Development Of Dye-sensitized Solar Cells Research Articles

Hierarchical Photocatalytic Surfaces: From 1D to 3D Photoactive TiO2 Nanotubes Grown By Plasma Assisted Deposition Techniques

Photoactivity of TiO2 is of extensive recognition in applications like photocatalytic removal of pollutants, self-cleaning coatings, photoelectrochemical and photovoltaic cells and optical filters [1, 2]. Photocatalytic activity is affected by both the TiO2 structure and microstructure. For example, parameters as crystal sizes, texturization, nano and microscale arrangement, and interface conditioning and engineering [3] have been demonstrated to determine the formation and migration to the surface of electron-hole pairs responsible for the photoactivity response [3]. Thus, A successful approach to enhance the specific surface area and light harvesting is the use of highly porous structures such as nanoparticles, nanotubes, nanowires, or 3D nanoarchitectures. In this latter case, the hierarchical distribution of the semiconducting oxide is expected to prompt light scattering effects which might allow high efficiencies in photocatalytic pollutant removal for finely controlled nanoscale motives.In this communication, we propose the development of photoactive highly porous TiO2 nanostructures, forming 1D nanotubes and 3D hierarchical systems as nanotrees and multistack of nanotrees. These nanoarchitectures are fabricated by the combination of plasma enhanced chemical vapour deposition of crystalline TiO2 layers with the use of small-molecule organic nanowires as 1D and 3D soft-templates. This same synthetic approach has been exploited recently in the development of dye-sensitized solar cells [4], piezoelectric nanogenerators [5], and icephobic, freezing-delay, surfaces [6].The study of nanostructure shape, density, and entanglement as well as the combination of crystalline phases in the same nanostructure are revealed as key factors controlling the photocatalytic performance of the system. A thorough characterization analysis is presented including XRD, XPS, Raman, SEM, and TEM providing crucial information on the chemical composition, structure, and microstructure. Moreover, wetting characterization has been also performed to relate the surface tension to the photoactivity of TiO2 nanostructures. Photoactivity has been studied in a home-made system able to be illuminated with UV irradiation and the “in-situ” optical monitoring of different dye concentrations, like methyl orange dye, methylene blue, or rhodamine 6G. Thus, photocatalysis behavior has been evaluated and associated with the nanostructured configuration.[1] M. Grätzel, Nature 2001, 414, 338[2] F. Parrino, A. Ramakrishnan, H. Kisch, Angew. Chem. 2008, 120, 7215[3] P. Romero-Gomez, A. Borras, A. Barranco. J.P. Espinos, A.R. Gonzalez-Elipe ChemPhysChem 2010, 12 (1) 191[4] A.N. Filippin, M. Macías-Montero, A. Borras, et al. Scientific Reports 2017, 7, 9621[5] A.N. Filippin, J.R. Sanchez-Valencia, A. Borras, et al. Nano Energy 2019, 58, 476[6] M. Alcaire, C. Lopez-Santos, A. Borras, et al. Langmuir 2019, 35(51) 16876 Acknowledgements. We thank the AEI-MICINN (PID2019-110430GB-C21 and PID2019-109603RA-I0), the Consejería de Economía, Conocimiento, Empresas y Universidad de la Junta de Andalucía (PAIDI-2020 through projects US-1263142, ref. AT17-6079, P18-RT-3480), and the EU through cohesion fund and FEDER 2014–2020 programs for financial support. CLS and JS-V thank the University of Seville through the VI PPIT-US and (JS-V) the Ramon y Cajal Spanish National programs. The project leadings to this article have received funding from the EU H2020 program under the grant agreements 851929 (ERC Starting Grant 3DScavengers) and 899352 (FETOPEN-01-2018-2019-2020 - SOUNDofICE).

On the Use of PEDOT as a Catalytic Counter Electrode Material in Dye-Sensitized Solar Cells

Dye-sensitized solar cells (DSSCs) emerged in the early 1990s as a promising alternative to the classic silicon-based solar cell due to their unique combination of low cost, ease of fabrication, color palette for building integration, and high efficiency in indoor applications. This review article describes the fabrication and the properties of poly (3,4-ethylenedioxythiophene) (PEDOT)-based catalytic counter electrodes (CEs) for DSSCs. In particular, the electrochemical reactivity PEDOT CEs used in conjunction with alternative redox mediators for DSSCs is outlined. Among alternative redox shuttles, cobalt and copper complexes, as well as totally organic thiolate/disulfide, have been considered. Finally, PEDOT can also be used as a hole conductor material in electrolyte-free solid-state dye-sensitized solar cells. This review clearly shows that the progress in DSSCs development is strongly linked to the introduction of PEDOT as a new counter electrode material.

Highly efficient MoS2/rGO electrocatalysts for triiodide reduction as Pt-free counter electrode for dye-sensitized solar cells

Developing large-scale and high-efficient electrocatalysts based on earth-abundant element is urgent to promote the development of dye-sensitized solar cells (DSSCs). As an attractive approach, ultrasonic spray pyrolysis (USP) could prepare large-scale micro-nano structured catalytic materials, whereas these spheroidal particles usually could not conduct electron well with each other, thus inhibits catalytic activity. Herein we introduce reduced graphene oxide (rGO) to improve the conductivity and catalytic performance of MoS2 synthesized by USP. The MoS2/rGO hybrids combines the abundant active sites of MoS2 and excellent conductivity of rGO, reduces the CE/electrolyte interfacial electron transfer resistance, increases the contact of film with substrate, thus exhibits decreased Rct (1.00 Ω), improved efficiency of 8.53% and enhanced stability. Due to the high yield and good reproducibility of USP method, the large-scale (10 cm × 10 cm) and flexible MoS2/rGO CE shows good consistency of catalytic activity and bending resistance. These results demonstrate that this synthetic approach and introducing of rGO offers a scalable and simple strategy for synthesizing efficient materials in various electrochemical applications.

Solvothermally synthesized anatase TiO2 nanoparticles for photoanodes in dye-sensitized solar cells

ABSTRACT Many researchers working on the development of dye-sensitized solar cells (DSCs) continue to focus on the synthesis of photoanode materials with high surface area, along with high light scattering ability to enhance light harvesting efficiency (LHE). Meanwhile, dye packing density, which also impacts the LHE significantly, is often overlooked. Solvothermally synthesized anatase TiO2 nanoparticles (SANP) were obtained by a new and simple approach using a mixed solvent, ethanol and acetic acid. SANP were applied in photoanodes of DSCs using either metal-free organic dye (D149) or organometallic (N719) dyes. Dye loading (packing density) was correlated with the isoelectric point (IEP) in addition to light scattering effects were shown to determine the devices photovoltaic efficiency (PCE); specifically when compared with ones employing commercially available TiO2 nanoparticles. SANP photoanodes sensitized with D149 dye were found to be optimised at 10 µm, yielding a PCE of 6.9%, superior to for transparent or transparent + scattering films from the commercial source (5.6% and 5.9%, respectively). Furthermore, a 7.7% PCE was achieved using a SANP photoanode sensitized with N719 dye, with 7.2% seen for the transparent photoanode and 7.9% with a scattering layer. The high PCEs of of SANP devices are attributed to the high dye loading capability in addition to light scattering. A further point of interest is that even with the increased reactivity of the surface towards dye adsorption, we did not observe any significant increase in recombination with the redox mediator, presumably due to the increased dye loading providing better shielding.

Anchoring CoS on three-dimensional porous rGO thin films as efficient counter electrodes for dye-sensitized solar cells

Rational design of advanced cost-effective counter electrode (CE) is vital for the development of dye-sensitized solar cells (DSSCs). Herein, we report a novel CoS/reduced graphene oxide (CoS/rGO) composite counter electrode via a facile and rapid microwave irradiation plus ion exchange method. CoS nanoparticles are strongly anchored on three-dimensional (3D) porous rGO thin films. Due to positive advantages including high catalytic properties, enhanced active area, and electrical conductivity, the DSSC based on CoS/rGO counter electrode is endowed with a power conversion efficiency (PCE) of 6.86%, superior to that based on sputtered Pt counter electrode (6.50%). Our results indicate that CoS/rGO composite thin film is a low-cost and highly efficient CE for DSSCs.

A Fractional Diffusion Model for Dye-Sensitized Solar Cells.

Dye-sensitized solar cells have continued to receive much attention since their introduction by O’Regan and Grätzel in 1991. Modelling charge transfer during the sensitization process is one of several active research areas for the development of dye-sensitized solar cells in order to control and improve their performance and efficiency. Mathematical models for transport of electron density inside nanoporous semiconductors based on diffusion equations have been shown to give good agreement with results observed experimentally. However, the process of charge transfer in dye-sensitized solar cells is complicated and many issues are in need of further investigation, such as the effect of the porous structure of the semiconductor and the recombination of electrons at the interfaces between the semiconductor and electrolyte couple. This paper proposes a new model for electron transport inside the conduction band of a dye-sensitized solar cell comprising of as its nanoporous semiconductor. This model is based on fractional diffusion equations, taking into consideration the random walk network of . Finally, the paper presents numerical solutions of the fractional diffusion model to demonstrate the effect of the fractal geometry of on the fundamental performance parameters of dye-sensitized solar cells, such as the short-circuit current density, open-circuit voltage and efficiency.

Interface Engineered Binary Platinum Free Alloy-based Counter Electrodes with Improved Performance in Dye-Sensitized Solar Cells

The high cost and platinum dissolution issues of counter electrodes (CEs) are two core problems for the development of dye-sensitized solar cells (DSSCs). In this work, different CEs based on binary alloy Ru81.09Co18.91, Ru80.55Se19.45 and Co20.85Se79.15 nanostructures for DSSCs were successfully synthesized and investigated by a facile and environmentally friendly approach. Here, we found that the Co20.85Se79.15 alloy CE-based device yields the higher photoelectric conversion efficiency of 7.08% compared with that (5.80%) of the DSSC using a pure Pt CE because of the larger number of active sites with improved charge transferability and reduced interface resistance by matching work function with the I3‒/I‒ redox electrolyte. The inexpensive synthesis method, cost-effectiveness and superior catalytic activity of the Co20.85Se79.15 alloy may open up a new avenue for the development of CEs for DSSCs in the near future.

Dye Sensitized Solar Cells (DSSCs) Electrolytes and Natural Photo-Sensitizers: A Review.

Dye-sensitized solar cells (DSSCs) have become the subject matter of significant interest for the research and due to their urge in the field of energy conservation. The safe supply of energy is welfare of human life. However, as an unattainable power-energy conservation source, also depletion of fossil fuels is an unfortunate mandate and, definitely it is imminent. To encounter this critical issue of energy, non-conventional sources of energy have gained lots of attention, especially solar energy because it's a device that converts light-energy directly to electrical-energy without harming the environment. DSSCs provides a reliable and a cheap alternative for different kinds of Photovoltaics. The spectacle realization of Dye-sensitized-solar-cell is typically relying on photosensitizer (Dye), electrolyte and metal oxide semiconductor. A natural dye has become most credible alternative for such expensive and rare inorganic/chemical sensitizers, due to its lower cost, easy fabrication, eco-friendly and abundance of raw material. Also, DSSC has easily implemented technology with significant efficiency. This review paper enlightens the emergence, operation/fabrication, components and development of DSSCs using natural photo-sensitizers and factors that affect the stability.

Orbital-free photophysical descriptors to predict directional excitations in metal-based photosensitizers.

The development of dye-sensitized solar cells, metalloenzyme photocatalysis or biological labeling heavily relies on the design of metal-based photosensitizes with directional excitations. Directionality is most often predicted by characterizing the excitations manually via canonical frontier orbitals. Although widespread, this traditional approach is, at the very least, cumbersome and subject to personal bias, as well as limited in many cases. Here, we demonstrate how two orbital-free photophysical descriptors allow an easy and straightforward quantification of the degree of directionality in electron excitations using chemical fragments. As proof of concept we scrutinize the effect of 22 chemical modifications on the archetype [Ru(bpy)3]2+ with a new descriptor coined "substituent-induced exciton localization" (SIEL), together with the concept of "excited-electron delocalization length" (EEDL n ). Applied to quantum ensembles of initially excited singlet and the relaxed triplet metal-to-ligand charge-transfer states, the SIEL descriptor allows quantifying how much and whereto the exciton is promoted, as well as anticipating the effect of single modifications, e.g. on C-4 atoms of bpy units of [Ru(bpy)3]2+. The general applicability of SIEL and EEDL n is further established by rationalizing experimental trends through quantification of the directionality of the photoexcitation. We thus demonstrate that SIEL and EEDL descriptors can be synergistically employed to design improved photosensitizers with highly directional and localized electron-transfer transitions.

Synthesis of Mesoporous TiO2 Spheres via the Solvothermal Process and Its Application in the Development of DSSC

This study examined the synthesis of the n-type nanostructured titanium dioxide semiconductor using a combined sol-gel/solvothermal method at 200°C, varying the concentrations of H2O and HCl used as a catalyst for the hydrolysis of the titanium isopropoxide precursor. A white powder of TiO2 nanoparticles was obtained via the solvothermal process. Scanning electron microscopy revealed a spherical morphology of the TiO2 nanoparticles, with their diameter ranging from 2 to 7 microns as the HCl concentration increases. High-resolution electron microscopy and X-ray diffraction showed that the spheres are mesoporous titanium oxide (TiO2m) composed of nanocrystals with an anatase crystalline phase whose crystallite diameter grows from 8 to 13 nm as the HCl concentration increases. On the contrary, optimizing the H2O concentration enabled a decrease in the crystallite size of TiO2m and increases in the surface area and the energy band gap of TiO2m. The enlarged surface area enabled an increase in the number of contact points between TiO2m and the dye of dye-sensitized solar cells (DSSCs), resulting in a better solar cell performance. The white powder was used to prepare a TiO2m film via the screen-printing technique, which was used in the development of DSSC. The performance parameters of the DSSC (ISC, VOC, FF, and η%) were correlated with the synthesis parameters of TiO2m. This correlation showed that H2O and HCl greatly influence the semiconductor properties of TiO2m, along with the short-circuit current JSC and the conversion efficiency η% of the DSSC.

Development of dye-sensitized solar cell based on combination of natural dyes extracted from Malabar spinach and red spinach

Abstract Herein, natural green and red dyes have been extracted from Malabar spinach (Basella alba) and red spinach (Amaranthus dubius), respectively, and were used as a sensitizer source for TiO2 photoanode based dye sensitized solar cell (DSSC). The cell efficiency of the developed DSSC sensitized with single individual green and red dyes were obtained, 0.466% and 0.531%, respectively. To improve the cell efficiency of natural dye-based DSSC, natural green and red dyes have been combined at 5 different volume ratios, to find the optimum combination of dyes. From the UV–Vis absorption spectrum, the combination of dyes showed cumulative absorption properties of both single individual dyes. DSSC co-sensitized with the optimum combination of dyes (20% green + 80% red) exhibited the best performance of open circuit voltage of 385 mV, short circuit current of 4.273 mA, fill factor of 0.515 and the highest cell efficiency of 0.847% under 100 mW/cm2 illumination at AM 1.5G condition. The optimised cell efficiency was found 0.847% which is almost 1.82 and 1.6 times higher than that of the single individual green and red dye-sensitized DSSC’s cell efficiency.

Low‐cost dye‐sensitized solar cells with ball‐milled tellurium‐doped graphene as counter electrodes and a natural sensitizer dye

This paper presents a facile and economic development of dye-sensitized solar cells using a nonprecious counter electrode made from ball-milled tellurium-doped graphene (Te-Gr) and a natural sensitizer extracted from Calotropis gigantea leaves. The prepared materials were characterized using various techniques, such as Raman spectroscopy, X-ray diffraction (XRD), atomic force microscopy (AFM), impedance spectroscopy, and scanning electron microscopy with built-in energy-dispersive X-ray spectroscopy (SEM with EDS). The electrochemical activity of the produced counter electrodes and the impedance of the fabricated cells were examined and discussed to devise plans for future enhancement of cell performance. A clear pattern of improvement was found when using cost-effective Te-Gr relative to the costly platinum counter electrodes, especially when compared with cells employing another natural sensitizer. The results show approximately 51% enhancement over chlorophyll-based cells made from spinach, where the added advantage in our approach is the utilization of an abundant plant extract with little nutritional appeal.

Effects of TiO2 Coating on WO3 Inverse Opal Photoelectrode for Dye-sensitized Solar Cells

This study is based on Research and Education (R&E) project in science high school. In this study, we compared the photoelectrochemical properties of pure WO3 and TiO2 coated WO3 inverse opal film after the development of dye-sensitized solar cells (DSSCs). That is, above the SnO2 inverse opal (IO), thin WO3 film was prepared by the facile electrodeposition, subsequently forming the TiO2 layer by dipping in the 0.05 M or 0.005 M TiCl4 solution. Their morphological, crystalline, optical and photoelectrochemical properties of the developed films and composed DSSCs were evaluated exploring the field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), UV-visible spectrophotometer and solar simulator. In particular, the fill factor of pure WO3 coated SnO2 IO, 0.005 M TiCl4 treated WO3/SnO2 IO and 0.05 M TiCl4 treated WO3/SnO2 IO existed in the similar value of approximately 32%. On the other hand, the TiO2 coated samples exhibit the more enhanced absorption and photocurrent, compared to that of pure WO3/SnO2 IO, resulting in the high conversion efficiency. This points out that the proper coating of TiO2 layer on the WO3 photoelectrode can induce to the high dye adsorption as well as the suppressed charge recombination, granting the possibility of the challenging photoelectrode.

Influence of grey and color filters on the electrical properties of the dye-sensitized solar cells

During the last decade, generating renewable energy has become more and more important, and so did solar cells. This led to a swift development of dye-sensitized solar cells (DSSCs). The highest efficiencies are achieved by cells which use synthetic ruthenium-based dyes; however, DSSCs can also be prepared from low-purity and nontoxic materials. Extracting anthocyanins from, e.g., fruit or commercially available tea offers an economic and ecological alternative to toxic dyes, while the solar cell efficiency is significantly reduced. This article reports on the possibility of using anthocyanin-based DSSCs under ambient light, which was modified by different grey and color filters. Dyes were tailored by modifying the pH value of the dye solution. While generally the lowest pH values resulted in the highest efficiencies, the performance of all DSSCs depended strongly on the light spectrum, for some color filters even favoring the original dye solution without pH modification.

Role of Nanostructured Photoanode and Counter Electrode on Efficiency Enhancement of DSSCs

In recent years, dye-sensitized solar cells (DSSCs) have received widespread attention due to their low cost compared to conventional silicon photovoltaic cells. However, to reach optimal device efficiencies, much work is still required. Nanotechnology opens a door to creating various nanostructures and tailing materials for use in DSSCs. Here we reviewed the development in nanomaterials based on modified electrodes which utilize the advantages of high electrocatalytic ability and high surface area due to their nanostructured morphology. This review highlights recent developments in DSSCs and their key components with respect to nanostructured modification, which will provide deep insights and guidance for researchers to design and develop cost-effective and efficient DSSCs.

Recent Progress of Graphene-Based Photoelectrode Materials for Dye-Sensitized Solar Cells

Graphite with a single atomic layer known as graphene shows great capability in energy conversion and storage devices. Dye-sensitized solar cells (DSSCs) have attracted intense interests due to offering high photo-to-electric conversion efficiencies. DSSCs are built from a photoelectrode (a dye-sensitized nanocrystalline semiconductor), an electrolyte with redox couples, and a counterelectrode. In this review article, we outline the strategies to enhance the efficiency and reduce the cost by introducing graphene into the DSSCs as the photoelectrode. First, the development of DSSCs and the properties of graphene are briefly described. Then, the applications of graphene-based materials for photoelectrodes (transparent electrode, semiconductor layer, and dye sensitizer) in DSSCs are deeply discussed. Finally, an outlook for graphene materials in DSSCs is provided.

Quasi‐Solid‐State Dye‐Sensitized Solar Cells Containing a Charged Thermoplastic Elastomeric Gel Electrolyte and Hydrophilic/phobic Photosensitizers

As the threat of global climate change due to combustion emissions becomes increasingly alarming, the search for clean and sustainable alternative energy is of paramount importance. With this objective in mind, harnessing solar energy is particularly attractive due to ongoing improvements in silicon‐, perovskite‐, and organic‐based solar cells. Of these, dye‐sensitized solar cells (DSSCs) constitute a promising technology due to their relatively low cost, moderate conversion efficiency, and robust mechanical properties. An important breakthrough in the development of DSSCs is the use of polymer gel electrolytes. In this work, we employ amphi­philic thermoplastic elastomers (TPEs) in the form of sulfonated block ionomer (SBI) homologs for this purpose. Since the midblock of each charged copolymer is hydrophilic, the resultant microphase‐separated nanostructures consist of continuous ionic channels that facilitate electron diffusion. A unique characteristic of the SBI archetype studied here is that the morphology can be solvent‐templated. We exploit this feature by introducing either hydrophilic or hydrophobic photosensitizers into the DSSCs. When the SBI exhibits a primarily lamellar morphology, a hydrophilic dye yields the highest efficiency (7.0%), whereas the opposite is observed when the nanostructure consists of a solvent‐templated nonpolar matrix. Photosensi­tizer tunability is augmented by the intrinsic mechanical and adhesive properties of a TPE.

Molecular Docking toward Panchromatic Dye Sensitizers for Solar Cells Based upon Tetraazulenylporphyrin and Tetraanthracenylporphyrin.

Novel dye sensitizers are highly expected in the development of dye-sensitized solar cells (DSSCs) because dye sensitizers can significantly affect the power conversion efficiency (PCE). Here, the molecular docking strategy is applied to design panchromatic dye sensitizers for DSSCs to improve light-harvesting efficiency covering the full solar spectrum. Considering the broad absorption bands of tetraanthracenylporphyrins (TAnPs) and tetraazuleneporphyrins (TAzPs), based upon porphyrin dye sensitizer YD2-o-C8, the panchromatic dye sensitizers coded as H2(TAnP)-α, H2(TAzP)-γ, H2(TAzP)-ε, and H2(TAzP)-δ are designed by the substitution of the porphyrin-ring in YD2-o-C8 with TAnPs and TAzPs moieties at different positions. The geometries, electronic structures, and excitation properties of the designed dye sensitizers are investigated using density functional theory (DFT) and time-dependent DFT methods. The analysis of geometries, conjugation lengths, electronic structures, absorption spectra, transition configurations, exciton binding energies, and free energy variations for electron injection and dye regeneration supports that the designed molecules are effective to be applied as potential candidates of dye sensitizers for DSSCs. Among the designed dye sensitizers, H2(TAzP)-γ and H2(TAnP)-α must have the better performance in DSSCs.

Influence of the pH value of anthocyanins on the electrical properties of dye-sensitized solar cells

In recent years the harvesting of renewable energies became of great importance. This led to a rapid development of dye-sensitized solar cells which can be produced from low-purity materials. The best electrical properties are provided by cells prepared using synthetical, ruthenium based dyes. Unfortunately, most of them are toxic and expensive. The anthocyanins extracted for example from hibiscus flowers yield a more cost-effective and eco-friendly alternative to toxic dyes, however, with a loss of solar cell efficiency. In this article the possibility of improvement of the conversion efficiency by modification of the pH value of the dye is investigated. By decrease of the pH value, an increase of efficiency by a factor of two was achieved.

Fluorous molecules for dye-sensitized solar cells: synthesis and properties of di-branched, di-anchoring organic sensitizers containing fluorene subunits

Four organic sensitizers having a di-branched molecular structure D–(π–A)2 were applied in the development of dye-sensitized solar cells (DSSCs).