Use In Dye-sensitized Solar Cells Research Articles

Pulsed-laser-ablation based nanodecoration of multi-wall-carbon nanotubes by Co\u2013Ni nanoparticles for dye-sensitized solar cell counter electrode applications

We report here on the use of pulsed KrF-laser deposition technique (PLD) for the decoration of Multi-wall carbon nanotubes (MWCNTs) by Co–Ni nanoparticles (NPs) to form highly efficient counter electrodes (CEs) for use in Dye-sensitized solar cells (DSSC). By varying the number of laser ablation pulses (NLP = 500–60,000) of the KrF laser, we were able to control the average size of the Co–Ni NPs and the surface coverage of the MWCNTs by the nanoparticles. The PLD-based decoration of MWCNTs by Co–Ni NPs is shown to form novel counter electrodes, which significantly enhance the power conversion efficiency (PCE) of the DSSCs. Indeed, the DSSCs based on the PLD-decorated Co–Ni counter electrodes (obtained at the optimal NLP = 40,000) are shown to exhibit a PCE value as high as 6.68%, with high short circuit current (Jsc = 14.68 mA/cm2) and open circuit voltage (Voc = 0.63 V). This represents a PCE improvement of ~190% in comparison to the DSSCs with pristine MWCNTs (PCE = 2.3%) and ~7.4% PCE increase than that of the conventional DSSC made with a sputtered Platinum-based counter electrode. By systematically investigating the local nanostructure of the Co–Ni decorated CEs, we found that the Co–Ni NPs layer exhibits a porous cauliflower-like morphology, of which surface roughness (RMS) is NLP dependent. Interestingly, both PCE and roughness of the Co–Ni NPs layer are found to exhibit the same NLP dependence, with a maximum located around the optimal NLP value of 40,000. This enabled us to establish, for the first time, a linear correlation between the achieved PCE of DSSCs and the local roughness of their CEs decorated by Co–Ni NPs. Such a correlation highlights the importance of maximizing the surface area of the Co–Ni coated MWCNTs on the CEs to enhance the PCE of the DSSCs. Finally, Ultra-violet Photoelectron Spectroscopy (UPS) measurements revealed a significant decrease in the local work function (Φ) of Co–Ni NPs decorated MWCNTs based CEs (at NLP = 40,000, Φ = 3.9 eV) with respect to that of either pristine MWCNTs (Φ = 4.8 eV) or sputtered-Pt (Φ = 4.3 eV) counter-electrodes. This Φ lowering of the Co–Ni/MWCNTs based CEs is an additional advantage to enhance the catalytic reaction of the redox couple of the electrolyte solution, and improve thereby the PCE of the DSSCs.

Sn- and Pd-Free Synthesis of D-π-A Organic Sensitizers for Dye-Sensitized Solar Cells by Cu-Catalyzed Direct Arylation.

<A variety of D-π-A-type functional organic dyes are facilely synthesized by direct C-H arylation catalyzed by inexpensive copper salts. Under optimized reaction conditions, a broad substrate scope with good functional group compatibility was demonstrated. Based on this synthetic strategy, three new dye sensitizers (CYL-5-7) were designed and fabricated for use in dye-sensitized solar cells (DSSCs). Photovoltaic characterization showed that these devices gave open-circuit voltages of 0.65-0.75 V, short-circuit currents of 5.90-12.60 mA cm-2 , and fill factors of 65.6-76.9 %, corresponding to power conversion efficiencies (PCEs) of 2.95-6.20 %. This work represents the first use of Cu-catalyzed C-H arylation for a step-saving, Sn-free synthesis of precursor dyes for DSSC applications.

Bifurcation of Regeneration and Recombination in Dye-Sensitized Solar Cells via Electronic Manipulation of Tandem Cobalt Redox Shuttles.

A cobalt(IV/III) redox shuttle, cobalt tris(2-(p-tolyl)pyridine), [Co(ptpy)3]+/0, was synthesized and investigated for use in dye-sensitized solar cells, DSSCs. An incredibly fast self-exchange rate constant of (9.2 ± 3.9) × 108 M-1 s-1 was determined for [Co(ptpy)3]+/0, making it an ideal candidate for dye regeneration. To avoid fast recombination and solubility limitations, we utilized a tandem electrolyte containing [Co(ptpy)3]+/0 and cobalt tris(2,2'-bipyridine), [Co(bpy)3]3+/2+. An improved short circuit current density is achieved for DSSCs employing the tandem electrolyte, compared to electrolytes containing only [Co(bpy)3]3+/2+, consistent with superior dye regeneration expected based on predictions using Marcus theory, which is also discussed.

Unsymmetrically Substituted Donor–π–Acceptor‐Type 5,15‐Diazaporphyrin Sensitizers: Synthesis, Optical and Photovoltaic Properties

The first examples of unsymmetrical β-substituted donor-π-acceptor (D-π-A)-type 5,15-diazaporphyrin (DAP) sensitizers with both p-aminophenyl and p-carboxyphenyl groups at their peripheral 3-, 7-, 13-, and/or 17-positions have been synthesized for use in dye-sensitized solar cells (DSSCs). UV/Vis absorption and emission spectroscopy, electrochemical measurements, and DFT calculations revealed that these D-π-A dyes exhibit high light-harvesting properties over the whole visible range because of the intrinsic charge-transfer character of their electronic transitions. The cell performances of TiO2 -based DSSCs fabricated with the newly prepared DAP derivatives were evaluated under standard AM1.5 conditions. Among the four dyes examined, 13,17-bis(p-carboxyphenyl)-3,7-bis[p-(N,N-dimethylamino)phenyl]-DAP showed the highest power conversion efficiency (2.0 %), which was 20 times larger than that obtained with 3-(p-carboxyphenyl)-DAP. These results show that the DAP chromophore could be used as the electron-accepting π unit in various types of functional dyes.

A detailed experimental and theoretical investigation of the role of cyano groups in the π-bridged acceptor of sensitizers for use in dye-sensitized solar cells (DSCs).

Three donor-π conjugated unit-acceptor (D-π-A) type zinc porphyrin sensitizers LX1, LX2 and LX3 bearing meso acrylic acid, α-cyanoacrylic acid, and α-cyanopentadienoic acid, respectively, as the π-bridged acceptors were designed and synthesized for use in dye-sensitized solar cells (DSCs). The interesting role of the cyano group attached to the α position of the acrylic and pentadienoic acid acceptor was investigated. It was shown that even though the introduction of the cyano group and the elongation of the π-bridge can both increase the light-harvesting as indicated by the UV-vis absorption spectra, the relevant cell performance dropped significantly. The photo to power conversion efficiencies (PCEs) of the devices increase in the order of LX1 > LX2 > LX3, with the highest PCE of 6.04% achieved for the LX1-based cell, which bears acrylic acid as the π-bridged acceptor. To further explore the effect of -CN and -CH[double bond, length as m-dash]CH- on the interaction between the absorbed dye and TiO2 substrates, their density of states (DOS) and partial density of states (PDOS), as well as electronic properties were investigated in detail using theoretical calculations. The results suggest that introducing the -CN group into the acceptor and extending the conjugation of the π-bridge have decreased the LUMO levels of the dyes, leading to weak interfacial coupling, low electron injection driving force, low Jsc, and thus poor cell performance.

High-Porosity Carbon Processed from Mixtures of Furfuryl Resin-Poly(ethylene glycol)-Benzenesulfonyl Chloride and Its Application for Catalyzing Tri-iodide Reduction

High-porosity carbon (HPC) was first prepared from a novel mixture system of furfuryl resin as carbon-yielding precursor, poly(ethylene glycol) with low molecular weight as pore-forming agent and benzenesulfonyl chloride (BSC) as cured catalyst, and then employed as catalyst for counter electrode in dye-sensitized solar cells (DSCs). The pore structures of HPC are tailored by changing BSC amount from 2% to 14%. Especially, when BSC amount ascends from 4% to 8%, the apparent porosity of HPC rises from 59.58% to 68.02% and the median pore size from 0.429 to 3.164 μm, except that some globular carbons initially occur on the carbon skeleton. Since the HPC derived from 4% BSC has high porosity and the most quantity of small-sized pores to enlarge its surface area allowing for the most catalytic active sites for tri-iodide reduction, the resulted counter electrode exhibits the best catalytic activity and the highest efficiency for use in DSCs.

Organic Dyes Containing Coplanar Dihexyl-Substituted Dithienosilole Groups for Efficient Dye-Sensitised Solar Cells

A chromophore containing a coplanar dihexyl-substituted dithienosilole (CL1) synthesised for use in dye-sensitised solar cells displayed an energy conversion efficiency of 6.90% under AM 1.5 sunlight irradiation. The new sensitiser showed a similar fill factor and open-circuit voltage when compared with N719. Impedance measurements showed that, in the dark, the charge-transfer resistance of a cell using CL1 in the intermediate-frequency region was higher compared to N719 (69.8 versus 41.3 Ω). Under illumination at AM 1.5G-simulated conditions, the charge-transfer resistances were comparable, indicative of similar recombination rates by the oxidised form of the redox couple. The dye showed instability in ethanol solution, but excellent stability when attached to TiO2. Classical molecular dynamics indicated that interactions between ethanol and the dye are likely to reduce the stability of CL1 in solution form. Time-dependent density functional theory studies were performed to ascertain the absorption spectrum of the dye and assess the contribution of various transitions to optical excitation, which showed good agreement with experimental results.

Influence of the nature of the anchoring group on electron injection processes at dye-titania interfaces.

We report (time-dependent) density functional theory calculations characterizing the changes in the electronic and optical properties of oligothiophene dyes when grafted on a titania surface via a carboxylic acid or catechol moiety as anchoring group, in relation to their use in dye-sensitized solar cells. The broadening of the LUMO level of the compounds upon adsorption has been extracted from the computed electronic structures and used to estimate electron injection times into the conduction band of the oxide. The strongly coupled carboxylic-containing dyes lead to faster electron injection times compared to catechol-substituted dyes. This difference is ascribed to the electron-donating character of the catechol moiety that polarizes the dye LUMO away from the dye@titania interface. The absorption spectra simulated at the TD-DFT level indicate that the grafted carboxylic-thiophene dyes undergo an indirect injection mechanism (type I) in which an intramolecular excitation is created before the charge is transferred to titania. In contrast, catechol dyes with a short conjugation length for the thiophene backbone are type II sensitizers exhibiting a direct injection mechanism leading to a direct photoexcitation from the dye HOMO to the titania conduction band. A mixed character prevails for the injection in the case of catechol dyes containing a longer oligothiophene chain.

Solvent-assisted microstructural evolution and enhanced performance of porous ZnO films for plastic dye-sensitized solar cells

Abstract A low-temperature process for fabricating porous ZnO films on plastic, indium tin oxide-coated polyethylene naphthalate substrates is developed for their use in dye-sensitized solar cells. A special attention is paid to modification of microscopic morphologies for enhancing interparticle connection. ZnO films having two kinds of macroscopic morphologies (flower-like particles and densely packed nanoparticles) are fabricated at temperatures below the heatproof temperature of the substrate, and subsequently immersed in mixed solvents composed of water and ethanol at 90 °C. The immersion leads to the growth of constituting ZnO particles and also the evolution of interparticle connection, depending on solvent compositions. The cell performance is largely improved especially in a short-circuit current density and a power conversion efficiency. The immersion effect is more remarkable for the cell using the densely packed ZnO film, with a 62% increase in the current density and an 84% increase in the conversion efficiency. In consequence, our plastic N719-sensitized ZnO cell shows the conversion efficiency as high as 4.1%.

Charge Transfer Enhancement in the D-π-A Type Porphyrin Dyes: A Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TD-DFT) Study.

The electronic geometries and optical properties of two D-π-A type zinc porphyrin dyes (NCH3-YD2 and TPhe-YD) were systematically investigated by density functional theory (DFT) and time-dependent density functional theory (TD-DFT) to reveal the origin of significantly altered charge transfer enhancement by changing the electron donor of the famous porphyrin-based sensitizer YD2-o-C8. The molecular geometries and photophysical properties of dyes before and after binding to the TiO2 cluster were fully investigated. From the analyses of natural bond orbital (NBO), extended charge decomposition analysis (ECDA), and electron density variations (Δρ) between the excited state and ground state, it was found that the introduction of N(CH3)2 and 1,1,2-triphenylethene groups enhanced the intramolecular charge-transfer (ICT) character compared to YD2-o-C8. The absorption wavelength and transition possess character were significantly influenced by N(CH3)2 and 1,1,2-triphenylethene groups. NCH3-YD2 with N(CH3)2 groups in the donor part is an effective way to improve the interactions between the dyes and TiO2 surface, light having efficiency (LHE), and free energy change (ΔGinject), which is expected to be an efficient dye for use in dye-sensitized solar cells (DSSCs).

Synthesis and characterization of new triphenylamine-based dyes with novel anchoring groups for dye-sensitized solar cell applications

Three new chromophores based on the triphenylamine (MM, DM, DN) with various novel electron withdrawing anchoring groups have been synthesized for use in dye-sensitized solar cells (DSSCs). The sensitizers were characterized by 1H and 13C NMR, Mass, UV–Vis, and electrochemical analysis. The HOMO and LUMO electron distributions of the sensitizers were calculated using density functional theory on a B3LYP level for geometry optimization. The DSSC device based on DM dye showed the best photovoltaic performance among MM and DN dyes: maximum monochromatic incident photon-to-current conversion efficiency (IPCE) of 98 %, short circuit current (JSC) of 4.58 mA/cm2, open circuit voltage (VOC) of 0.62 V, fill factor (FF) of 0.77, and overall power conversion efficiency (PCE) of 2.01 %. The results reveal that the difference in number and type of anchoring groups of the dyes significantly influence the photovoltaic performance of their DSSCs.

Cyclopentadithiophene bridged organic sensitizers with different auxiliary acceptor for high performance dye-sensitized solar cells

A series of triphenylamine-based dye sensitizers were designed by modifying the auxiliary acceptors and their positions for the potential use in dye-sensitized solar cells (DSSCs). The geometrical structures, photoinduced charge transfer character together with optical properties for these dyes adsorbed on (TiO2)6 have been investigated using density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods. The effects of auxiliary units and their positions on the optoelectronic properties of the dyes are demonstrated. The results illustrate that the dyes with auxiliary acceptors close to the cyanoacrylic acid show very narrow band gap (HOMO-LUMO), leading to an obvious red-shifted absorption band in contrast to the dyes with additional acceptors next to the donor part. Further analyses of the dye-(TiO2)6 systems manifest that there has strong electronic coupling between the dyes and the (TiO2)6 surface. The results are expected to provide a useful reference to the future design and optimization for new highly efficient metal-free organic dyes.

Studies on D-A-π-A structured porphyrin sensitizers with different additional electron-withdrawing unit

Abstract The introduction of an additional acceptor to a typical donor-π bridge-acceptor (D-π-A) type porphyrin sensitizer results in a D-A-π-A featured porphyrin. Two porphyrins containing an additional acceptor with different electron-withdrawing abilities such as 2,3-diphenylquinoxaline ( DPQ ) for LP-11 and 2,1,3-benzothiadiazole ( BTD ) for LP-12 between the porphyrin core and the anchoring group have been synthesized for use as sensitizers in dye-sensitized solar cells (DSCs). Compared to LP-11 , LP-12 with the stronger electron-withdrawing additional acceptor BTD possesses better light harvesting properties with regard to red-shifted Q-band absorption and a broader IPCE spectrum, resulting in a greater short circuit photocurrent density ( J sc ) output. Interestingly, the steric hindrance of the DPQ group is favorable for suppressing dye aggregation, leading to a larger open-circuit voltage ( V oc ) value for LP-11 -based cell. However, the loss in V oc of LP-12 is overcompensated by an improvement in J sc . The optimized cell based on LP-12 achieves the better performance with a J sc of 15.51 mA cm −2 , a V oc of 674 mV, a fill factor (FF) of 0.7 and an overall power conversion efficiency (PCE) of 7.37% under standard AM 1.5 G irradiation. The findings provide a guidance for the future molecular design of highly efficient porphyrin sensitizers for use in DSCs.

Improvement of the DSSC Performance By Using a Phosphonium-Type Ionic Liquid Modified TiO2 Electrode

Dye-sensitized solar cells (DSSCs) have been widely investigated as next generation solar cells because of their simple structures, low-cost and facile manufacturing. However, its low energy conversion efficiency prevents the widespread use of DSSCs. The low efficiency of DSSCs is mainly caused by the dye aggregation and the electron recombination. One effective way to solve the dye aggregation and the electron recombination is the use of coadsorbents like chenodeoxycholic acid (CDCA).1) The coadsorbents form a thin layer on the TiO2 surface, which relaxes dye aggregation and/or suppresses the electron recombination. However, in this case, only slight increase of the photocurrent density often observed because the amount of dyes adsorbed on the TiO2 surface decreases. Therefore, the relaxation of the dye aggregation with keeping the amount of dyes on the TiO2 surface is required in order to improve the DSSC performance.2) To prevent the dye aggregation, we have used ionic liquid (IL)-modified TiO2 electrode. IL is a salt in the liquid state at room temperature. Recently, we reported the self-assembled monolayers (SAMs) of bulky phosphonium- and ammonium-type ILs with disulfide groups.3-5) The steric and electrostatic repulsion among the bulky IL molecules prevent them from packing closely and form the enough space to entrap external molecules on the surface. We tried to utilize the space formed by the bulky phosphonium-type IL on the TiO2 surface to trap dye molecules. The ILs on the TiO2 surface probably reduce the dyes aggregation with keeping the amount of dyes on the surface. Furthermore, it is also expected that the electron recombination between the electrolyte and the TiO2 surface is suppressed because the surface is covered with the alkyl chains of IL. In this study, a bulky phosphonium-type ionic liquid (IL) with a carboxylic acid group was newly synthesized. Subsequently, TiO2 electrodes modified with N3 6) dye and IL with various ratios were prepared. DSSCs based on the IL-modified TiO2 photoanodes have been fabricated and their photovoltaic performance have been evaluated. The surface ratio of N3 dye and IL were determined by the wavelength dispersive X-ray analysis (WDS). When the TiO2 electrode was dipped into the t BuOH/CH3CN (1/1, v/v) solution containing 0.3 mM N3 dye and 30mM IL, the electrode modified with 1/1 ratio was obtained. The DSSC using N3- and N3, IL-modified TiO2 photoanodes were fabricated and their J-V characteristics were measured. All parameters of the DSSCs (the short-circuit photocurrent (J sc), the open-circuit photovoltage (V oc), fill factor (ff), and the power conversion efficiency (η)) have been improved. These results indicate that the DSSCs based on the IL-modified TiO2 electrodes prevented the charge recombination among dyes and/or between the electrolyte and the TiO2surface.1) M. K. Nazeeruddin,et al.,Nanotechnology,2008, 19, 424005.2) K. Char, et al., ACS Appl. Mater. Interfaces, 2015, 7, 25741.3) H. Masuda, et al., Chem. Commun., 2013, 49, 10184.4) H. Masuda, et al., Chem lett, 2016, 45, 4, 436.5) H. Masuda, et al., Chem. Commun., 2016, 52, 4780.6) M. K. Nazeeruddin, et al., J. Am. Chem. Soc., 1993, 115, 6382. Figure 1

Porphyrin Dye-Sensitized Zinc Oxide Aggregated Anodes for Use in Solar Cells.

Porphyrin YD2-o-C8-based dyes were employed to sensitize room-temperature (RT) chemical-assembled ZnO aggregated anodes for use in dye-sensitized solar cells (DSSCs). To reduce the acidity of the YD2-o-C8 dye solution, the proton in the carboxyl group of a porphyrin dye was replaced with tetrabuthyl ammonium (TBA+) in this work. The short-circuit current density (Jsc) of the YD2-o-C8-TBA-sensitized ZnO DSSCs is higher than that of the YD2-o-C8-sensitized cells, resulting in the improvement of the efficiency of the YD2-o-C8-based ZnO DSSCs. With an appropriate incorporation of chenodeoxycholic acid (CDCA) as coadsorbate, the Jsc and efficiency of the YD2-o-C8-TBA-sensitized ZnO DSSC are enhanced due to the improvement of the incident-photon-to-current efficiency (IPCE) values in the wavelength range of 400–450 nm. Moreover, a considerable increase in Jsc is achieved by the addition of a light scattering layer in the YD2-o-C8-TBA-sensitized ZnO photoanodes. Significant IPCE enhancement in the range 475–600 nm is not attainable by tuning the YD2-o-C8-TBA sensitization processes for the anodes without light scattering layers. Using the RT chemical-assembled ZnO aggregated anode with a light scattering layer, an efficiency of 3.43% was achieved in the YD2-o-C8-TBA-sensitized ZnO DSSC.

Aggregation of metal-free organic sensitizers on TiO2(1 0 1) surface for use in dye-sensitized solar cells: A computational investigation

We present a theoretical investigation of the aggregation effects of two 4H-Pyran-4-ylidene-based organic sensitizers on the TiO2(101) surface, which are used in dye-sensitized solar cells (DSSCs). Our results combining density functional theory (DFT), time-dependent DFT, and density functional tight binding (DFTB) methods show that 4H-Pyran-4-ylidene-based organic sensitizers are prone to aggregate on the TiO2 surface due to the strong intermolecular π…π interactions. The aggregation has obvious effects on electronic structures and absorption spectra of the organic sensitizers. The incorporation of an electron-deficient benzothiadiazole (BT) unit in the spacer part of the organic dye leads to a broader absorption band in the red portion of the UV–visible spectra, which is desirable for enhanced spectral responses. However, the BT moiety also leads to more aggregation on the TiO2 surface and stronger electron coupling within the dimers, which might retard the electron transfer at the dye-TiO2 interface and therefore limit the photovoltaic efficiency. This study sheds light on the aggregation effects of metal-free organic dyes and is expected to assist in the rational design of novel and efficient all-organic sensitizers for the further optimization of DSSCs.

First-Generation Subporphyrinatoboron(III) Sensitizers Surpass the 10 % Power Conversion Efficiency Threshold.

Subporphyrinatoboron(III) (SubB) sensitizers were synthesized for use in dye-sensitized solar cells (DSSCs). The prototype, which comprises a sterically demanding 3,5-di-tert-butylphenyl scaffold, a meso-ethynylphenyl spacer, and a cyanoacrylic acid anchoring group, achieved an open-circuit voltage VOC of 836 mV, short-circuit current density JSC of 15.3 mA cm(-2) , fill factor of 0.786, and a photon-to-current conversion efficiency of 10.1 %. Such astonishing figures suggest that a bright future lies ahead for SubB in the realm of DSSCs.

Synthesis and evaluation of simple molecules for dye sensitized solar cells

Four metal-free organic dyes comprising an arylamine-based D-π-A construction was designed at the molecular level and synthesized for use in dye-sensitized solar cells (DSSCs). The absorption spectra, electrochemical and photovoltaic properties of these dyes were extensively investigated. The results revealed that the absorption characteristics of all the newly prepared dyes were strongly shifted with an end-absorption far into the near infrared region due to the introduction of different chromophore groups, and the LUMO levels of the dyes were also modulated to some different extent. Otherwise, it was found that D2 showed an overall conversion efficiency of 2.61% reaching 86% with respect to that of an N719-based device fabricated under similar conditions. The origin of this correlation and its implications in materials design and device performance are discussed.

Fe3O4–carbon black nanocomposite as a highly efficient counter electrode material for dye-sensitized solar cell

Iron oxide–carbon black (Fe3O4–CB) nanocomposite has been proposed as a cost–effective alternative counter electrode (CE) to the conventional Pt in a dye sensitized solar cell (DSSC). The Fe3O4–CB nanocomposite at three different weight ratio (1:1, 1:2 and 2:1) was prepared by a simple solution mixing process and the material was characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning and transmission electron microscopy techniques. The performance of the three Fe3O4–CB nanocomposite CEs was assessed with respect to Fe3O4, CB and Pt in a conventional DSSC consisting of N719 dye sensitized TiO2 (P25) photoanode in contact with an electrolyte containing the I−/I3− redox couple. The electrocatalytic activities of the various CEs towards triiodide (I3−) reduction were analyzed by cyclic voltammetry, electrochemical impedance spectroscopy and Tafel polarization analysis. The photocurrent voltage (J–V) characteristics of the DSSCs assembled with various counter electrodes were assessed at a light intensity of 80mWcm−2. The DSSC assembled with Fe3O4–CB nanocomposite (1:2) CE showed the best photovoltaic performance in terms of a high power conversion efficiency of 6.1% which is superior to that of sputtered Pt (4.1%). The simple preparation, excellent electrocatalytic activity and low-cost nature allow the Fe3O4–CB nanocomposite to be a promising alternative CE to Pt for use in DSSCs.

The Effect of Lithium Iodide to the Properties of Carboxymethyl κ-Carrageenan/Carboxymethyl Cellulose Polymer Electrolyte and Dye-Sensitized Solar Cell Performance

This study was undertaken to investigate the solid biopolymer electrolytes based on a carboxymethyl κ-carrageenan/carboxymethyl cellulose blend complexed with lithium iodide of various weight ratios. The complexation of the doping salt with the polymer blend was confirmed by Fourier transform infrared spectroscopy. Ionic conductivity of the film was determined by impedance spectroscopy in the frequency range of 10 Hz to 4 MHz and in the temperature range of 303–338 K. The ionic conductivity increased with the increase in lithium iodide concentration as well as temperature. The membrane comprising 30 wt % of lithium iodide was found to give the highest conductivity of 3.89 × 10−3 S·cm−1 at room temperature. The increase in conductivity was associated with the increase in the number as well as the mobility of the charge carries. The conductivity increase with temperature followed the Vogel–Tamman–Fulcher model. The fabricated dye-sensitive solar cell, FTO/TiO2-dye/CMKC/CMCE-LiI (30 wt %) +I2/Pt exhibited the highest conversion efficiency of 0.11% at a light intensity of 100 mW·cm−2. This indicated that the biopolymer blend electrolyte system has potential for use in dye-sensitized solar cells.