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Gelling polysaccharide as the electrolyte matrix in a dye-sensitized solar cell
Abstract
Hydrophilic polysaccharide, κ-carrageenan, was utilized as the polymer matrix in gel-electrolyte systems for dye-sensitized solar-cell (DSSC) applications. The influence of the solvent system was investigated to optimize the solubility of κ-carrageenan and tetrabutylammonium-iodide (TBAI)/I2 electrolytes by minimizing the water content because of its unfavorable effect on DSSCs. We report herein that two solvent systems, a water/acetonitrile mixed solvent and DMSO, were found to effectively dissolve the components. The composite natures of the κ-carrageenan-electrolyte systems in these solvents were confirmed with an FTIR analysis. The presence of κ-carrageenan did not impede the electrochemical properties of the electrolytes, as confirmed with cyclic voltammetry, electrochemical impedance spectroscopy and linear sweep voltammetry. The incorporation of the gel electrolytes in DSSCs showed that the DMSO system exhibited better solar-cell efficiency compared to the mixed-solvent system.
... The second generation of PV resembles the use of cadmium telluride (CdTe) and gallium arsenide (GaAs) as thin-film technology media. The third generation of PV can be a dye-sensitized solar cell (DSSC) otherwise known as Grӓtzel cell, perovskite solar cell, quantum dot solar cell, or such emerging technology that can pass the 31-41% efficiency rating standardized using Shockley-Queisser limit [1][2][3]. ...
... Flowers such as Bougainvillea spectabilis [17] and hibiscus [18] have been used for the extraction of betalain pigment. κ-carrageenan extracted from seaweeds was used as an optimizer for DSSC [2]. The Harum Manis mango that is available in Malaysia has been experimented with as a photosensitizer [19] concerning extracting temperature and as well as dragon fruit [20]. ...
... The ES-based DSSC was able to complete the stability test with 170.4% and 142.6% reduction in current and voltage readings based on a single light source. The reduction appeared to be caused by the open case of the fabricated DSSC as no thermoplastic Surlyn was used to seal the solar cells as compared to [2]. However, it was seen in this stability verification test that even the fabricated system is partially open allowing the iodide/triiodide redox couple electrolyte and the natural lettuce pigment adsorbed by the TiO 2 thin film layer to be easily evaporated, the measured photoelectrical properties still abide the principle of biomimicry of plant leaves especially the evolutionary strategy-based dye-sensitized solar cell with 16.5% green and 83.5% violet concentrations. ...
To enhance the power efficiency of a dye-sensitized solar cell (DSSC) or Grӓtzel cell, photosensitizer concentration must be fine-adjusted within the ultraviolet and near-infrared spectrum. In this study, evolutionary computing through genetic algorithm (GA) and evolutionary strategy (ES) was employed to determine the optimal combination of chlorophyll a and anthocyanin concentrated dyes extracted from cultivated Lactuca Sativa var. Altima (green) and Rania (violet). ES configured with 0.6 selection rate, 0.08 Gaussian mutation rate, and 0.4 crossover rate generated the optimal dye concentration of 16.5% green and 83.5% violet yielding 24.093% efficiency in AM 1.5 sunlight intensity. It also exhibited the maximum short-circuit current (4.591 mA), open-circuit voltage (688.7 mV), filling factor (0.762), and power (3.162 mW). UV-Vis spectrophotometry confirmed that combining chlorophyll (663 nm) and anthocyanin (520 nm) pigments increases photon energy utilization. It is supported by the 2.39 eV optical energy bandgap and 2.009 Km⁻¹ absorption coefficient of the ES-based cell. FTIR verified that no new bond or reaction was formed by combining pigments rather they coexist with each other allowing a broader light spectrum to excite the ground state electrons in the TiO2 layer. Thus, ES-combined dyes increased the efficiency by a factor of 9.965 and 2.299 from green and violet pigments respectively.
... However, the use of a hydrogel is much less explored in the literature. Camacho et al. employed a K-carrageenan hydrophilic polymer as a gelling agent in pure water, but the overall performance was lower than 0.01% [25]. More recently, Saraubh and coworkers [26] reported on the use of a saturated chenodeoxycholic acid (CDCA) liquid electrolyte that was then jellified with 62% w/w block copolymer (EO52-PO35-EO52), resulting in photoconversion efficiency (PCE) ≈ 1%. ...
The investigation of innovative electrolytes based on nontoxic and nonflammable solvents is an up-to-date, intriguing challenge to push forward the environmental sustainability of dye-sensitized solar cells (DSSCs). Water is one of the best choices, thus 100% aqueous electrolytes are proposed in this work, which are gelled with xanthan gum. This well-known biosourced polymer matrix is able to form stable and easily processable hydrogel electrolytes based on the iodide/triiodide redox couple. An experimental strategy, also supported by the multivariate chemometric approach, is used here to study the main factors influencing DSSCs efficiency and stability, leading to an optimized system able to improve its efficiency by 20% even after a 1200 h aging test, and reaching an overall performance superior to 2.7%. In-depth photoelectrochemical investigation demonstrates that DSSCs performance based on hydrogel electrolytes depends on many factors (e.g., dipping conditions, redox mediator concentrations, etc.), that must be carefully quantified and correlated in order to optimize these hydrogels. Photovoltaic performances are also extremely reproducible and stable in an open cell filled in air atmosphere, noticeably without any vacuum treatments.
In the last decade, the development of high-efficiency electrolytes based on polymeric materials has drawn increasing attention. Polysaccharides are widespread biopolymers with properties suitable for the fabrication of high-efficiency polymer electrolytes. In specific, algal-based polysaccharides are promising eco-friendly and biodegradable alternatives to conventional polymer electrolytes. This review focuses on the recent progress of polymer electrolytes based on algal polysaccharides. We set the basic consideration for high-performance polymer electrolytes and discuss the materials science aspects of algal-based polysaccharides involved. Then, we review the recent progress of algal polysaccharides-based electrolytes, including the various physical and chemical treatments applied for the enhancement of ionic conductivity and mechanical properties. Lastly, we summarize the applications of the algal polymer electrolytes in batteries, fuel cells, supercapacitors, and dye-sensitized solar cells and their performance. Algal polysaccharides are presented as biodegradable, cost-efficient, high-performance, and eco-friendly alternatives for the development of high-performance solid polymer electrolytes for modern electrochemical applications.
Continual escalation of our world population demands a vast and safe energy supply, the majority of which has been produced by fossil fuel sources. However, because of the huge energy demand, exponential depletion of these nonrenewable energy sources is inescapable and forthcoming in the coming century. Hence, utilization of renewable energy such as solar energy has gained attention because of its direct conversion of light energy into electrical power without any harmful environmental impacts. Solar energy has been harvested by different types of solar cells varying from inorganic to organic to the combination of both. Among them, the dye-sensitized solar cell (DSSC) with a biopolymer-based electrolyte has gained enormous consideration from researchers because of its sustainability, abundance of available raw material, low production cost, and easy production in addition to the low volatilization of electrolytes compared to liquid state electrolytes. This review aims to give an overview of the recent inputs in the development of biopolymer-based DSSCs. The performance of the biopolymers as electrolytes in DSSCs will be critically reviewed based on the physicochemical properties of the biopolymers. Key technical challenges and future research areas for the advancement of biopolymer-based DSSCs are also discussed.
The electrolyte gel preparation from natural polymers has been made as a component of Dye Sensitized solar cells (DSSC). Electrolyte gel is made from a mixture of alginate, potassium iodide (KI) and Iodine (I2) with a solvent casting method. Alginate gel is used as a matrix to bind KI/I2 solutions which act as electrolytes. In this study, KI/I2 electrolyte solution was made with a ratio of 10:1 then added alginate gel. To study the effect of the concentration of electrolyte solution on the electrolyte gel made by varying the amount of KI salt 10; 20; 30; 40 and 50%. In this study also studied the effect of polymer composites on the manufacture of electrolyte gels carried out by mixing alginate/PVA; Alginate/PEG and alginate/PVA/PEG. Based on the cyclic voltammetry data, the alginate-KI/I2 composite showed an oxidation and a reduction peak. This shows the occurrence of the redox cycle in the alginate-KI/I2 composite so that it can act as an electron flow mediator in the DSSC system. The effect of the amount of KI salt on the electrolyte gel shows the difference in the redox peak current produced. The highest peak current is obtained by adding KI salt 50% which is 2.5 mA. FTIR spectra data show the presence of carbonyl groups (C=O) and ether groups (C-O-C) which prove the occurrence of complexation between alginates and KI/I2 salts.
Increasing the photocurrent is one of the main objectives of the current research on aqueous photovoltaic cells, the emerging green, alternative technology in solar energy conversion devices. In such a scenario, this work deals with the thorough understanding of the electrochemical and photoelectrochemical effects of the TiCl 4 treatment onto TiO 2 electrodes, a well-known process for traditional dye-sensitized solar cells, and here, to our knowledge, investigated for the first time in water-based systems. From the quantitative evaluation of the photoelectrochemical parameters, it emerges that the TiCl 4 treatment beneficially affects the photovoltaic parameters: it doubles the sunlight conversion efficiency values, inhibits the recombination of photogenerated electrons with oxidized redox mediator ions, and ensures stable and reproducible cell performance at the laboratory scale.
The electrolyte system is a critical component in a dye-sensitized solar cell (DSSC). A starch-based gel polymer electrolyte (GPE) is described herein as a potential quasi-solid-state electrolyte system for DSSC. Potato starch was modified by grafting 1-glycidyl-3-methylimidazolium chloride (GMIC) ionic liquid onto the polysaccharide chain to afford a cationic starch (CS) as confirmed by elemental analysis (nitrogen content = 1.33%), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). Despite its low degree of substitution (0.084), the resulting properties of the new cationic starch such as its coarse yellowish brown coloration, high-water solubility, flaky morphology, higher thermal stability, and higher gelatinization temperature differentiate it distinctly from the raw starch. In DMSO solvent, the cationic starch (CS) forms a gel and addition of GMIC ionic liquid (CS:GMIC ratio 1:3) as plasticizer afforded a gel polymer electrolyte (GPE) system after doping with the KI/I2 (70 wt%) redox couple. Electrochemical impedance spectroscopy revealed high conductivity and efficient ion migration. The optimized CS-GPE was incorporated in DSSC as quasi-solid-state electrolyte system affording 0.514% efficiency. Despite its low performance against the liquid electrolyte control, it exhibited relative stability due to its good filling contact between the electrodes.
Photovoltaic technologies represent one of the leading research areas of solar energy which is one of the most powerful renewable alternatives of fossil fuels. In a common photovoltaic application the batteries play a key role in storage of energy generated by solar panels. Although it will take time for dye sen-sitized solar cells (DSSCs) and batteries based on biopolymer electrolytes to take their places in the market, laboratory studies prove that they have a lot to offer. Most efficient DSSCs and batteries available in market are based on liquid electrolytes. The advantages of liquid electrolytes are having high conductivity and good electrode-electrolyte interface whereas, disadvantages like corrosion and evaporation limit their future sustainability. Biopolymer electrolytes are proposed as novel alternatives which may overcome the problems stated above. In this review, we focus on fabrication, working principle as well as up to date status of DSSCs and batteries using biopolymer electrolytes. The effects of structural and electrical properties of biopolymer based electrolytes on the solar energy conversion efficiencies of DSSCs and their compatibility with lithium or other salts in battery applications are summarized. Biopolymer electrolyte based DSSCs are categorized on the basis of types of additives and recent outcomes of author's laboratory studies on biopolymer electrolyte based DSSCs and batteries are also presented.
The effect of lithium iodide (LiI: 0–85wt%) on the electrochemical behavior of agarose-based polymer electrolytes for dye-sensitized solar cells (DSSC) was investigated. Fourier Transform Infrared Spectroscopy (FTIR) and scanning electronic microscopy (SEM) were employed to characterize the interactions between polymer matrix and salt and the morphology of the agarose electrolytes, respectively. From the AC impedance spectra study, it was determined that the conduction behavior of the agarose-based polymer electrolyte matches the “salt-in-polymer” like behavior of low LiI content (0–25wt%) and “polymer-in-salt” like behavior of high LiI content (25–85wt%). Detailed analysis of characteristic electrochemical processes occurring in DSSC with these agarose electrolytes was also obtained by employing the EIS technique. The impedance spectra showed that the electron lifetime of DSSC was shortened with increasing LiI concentration, while the charge transfer resistance and charge recombination resistance were reduced when LiI concentration was increased.
Various iodide ion conducting polymer electrolytes have been studied as candidate materials for fabricating photoelectrochemical
(PEC) solar cells and energy storage devices. In this study, enhanced ionic conductivity values were obtained for the ionic
liquid tetrahexylammonium iodide containing polyethylene oxide (PEO)-based plasticized electrolytes. The analysis of thermal
properties revealed the existence of two phases in the electrolyte, and the conductivity measurements showed a marked conductivity
enhancement during the melting of the plasticizer-rich phase of the electrolyte. Annealed electrolyte samples showed better
conductivity than nonannealed samples, revealing the existence of hysteresis. The optimum conductivity was shown for the electrolytes
with PEO:salt = 100:15 mass ratio, and this sample exhibited the minimum glass transition temperature of 72.2 °C. For this
optimum PEO to salt ratio, the conductivity of nonannealed electrolyte was 4.4 × 10−4 S cm−1 and that of the annealed sample was 4.6 × 10−4 S cm−1 at 30 °C. An all solid PEC solar cell was fabricated using this annealed electrolyte. The short circuit current density (I
SC), the open circuit voltage (V
OC), and the power conversion efficiency of the cell are 0.63 mA cm−2, 0.76 V, and 0.47% under the irradiation of 600 W m−2 light.
The vast use of fossil fuel demands the development of new sources of renewable energy. Dye-sensitized solar cells (DSSCs) have been extensively studied due to their competitive cost, ease of fabrication, high degree of tunability and relatively good-energy conversion efficiencies. The performance and stability of DSSCs are limited by leakage and solvent evaporation. This study explores the effects of nanofillers in the performance of dye-sensitized solar cells by incorporating nano-sized titanium dioxide, iron (III) oxide and halloysite fillers into the polymer electrolytes based on κ-carrageenan/DMSO/TBAI:I 2. Optimization and characterization of various concentrations of fillers were done before incorporation in solar cells. The effect of ionic conductivity and diffusion coefficient to the overall conversion efficiency of the cells were studied. The effect of squaraine dye was also investigated. The addition of various fillers to the polymer electrolyte system increased the dissociation of iodide ions and improved the ionic conductivity of the cells. The diffusion coefficient of tri-iodide ions was also greatly enhanced because of the increased volume of the system brought about by reducing polymer-polymer interaction, which increased the mobility of the redox couple (I 3-/ I-). DSSC characterization revealed a low efficiency due to a relatively high charge transfer resistances at the TiO 2 /dye/electrolyte interface.
In this work we study the effects of TiO2, Co3O4, and NiO nanoparticle additives on the properties of agarose polymer electrolytes. We characterize the crystallinity, surface morphology, ion concentration, ionic conductivity, and pore filling capability of the modified electrolytes using a variety of experimental methods. Solid-state dye-sensitized solar cells are also fabricated using the modified agarose electrolytes, and their photovoltaic and electrochemical performances are examined. The DSSC based on Co3O4-modified agarose electrolyte shows the best device performance including a power conversion efficiency of 2.11% and good device stability after 400 h of testing.
Renewable energy systems represent a milestone of third millennium applied scientific research. As a viable, economic and environmentally friendly alternative to the solid electrolytes currently used in dye-sensitized solar cells (DSSCs), here we propose a biopolymer derived from seaweeds, which undergoes a process of selective carboxylation to improve its transport properties. Subsequently, a chemometric approach is used to tune the amount of salts and additives, and the highest ever measured ionic conductivity for a biopolymeric solid electrolyte has been reached (5.53 ∙ 10−2 S cm−1). To make this material suitable for DSSC application, an innovative sublimation process has been developed to allow a molecule-by-molecule activation of the electrolyte, and an efficiency of 2.06% (stable in aging tests) was measured in a first device prototype. Green chemistry, low cost materials, multivariate-based preparation methods and activation via spontaneous sublimation make this investigation a concrete starting point for the new generation of solid electrolytes for DSSCs.
Poly (vinylidene fluoride-co-hexafluropropylene) (PVDF-HFP) and poly (acrylonitrile-co-vinyl acetate) (PAN-VA) are used as gelator to prepare gel- and solid-state polymer electrolytes for dye sensitized solar cells (DSSCs) applications. The electrolytes prepared using PVDF-HFP have higher conductivities than those prepared using PAN-VA. In blended polymers, the conductivities of the electrolytes increase with increasing composition of PVDF-HFP; at 75% PVDF-HFP, conductivity of the blended polymer surpassed that of pure polymers. It is also found that the viscosity of the electrolyte prepared by PAN-VA (1.2 kPaS) is much lower than that by PVDF-HFP (11 kPaS). Therefore, increasing PAN-VA composition can decrease the viscosity of the electrolyte, improving the penetration of electrolytes in the TiO2 matrix. By controlling the ratio of PVDF-HFP/PAN-VA, the conductivity and viscosity of the electrolyte can be regulated and an optimal ratio based on the conversion efficiency of the gel- and solid state DSSCs is obtained at the ratio of 3/1. The highest efficiency achieved by the gel- and solid-state cells using the blending polymers are 6.3% and 4.88%, respectively, which are higher than those prepared using pure polymers (5.53% and 4.56%, respectively). The introduction of TiO2 fillers to the solid electrolyte can further increase the cell efficiency to 5.34%.
With an aim of elevating liquid electrolyte loading, ionic conductivity, and electrocatalytic activity of gel electrolyte toward triiodides, freeze-dried microporous poly(acrylic acid)–poly(ethylene glycol) (PAA–PEG) matrix is employed to uptake conducting polymers, such as polyaniline (PANi) and polypyrrole (PPy). An ionic conductivity of 19.18 mS cm−1 at 65 °C is obtained from PAA–PEG/PANi conducting gel electrolyte which is nearly similar to 19.22 mS cm−1 from pure liquid electrolyte. The conducting polymers can form interconnected channels within insulating microporous PAA–PEG matrix, therefore, the reduction reaction of triiodide ions in the dye-sensitized solar cells (DSSCs) can be extended from Pt/gel electrolyte interface to both interface and three-dimensional framework of microporous conducting gel electrolyte. The resultant DSSCs from PAA–PEG/PANi and PAA–PEG/PPy conducting gel electrolytes display power conversion efficiencies of 7.12% and 6.53%, respectively, which are much higher than 5.02% from pure PAA–PEG-based DSSC. The new concept along with easy fabrication promises the microporous conducting gel electrolytes to be good alternatives in efficient quasi-solid-state DSSCs.
The fundamental electrochemical characteristics of tight and elastic polysaccharide solids involving a nanostructured network and excess water were investigated. The diffusion of redox molecules, charge transfer resistance at the electrode|solid interface, and double layer capacitance on the electrode surface were studied. The cyclic voltammograms in the agarose and the κ-carrageenan solids show very similar features as in liquid water including the redox potential and peak currents, but with a slightly larger peak separation for the solid systems. The electrochemical impedance spectrum (EIS) was measured in the polysaccharide solid. The apparent diffusion coefficient (Dapp) of Fe(CN)63− in the solids is almost the same as in an aqueous solution. The charge transfer resistance (Rct) on the electrode surface in a κ-carrageenan solid was even smaller in a κ-carrageenan solid than that in an aqueous solution, although it was larger in an agarose solid. The Rct tends to decrease with the polysaccharide concentration in the solid. The double layer capacitance (Cdl) on the electrode surface in a Fe(CN)63− aqueous solution tends to increase with the Fe(CN)63− concentration, but for the solid systems Cdl values are only weakly dependent on the Fe(CN)63− concentration, and similar to that in an aqueous solution at 5 mM Fe(CN)63− concentration. It was elucidated that the polysaccharide solid can work well as a new solid medium for conventional electrochemical measurements and electrochemistry.
Four surfactants, sodium dodecyl sulfate (SDS), polyvinylpyrrolidone (PVP), polyethylene glycol (PEG200) and polysorbate 80 (TW-80), were added to disperse Fe3O4 nanoparticles in agarose based magnetic polymer electrolyte, for the purpose of improving the performance of dye-sensitized solar cell (DSSC). Fourier transform infrared spectroscopy (FTIR) was employed to characterize the interactions between surfactants and magnetic polymer electrolyte. TW-80 and PEG200 showed good dispersion properties according to surface morphology tests. Through electrochemical impedance spectroscopy (EIS) study, the ionic conductivity, charge transfer resistance, charge recombination resistance and electron lifetime of polymer electrolytes were all improved by modification, while TW-80 modified electrolyte reached the highest ionic conductivity of 2.98 × 10−3 S/cm. Moreover, the photoelectric properties were also significantly enhanced and the best energy conversion efficiency achieved 1.83% with TW-80 modification.
The development of polymer electrolytes which have potential applications in battery technology has resulted in an escalation of research into the synthesis of new macromolecular supports and the mechanisms of ionic transport within the solid matrix. Investigation of the properties of polymer electrolytes has brought together polymer chemists and electrochemists, and the understanding of the solubility and transport of electrolytes in organic polymers is now developing from this pooled experience. This book deals with experimental, theoretical and applied aspects of solid solutions of electrolytes used in coordinating polymer matrices. Attention is focused on the synthesis and properties of these new materials, the mechanisms of conduction processes and practical applications, especially with regard to battery technology.
A solid polymer electrolyte system based on poly(vinyl pyrrolidone) (PVP) complexed with sodium chlorite (NaClO3) salt has been prepared by a solution — cast technique. Several experimental techniques, such as composition-dependence conductvity, temperature-dependence conductivity in the temperature range of 303–398K and transport number measurements, have been employed to characterize this polymer electrolyte system. The conductivity of the (PVP+NaClO3) electrolyte is about 104 times larger than that of pure PVP at room temperature. Transport number measurements show that the charge transport is mainly due to ions. An electrochemical cell with the configuration Na/(PVP+NaClO3)/(I2+C+electrolyte) has been fabricated and its discharge characteristics studied. The open-circuit voltage and short-circuit current are 2.77V and 1.35mA, respectively. A number of other cell parameters are reported.
The liquid of a dye-sensitized solar cell composed of a nanoporous titanium dioxide (TiO2) film and a bipyridine–Ru complex dye (N3 dye) was solidified by utilizing a tight and elastic solid polysaccharide (κ-carrageenan or agarose) containing excess liquid. The solid type cell exhibited similar characteristics and light-to-electricity conversion efficiency as a conventional liquid type cell. The electric resistance of the solid containing the solution of redox electrolytes (I−/I3−) was of the same order of magnitude as a liquid, and the charge transfer resistance on the electrode surface was even smaller for the solid than for the liquid. The increase of the polysaccharide solid hardness did not greatly affect the conversion efficiency. On exchanging the water of the polysaccharide solid with an organic medium solution containing redox electrolytes, the soaking time (from 1 to 3 h) and the repeated change to a fresh solution did not greatly affect the performance of the solid type cell. For both the solid and liquid type cells the thinner electrolyte layer gave a higher conversion efficiency. The investigation of both the solid and liquid type cells by alternating current impedance spectroscopy showed almost similar behavior in every step of the charge transfer event.
The potential of κ-carrageenan derivatives as a green polymer electrolyte has been explored. κ-Carrageenan extracted from marine red algae was reacted with monochloacetic acid to form carboxymethyl κ-carrageenan. The powders were characterized by reflection fourier transform infrared (ATR-FTIR) spectroscopy,13C nuclear magnetic resonance, 1H nuclear magnetic resonance, X-ray diffraction and elemental analysis to confirm the structural, crystallinity and the degrees of substitution. A green polymer electrolyte of κ-carrageenan and carboxymethyl κ-carrageenan were prepared by solution-casting technique. The films were characterized by reflection fourier transform infrared (ATR-FTIR) spectroscopy and electrochemical impedance spectroscopy to determine the chemical interaction and ionic conductivity. The decrease in intensity of hydroxyl, carbonyl, sulfate and ether band confirmed the polymer solvent complex formation. XRD spectra show that chemical modification of κ-carrageenan does not change its amorphous properties. The ionic conductivity was found to increase by three magnitudes higher with the chemical modification of κ-carrageenan. The conductivity achieved was 2.0 × 10− 4 S cm− 1 for carboxymethyl κ-carrageenan in comparison to 5.3 × 10− 7 S cm− 1 for κ-carrageenan.
The cellulose was grafted homogeneously with acrylic acid by in situ polymerization in an ionic liquid 1-butyl-3-methylimidazolium iodide ([Bmim]I) as reaction medium. This polymer is suitable for quasi-solidification of electrolytes in DSSCs by in situ synthesis because the polymerization reaction proceeds in the ionic liquid containing iodide ion. Using the matrix as polymer host, KI and I2 as ionic conductors, an ionic conductivity of the gel polymer electrolyte was achieved 7.33 mS cm−1. Based on the optimized gel electrolyte, the best result of the quasi-solid state dye-sensitized solar cell (QS-DSSC) was the light-to-electricity conversion efficiency of 5.51% under a light intensity of 100 mW cm−2 (AM 1.5).Highlights► The grafted cellulose was prepared in an ionic liquid as reaction medium. ► The QS-DSSCs were assembled with the gel grafted cellulose electrolytes. ► The general behavior of impedance spectra was similar for gel or liquid electrolyte. ► The best result of the QS-DSSC was the photoelectric conversion efficiency of 5.51%.
The chemical stability of dye-sensitized solar cells (DSSC) determines both the cell performance and the cell life-time. The presence of water in the solar cell from surrounding leakage through the imperfection packaging sealants causes the decrease in life-time of photogenerated electrons on the working electrodes, which induces the occurrence of the dark current to the electrolytes and thus leakage current significantly deteriorated the life-time of the DSSC. Reliable electrolyte additives diminishing the influences of water to the DSSCs degradation process becomes a critical issue in maintaining an acceptable cell life-time.In this work, the effects of four benzimidazole derivatives a–d as the electrolyte additives in the presence of water were comprehensively examined by time-dependent photovoltaic performance of the cells. As a result, open-circuit voltage (Voc), short-circuit current (Jsc), efficiency (η), and fill factor (FF) collected from I–V curves were studied. In addition, electrochemical impedance spectroscopy (EIS) technique was implemented to evaluate the effects of the charge-transfer resistance (Rct) at the interfaces between TiO2/dye/electrolyte. Results showed that the bis-benzimidazole derivative c gives significant improvement in the long-term stability due to the effective protection of the ligands between dye and working electrodes from the attack by environmental water molecules.
We have studied the influence of electrolytes on the photovoltaic performance of mercurochrome-sensitized nanocrystalline TiO2 solar cells using LiI, LiBr, and tetraalkylammonium iodides as the electrolyte. Short-circuit photocurrent density (Jsc) and open-circuit photovoltage (Voc) depended strongly on the electrolyte. Jsc of 3.42 mA cm−2 and Voc of 0.52 V were obtained for the LiI electrolyte and Jsc of 2.10 mA cm−2 and Voc of 0.86 V were obtained for the Pr4NI electrolyte. This difference in photovoltaic performance was due to the change in the conduction band level of the TiO2 electrode. Large Voc of 0.99 V was obtained for the LiBr electrolyte due to the large energy gap between the conduction band level of TiO2 and the Br/Br2 redox potential. Solar cell performance also depended strongly on organic solvent, suggesting that the physical properties of solvents such as Li ion conductivity and donor number affect photovoltaic performance.
Stable and efficient dye-sensitized solar cells based on water-containing electrolytes are shown. For water contents up to 40%, no decrease in efficiency is seen. The cells are demonstrated to be stable for long periods of continuous illumination.This work lays a foundation for the further development of water-based cells for commercial production.
Carrageenan-Ionic Liquid Composite: Development of Polysaccharide-Based Solid Electrolyte System
- D H Camacho
- S J M Tambio
- M I A Oliveros
D. H. Camacho, S. J. M. Tambio, M. I. A. Oliveros, Carrageenan-Ionic Liquid Composite: Development of Polysaccharide-Based
Solid Electrolyte System, The Manila J. of Science, 6 (2011), 8-15
A Novel Biopolymer Gel Electrolyte System for DSSC Applications
- P Bantang
- D Camacho
P. Bantang, D. Camacho, A Novel Biopolymer Gel Electrolyte
System for DSSC Applications, Proceedings of the DLSU Research
Congress, 3, 2015