Reference Dye Research Articles

Ratiometric Singlet Oxygen Sensor Based on BODIPY-DPA Dyad.

Compounds sensitive to reactive oxygen species are widely used in the study of processes in living cells and in the development of therapeutic agents for photodynamic therapy. In the present work, we have synthesized a dyad in which the BODIPY dye is chemically bound to 9,10-diphenylanthracene (DPA). Here, DPA acts as a specific sensor of singlet oxygen and BODIPY as a reference dye. We studied the photophysical properties of the BODIPY-DPA dyad and showed that energy transfer occurs between the chromophores. As a result, the compound has excitation maxima in the absorption region of both DPA and BODIPY, but the fluorescence emission occurs mainly from BODIPY. In the presence of singlet oxygen, the excitation maximum of DPA decreases, while the intensity of the excitation maximum of BODIPY remains almost unchanged. This allows the BODIPY-DPA dyad to be used as a ratiometric sensor of singlet oxygen.

Efficient and tunable enhancement of NLO performance for indaceno-based donor moiety in A-π-D-π-D-π-A type first DSSC design by end-capped acceptors

The organic dyes with non-fullerene acceptors (NFAs) have aided in the creation of competitive organic solar cells (OSCs) with long-term sustainability. A series of NFA dyes (IDIC-R1-IDIC-R9) have been designed by varying the end-capped fluorinated moieties (PD1-PD6) at indaceno (IDIC) core. All the calculations were performed by density functional theory (DFT) and time-dependent DFT (TD-DFT)-based approaches. All the geometries were optimized at B3LYP/6-31G + (d,p) of DFT level at their ground state energies. Out of several density functionals, the CAM-B3LYP with 6-31G + (d,p) basis sets was selected after a benchmark study to carry out further calculations. All the dyes had their bandgaps in 0.11-3.12eV while their starting reference dye had a bandgap value of 2.01eV. Their ionization potential (IP) implied that these dyes have strong tendency to lose electrons. The λmax of the dyes was slightly redshifted from the IDIC (476nm) and IDIC-R (479nm) when changing solvent polarity from methanol to DCM and then chloroforms. The natural bond orbital (NBO) analysis showed the (S63)LP → (C61-C62)π* with highest stabilization energy. Their electron injection analysis showed that these dyes can be a good anode material against the aluminum and gold electrodes. The intramolecular charge transfer (ICT) process and stability of the dyes were investigated using frontier molecular orbital (FMO) and natural bond orbital (NBO) analysis. Among all dyes, IDIC-R8 has the highest linear polarizability and second-order hyperpolarizability (βtotal). All the dyes demonstrated promising non-linear optical (NLO) properties due to their low charge transfer barriers. Scientistswould be able to exploit these properties to identify the best NLO materials for existing applications.

Statistical Analysis and Optimization of the Brilliant Red HE-3B Dye Biosorption onto a Biosorbent Based on Residual Biomass.

Using various techniques, natural polymers can be successfully used as a matrix to immobilize a residual microbial biomass in a form that is easy to handle, namely biosorbents, and which is capable of retaining chemical species from polluted aqueous media. The biosorption process of reactive Brilliant Red HE-3B dye on a new type of biosorbent, based on a residual microbial biomass of Saccharomyces pastorianus immobilized in sodium alginate, was studied using mathematical modeling of experimental data obtained under certain conditions. Different methods, such as computer-assisted statistical analysis, were applied, considering all independent and dependent variables involved in the reactive dye biosorption process. The optimal values achieved were compared, and the experimental data supported the possibility of using the immobilized residual biomass as a biosorbent for the studied reference dye. The results were sufficient to perform dye removals higher than 70–85% in an aqueous solution containing around 45–50 mg/L of reactive dye, and working with more than 20–22 g/L of prepared immobilized microbial biosorbent for more than 9.5–10 h. Furthermore, the proposed models agreed with the experimental data and permitted the prediction of the dye biosorption behavior in the experimental variation field of each independent variable.

Advanced Dye Sorbents from Combined Stereolithography 3D Printing and Alkali Activation of Pharmaceutical Glass Waste.

Additive manufacturing (AM) technologies enable the fabrication of objects with complex geometries in much simpler ways than conventional shaping methods. With the fabrication of recyclable filters for contaminated waters, the present work aims at exploiting such features as an opportunity to reuse glass from discarded pharmaceutical containers. Masked stereolithography-printed scaffolds were first heat-treated at relatively low temperatures (680 and 730 °C for 1 h) and then functionalized by alkali activation, with the formation of zeolite and sodium carbonate phases, which worked as additional adsorbing centers. As-sintered and activated scaffolds were characterized in terms of the efficiency of filtration and removal of methylene blue, used as a reference dye. The adsorption efficiency of activated printed glass was 81%. The 3D-printed adsorbent can be easily separated from the solution for reuse.

Nanoliposomes for Sensing Local Osmolarity of the Tear Film on the Corneal Surface.

Purpose: Local hotspots of elevated tear hyperosmolarity (exceeding 900 mOsM) are predicted in dry eye disease (DED) but have not been measured. This study aims to develop, characterize, and evaluate the suitability of fluorescent nanoliposomes for noninvasive sensing of the local osmolarity of the tear film. Methods: Fluorescent nanoliposomes, loaded with calcein (susceptible to self-quenching; sensor dye) and sulforhodamine 101 (SR101; reference dye), were produced by the thin-film hydration method. Results: Dynamic light scattering measurements and Cryo-TEM showed that liposomes were negatively charged (-23.7 ± 1.5 mV), spherical (diameter = 117.9 ± 6.4 nm), and uniform in size (polydispersity index = 0.15 ± 0.02). These properties were unaffected by cold storage (4°C; 14 days), but dye leakage was significant after 3 days. Swelling and shrinkage of the liposomes by exposure to hypoosmotic and hyperosmotic media led to rapid dequenching and quenching of calcein fluorescence (FGreen), with no effect on SR101 fluorescence (FRed). The ratio FGreen/FRed decreased with increasing osmolarity and vice versa, obeying the Boyle van't Hoff relationship. When liposomes were dispersed in a gelatin film with dynamic radial sucrose gradients, local FGreen/FRed decreased with increasing hyperosmolarity as predicted. When instilled on the hydrophilic surface of contact lenses or ex vivo corneas, nanoliposomes dispersed evenly as thin films. Importantly, the measured FGreen/FRed declined continuously with evaporation and consequent increase in their osmolarities. Conclusions: The study provides proof of principle for noninvasive measurement of local tear film osmolarity based on osmosensitive fluorescent nanoliposomes. The strategy can potentially advance our understanding of the pathophysiology of DED.

Microenvironment‐Tailored Catalytic Nanoprobe for Ratiometric NIR‐II Fluorescence/Photoacoustic Imaging of H2O2 in Tumor and Lymphatic Metastasis

AbstractIn vivo H2O2 visualization is crucial for disease diagnosis. Catalytic reaction‐based probes show potential in H2O2 detection, yet their in vivo application remains challenging because catalysts always require a specific pH to function and cellular glutathione (GSH) may suppress signaling by depletion of hydroxyl radicals and oxidized substrates. Here, a microenvironment‐tailored catalytic nanoprobe (MTCN) comprising Fe2+, citric acid (CA), 2,2′‐azino‐bis(3‐ethylbenzothiazoline‐6‐sulfonic acid) diammonium salt (ABTS), and downconversion nanoparticles in the liposomal cavity as well as a reference dye in the lipid membrane is reported, which utilizes the selective permeability of the liposomal membrane to offer a favorable pH for Fe2+ catalyst with the aid of CA and to avoid GSH‐triggered signal loss by preventing entry of GSH into the cavity. The MTCN displays a large NIR‐II fluorescence (FL) ratio between 1550 and 1080 nm (FL1550Em,808Ex/FL1080Em,980Ex), but a small photoacoustic (PA) ratio between 808 and 1048 nm (PA808/PA1048). Upon exposure of MTCN to H2O2, catalytic conversion of ABTS into its oxidized form ABTS·+ with 808 nm absorption causes a noticeable increment in PA808/PA1048 accompanied by an apparent decrement in FL1550Em,808Ex/FL1080Em,980Ex, enabling bimodal ratiometric imaging of H2O2 in the tumor and lymphatic metastasis.

Sensors in a Flash! Oxygen Nanosensors for Microbial Metabolic Monitoring Synthesized by Flash Nanoprecipitation.

Flash nanoprecipitation (FNP) is an efficient and scalable nanoparticle synthesis method that has not previously been applied to nanosensor fabrication. Current nanosensor fabrication methods have traditionally exhibited poor replicability and consistency resulting in high batch-to-batch variability, highlighting the need for a more tunable and efficient method such as FNP. We used FNP to fabricate nanosensors to sense oxygen based on an oxygen-sensitive dye and a reference dye, as a tool for measuring microbial metabolism. We used fluorescence spectroscopy to optimize nanosensor formulations, calibrate the nanosensors for oxygen concentration determination, and measure oxygen concentrations through oxygen-sensitive dye luminescence. FNP provides an effective platform for making sensors capable of responding to oxygen concentration in gas-bubbled solutions as well as in microbial environments. The environments we tested the sensors in arePseudomonas aeruginosa biofilms andSaccharomyces cerevisiae liquid cultures—both settings where oxygen concentration is highly dependent on microbial activity. With FNP now applied to nanosensor fabrication, future nanosensor applications can take advantage of improved product quality through better replicability and consistency while maintaining the original function of the nanosensor.

Effect of direct linkage of pyrazole carboxylic acid acceptor/anchoring group on the photovoltaic performance for phthalocyanine-sensitized solar cells

An unsymmetrical zinc phthalocyanine dye (PCA-ZnPc-4) containing six electron donating hexylsulfanyl groups and a pyrazole-3-carboxylic acid anchoring group which is directly linked to the macrocycle was synthesized to evaluate the photophysical, electrochemical, and theoretical characteristics as well as photovoltaic properties. Previously studied dye PCA-ZnPc-2, which contains the same electron donating groups and pyrazole-3-carboxylic acid anchoring group with the bridging oxygen atom, was used as a reference dye. The optimized dye-sensitized solar cell (DSSC) based on PCA-ZnPc-4 exhibited an impressive power conversion efficiency of 2.52% (JSC = 6.53 mA cm−2, VOC = 0.584 V, FF = 0.66), exceeding that of the DSSC based on PCA-ZnPc-2 (1.86%) under the same conditions. The better photovoltaic performance of PCA-ZnPc-4 is mainly due to its conjugated anchoring group, leading to efficient electron injection. This work demonstrates that the anchoring groups attached to the macrocycle without oxygen linker may enhance the photovoltaic performance of the phthalocyanine-sensitized solar cells.

D-A-π-A organic dyes with fluorenyl-substituted bulky donor for efficient dye-sensitized solar cells

Improving light-harvesting efficiency and suppressing interfacial charge recombination are of paramount importance to the development of Cu (II/I) redox shuttle-based dye-sensitized solar cells (DSSCs). Here, we present a rational molecular engineering on D-A-π-A organic sensitizers featuring with fluorenyl-substituted bulky donor (HY57, HY60, and HY61) for Cu (II/I) mediated DSSCs. By gradually enhancing conjugation and rigidity of the π-spacer and auxiliary acceptor moieties, the light-harvesting and electron-injection efficiencies can be simultaneously improved. The large size of fluorenyl-substituted arylamine donor together with abundant alkyl chains decorated on the molecular structures assist dense assembly of dye monolayer at surface of nanocrystalline TiO2, which largely suppress interfacial charge recombination losses. When applied in Cu (II/I) mediated DSSCs, the combination of an auxiliary acceptor of phenanthrene-fused-quinoxaline (PFQ) and a π-spacer of cyclopentadithiophene (CPDT) in dye HY61 results in a simultaneous enhancement in short-circuit current (JSC) and open-circuit voltage (VOC), thus improving the power conversion efficiency (PCE) from 7.3% for reference dye HY59 to 10.3% for HY61. This study demonstrates that rigid and fused building block is promising towards constructing highly efficient organic sensitizers.

Adamantyl Side Chains as Anti-Aggregating Moieties in Dyes for Dye-Sensitized Solar Cells.

Designing and evaluating novel dye concepts is crucial for the development of the field of dye‐sensitized solar cells (DSSCs). In our recent report, the novel concept of tethering the anti‐aggregation additive chenodeoxycholic acid (CDCA) to dyes for DSSC was introduced. Based on the performance improvements seen for this modification, the aim of this study is to see if a simplified anti‐aggregation unit could achieve similar results. The following study reports the synthesis and photovoltaic characterization of two novel dyes decorated with the steric ethyladamantyl moiety on the π‐spacer, and on the triarylamine donor. This modification is demonstrated to be successful in increasing the photovoltages in devices employing copper‐based electrolytes compared to the non‐modified reference dye. The best photovoltaic performance is achieved by a device prepared with the adamantyl decorated donor dye and CDCA, this device achieves a power conversion efficiency of 6.1 % (Short‐circuit current=8.3 mA cm−2, Open‐circuit voltage=1054 mV, Fill factor=0.69). The improved photovoltaic performance seen for the adamantyl decorated donor demonstrate the potential of ethyladamantyl side chains as a tool to ensure surface protection of TiO2.

Bulky 3D Structures of Dithienopyrrol Dye with Copper(II/I) Redox Mediator Enabling Efficient Solar Cells with an Open-Circuit Voltage of 1.13 V

Efficiently suppressing on interface recombination of dye-sensitized solar cells (DSCs) enables high open-circuit photovoltage (Voc) through exploiting photosensitizers. Herein, a dithienopyrrol derivative photosensitizer C260A featuring a bulky auxiliary donor N-(2′,4′-bis(hexyloxy)-[1,1′-biphenyl]-4-yl)-2′,4′-bis(hexyloxy)-N-methyl-[1,1′-biphenyl]-4-amine (BP-DPA) and a traditional electron-acceptor cyanoacrylic acid (CA) was reported. Dye C260A with a bulky auxiliary donor moiety in the DSC outperforms the reference dye C260 with the state-of-the-art donor bis(4-(hexyloxy)phenyl)amine (DPA). Although the substitution of bulky auxiliary donor hardly alters the optical energy gap, C260A possesses prolonged equilibrium excited-state lifetimes in both dye-diluted solution and dye-grafted alumina film than the C260-based counterpart. These two photosensitizers are used to make coadsorbate-free, high-photovoltage-output DSCs in combination with a Cu(II/I) redox mediator. Electric and photophysical measurements show that the C260A-based DSC endows a higher charge collection efficiency and a lower charge recombination rate with the copper electrolyte than the C260-based counterpart. DSC with the bulky auxiliary donor-based photosensitizer C260A achieves a high open-circuit photovoltage of 1.13 V, yielding a good power conversion efficiency (PCE) of 10.3% at 100 mW cm–2, simulated AM1.5G conditions. The cosensitization of C260A with the perylene dye C272 obtains an efficient DSC with an impressive PCE of 11.0%.

Effects of swine microRNA mimics on lipopolysaccharide (LPS) induced inflammatory changes in 3D4/21 cells

There have been limited studies focused on validation of swine microRNAs (miRNA) with mRNA targets. The objective of this study was to validate a defined set of targets using artificial miRNA mimics transfected into cell lines to confirm specific targets of endogenous miRNAs after administration of Escherichia coli lipopolysaccharide (LPS). Sixteen hours after mimic transfection of 3D4/21 cell lines, the cells were stimulated with 1 μg/ml LPS or phosphate-buffered saline (PBS). The cells were harvested and collected at 0, 1, 3, and 8 h post administration. The selected genes DAD1, IL8, and ESR, which are involved in known pathways of inflammation. and are predicted or validated human targets of either miR-146a, let-7a, or miR-22-3p. These were then evaluated by quantitative real-time-PCR (qRT-PCR) to verify microRNA-mRNA interaction in swine. Using the ROX reference dye, mRNA changes in expression were assessed using the comparative CT Method (ΔΔCT method) for normalization against the PBS control group. DAD1 and ESR1 were negatively regulated by miR-22-3p and miR-146a-5p, respectively in 3D4/21 cells after LPS stimulation. However, miR-146a-5p may play an indirect positive regulatory role of both DAD1 and IL8 mRNA expression. Furthermore, we found an inverse relationship between LPS stimulation compared with the let-7a-5p overexpression with DAD1. Our inflammation study provides new evidence on the roles and predicted targets of miR-146a, let-7a, and miR-22-3p in swine.

Cost‐Effective Dyes Based on Low‐Cost Donors and Pd‐Free Synthesis for Dye‐Sensitized Solar Cells

The structural design of photosensitizers for dye‐sensitized solar cells (DSSCs) usually involves modification of the donor and π‐spacer moieties using expensive Pd crosscoupling reactions. Herein, the concept of more sustainable and cost‐effective dyes to realize large‐scale production is presented. Two dyes, coded BzC and PTZC, with low‐cost donors, phenyl and phenothiazine, respectively, and 4H‐cyclopenta[2,1‐b:3,4‐b’]dithiophene π‐spacer, are synthesized by Pd‐free reactions, including Horner–Wadsworth–Emmons, with high overall yield (68% for BzC and 55% for PTZC). The best photovoltaic performances exhibit 3.00% and 5.92% together with relatively low ideality factor of 1.03 and 1.12 for BzC and PTZC, respectively, indicating efficient retardation of electron recombination from surface trap states. Finally, the synthesis costs for BzC and PTZC are estimated to be about 7.5–9 times lower than that of LEG‐4 (as a commercial reference dye). The cost performances of BzC and PTZC are estimated to be around 5 times better than that of LEG‐4.

Ratiometric Optical Fiber Dissolved Oxygen Sensor Based on Fluorescence Quenching Principle.

In this study, a ratiometric optical fiber dissolved oxygen sensor based on dynamic quenching of fluorescence from a ruthenium complex is reported. Tris(4,7-diphenyl-1,10-phenanthrolin) ruthenium(II) dichloride complex (Ru(dpp)32+) is used as an oxygen-sensitive dye, and semiconductor nanomaterial CdSe/ZnS quantum dots (QDs) are used as a reference dye by mixing the two substances and coating it on the plastic optical fiber end to form a composite sensitive film. The linear relationship between the relative fluorescence intensity of the ruthenium complex and the oxygen concentration is described using the Stern–Volmer equation, and the ruthenium complex doping concentration in the sol-gel film is tuned. The sensor is tested in gaseous oxygen and aqueous solution. The experimental results indicate that the measurement of dissolved oxygen has a lower sensitivity in an aqueous environment than in a gaseous environment. This is due to the uneven distribution of oxygen in aqueous solution and the low solubility of oxygen in water, which results in a small contact area between the ruthenium complex and oxygen in solution, leading to a less-severe fluorescence quenching effect than that in gaseous oxygen. In detecting dissolved oxygen, the sensor has a good linear Stern–Volmer calibration plot from 0 to 18.25 mg/L, the linearity can reach 99.62%, and the sensitivity can reach 0.0310/[O2] unit. The salinity stability, repeatability, and temperature characteristics of the sensor are characterized. The dissolved oxygen sensor investigated in this research could be used in various marine monitoring and environmental protection applications.

Data-Driven and Multiscale Modeling of DNA-Templated Dye Aggregates.

Dye aggregates are of interest for excitonic applications, including biomedical imaging, organic photovoltaics, and quantum information systems. Dyes with large transition dipole moments () are necessary to optimize coupling within dye aggregates. Extinction coefficients () can be used to determine the of dyes, and so dyes with a large (>150,000 M−1cm−1) should be engineered or identified. However, dye properties leading to a large are not fully understood, and low-throughput methods of dye screening, such as experimental measurements or density functional theory (DFT) calculations, can be time-consuming. In order to screen large datasets of molecules for desirable properties (i.e., large and ), a computational workflow was established using machine learning (ML), DFT, time-dependent (TD-) DFT, and molecular dynamics (MD). ML models were developed through training and validation on a dataset of 8802 dyes using structural features. A Classifier was developed with an accuracy of 97% and a Regressor was constructed with an of above 0.9, comparing between experiment and ML prediction. Using the Regressor, the values of over 18,000 dyes were predicted. The top 100 dyes were further screened using DFT and TD-DFT to identify 15 dyes with a relative to a reference dye, pentamethine indocyanine dye Cy5. Two benchmark MD simulations were performed on Cy5 and Cy5.5 dimers, and it was found that MD could accurately capture experimental results. The results of this study exhibit that our computational workflow for identifying dyes with a large for excitonic applications is effective and can be used as a tool to develop new dyes for excitonic applications.

DFT exploration to tune the silyl group as anchoring unit on the performance of dye-sensitized solar cells: an approach to suppress dye leaching from semiconductor surface.

In this work, we report the lower stability of dyes containing cyanoacrylic acid anchoring group on semiconductor TiO2 surface compared to the corresponding silyl unit in dye-sensitized solar cell. Density functional theory (DFT) calculations have been performed with simple donor (N,N diphenylamine) and π-conjugated spacers, with silyl anchoring groups to examine the efficiency of DSSCs. The calculated results in CAM-B3LYP/6-31G(d)/CPCM(THF) reveal that the cyanoacrylic acid anchoring group would have weaker coordination on semiconductor TiO2 surface compared to the silyl anchoring group on the same surface. The designed dyes 1-7 exhibit comparable or in cases superior optical properties than that of the reference dye molecule with cyanoacrylic acid as an anchoring group. All designed dyes have lower ΔGrejection values implying efficient and faster electron recombination between the dye and electrolyte. The electron transition coefficient for these dyes is higher enough (~72-87%) suggesting successful electron propagation from dye to the semiconductor. The electron-donating methyl and ethyl groups show lower ΔGrejection values than the commonly studied -OEt substitution with the silyl anchoring group. The extended π conjugation for better electronic propagation and higher λmax values have been achieved with simple ethylene and butadiene units in the dye molecules. Dye 7 with butadiene as π-spacer unit shows superior oscillatory strength (f) of 2.19 and light-harvesting efficiency (LHE) of 0.99 than the other studied dyes and reference dye with carboxylic anchoring group (TA-ST-CA). The lowest ΔGrejection value (0.53 eV) of dye 7 suggests better electronic recombination than all the other dyes studied here. Transition Density matrix and PDOS calculations with the representative dye 7 suggest a good electronic propagation from the dye to the semiconductor. The incorporation of a highly π-conjugated spacer 4,8-di(thiophen-2-yl)-1H,5H-benzo[1,2-c:4,5-c']bis([1,2,5]thiadiazole) in dye 7 (7-BBT) showed remarkable enhancement in the absorption maxima ~800 nm corresponds to the UV-vis and NIR regions. The DFT calculated results shed light on designing new DSSCs with silyl anchoring groups for enhanced stability and superior efficiency.

Highly Efficient Sulfur and Nitrogen Codoped Graphene Quantum Dots as a Metal-Free Green Photocatalyst for Photocatalysis and Fluorescent Ink Applications.

The demand for modern organic pollutant treatment has prompted the development of environmentally acceptable photocatalytic processes. In this work, we report novel nitrogen and sulfur codoped graphene quantum dot (S,N-GQD) based photocatalysts and fluorescent ink for the first time. For the degradation of organic dyes under visible irradiation, a hydrothermal technique was employed to generate S,N-GQD green nanomaterials. The synthesized samples were examined using XRD, HR-TEM, EDX, FT-IR, PL, and UV–vis spectroscopy. UV-DRS was used to determine the energy band gap of S,N-GQDs, and it was obtained to be around ∼2.54 eV. To explore the catalytic behavior of the produced S,N-GQDs as green nanomaterials, organic dyes (i.e., crystal violet and Alizarin yellow) have been used as a reference dye in this study. Using several radical scavenging agents, the photocatalytic mechanism was examined. This novel photocatalyst offers a promising alternative for the breakdown of organic pollutants. Moreover, these S,N-GQDs can also be used as fluorescent ink for imaging purposes and security reasons.

Pyridyl anchored indolium dyes for the p-type dye sensitized solar cell

Three new thiophenyl bridged triarylamine-donor based dyes with pyridyl anchoring groups and indolium acceptors have been synthesized and studied as sensitizers for the p-type dye-sensitized solar cell (p-DSSC). Compared to known dicyano and pyridinium dyes with the same triarylamine cores, these new sensitizers have broadened and red-shifted UV–vis absorption spectra, with high extinction coefficients and absorption extending beyond 700 nm. TD-DFT calculations on the indolium family indicate that these dyes combine strong donor acceptor communication, with a high degree of charge separation in the excited state – an ideal combination for sensitizer dyes. The phenylpyridyl anchored bis-indolium gives the highest power conversion efficiency (0.097%) through a short circuit photocurrent (JSC) of 3.04 mA cm−2, open circuit voltage (VOC) of 97 mV and fill factor of 36%. This exceeds the performance of the P1 reference dye in this study, and represents the best performance so far for a cationic, pyridine anchored p-DSSC dye.

Theoretical design of new carbazole based organic dyes for DSSCs applications. A DFT/TD-DFT insight

New series of organic dyes Mi (i = 2–10) derived from M1 have been investigated by using density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods, to find out the effect of different internal acceptor groups on their efficiency in DSSCs. The geometries, electronic structures, absorption spectra, dipole moments, and molecular electrostatic potential of these isolated dyes and dye-(TiO2)6 systems were investigated and discussed. Besides, some quantify parameters influencing the power conversion efficiency (PCE) such as light-harvesting efficiency (LHE), electron injection driving force (ΔGinject) and regeneration driving force (ΔGreg) were also calculated to examine the most appropriate organic dyes for DSSC applications. Theoretical results indicated that all designed dyes exhibit a significant decrease in the gap energy with increasing dipole moments, and red-shifted absorption spectra (except that M2 is blue shifted) compared to M1 (reference dye), which revealed that these designed dyes are promising candidates for DSSC applications. Accordingly, the introduction of new internal acceptor group in D-A-π-A structure may be the best strategy for improving the photovoltaic performances.

Experimental and theoretical study of organic sensitizers for solid-state dye-sensitized solar cells (s-DSSCs)

The effect of a series of triarylamine based D-π-A organic dyes, namely RK1, BA504, BA741 and the simple L1 reference dye on solid-state dye sensitized solar cells (s-DSSCs) performances was studied. The solid hole transporting material (HTM) was obtained by in-situ photoelectrochemical polymerization (in-situ PEP) process applied in two different media (water and acetonitrile) to produce the poly-3,4 ethylenedioxythiophene (PEDOT) conducting polymer (CP). A joint experimental and theoretical (density functional theory and time-dependent density functional theory) study is conducted to correlate the dye molecular structure containing different donor, π-bridge or acceptor with several physicochemical characteristics such as optical (absorption and emission), electronic and redox properties of dyes in organic and aqueous medium; in-situ PEP process and charge transfer kinetics at the DSSC interfaces (Dye/TiO2 and Dye/HTM) through the alignment of the different energy levels of the dyes and electrodes. These properties are considered since they govern the performance of s-DSSCs denoted by the short-circuit current (Jsc), open circuit cell potential (Voc) and fill factor (FF). Among the four studied dyes, the s-DSSCs based on RK1, shows the best power conversion efficiency of 1.75% resulting from highest FF (0.57), Voc (550 mV) and Jsc (5.6 mA/cm2). The large differences in experimental photovoltaic performances of the obtained s-DSSCs have been well outlined and provide the guidelines for future development of more efficient solar-cell sensitizers.