Dye Loading Time Research Articles

Influence of functionalized diketopyrrolopyrrole sensitizer on the performance of CdS nanowire based-DSSC applications

Synthesis of chromophore (E)-2-(2-(2-(5-(2,5-bis(2-ethylhexyl)-3,6-dioxo-4-(thiophen-2-yl)-2,3,5,6 tetrahydropyrrolo [3,4-c] pyrrol-1-yl) thiophen-2-yl) vinyl)-4H-chromen-4 ylidene) malononitrile (DPP-CM-CN) has been designed and achieved in multistep reaction strategy. The experimental, photophysical and electrochemical properties along with theoretical calculations were explored. DPP-CM-CN dye was – chemically anchored on CdS nanowires (NWs) to investigate its influence on the dye-sensitized solar cell (DSSC) applications. Under the illumination of standard sunlight conditions, the photovoltaic performance of DPP-CM-CN based CdS nanowire device displayed a power conversion efficiency (PCE) of 0.38 %, which is 3.30 times higher as compared to a bare CdS nanowire (0.115 %) based DSSC device; ascribed to the dye loading time on CdS nanostructures. The present results suggest the potential ability of DPP-CM-CN to enhance DSSC device efficiency and reveal the importance of dye molecules in device fabrication, a key step towards the development of DSSC technology.

2,1,3-Benzothiadiazole-based bis-silylated compounds: Synthesis and use in the preparation of highly fluorescent low-contend organic–inorganic hybrid materials

Herein, we report the synthesis of bis-silylated 2,1,3-benzothiadiazole derivatives and their use in the preparation of photoactive organic–inorganic hybrid materials with extremely low fluorophore/tetraethylorthosilicate molar ratios. The organic compounds were synthesized in good to excellent yields (55 %-94 %) using Pd-catalyzed Sonogashira cross-coupling as the key step. The bis-silylated benzothiadiazoles exhibited absorption in the UV-A region (∼376 nm), attributed to fully spin- and symmetry-allowed π-π* electronic transitions. An emission located in the blue-cyan region with a high quantum yield and large Stokes shift was observed, most likely due to a charge-transfer mechanism in the excited state. BTD-containing hybrid materials were obtained through a sol–gel process, for which the dye loading and aging time were studied. Optimal reproducibility of the photophysical results was achieved when the sol–gel reaction was conducted for 10 d at 60 °C. In the solid state, the obtained hybrid materials exhibited fluorescence emission in the blue-cyan-green regions, with relatively high quantum yields (∼ 30 %). The protocol allows for the preparation of analogous photoactive hybrid materials containing very low amounts of BTD, behaving as fluorescent fumed silica.

Chlorophyll-a functionalised Zn-Cd-S thin film fabricated by SILAR technique for dye sensitised solar cells

Photoelectrochemical performance of DSSCs based on natural extracted chlorophyll-a dye sensitised Zn-Cd-S thin film semiconductor electrodes on Cr-plated stainless steel substrates as photoanodes are studied. Thin film electrode materials prepared by successive ionic layer adsorption and reaction (SILAR) method are characterised by using Powder X-ray diffraction (PXRD) spectroscopy, Field Emission Scanning Electron Microscopy (FESEM) and UV–VIS spectroscopy. The prepared Zn-Cd-S thin films are found to be nanocrystalline with a crystal size of ≈ 6.6 nm. The optical band gap energy of the thin films found is to be ≈ 2.9 eV. Chlorophyll-a dye used as sensitizer for DSSC, is extracted from Marigold leaves using acetone as solvent. The optical to electrical energy conversion efficiency of the DSSC using 6 h chlorophyll-a dye loaded Zn-Cd-S thin film is estimated to be 0.988% with fill factor of 52%.

Effect of Binder Concentration and Dye Loading Time on Titania based Photoanode in DSSC Application

Effect of Binder Concentration and Dye Loading Time on Titania based Photoanode in DSSC Application

Organic dye-sensitized f-MWCNTs-TiO2 composite for optically controlled resistive switching memory applications

Abstract Herein, we have developed organic dye (turmeric) sensitized functionalized multi-walled carbon nanotubes (MWCNTs)-titanium dioxide (TiO2) composite and investigated it's optically controlled resistive switching (RS) and non-volatile memory properties. The composite was synthesized using a single-step hydrothermal method and the dye sensitization period was varied to investigate the effect of the dye loading time (6, 12, 18, and 24 h) on the different properties of the composite. The structural, morphological, and optical properties of the bare and dye-sensitized composites were characterized using X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and UV–visible spectrometer. The electrical properties of the bare and dye-sensitized composite based devices were tested in the dark, UV, visible, and UV + visible light illumination conditions. Due to the good absorbance properties of the TiO2 in UV region and dye in the visible region, the dye-sensitized composite devices show excellent bipolar RS and non-volatile memory properties in the UV + visible light illumination condition. In this work, the 18 h dye-sensitized device shows superior optical RS properties than other devices. The memristive properties of the optimized devices are reported and demonstrated that the UV + visible light illumination condition provides double valued charge-flux property and best in class charge driving capability. The electrical transport and possible optically controlled RS mechanisms are discussed. The results suggested that the optical stimulus can be an additional parameter in conjunction with the electric stimulus to control the RS properties of the devices.

Flow Cytometric Monitoring of Dynamic Cytosolic Calcium, Sodium, and Potassium Fluxes Following Platelet Activation.

The interaction of platelet agonists with their respective membrane receptors triggers intracellular signaling, among which cytosolic ion fluxes play an important role in activation processes. While the key contribution of intercellular free calcium is accepted, sodium and potassium roles in platelet activation have been less investigated in recent studies. Here, we implemented a novel flow-cytometric method to monitor over time cytosolic free calcium, sodium, and potassium ion fluxes upon platelet activation and we demonstrate the feasibility of real-time visualization of ion kinetics, in particular with a focus on sodium and potassium. Platelets were loaded with selective ion indicators, Fluo-3 (Ca2+ ), ION NaTRIUM Green-2 (Na+ ), and ION Potassium Green-2 (K+ ). Fluorescence was monitored by flow cytometry. After measurement of a stable baseline, platelets were activated and ion indicator fluorescence was acquired over time, up to 10 min. Platelets were activated with either thromboxane analogue U46619, ADP, thrombin, TRAP6 (PAR-1 agonist), AYPGKF (PAR-4 agonist), convulxin (collagen receptor GPVI agonist), or combinations thereof. We evaluated preanalytical parameters (in particular dye loading time and concentration) to implement an accurate method. Subsequently, we characterized cytosolic calcium, sodium, and potassium kinetics in response to platelet agonists. We observed different patterns of agonist synergism. In conclusion, the present work highlights the use of cytosolic ion monitoring by flow cytometry to investigate characteristic calcium, sodium, and potassium mobilization patterns following platelet activation. This easy technique opens a new way to analyze signaling in different platelet subpopulations and it should prove useful for investigating platelet pathophysiology. © 2020 International Society for Advancement of Cytometry.

Performance enhancement of dye-sensitized solar cells by plasma treatment of BaSnO3 photoanode

We describe here the synthesis of BaSnO3 nanopowder via simple co-precipitation method and its application as a substitute photoanode material in dye-sensitized solar cells. Different values of pH and calcination temperature have been applied and optimized. The production has been characterized by X-ray diffraction technique to understand the effect of pH and calcination temperature on its crystallinity and phase purity. Crystalline BaSnO3 with an average size of about 18 nm presented an excellent dye-loading capability within a short duration of time. In this report, also, porosity and microstructure improvement in the BaSnO3 layer was achieved by using non-equilibrium atmospheric pressure plasma jet treatment for the first time, which modified dye-loading and charge transport properties in BaSnO3 photoanodes, resulted in a brilliant enhancement of the DSSC efficiency. The DSSCs were fabricated using untreated and plasma-treated BaSnO3 photoanodes. The highest photon conversion efficiency of about 2.6% was observed for the highly crystalline BaSnO3 nanoparticles synthesized within pH 12, calcined in temperature 900 °C and 3 h dye-loading with a significantly high JSC = 7.10 mA/cm2, VOC = 0.74 V and FF ≈ 0.50. This value of efficiency is considerable in comparison to the previous phase pure BaSnO3-based DSSCs. After enhancement of plasma treatment time and modification of dye-loading duration, an improvement of more than 50% was recognized in DSSC efficiency (about 4%), and a reduction in dye-loading time was observed by one third, compared to the bare one.

Electric-field assisted spray technique for controlled pore filling of nanostructured films: device applications

A novel pore-filling system was prepared using spray as the key-technique, for solar cells and various other applications. High performance in perovskite, dye-sensitized and eta cells is often achieved using metal oxide layers or their mesoporous analogues. One dimensional scaffold materials such as nanorods or nanotubes are also employed in order to improve charge collection. Herein, we introduce a method to more efficiently fill the pores in the most common nanostructure architecture namely mesoporous, nanorods or nanotubes. The method employs the use of spray technique with applied DC voltage (through two different voltage supplies) as the cost-effective technology for time efficient pore filling. SnS nanoparticles and N719 dye have been pore-filled onto a previously deposited ZnO nanorods and mesoporous TiO2 film, respectively, using the novel setup. Scanning electron microscopy images revealed an improved pore-filling, the complementary enhancement of ~ 24% in the DSSC efficiency and ~ 16% and 7% in terms of current density and fill factor, respectively has been found in comparison to the reference standard device. It is attributed to an increase in the concentration of dye molecules into the pores of TiO2 nanostructures due to better dye loading and hence observed an improvement in light absorption, electron transportation and charge collection. This pioneer pore filling technique exponentially reduced the dye loading time duration from overnight immersion of photo anodes in dye solution to 15–20 min.

Effect of dye-loading time and device-architecture on the performance of natural dye-sensitized solar cells based on zinc oxide and red frangipani dye

Zinc oxide (ZnO) is typically susceptible to acidic dye due to its high isoelectric point which dampened its performance and need to be sensitized in limited time. In other hand, by increasing the thickness of ZnO layer could increase the adsorption of dye and photoexcited electrons but also increase the probability of recombination and reduced electron injection. Herein, we sensitized the ZnO layer with red frangipani dye (RFD) with different dye-loading duration which shows 4 h as optimum with photo conversion efficiency (PCE) ≈ 0.0014%. We also double the thickness of ZnO layer with different architectures and sensitized it in 4 h. It shows that the split ZnO layer on each photoanode and CE tremendously increased the DSSCs performance with PCE ≈ 0.0029%. This work evidenced of splitting sensitized metal oxide in photoanode and counter electrode (CE) respectively and enhanced the performance of DSSCs.

Improving the Dye Loading of TiO2/MWCNT Composite Based Dye Sensitized Solar Cells By Vacuum Assisted Dye Adsorption Technique

The most attractive properties of Dye Sensitized Solar Cells (DSSCs) are their low cost and simple manufacturing processes which makes them as one of the promising third generation solar cells. Each part of the device and the fabrication process heavily determines the cost and efficiency. Dye loading is such one process where the dye sensitizers are made to adsorb on the surface of the mesoporous TiO2/MWCNT nanocomposites. The type of the dye, situations and time of dye loading plays a vital role in performance of the DSSCs. This work reports the synthesis of TiO2/MWCNT nanocomposite and its structural characterization done using Field Emission Scanning Electron Microscope (FESEM) and BET surface area analyzer. Photoandoes were prepared by doctor blade technique with a thickness of 21µm. The dye loading process in ambient condition and in a self developed low cost set up to load the dye under vacuum are compared. The work also reports effects of dye loading time on the amount of dye loaded, chemical stability of photoanode and the light conversion efficiency of the DSSCs. It was seen that dye adsorption increased by 29.6% when loaded in vacuum compared to normal loading conditions. Over all time required to reach the saturated level of dye adsorption was decreased to 8 hours from 18 hours of soaking in ambient conditions.

Dye‐Sensitized Solar Cell Based on Novel Star‐Shaped Ruthenium Polypyridyl Sensitizer: New Insight into the Relationship between Molecular Designing and Its Outstanding Charge Carrier Dynamics

AbstractIn this work, we have introduced a star‐shaped sensitizer for dye sensitized solar cells (DSSCs) consist of three anchoring groups of benzene sulfonic acid with a significant improvement of interfacial electron transfer rate of dye/TiO2‐anatase nanostructures compared to corresponding sensitizers containing only one anchoring group. Physical chemistry aspect of the robust star‐shaped sensitizer has been investigated, employing the Current over Voltage analysis (I−V) and Transient Absorption Spectroscopy (TAS) methods.The computational studies based on density functional theory (DFT) and quantum calculations were clearly indicated that the rate of the Interfacial electron transfer (IET) significantly depends on the binding mode of a sensitizer to semiconductor surface and the nature of the electronic population in lowest unoccupied molecular orbitals (LUMOs) that initially localized on the adsorbate molecule, which is in a good agreement with experimental results. Our main result is that, among different possible binding modes of anchoring group to TiO2 surface, the bridging mode has the shortest life time of 28 fs in the presence of visible light as the excitation source. To investigate negative effect of the sensitizer molecules aggregation on TiO2 surface, on the performance of the cell, was examined the dye loading time on TiO2 surface for 10, 16 and 20 hours, which 16 hours of dye loading on surface exhibited the best DSSC performance. Moreover, transient absorption studies consistently show that the star‐shaped dye (consist of three anchoring groups) has better performance compared to the other dyes (consist of one anchoring groups) (1 and 3), in all aspects of critical parameters for DSSCs, including electron lifetime in TiO2, electron injection, dye regeneration and recombination resistance. The present work explains the fundamental physical chemistry aspects of the excited‐state in star‐shaped ruthenium polypyridyl complexes, along with opening new insight into the design of new sensitizers for enhancing the interfacial electron transfer rate and lowering the charge recombination process, which results in high power conversion efficiency of DSSC.

Low cost dye-sensitized solar cells based on zinc oxide and natural anthocyanin dye from Ardisia elliptica fruits

Natural dye is attractive to be used in dye sensitized solar cell (DSSC) as an alternative sensitizer. The main advantage of natural dye is its low cost production. Only simple procedure is needed to produce natural dyes where the pigments of plant parts like flowers, leaves, fruits and tubers were extracted using common solvents in the laboratory. In addition, the resources of natural dye are not only abundant, but also completely biodegradable. In this work, the natural dye was produced by extracting anthocyanin pigment from Ardisia elliptica fruits and called as Ardisia elliptica dye (AED). The highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) level of AED was −6.06 eV and −3.88 eV respectively. AED is absorbed light in the green region with maximum absorption at a wavelength of 536.49 nm and the band gap was 2.31 eV which is acceptable as sensitizer for DSSC. Our photoelectrode of DSSC was fabricated by sensitizing zinc oxide (ZnO) nanoparticles layer with AED in different sensitizing duration (dye-loading time) and the best obtained photo conversion efficiency (PCE) was 0.04% which has been sensitized for 20 min.

Rose bengal-sensitized ZrO2 photoanode for dye-sensitized solar cell

The present work reports the first demonstration of zirconium oxide (ZrO2) as a photoanode and rose bengal (RB) as a sensitizer. ZrO2 photoanode films were deposited on indium-doped tin oxide (ITO)-coated glass substrate by doctor blade technique. ZrO2 photoanodes were sensitized by rose bengal dye. Scanning electron microscopy (SEM) was applied to reveal the surface morphological changes for the RB-sensitized and unsensitized ZrO2 photoanodes. Using UV–vis spectrophotometer, optical absorption analyses were carried out for the RB-sensitized photoanodes. Platinum-coated ITO electrode was used as a counter electrode for electrons collection. The electron transfer at the interfaces was studied by electrochemical impedance spectroscopy. The device fabricated using the photoanode with dye loading time of 24 h performed better, it showed the photocurrent density (J SC), open-circuit voltage (V OC), and fill factor (FF) of about 0.01 mA/cm2, 258 mV, and 34%, respectively.

Template-free TiO2 photoanodes for dye-sensitized solar cell via modified chemical route

Surfactant and template-free Titanium dioxide (TiO2) spheres have been deposited via ultrasonic rinsing assisted modified successive ionic layer adsorption and reaction (M-SILAR) method. The effect of M-SILAR cycle variation on the growth of TiO2 films and power conversion efficiency (PCE) of dye-sensitized solar cells (DSSCs) has been reported. Also, the significant influence of the dye adsorption time of photoelectrodes on the overall PCE of TiO2 based DSSCs has been investigated systematically. The SEM images reveal that the TiO2 microspheres are made up of densely packed and interconnected nanospheres. After dye loading maximum absorption peak around 500nm is seen with broader coverage in the visible region of the solar spectrum. The excess amount of dye for dye loading time 15h did not contribute to current and is suspected to be present either in multilayers or physisorbed on the surface of TiO2. The DSSC prepared using photoelectrode TO125 and dye loading time of 12h exhibited the highest power conversion efficiency (PCE) of 1.16% with short-circuit current density (Jsc) of 8.17mA/cm2, open circuit voltage (Voc) of 0.42V and fill factor of 0.34. The PCE is attributed to the large molecular interconnected TiO2 spheres diffusing visible light to enhance the light absorption. Also, it possesses relatively superior 3-D microsphere like structure and thus provides the effective pathway to the photogenerated electrons with low recombination rate, leading to attaining the high PCE.

Influence of Zn concentration and dye adsorption time on the photovoltaic performance of M-SILAR deposited ZnO-based dye sensitized solar cells

Abstract Zinc oxide (ZnO) thin films have been deposited with ultrasonic rinsing assisted modified successive ionic layer adsorption and reaction (M-SILAR) method. The effect of Zn concentration on the growth of ZnO films and power conversion efficiency (PCE) of dye-sensitized solar cells (DSSCs) have been studied. The surface morphology changes from nanorods to the nanoflowers like structure as a result of coalescence of the nanorods. Also, the significant effect of the dye adsorption time of photoelectrodes on the overall PCE of ZnO based DSSCs has been investigated systematically. It is found that the chemical stability is the foremost issue for ZnO photoelectrode. The prolonged dye adsorption time is responsible for the deterioration of the ZnO nanostructure due to the formation of Zn2+/N3 dye aggregates. The DSSC prepared using photoelectrode of 0.1 M Zn concentration and dye loading time of 18 h exhibited a highest PCE of 0.70%, since it possesses well-defined 1D nanostructure which facilitates very low reverse saturation current density and longer electron lifetime.

Exploring the potential of laser assisted flow deposition grown ZnO for photovoltaic applications

Zinc oxide (ZnO) is a widely studied wide band gap semiconductor with applications in several fields, namely to enhance solar cells efficiency. Its ability to be grown in a wide variety of nanostructured morphologies, allowing the designing of the surface area architecture constitutes an important advantage over other semiconductors. Laser assisted flow deposition (LAFD) is a recently developed growth method, based on a vapour-solid mechanism, which proved to be a powerful approach in the production of ZnO micro/nanostructures with different morphologies as well as high crystallinity and optical quality. In the present work we report the use of the LAFD technique to grow functional ZnO nanostructures (nanoparticles and tetrapods) working as nano templates to improve the dye-sensitized solar cells (DSSCs) efficiency. The structural and morphological characterization of the as-grown ZnO crystals were performed by X-ray diffraction and electron microscopy, respectively, and the optical quality was assessed by photoluminescence spectroscopy. DSSCs were produced using a combination of these nanostructures, which were subsequently sensitized with N719 dye. An efficiency of ∼3% was achieved under simulated AM 1.5 illumination conditions for a dye loading time of 1 h.

Functionalized Carboxylate Deposition for rapid sensitization of dye-sensitized solar cells

The current state-of-the-art dye loading process for modern dye-sensitized solar cells (DSCs), essentially unchanged for the last 24years, entails dip-coating nanoporous TiO2 photoelectrodes in a concentrated solution of dye for an average of 16h. This process constitutes up to 80% of the fabrication time, leads to significant dye waste, and necessitates the use of organic solvents. A promising gas-phase deposition technique, coined Functionalized Carboxylate Deposition (FCD), was used to rapidly deposit a self-assembled monolayer of targeted α-carbon modified carboxylic acid containing dye molecules on TiO2 photoelectrodes. The FCD process successfully reduced the dye loading time by 98% (i.e., 15–20min compared to an average of 16h). Moreover, the FCD-sensitized photoelectrodes produced DSCs with equivalent or higher efficiencies than dip-coating for the dyes used (both in this study and by other researchers). The performance of FCD dye sensitization in this study indicates its potential applicability as a foundational technology for rapid fabrication of efficient DSCs.

Optimization of TiO2 Based Henna Dye Sensitized Solar Cell using Grey-Taguchi Technique

Low efficiency is a major drawback associated with Dye Sensitized Solar Cells (DSSCs). However, the efficiency can be enhanced by multi-objective optimization based on process parameters. In this work, four process variables have been identified as important parameters for influencing DSSC responses (efficiency, shunt and series resistance). These are thickness of the working electrode (A), annealing temperature (B), annealing time (C) and dye loading time (D). An optimal combination of the response parameters of the resulting DSSC was obtained by simultaneously adjusting these input parameters. With three different levels for each process variable, FTO glasses as components and henna leave extract as sensitizer, 9 unique DSSCs were fabricated following Taguchi Design of experiment. Each cell was illuminated with constant light intensity of 100 mW/cm 2 to measure the photovoltaic parameters. The optimal combination of process parameters was determined by applying Grey Relational Analysis (GRA). The experimental best condition (A 3 B 1 C 3 D 2 ) obtained from Taguchi array corresponded to average thickness of 9.67 µm for TiO 2 film , annealing temperature of 300 °C, annealing time of 6 hours and dye loading time of 4 hours. With optimization, the annealing time is reduced by ~67% with other responses remain the same. The global best DSSC has higher efficiency, higher shunt resistance and lower series resistance of 0.66 %, 24844.44 Ω and 8.4281 Ω, respectively. This translates to 1.3% higher efficiency, 12.4% higher shunt resistance and 10.8% lower series resistance. These results indicate that solar cell responses can be optimized significantly.

Effect of Solvent, Dye-Loading Time, and Dye Choice on the Performance of Dye-Sensitized Solar Cells

Anatase titania films with a thickness of up to 20 μm and deposited over a fluorine-doped tin-oxide substrate are impregnated with ruthenium dyes N-719 and N-749 using Dip and supercritical-fluid methods for the purpose of fabricating dye-sensitized solar cell devices. The dyes are dissolved in different solvent mixtures, including supercritical carbon dioxide, as well as combinations of more traditional solvents including mixtures of acetonitrile, and t-butanol. Analytical studies included thin-film analyzing and scanning electron microscopy to measure titania film thickness and porosity, UV-Vis spectroscopy to quantify dye concentration, and current-voltage device characterizations to assess energy conversion efficiency, as well as open-circuit voltage decay measurements and quantum efficiency to examine electron collection efficiency. A significant result is that using the dye N-749 in a solvent that includes supercritical carbon dioxide leads to energy conversion efficiencies that are higher for devices with a thick 20 μm semiconductor film than for the case of devices with thinner films, including the 10 μm film thickness that is traditionally considered an upper threshold. The supercritical-fluid method for the N-719 dye also enabled shorter impregnation duration than more conventional classical Dip Methods.

Optimization of dye loading time for SnO2 based Rose Bengal dye-sensitized solar cell

Tin oxide (SnO2) nanostructures were synthesized by simple chemical precipitation route and SnO2 photoelectrode films were fabricated on fluorine doped SnO2 substrate. Using Rose Bengal dye as a sensitizer, scanning electron microscopic analysis was performed for the unsensitized and sensitized SnO2 photoelectrodes to study the changes in surface morphology. Optical absorption studies for Rose Bengal dye in solution and the photoelectrodes sensitized with it were conducted using UV–vis spectrophotometer. Effects of dye loading time on photovoltaic characteristics of the cell fabricated using the sensitized photoelectrode were studied. The highest performance of device was obtained for the photoelectrode with 24 h dye loading time which showed the V OC , J SC and FF of about 385 mV, 0.874 mA/cm2 and 78 %, respectively.