Photostability of low cost dye-sensitized solar cells based on natural and synthetic dyes

Nature of Linear Spectral Properties and Fast Relaxations in the Excited States and Two-Photon Absorption Efficiency of 3-Thiazolyl and 3-Phenyltiazolyl Coumarin Derivatives

Coumarin-based fluorescent agents play an important role in the manifold fundamental scientific and technological areas and need to be carefully studied. In this research, linear photophysics, photochemistry, fast vibronic relaxations, and two-photon absorption (2PA) of the coumarin derivatives, methyl 4-[2-(7-methoxy-2-oxo-chromen-3-yl)thiazol-4-yl]butanoate (1) and methyl 4-[4-[2-(7-methoxy-2-oxo-chromen-3-yl)thiazol-4-yl]phenoxy]butanoate (2), were comprehensively analyzed using stationary and time-resolved spectroscopic techniques, along with quantum-chemical calculations. The steady-state one-photon absorption, fluorescence emission, and excitation anisotropy spectra, as well as 3D fluorescence maps of 3-hetarylcoumarins 1 and 2 were obtained at room temperature in solvents of different polarities. The nature of relatively large Stokes shifts (∼4000-6000 cm^-1), specific solvatochromic behavior, weak electronic π → π* transitions, and adherence to Kasha's rule were revealed. The photochemical stability of 1 and 2 was explored quantitatively, and values of photodecomposition quantum yields, on the order of ∼10^-4, were determined. A femtosecond transient absorption pump-probe technique was used for the investigation of fast vibronic relaxation and excited-state absorption processes in 1 and 2, while the possibility of efficient optical gain was shown for 1 in acetonitrile. The degenerate 2PA spectra of 1 and 2 were measured by an open aperture z-scan method, and the maximum 2PA cross-sections of ∼300 GM were obtained. The electronic nature of the hetaryl coumarins was analyzed by quantum-chemical calculations using DFT/TD-DFT level of theory and was found to be in good agreement with experimental data.

Viable production of hydrogen and methane from polluted water using eco-friendly plasmonic Pd-TiO2 nanocomposites

Solar-to-fuel conversion is a novel clean energy approach that has gained the interest of many researchers. Solar-driven photocatalysts have become essential to providing valuable fuel gases such as methane and hydrogen. Solar energy has emerged as a renewable, abundant energy source that can efficiently drive photochemical reactions through plasmonic photocatalysis. As a capping agent, orange peel extract was used in this study in a microwave-assisted green method to incorporate titanium dioxide with distinct amounts (3, 5, and 7 wt%) from Pd-plasmonic nanoparticles (2-5 nm). The leading role for plasmonic nanoparticles made from Pd-metal is enhancing the photocatalyst's ability to capture visible light, improving its performance. X-Ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), Brunauer, Emmett, and Teller (BET) surface area analysis, and UV-vis DRS analyses have investigated the obtained plasmonic photocatalysts' crystallographic, morphological, and optical characteristics. The UV-vis absorption spectra demonstrated the visible light absorption capacity attributed to the localized surface plasmonic resonance (LSPR) behavior of the newly formed nanoplasmonic photocatalysts. The generated Pd-TiO2 nanomaterials' photocatalytic activity has been examined and evaluated for combustible gas production, including the formation of CH4 and H2 from the photocatalytic degradation of Reactive Yellow 15 (RY) during a deoxygenated photoreaction in a homemade solar photobiogas reactor.

“Paper Dye-Sensitized Solar Cell” Based on Carbon-Nanotube-Composite Papers

We propose a paper solar cell based on carbon nanotube (CNT)-composite papers. To fabricate this cell, we use dye-sensitized solar cells (DSCs) for generating power through the redox reaction of dyes in conjunction with CNT-composite papers, which are composite materials containing CNTs and pulp (raw paper material) that can be fabricated easily by using a method based on the Japanese washi papermaking technique. The demand for CNT applications is expected to increase due to their high conductivity and metallic or semiconducting characteristics. This CNT-composite paper can also have metallic or semiconducting characteristics based on the contained CNTs in the composite paper. We previously fabricated a DSC that generates electricity by using CNT-composite papers stacked in a typical DSC structure. However, the conversion efficiency of this DSC was just 0.188%, which is not practical. To overcome this low power generation issue, we tried improving the DSC structure by applying electrodes to the CNT-composite papers in grid patterns for efficient current collection and applying an optimally mixed dye for efficient electron excitation. Results showed that the conversion efficiency improved to 0.58%. Moreover, we demonstrated that using a mixed dye can improve the conversion efficiency of the paper DSC. We expect these types of CNT-composite papers to be used as material for new DSCs.

Photovoltaic and spectroscopic characteristics of perovskite/TiO2 heterostructure photoanodes for improving the efficiency of dye sensitized solar cells

Perovskite-type ternary oxide nanostructured materials have gained great attention in recent years as promising materials for solar cell applications. However these ternary oxides have failed to be applied as a working electrode in DSSCs due to its poor performance and its inability to bind dye molecules to the surface. A heterostructure perovskite/TiO₂ photoactive electrodes is a new strategy to improve the photon-to-current efficiency (PCE) of DSSCs. In this paper, BaZrO₃ (BZ), BaTiO₃ (BT) and nanocomposite [1:1] molar% from BaTiO₃-BaZrO₃ perovskite nanostructured materials synthesized via sonochemical sol-gel methods, are coated on the top of the TiO₂ photoactive electrode. This heterostructured (perovskite/TiO₂) photoelectrode has been applied for improving the performance of dye-sensitized solar cells (DSSCs). The crystallographic, morphological and optical characteristics of the different prepared perovskite nanomaterials has been investigated by XRD, SEM, TEM, Raman and UV-Vis Diffuse reflectance spectroscopic analysis, respectively. Dye-sensitized solar cells based on the different heterostructure perovskite/TiO₂ electrodes are assembled, and high conversion efficiency (η) are calculated from the current density-voltage (J-V) characteristics of the solar cells. The results show an efficiency enhancement with about ∼22%, 37% and 51% in case of BZ, BTZ and BT respectively. These enhancements is attributed to high refractive index of the perovskite nanoparticles, higher incident photon-to-current conversion yield which is due to greater fraction of light scattered, as well as the less recombination of the photogenerated electrons.

Anthocyanic pigments from elicited in vitro grown shoot cultures of Vaccinium corymbosum L., cv. Brigitta Blue, as photosensitizer in natural dye-sensitized solar cells (NDSSC)

We investigated the effect on anthocyanins and total phenols content and antioxidant capacity of in vitro shoot cultures of Vaccinium corymbosum L., cv. Brigitta Blue, grown on an eliciting medium supplied with 10 μM naphthalene acetic acid, in combination with reduced content of salts and organics in respect to the basal medium. After 45 days, higher content of total phenols and anthocyanins was obtained from extracts of shoots grown on the elicitation medium. Anthocyanin molecules, absent in control shoots, were identified by HPLC-MS as delphinidine-glycoside, cyanidine-glycoside, delphinidine-arabinoside, cyanidine- arabinoside and cyanidine-acetylglycoside. Chlorogenic acid, present in control shoots, was nearly absent in elicited shoots. We exploited the anthocyanin - based raw extracts of "Brigitta Blue" shoots grown on the elicitation medium as a source of natural dye photosensitizers for Dye Sensitized Solar Cells, taking into account that such raw extracts showed antioxidant properties and photostability features. A purified dye was also prepared and the comparison of the latter with the raw one has been analysed by spectrophotometric, chromatographic and power conversion efficiency determination. The power conversion efficiencies from the raw and the purified dye were not different and they were comparable to the data obtained by other authors with anthocyanin-based dyes from in vivo grown plants.

Photovoltaic characteristics of natural light harvesting dye sensitized solar cells

In this work of research, anthocyanin as a natural dye obtained from raspberry fruits, was used and tested as a photon harvesting/electron donating dye in titanium dioxide nanoparticle-based DSSCs. A working photoelectrode made from TiO₂ nanoparticles with an average particle size (10-40nm) that is coated on Florine doped tin-oxide substrate, was prepared via a simple and low cost hydrothermal method. A detailed structural and morphological analysis of the TiO₂ photoactive electrode was investigated by X-ray diffraction (XRD), diffuse reflectance spectrometer, transmission electron microscope (TEM) and scanning electron microscope (SEM). Complete photovoltaic characteristics including (current, voltage, outpower, and responsivity) of the natural anthocyanin based dye sensitized solar cell have been investigated under different illumination intensity ranging from 10 to 100mW.cm^-2. The cell responsivity and efficiency of the fabricated solar cell under different illumination intensity were found to be in the range (R=15.6-23.8mA.W^-1 and η=0.13-0.25) at AM=1.5 conditions. This study is important for enhancing the future applications of the promising DSSC technology.

Application of dyes extracted from Alternanthera dentata leaves and Musa acuminata bracts as natural sensitizers for dye-sensitized solar cells

The natural dyes anthocyanin and chlorophyll were extracted from Musa acuminata bracts and Alternanthera dentata leaves, respectively. The dyes were then applied as sensitizers in TiO₂-based dye-sensitized solar cells (DSSCs). The ethanol extracts of the dyes had maximum absorbance. High dye yields were obtained under extraction temperatures of 70 to 80°C, and the optimal extraction temperature was approximately 80°C. Moreover, dye concentration sharply decreased under extraction temperatures that exceeded 80°C. High dye concentrations were obtained using acidic extraction solutions, particularly those with a pH value of 4. The DSSC fabricated with anthocyanin from M. acuminata bracts had a conversion efficiency of 0.31%, short-circuit current (I_sc) of 0.9mA/cm², open-circuit voltage (V_oc) of 0.58V, and fill factor (FF) of 62.22%. The DSSC sensitized with chlorophyll from A. dentata leaves had a conversion efficiency of 0.13%, I_sc of 0.4mA/cm^-2_,V_oc of 0.54V, and FF of 67.5%. The DSSC sensitized with anthocyanin from M. acuminata bracts had a maximum incident photon-to-current conversion efficiency of 42%, which was higher than that of the DSSC sensitized with chlorophyll from A. dentata leaves (23%). Anthocyanin from M. acuminata bracts exhibited the best photosensitization effects.

Identifikasi dan Kuantifikasi Antosianin dari Fraksi Bunga Rosela (Hibiscus Sabdariffa L) dan Pemanfaatannya sebagai Zat Warna Dye-Sensitized Solar Cell (DSSC)

Identifikasi antosianin dari fraksi bunga Rosela (Hibiscus Sabdariffa L.) dan pemanfaatannya sebagai zat warna dye-sensitized solar cell (DSSC) telah dilakukan. Penelitian ini bertujuan untuk mengkuantifikasi kadar antosianin dari fraksi bunga rosela dan menentukan hubungan kadar antosianin terhadap efisiensi sel pada DSSC. Metode yang digunakan adalah (i) ekstraksi antosianin dengan maserasi, (ii) fraksinasi ekstrak antosianin secara kromatografi kolom dengan fasa gerak air-metanol (100:0, 75:25, 50:50, 25:75, 0:100) dan fasa diam sephadex LH-20, (iii) identifikasi senyawa antosianin dengan KLT dan penampak bercak (AlCl3 dan uap amoniak), (iv) kuantifikasi kadar antosianin, (v)  aplikasi zat warna antosianin ke DSSC dan (vi) karakterisasi senyawa antosianin pada fraksi yang memiliki performansi DSSC paling tinggi menggunakan spektroskopi UV-Vis dan IR. Hasil penelitian menunjukan kadar relatif antosianin mempengaruhi nilai efisiensi sel surya DSSC. Semakin besar kadar relatif antosianin maka nilai efisiensi sel surya semakin tinggi. Fraksi 1 menunjukkan nilai kadar relatif antosianin 3,56% dan nilai efisiensi sel surya yaitu 1,014 x 10-4%, sedangkan fraksi 2 menunjukkan nilai kadar relatif antosianin 40,29% dan nilai efisiensi sel surya fraksi 2 yaitu 6,59 x 10-4 %.

Efficient photocatalytic oxidation of benzene to phenol by metal complex-clay/TiO2 hybrid photocatalyst

Synthetic saponite containing a photosensitizing metal complex was complexed with colloidal anatase and used for the visible light photocatalytic reaction of aqueous benzene to phenol.

Visible-Light-Responsive Photocatalytic Flow Reactor Composed of Titania Film Photosensitized by Metal Complex-Clay Hybrid

Synthetic saponite containing a photosensitizing metal complex, tris(2,2'-bipyridine)ruthenium(II)), in the interlayer space was complexed with anatase nanoparticles to obtain transparent hybrid film photocatalyst. The catalyst film was mounted in a flow reactor device to catalyze such photocatalytic reactions as the decomposition of aqueous acetic acid and N-alkylation of benzylamine with ethanol.

Effect of solvents on the extraction of natural pigments and adsorption onto TiO2 for dye-sensitized solar cell applications

Nine solvents, namely, n-hexane, ethanol, acetonitrile, chloroform, ethyl-ether, ethyl-acetate, petroleum ether, n-butyl alcohol, and methanol were used to extract natural dyes from Cordyline fruticosa, Pandannus amaryllifolius and Hylocereus polyrhizus. To improve the adsorption of dyes onto the TiO2 particles, betalain and chlorophyll dyes were mixed with methanol or ethanol and water at various ratios. The adsorption of the dyes mixed with titanium dioxide (TiO2) was also observed. The highest adsorption of the C.fruticosa dye mixed with TiO2 was achieved at ratio 3:1 of methanol: water. The highest adsorption of P.amaryllifolius dye mixed with TiO2 was observed at 2:1 of ethanol: water. H.polyrhizus dye extracted by water and mixed with TiO2 demonstrated the highest adsorption among the solvents. All extracted dye was adsorbed onto the surface of TiO2 based on Fourier Transform Infrared Spectroscopy (FTIR) analysis. The inhibition of crystallinity of TiO2 was likewise investigated by X-ray analysis. The morphological properties and composition of dyes were analyzed via SEM and EDX.

Optical properties and device characteristics of 2-(antipyrin-4-ylhydrazono)-2-(4-nitrophenyl)acetonitrile thin films for photodiode applications

2-(Antipyrin-4-ylhydrazono)-2-(4-nitrophenyl)acetonitrile (AHNA) films were deposited via thermal evaporation technique. The optical properties of AHNA films and electrical characteristics of Au/AHNA/n-Si/Au heterojunction diode have been reported. The optical properties of AHNA films were investigated using the spectrophotometric measurements of optical transmittance and reflectance over spectral range 190-2500 nm. The films have indirect allowed optical band gap of 3.6 eV. The refractive index of the films was calculated and the dispersion parameters of the films were determined on the light of the single oscillator model. The electrical properties of Au/AHNA/n-Si/Au heterojunction diode were studied in terms of current-voltage characteristics. The device showed rectification behaviour with a rectification ratio of 100 at ±1 V. The conduction mechanisms and diode parameters such as ideality factor, barrier height and series resistance of the device were determined. The device under illumination showed photovoltaic properties. The short circuit current and open circuit voltage were found to be function of illumination intensity. The device satisfies the conditions to be used as photodiode.

Performance of Caesalpinia sappan heartwood extract as photo sensitizer for dye sensitized solar cells

A natural dye extracted from Caesalpinia sappan heartwood was used as photo sensitizer for the first time to fabricate titanium dioxide (TiO2) nanoparticles based dye sensitized solar cells. Brazilin and brazilein are the major pigments present in the natural dye and their optimized molecular structure were calculated using Density functional theory (DFT) at 6-31G (d) level. The HOMO-LUMO were performed to reveal the energy gap using optimized structure. Pure TiO2 nanoparticles in anatase phase were synthesized by sol-gel technique. The pure and natural dye sensitized TiO2 nanoparticles were subjected to structural, optical, spectral and morphological studies. Low cost and environment friendly dye sensitized solar cells were fabricated using natural dye sensitized TiO2 based photo anode. The solar light to electron conversion efficiency of Caesalpinia sappan heartwood extract sensitized dye sensitized solar cell is 1.1%.

Vegetable-based dye-sensitized solar cells

In this review we provide an overview of vegetable pigments in dye-sensitized solar cells, starting from main limitations of cell performance to cost analysis and scaling-up prospects.

Natural dye extract of lawsonia inermis seed as photo sensitizer for titanium dioxide based dye sensitized solar cells

Natural dye extract of lawsonia inermis seed were used as photo sensitizer to fabricate titanium dioxide nanoparticles based dye sensitized solar cells. Pure titanium dioxide (TiO2) nanoparticles in anatase phase were synthesized by sol-gel technique and pre dye treated TiO2 nanoparticles were synthesized using modified sol-gel technique by mixing lawsone pigment rich natural dye during the synthesis itself. This pre dye treatment with natural dye has yielded colored TiO2 nanoparticles with uniform adsorption of natural dye, reduced agglomeration, less dye aggregation and improved morphology. The pure and pre dye treated TiO2 nanoparticles were subjected to structural, optical, spectral and morphological studies. Dye sensitized solar cells (DSSC) fabricated using the pre dye treated and pure TiO2 nanoparticles sensitized by natural dye extract of lawsonia inermis seed showed a promising solar light to electron conversion efficiency of 1.47% and 1% respectively. The pre dye treated TiO2 based DSSC showed an improved efficiency of 47% when compared to that of conventional DSSC.

Light harvesting over a wide range of wavelength using natural dyes of gardenia and cochineal for dye-sensitized solar cells

Two natural dyes extracted from gardenia yellow (Gardenia jasminoides) and cochineal (Dactylopius coccus) were used as sensitizers in the assembly of dye-sensitized solar cells (DSSCs) to harvest light over a wide range of wavelengths. The adsorption characteristics, electrochemical properties and photovoltaic efficiencies of the natural DSSCs were investigated. The adsorption kinetics data of the dyes were obtained in a small adsorption chamber and fitted with a pseudo-second-order model. The photovoltaic performance of a photo-electrode adsorbed with single-dye (gardenia or cochineal) or the mixture or successive adsorption of the two dyes, was evaluated from current-voltage measurements. The energy conversion efficiency of the TiO2 electrode with the successive adsorption of cochineal and gardenia dyes was 0.48%, which was enhanced compared to single-dye adsorption. Overall, a double layer of the two natural dyes as sensitizers was successfully formulated on the nanoporous TiO2 surface based on the differences in their adsorption affinities of gardenia and cochineal.