatures fell within the range 462–512 °C; the highest decomposition temperature was recorded for a carbazole‐containing dye. The oxidation propensity of the dyes increased on the introduction of electron‐rich chromophores, such as triphenylamine or carbazole. The application of selected dyes that featured additional chromophores such as pyrene, carbazole, and triphenylamine as blue‐emissive dopants into multilayered organic light‐emitting diodes with a 4,4′‐bis(9H‐carbazol‐9‐yl)biphenyl (CBP) host was investigated. Devices that were based on triphenylamine‐ and carbazole‐containing dyes exhibited deep‐blue emission (CIE 0.157, 0.054 and 0.163, 0.041), whereas a device that was based on a pyrene‐containing dye showed a bright‐blue emission (CIE 0.156, 0.135).     

Synthesis,DFT calculations,cyclic voltammetry and antibacterial activities of a new blue-violet dye and a new blue-green fluorescent heterocyclic system

The new blue-violet dye 2-(3-hydroxyimino-2,3-dihydroimidazo[1,2-a]pyridin-2-yliden)-2-(2-thienyl)acetonitrile was prepared in high yield from the reaction of 3-nitroimidazo[1,2-a]pyridine with 2-(2-thienyl)acetonitrile by nucleophilic substitution of hydrogen. Acylation of the hydroxyl group led to a new heterocyclic system, (pyrido[2′,1′:2,3] imidazo[4,5-b]thieno[2,3-e]pyridine-11-carbonitrile) with very strong blue-green fluorescent properties. Physical, spectral and analytical data have confirmed the structures of the synthesized dyes. The optical and solvatochromic properties of these compounds were investigated and showed interesting photophysical properties. Density functional theory calculations of blue-violet and fluorescent dyes were performed to provide the optimized geometries, Mulliken atomic charges, relevant frontier orbitals and the prediction of ¹H NMR chemical shifts. The electrochemical properties of these dyes were investigated by cyclic voltammetry and an oxidation wave was observed at a half-wave potential of −0.143 V versus SCE for the blue-violet dye. Also, these new compounds exhibited potent antibacterial activity against Gram positive and negative bacterial species.     

Dipolar Compounds Containing Fluorene and a Heteroaromatic Ring as the Conjugating Bridge for High‐Performance Dye‐Sensitized Solar Cells

A novel series of dipolar organic dyes containing diarylamine as the electron donor, 2‐cyanoacrylic acid as the electron acceptor, and fluorene and a heteroaromatic ring as the conjugating bridge have been developed and characterized. These metal‐free dyes exhibited very high molar extinction coefficients in the electronic absorption spectra and have been successfully fabricated as efficient nanocrystalline TiO₂ dye‐sensitized solar cells (DSSCs). The solar‐energy‐to‐electricity conversion efficiencies of DSSCs ranged from 4.92 to 6.88 %, which reached 68–96 % of a standard device of N719 fabricated and measured under the same conditions. With a TiO₂ film thickness of 6 μm, DSSCs based on these dyes had photocurrents surpassing that of the N719‐based device. DFT computation results on these dyes also provide detailed structural information in connection with their high cell performance.     

A spectral approach to determine location and orientation of azo dyes within surfactant aggregates

The UV–vis absorption properties of azo dyes are known to exhibit a variation with the polarity and acidity of the dye environment. The spectral properties of a series of anionic azo dyes were characterized to further probe the interaction of these dyes with two types of surfactant aggregates: (1) the spherical micelles formed in aqueous solution by alkyltrimethylammonium bromide (C_nTAB) surfactants with n = 10–16 and (2) the unilamellar vesicles spontaneously formed in water from binary mixtures of the oppositely-charged double-tailed surfactants cationic didodecyldimethylammonium bromide (DDAB) and anionic sodium dioctylsulfosuccinate (Aerosol OT or AOT). The observed dye spectra reflect the solvatochromic behavior of the dyes and suggest the location and orientation of the dye within the surfactant aggregates. Deconvolution of the overall spectra into sums of Gaussian curves more readily displays any contributions of tautomeric forms of the azo dyes resulting from intramolecular hydrogen bonding. The rich variation in UV/vis absorption properties of these anionic azo dyes supports their use as sensitive tools to explore the nanostructures of surfactant aggregates.     

Time-dependent density functional theory investigations on structural modification in carbazole-based organic photosensitizers to improve electron injection in dye-sensitized solar cell

The time-dependent density functional theory approach, implemented at hybrid-B3LYP, GGA-PBE, and density functional-based tight binding levels of theory, was used to model photoinjection in organic dye/TiO₂ quantum dot to explore the prospects of improvement of dye-sensitized solar cell (DSSC). The photosensitizer used in this study consisted of six carbazole-based organic dyes, a cyanoacrylic acid group as an acceptor and an oligothiophene π-bridge spacer. The modifications were made in the dyes by increasing the length of the spacer by adding thiophene and oxadiazole rings at different positions of the donor-acceptor bridge. The structural variations appeared to alter the electronic and optical properties of dyes studied via energy levels and excitation spectra. The UV-Vis spectra calculated for all the dyes in solvents exhibited a red shift in spectral peaks with an increase in the polarity of the solvents. The findings of the study pointed toward the indirect photoinjection of the dye-(TiO₂)₉₆ complex for six different dyes. The substitution of the oxadiazole ring at the center and addition of a thiophene ring at the edge of the spacer produced two dyes that exhibited the lowest injection energies of 0.11 and 0.17 eV, along with the regeneration energies of 1.18 and 1.12 eV, respectively. The dyes reported here may have promising applications in photoanode for enhancing the performance of DSSC.     

Synthesis and evaluation of a series of symmetrical hot brand bis azo reactive dyes using 4,4′-methylene-bis-metanilic acid on various fibre

4,4′-Methylene-bis-metanilic acid (A) was synthesized by the reaction between metanilic acid and formaldehyde. The compound (A) was used as a bifunctional middle component in the preparation of several symmetrical hot brand bis azo reactive dyes. The compound (A) was tetrazotized and coupled with various m-nitro anilino cyanurated coupling component to give various hot brand bis azo reactive dyes. The entired compounds have been identified by IR, ¹H NMR spectra and elemental analysis. The dyes were applied on silk, wool and cotton fabrics and their fastness properties were evaluated. All the dyes give good fastness properties. The percentage dye bath exhaustion was also been studied.     

Enhanced visible light-driven photocatalytic degradation of crystal violet dye using Cr doped BaFe12O19 prepared via facile micro-emulsion route

The Cr ion doping effect on various properties of Cr doped BaCr_xFe_12-xO₁₉ nanoparticles was investigated, which were synthesized via a facile microemulsion approach and properties were studied using XRD, SEM, FTIR, Raman, photoluminescence and UV–visible techniques along with dielectric, optical and ferroelectric properties. The BaCr_xFe_12-xO₁₉ structure was hexagonal involving P63/mmc space group with average crystalline size of 9–18 nm. The NPs exhibited agglomerated platelet heterogeneous morphology. The presence of the Ba-O-Fe functional group was also confirmed by FTIR analysis. The PL analysis revealed that the doping reduced the recombination rate and charge (e^?-h⁺) separation is facilitated. The coercivity (H_c) and saturation polarization (Ps) increased with doping content and dielectric loss reduces with frequency and dopant concentration. The dopant contents also increased the AC conductivity and the optical bandgap found in 1.75–2.83 (eV) range. The BaCr_xFe_12-xO₁₉ exhibited a significantly higher photocatalytic efficiency versus BaFe₁₂O₁₉, and 91 % CV dye was degraded in 90 min under visible light irradiation. Additionally, a recycling experiment was conducted to confirm the stability of the prepared photocatalyst and Cr doped BaCr_xFe_12-xO₁₉ exhibited excellent stability and reusability. The Cr doping affected the dielectric, optical and ferroelectric properties and based on photocatalytic properties of BaCr_xFe_12-xO₁₉, it has potential applications for the destruction of dyes in wastewater under visible light exposure, which will make the process highly feasible for photocatalytic applications.     

Thieno[2,3-a]carbazole-based donor–π–acceptor organic dyes for efficient dye-sensitized solar cells

New donor–π–acceptor organic dyes K-1 and K-2 containing thieno[2,3-a]carbazole as an electron donor were designed and synthesized for dye-sensitized solar cells (DSCs). Photophysical and electrochemical properties of K-dyes were investigated. DSCs based on K-dyes showed a high conversion efficiency of 6.6–6.7% with a J_sc of 12.40–12.49 mA cm⁻² and a V_oc of 0.70–0.71 V. The molecular geometry calculation indicated that the existence of thienocarbazole donor in K-dyes enhanced the molecular planarity compared to the carbazole analogue dye MK-3. As a result, DSCs based on K-dyes showed high IPCEs, perhaps due to efficient intramolecular charge transfer and electron injection from excited dye to TiO₂ conduction band.     

Polymer gel/organic dye complexes in aqueous salt solutions

The present work is devoted to the study of the complex formation of polymer gel with organic dye and their properties in the aqueous salt solutions. Two systems were studied: 1) polyelectrolyte gel based on poly(diallyldimethylammonium chloride) and water soluble oppositely charged organic dyes (alizarin red S and catechol violet) and 2) organogel based on poly(N-vinylcaprolactam) and dithizone. The collapse of the polyelectrolyte gels in the presence of oppositely charged dyes together with the effective absorption of dyes was observed. The shrinking degree and the dye absorption by the gel depends on the dye concentration. In the case of PVCa gel in organic media the dye absorption takes place. The main attention has been concentrated on the study of the behaviour of gel/dye complex immersed in the salt solution if dye is the chelating ligand for metal ions. It was shown that polyelectrolyte gels generally form stable complexes with oppositely charged dyes. The behaviour of PVCa-dithizone-chloroform system was studied in AgNO₃ aqueous solution. The release of dithizone to the external aqueous solution of AgNO₃ reservoir is completely suppressed. Absorption spectra of gel/dye and gel/dye/metal ion systems were studied. It was shown that metal ions penetrate inside the gel phase and the dye/metal ion complexes form within the gel. The dependence of the optical density for the systems of gel/dye/metal ion on the salt concentration is observed.     

Synthesis and Characterization of Organic Dyes with Various Electron‐Accepting Substituents for p‐Type Dye‐Sensitized Solar Cells

Four new donor‐π‐acceptor dyes differing in their acceptor group have been synthesized and employed as model systems to study the influence of the acceptor groups on the photophysical properties and in NiO‐based p‐type dye‐sensitized solar cells. UV/Vis absorption spectra showed a broad range of absorption coverage with maxima between 331 and 653 nm. Redox potentials as well as HOMO and LUMO energies of the dyes were determined from cyclic voltammetry measurements and evaluated concerning their potential use as sensitizers in p‐type dye‐sensitized solar cells (p‐DSCs). Quantum‐chemical density functional theory calculations gave further insight into the frontier orbital distributions, which are relevant for the electronic processes in p‐DSCs. In p‐DSCs using an iodide/triiodide‐based electrolyte, the polycyclic 9,10‐dicyano‐acenaphtho[1,2‐b]quinoxaline (DCANQ) acceptor‐containing dye gave the highest power conversion efficiency of 0.08 %, which is comparable to that obtained with the perylenemonoimide (PMI)‐containing dye. Interestingly, devices containing the DCANQ‐based dye achieve a higher V_OC of 163 mV compared to 158 mV for the PMI‐containing dye. The result was further confirmed by impedance spectroscopic analysis showing higher recombination resistance and thus a lower recombination rate for devices containing the DCANQ dye than for PMI dye‐based devices. However, the use of the strong electron‐accepting tricyanofurane (TCF) group played a negative role in the device performance, yielding an efficiency of only 0.01 % due to a low‐lying LUMO energy level, thus resulting in an insufficient driving force for efficient dye regeneration. The results demonstrate that a careful molecular design with a proper choice of the acceptor unit is essential for development of sensitizers for p‐DSCs.     

Influence of electrodeposition conditions on the properties of CdTe films

The results of the influence of electrodeposition conditions on the structural, compositional, optical, and photoelectrochemical properties of CdTe thin films deposited in one-step electrochemical method are presented. The CdTe films were prepared electrochemically from aqueous acidic solution with low ratios of Cd²⁺ ions to Te(IV) ions concentration. Instead of commonly used TeO₂, water-soluble Na₂TeO₃ was used as a source of tellurium ions. The cathodic deposition of CdTe was performed at different constant potentials from solutions containing different cadmium and tellurium ions concentration. As-deposited CdTe thin films were studied by different analytical techniques. The X-ray photoelectron spectroscopy spectra exhibited CdTe formation on the electrode with some amount of tellurium oxides and cadmium oxides. The best quality CdTe deposits, free of TeO₂, were formed in bath containing excess of Cd²⁺ ions and at the potential of ?0.65 V vs. saturated calomel electrode, slightly more positive than E _eq of Cd/Cd²⁺ system. Structural X-ray diffraction studies revealed polycrystallinity of deposits with the highest content of the (111)-oriented cubic (111) form. Optical band gap energy values were found in the range from 1.36 to 1.6 eV for CdTe films prepared at various synthesis conditions. The preliminary photoelectrochemical studies have shown that the variation of the deposition potential as well as bath composition leads to the formation of p- or n-type CdTe films. As-deposited CdTe films were not stable in polysulfide solution under illumination.     

Selective encapsulation-release and photodegradation characteristics of organic dyes by cross-linked fluoroalkyl end-capped oligomeric nanocomposites possessing aromatic siloxane segments as core units

Cross-linked fluoroalkyl end-capped oligomeric nanocomposites possessing aromatic siloxane segments as core units [R_F-oligomer/Ar-SiO ₂ ] exhibited an encapsulation ability toward organic dyes such as methylene blue (MB), rhodamine B (RB), 4-hydroxyazobenzene-4′-sulfonic acid sodium salt, and methyl orange (MO). In these organic dyes, MB and RB are effectively encapsulated into these nanocomposites in aqueous solutions. R_F-oligomer/Ar-SiO ₂ nanocomposite-encapsulated organic dyes were found to exhibit a controlled releasing characteristic toward these encapsulated dyes, and encapsulated MB was not released into water; however, this encapsulated dye was smoothly released into acetone under similar conditions. Interestingly, R_F-oligomer/Ar-SiO ₂ nanocomposites possessing biphenylene segments as core units were able to exhibit not a photostable characteristic but extremely higher photodegradation ability toward MO under UV light irradiation.     

Effect of organic dye on the performance of dye-sensitized solar cell utilizing TiO2 nanostructure films synthesized via CTAB-assisted liquid phase deposition technique

This work is concerned with the growth of TiO₂ nanostructures as photovoltaic materials of dyesensitized solar cell (DSSC) via phase liquid deposition technique treated with CTAB surfactant. This work investigates the influence of organic dyes, N719, N3 and Z907 as photosensitizer on the photovoltaic parameters of TiO₂ nanostructures dye-sensitized solar cells (DSSCs). It also highlights the effect of the concentration of the best dye, N719 on the performance of the cell. The platinum films as counter electrode of the DSSC were prepared by sputtering platinum pellet on ITO substrate. The redox couple of the electrolyte utilized in the DSSC was iodide/triiodide. The cell sensitized with N719 dye demonstrated the best performance compared with the cell sensitized with another two dyes, N3 and Z907. This is due to N719 dye possess the highest optical absorption in visible region. The cell sensitized with 0.8 mM N719 dye performs the highest short-circuit current density, J _sc and power conversion efficiency, η since it posses the highest absorption in visible region. The DSSC utilizing 0.8 mM N719 dye demonstrated the highest J _sc and η of 6.48 mA cm^?2 and 1.69%, respectively.     

Novel multi-branched two-photon polymerization initiators of ketocoumarin derivatives

Novel multi-branched two-photon absorbing dyes containing highly efficient UV–vis curing initiator, ketocoumarin (3-acetyl-7-diethylaminocoumarin), were synthesized. There linear and non-linear optical properties were studied and the cooperatively enhanced two-photon absorption of two- and three-branched dyes were confirmed by femtosecond laser pulses. The largest two-photon absorption cross-section was obtained as 1117 GM. The results of photobleaching experiments showed that all dyes had very fast electron transferring speed with the commercial coinitiator o-Cl-hexaarylbisimidazoles (HABI). The two-photon polymerization initiated by a bimolecular system composed of the two-branched dye and HABI was investigated. This photopolymer system presented high photoinitiating efficiency. The single-shot two-photon exposure of the resin film was achieved with a threshold as 1 TW/cm² at 800 nm.     

Synthesis and applications of novel acceptor-donor-acceptor organic dyes with dithienopyrrole- and fluorene-cores for dye-sensitized solar cells

Four novel symmetrical organic dyes (S1-S4) configured with acceptor-donor-acceptor (A-D-A) structures containing electron donating fluorene (S1 and S2) and N-alkyl dithieno[3,2-b:2′,3′-d]pyrrole (DTP) (S3 and S4) cores terminated with two anchoring cyanoacrylic acids (as electron acceptors) were synthesized and applied to dye-sensitized solar cells (DSSCs). The DSSC device based on S2 dye showed the best photovoltaic performance among S1-S4 dyes: a maximum monochromatic incident photon-to-current conversion efficiency (IPCE) of 76%, a short circuit current (J_SC) of 12.27 mA/cm², an open circuit voltage (V_OC) of 0.61 V, a fill factor (FF) of 0.63, and an overall power conversion efficiency (η) of 4.73%. Besides, the utilization of chenodoxycholic acid (CDCA) as a co-adsorbent in the DSSC device based on S3 dye showed a significant improvement in its η value (from 3.70% to 4.31%), which is attributed to the suppression of dye aggregation on TiO₂ surface and thus to increase the J_SC value eventually.     

Crown ether styryl dyes

New crown ether-containing styryl dyes of the benzothiazole series containing an aza-15-crown-5-ether moiety were synthesized. Thetrans-cis-photoisomerization of these dyes and their analogs was studied; the effect of metal cations on the kinetics of darkcis-trans-isomerization was elucidated. The stability constants of the complexes of thecis-isomers of these dyes with Ca(ClO₄)₂ were estimated. The dramatic increase (by more than three orders of magnitude) in the stability of the complexes on passing from a cationic dye to a betaine was attributed to the formation of an intramolecular bond in thecis-complexes between the sulfo group of theN-substituent and the metal cation located in the cavity of the azacrown-ether moiety.