Application In Dye-sensitized Solar Cells Research Articles

Synthesis and characterizations of sol–gel derived LaFeO3 perovskite powders

In this study, LaFeO3 perovskite powders were prepared via the sol–gel method in two different annealing temperatures (500 and 850 °C-according to DTA/TG results) for use in dye-sensitized solar cell applications. The thermal, structural, microstructural, particle size, optical and magnetic properties of the samples were characterized by differential thermal analysis (DTA)/thermogravimetric analysis (TG), Fourier transforms infrared spectrometer (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), particle size analysis (PSA), UV–Vis spectrometer and vibrating sample magnetometer (VSM). Our XRD findings show that the as-synthesized powders have an excellent crystallinity, and Scherrer’s Equation is used for the estimation of crystallite sizes (within 26–29 nm). Samples were analyzed to reveal the valence states of elements through XPS. Survey scan XPS spectra and high-resolution XPS spectra of La-3d5 and Fe-2p for LaFeO3 samples are given. SEMs employed to observe surface morphologies of all xerogel and ceramic perovskite powder materials and SEM images were verified with PSA results. UV–Vis spectrometer analysis results show that the optical bandgap values (Eg) as measured on both particles were found 2.42 eV. In addition to all analyses, the powders show ferromagnetic behavior, and VSM analyses are used to determine ferromagnetic properties. These results, especially low bandgap, make LaFeO3 powders possible to further increase the performance and efficiency of perovskite-based cells.

Preparation of Cu-doped ZnO nanoparticles via layered double hydroxide and application for dye-sensitized solar cells

It has been reported that doping ZnO with metal ions can alter the band gap and immensely enhance electron transport. In this regard, to increase the efficiency of cost-effective dye-sensitized solar cells (DSSCs), we synthesized Cu-doped ZnO nanocomposites from layered double hydroxide (LDH) precursors via a facile method. LDH layers were homogeneously doped with Cu ions, and mixed metal oxides (MMOs) were obtained after annealing. The morphology and optical and electrochemical properties of the as-synthesized Cu-doped ZnO nanocomposites were systematically studied. The introduction of Cu ions increases the specific surface area of ZnO and increases light absorption in the visible region. The Cu-doped ZnO MMOs were used as the photoanode of DSSCs, and the effect of the amount of the Cu dopant on the performance of the solar cells was studied. At the optimal doping weight percentage of Cu (0.25 wt%), the solar cell based on Cu-doped ZnO MMO and D149 dye achieved the highest short-circuit current of 7.12 mA cm−2 and the highest power conversion efficiency of 1.50%.

FT-IR and FT-RAMAN analysis and light-harvesting efficiency (LHE) enhancement for DSSC applications of hydrazide derivatives

The vibrational frequencies obtained by the recorded the spectra of FT-IR and FT-Raman are precisely assigned and compared with the theoretical frequencies. The stabilities of p-hydroxybenzoylhydrazine (HBH) and p-aminobenzoylhydrazide(ABH) are analyzed through PES scan, and most stable structures are obtained. On the most stable structures of these two compounds, the HOMO–LUMO analysis is carried out at B3LYP/6-31G (d,p) level for the zero field and with fields (0.015 and 0.025 VA−1). The HOMO–LUMO gap widely decreases from 4.0592 eV to 0.6323 eV and 3.7645 eV to 0.4040 eV, respectively, as the field increases (0.0—0.025 VA−1). The HOMO–LUMO gap is also measured from the DOS spectrum which is also in line along with the calculated value using the Gaussian 09 W program package. The DOS spectrum predicts that the HOMO–LUMO gap decreases when there is the increase in the electric field. The donors studied theoretically in this study are azulene, pyrrole, furan, tetrafuran and thiophene. The global reactivity descriptors, i.e., ionization potential (IP), hardness (η), chemical potential (μ), electron affinity (EA), softness (s), electronegativity (χ), electrophilicity index (ω), maximum amount of electronic charge (∆Nmax), nucleofugality (∆En), electrofugality (∆Ee) and ΔEback-donation are calculated for all hydrazide derivatives. The best dye sensitized solar cell (DSSC) performance is observed in HBH and ABH derivatives with thiophene donor group compared to other donor groups.

Coumarin-based D–π–A dyes for efficient DSSCs: DFT and TD-DFT study of the π-spacers influence on photovoltaic properties

A series of D–π–A architectures dyes with Coumarin-based derivatives as difluorenylaminocoumarin (DF) and diphenylaminocoumarin (DP) have been designed by modifying the π-bridge for potential application in dye-sensitized solar cells (DSSCs). Three different π-bridges viz. benzothiadiazole (BTD), diketopyrrolopyrrole (DPP) and quinoxaline (QX) with are used to design six different dye systems DFi (i = 1–3) on difluorenylaminocoumarin-thiophene-cyanoacrylic acid (R1) and DPi (i = 1–3) on diphenylaminocoumarin-thiophene-cyanoacrylic acid (R2). The electronic, optical and photovoltaic properties have been evaluated, using the density functional theory (DFT), and time dependant DFT methods to study the effect of these spacers on the cell performance. In addition, we have used four functionals to establish our calculation method, in order to compare the theoretical with the experimental results of R1 and R2 dyes. Thus, the CAM-B3LYP functional was sufficient to predict the UV–visible spectra. Moreover, the gap energy (Egap), Voc, the electronic injection free energy (ΔGinject), light harvesting efficiency (LHE), total reorganization energy (λtotal), and absorption spectra of all dyes were discussed. In addition the DF2, DP2 dyes are displayed smaller Egap, negative ΔGinject and absorption spectra shifted to red compared to R1 and R2, respectively. The results of these dyes reveal that the DF2 and DP2 dyes molecules are favourable candidates for DSSCs application.

Multistep Electron Injection Dynamics and Optical Nonlinearity Investigations of π-Extended Thioalkyl-Substituted Tetrathiafulvalene Sensitizers

A comprehensive investigation is presented on the photophysical and third-order nonlinear optical (NLO) properties of two thioalkyl-substituted tetrathiafulvalene molecules (referred here as G1 and G3) to understand their utility as photosensitizers for dye-sensitized solar cell (DSSC) and optoelectronic applications. Both steady-state and time-resolved (in the fs–ns time regime) absorption and photoluminescence (PL) spectroscopy techniques were employed to comprehend the excited-state properties of the molecules in solution as well as in thin films deposited on both quartz and mesoporous TiO2 layers. The spectroscopy measurements in solution and thin films deposited on quartz provided the excited-state properties of dye molecules. Time-resolved PL measurements at the dye–TiO2 interface provided initial evidence of electron injection by fast PL quenching decay dynamics for both the molecules. Detailed target analysis of the femtosecond transient absorption spectroscopy (TAS) data of the dye–TiO2 sample revealed a multistep ultrafast electron injection for both molecules with the fastest injection component being 374 and 314 fs for G1 and G3 molecules, respectively. The ultrafast NLO properties of G1 and G3 were studied using the Z-scan technique with 800 nm, ∼70 fs laser pulses. The open aperture measurements showed three-photon absorption with magnitudes of coefficients 4.7 × 10–5 cm3/GW2 and 5.2 × 10–5 cm3/GW2, and the closed aperture measurements provided second hyperpolarizability (γ) values of 3.5 × 10–31 esu and 4.2 × 10–31 esu for G1 and G3, respectively. Additionally, the onset of optical limiting was estimated to be 5.8 × 10–3 J/cm2 and 5.7 × 10–3 J/cm2 for G1 and G3 molecules, respectively.

Optical and photovoltaic properties of substituted alizarin dyes for dye-sensitized solar cells application

ABSTRACT This paper presents the theoretical study on photovoltaic and absorption properties of alizarin derivatives. Optimization of structures and calculations were performed by density functional theory and time-dependent density functional theory using B3LYP hybrid functional and 6–31 G (d,p) basis set. The dyes were formed by substituting 2-hexylthiophene mixed with carboxylic acid and 4-(benzo[c][1,2,5]thiadiazol-4-yl)benzoic acid. The performed substitution shows improvement in most of the properties. The highest occupied molecular orbital and lowest unoccupied molecular orbital energy levels of molecular dyes showed positive effect upon electron injection to semiconductor and subsequent regeneration by the electrolyte. Almost all necessary and important parameters to demonstrate the usefulness of molecular dyes as photo-sensitizers are detailed discussed. Based on the discussion and analysis, all considered molecules are proved to be useful in dye-sensitized solar cells using TiO2 semiconductor and couple electrolyte. Collectively, dyes DY3 and DY2 showed better results than others with LHE and V oc of 0.2142 and 0.6722 eV, respectively, for DY3 and 0.7033 and 0.6224 eV, respectively, for DY2.

The influence of π-linkers configuration on properties of 10-hexylphenoxazine donor-based sensitizer for dye-sensitized solar cell application – Theoretical approach

10-Hexylphenoxazine based dyes with A-(π)n-D-(π)n-A architecture is designed and investigated systematically for dye-sensitized solar cell (DSSC) application by Density Functional Theory (DFT) and Time-dependent Density Functional Theory (TD-DFT). The designed sensitizers consist of 10-Hexylphenoxazine as electron donor and cyanoacrylic acid as an acceptor, connected by the Thiophene and Cyanovinyl π-spacers configurations with symmetrical and asymmetrical form. The effect of π-spacers configurations on the electronic and optical properties of the dyes is also investigated. The optimized structure, electronic properties and absorption characteristics of A-(π)n-D-(π)n-A dyes were investigated. The charge separation and polarization properties are analyzed by co-planarity, natural bond orbital (NBO), dipole moment and linear polarizability studies. The free energy change of electron injection and dye regeneration of the sensitizers are also calculated. The addition of a greater number of π-spacers improves the electronic, spectroscopic, optical, and free energy properties of the designed sensitizer. The DFT studies also reveal that the position of the π-spacers plays an important role in the electronic and spectroscopic properties.

Design and theoretical study of phenothiazine-based low bandgap dye derivatives as sensitizers in molecular photovoltaics

Modulation of metal free organic (MFO) molecules become imperative to researchers to obtain low-cost sensitizer for dye sensitized solar cells (DSSCs) purposes. A series of metal free phenothiazine-based (PTZ) organic dyes are designed and optimized as sensitizers for DSSCs application. Their electronic and optical properties were probed using Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TD-DFT) approaches. Effects of additional donor unit, π-conjugation bridges, and benzothiadiazole (BTDA) were investigated. Introducing BTDA in the acceptor unit leads to the tailoring of the energy band gap and promotion of charge transfer within donor and anchor groups with increased effective parameters in DSSC efficiency. The addition of diphenylamine, triphenylamine, or hexyloxyphenyl to the PTZ unit increased electron delocalization and enhanced intramolecular charge transfer. Changing π-spacer from phenyl to thiophene has a great effect on the electronic properties and absorption spectra of the dyes. The relationship between light harvesting efficiency (LHE) and chemical hardness (ƞ) shows that structural design that consists of BTDA and thiophene as π-spacer tends most towards excellent performance as dye sensitizers in DSSCs.

Facile Synthesis of Nanoporous NiS Film with Inverse Opal Structure as Efficient Counter Electrode for DSSCs.

To satisfy the high requirement of catalytic activity for efficient dye-sensitized solar cells (DSSCs), a novel nanoporous NiS film with inverse opal structure and outstanding electrocatalytic properties was prepared by a facile template-assisted electrodeposition method. The inverse opal structure makes the film have a larger specific surface area and more catalytic sites, thereby result to a higher electrocatalytic activity. Compared with the flat NiS/FTO electrode, this kind of nanoporous NiS film with inverse opal structure has higher catalytic activity and can be used as a cheap and efficient Pt-free electrode to replace the traditional Pt/FTO electrode. It is of great significance to reduce the cost and promote the wide application of DSSCs. This study opens up a new experimental exploration for further improving the catalytic activity of NiS electrode and the according photovoltaic efficiency of DSSCs. The template-assisted electrodeposition method proposed in this work provides a facile method for morphology control and an easy to be realized way to optimize the catalytic performance of the metal sulfides counter electrode.

Hybrid structure of ionic liquid and ZnO nano clusters for potential application in dye-sensitized solar cells

“Green processes” for the production of renewable energy such as the utilization of solar energy would decisively help to avoid depletion of resources and environmental degradation. In this connection, we have investigated hybrid structures of the ionic liquid (IL) 1-ethyl-3-methylimidazolium tetrafluoroborate (C2mim BF4) and (ZnO)n nano clusters as charge-transfer promoters concerning their application in highly efficient dye-sensitized solar cells (DSSCs) using density functional theory (DFT). Structural properties, frontier molecular orbitals, and energy gaps (Eg) were analyzed to understand the interaction mechanism between the IL and ZnO nano clusters. The influence of (ZnO)n nano clusters on electronic properties of the IL was investigated by analyzing electrostatic potential (ESP) mapping, work function (ϕ), and density of states. The highest binding energy between IL and ZnO nano cluster was obtained for the IL/(ZnO)2 hybrid structure, which has enhanced charge-transfer and a smaller energy gap (3.09 eV) compared to the other considered systems. The photo-energy-conversion efficiencies (η) of DSSCs based on IL/(ZnO)n (n = 2–12) hybrid systems were predicted under irradiance with an air mass 1.5 global (AM 1.5 G) spectrum. Solar parameters such as open-circuit voltage Voc, fill factor FF, and short-circuit current density Jsc were determined to evaluate η. The maximum efficiency (1.96%) is found for the IL/(ZnO)2 system due to the high short-circuit-current density, improved electron extraction, and low work function, which allows the injection of more electrons into the TiO2 surface. Our results on the hybrid structures of IL and ZnO nano clusters reveal a possibility for the design of highly efficient next-generation DSSCs.

Recent Advances in the Development of Nano-Sculpted Films by Magnetron Sputtering for Energy-Related Applications.

In this paper, we overview the recent progress we made in the magnetron sputtering-based developments of nano-sculpted thin films intended for energy-related applications such as energy conversion. This paper summarizes our recent experimental work often supported by simulation and theoretical results. Specifically, the development of a new generation of nano-sculpted photo-anodes based on TiO2 for application in dye-sensitized solar cells is discussed.

The Effect of Acidity and Rotation Speed in Titanium Dioxide Synthesize Process

The aims of this study are to analyze the effect of acidity and rotational speed in the synthesis of TiO2 using the sol-gel method and to analyze the morphology of synthesized TiO2 nanoparticles and commercial TiO2 using XRD to produce semiconductors for Dye-Sensitized Solar Cell (DSSC) applications. The sol-gel method was used to synthesize TiO2 Nanoparticles. Titanium tetra-isopropoxide (TTIP) was used as a precursor with the variable of the magnetic stirrer rotation speed of 500, 1000 and 1500 rpm. Acidification was achieved by adding acetic acid to Sol-gel solution to produce a pH number of 1, 2, and 3. Nanomaterial was observed with an optical microscope and X-ray Powder Diffraction (X-RD) to determine the morphology and phase of TiO2 crystalline. The results showed that the rotational speed and acidity level of the Sol-gel solution ware played an important role to get the best form of a nanoparticle. At a rotation speed of 1500 rpm with pH 3 and 1000 rpm with pH 2 ware shown characteristics similar to commercial TiO2. In addition to that, the results of XRD characterization of synthesized TiO2 was shown a crystal phase of anatase structure with 18,046 nm crystal size compared to commercial TiO2 with anatase structure and crystal size of 15,554 nm.

Large-area spray deposited Ta-doped SnO2 thin film electrode for DSSC application

Large-area (10 × 10 cm2) Ta-doped SnO2 (TTO) thin film was deposited by a facile spray pyrolysis method. The crystallinity, phase purity, and texture properties of the film are studied using XRD analysis. The XPS study confirmed the charge state of Sn to be in 4+, O1s in 2−, and Ta to be in 5+ state. A homogeneous polyhedron morphology was witnessed owing to the Ta dopant effect. The TTO film was highly transparent in the visible to near infrared region (NIR) with an average transmittance value of 81% at 550 nm. The TTO film was having a free carrier concentration of 5.42 × 1021 cm−3 and mobility of 41.7 cm2/Vs. The 4 wt% Ta doped SnO2 electrode exhibits a low sheet resistance of 26 Ω/□ and a high figure of merit value of 6.15 × 10−3 Ω−1. The resistance stability of sheet resistance was fairly good up to 400 °C indicating suitability of the TTO electrode to serve as conducting photoanode/counter electrode in dye-sensitized solar cell (DSSC) device. The DSSC device fabricated with the TTO electrode exhibited appreciable efficiency of 3.26% which is attributed to the enhanced electrical and optical properties by way of doping with Ta element.

Regulating Back Electron Transfer through Donor and π-Spacer Alterations in Benzothieno[3,2-b]indole-based Dye-sensitized Solar Cells.

Three metal-free organic D-π-A dyes with benzothieno[3,2-b]indole as electron donor, cyanoacrylic acid as both electron acceptor and anchoring group with benzene (BID-1), thiophene (BID-2) and furan (BID-3) as π-spacers were designed and synthesized for application in dye-sensitized solar cells (DSSCs). A planar and electron-rich heterocycle such as benzothieno[3,2-b]indole offers better backbone rigidity and improves charge transport properties in comparison to indolo[3,2-b]indole donor, previously reported from our group. Additionally, we synthesized a benzothieno[3,2-b]indole donor grafted with longer alkyl chains which efficiently prevented the approach of oxidized species in the electrolyte coming closer to semiconductor thereby arresting recombination. A power conversion efficiency of 4.11 % was achieved for dye-sensitized solar cells based on the furan π-spacer benzothieno[3,2-b]indole dye BID-3 in comparison to the corresponding indolo[3,2-b]indole dye (IID-3) having an efficiency of 1.71 %. Detailed interfacial electrical measurements along with theoretical calculations disclosed the mechanism of back electron transfer and improvement in photovoltaic performance with respect to variation in both donor and π-spacer.

Enhanced electrochemical and photovoltaic performance for MoO3 nanorods at different calcination temperature based counter electrode in Pt-free dye-sensitized solar cells applications

Owing to increase in energy demands and depletion in fossil fuels, solar energy conversion is the reliable and sustainable one for future. Among the solar energy conversion techniques, dye-sensitized solar cells (DSSC) have received much attention due to their ease of fabrication, cost-effectiveness, reliable and high proficiency in converting solar energy. The commercialization of DSSC is still hindered by usage of expensive materials like platinum counter electrodes. Therefore, researchers are focusing on developing low-cost and earth abundant alternatives. The present work involves hydrothermal synthesis of molybdenum trioxide (MoO3) at various temperature ranges such as 400, 500, 600 and 700 °C and several other characterizations through various analytical techniques. On increasing the temperature range, the MoO3 forms nanorod like structure. The synthesized materials are employed as counter electrode in DSSC, showed enhanced power conversion efficiency (PCE) on increasing the calcination temperature range. The maximum PCE of 4.13% is obtained for MoO3 calcined at 600 °C, which is highly comparable with the high cost platinum CE based DSSC.

Synthesis, density functional theory and sensitization of indole dyes

Herein, the two typical anchoring groups are tethered into the indole chromophore and studied their impact on the molecular orbital energy levels and titania sensitization. The synthesized indole derivatives were meticulously characterized. The photophysical and time dependent density functional theory results were revealed that the indole connected rhodanine-3-acetic acid group is an efficient light harvester. The favorable electronic excitation from the highest occupied molecular orbital to the lowest unoccupied molecular orbital indicated that the dye comprised with rhodanine-3-acetic acid could be used as a prospective material for dye-sensitized solar cell applications.

Eutectic ionic liquids as potential electrolytes in dye-sensitized solar cells: Physicochemical and conductivity studies

Ionic liquids (ILs) have been introduced as the electrolyte in dye-sensitized solar cells (DSSC) to replace organic solvents due to their non-flammability, chemical, and thermal stability, as well as less prone to evaporation and leakage. A series of eutectic ILs mixtures composed of 1-ethyl-3-methylimidazolium iodide, [C2C1im]I, 1-ethylpyridinium iodide [C2py]I, 1-propylpyridinium iodide, [C3py]I and 1-butylpyridinium iodide, [C4py]I was developed. The structures and purity of the compounds were validated by nuclear magnetic resonance and Karl Fischer Titration. Their physicochemical properties, such as viscosities and ionic conductivities were evaluated for their potential use as electrolytes in DSSCs. The melting temperature of pure ionic liquids and the mixtures were determined using differential scanning calorimetry in the temperature range of 123.15 K to 393.15 K. It is found that eutectic mixtures were formed at the molar ratios of {0.75[C2py]I:0.25[C2C1im], {0.25[C2py]I:0.75[C2C1im]I}, {0.50[C2py]I:0.50[C2C1im]I}, {0.25[C2C1im]I:0.75 [C4py]I}, {0.75[C2C1im]I:0.25[C4py]I}, and {0.50[C2C1im]I:0.50[C4py]I} with the latter forming a highly stable liquid with no apparent melting peak in the studied temperature range. To understand the formation of eutectic composition, a correlation between molecular structures and the interaction energies of the cations and anions of ILs was performed using the Conductor-like Screening Model for Real Solvents (COSMO-RS). Dynamic viscosities of the binary mixtures were evaluated in the temperature range of 283.15 K to 353.15 K with 10 K increment. The highest ionic conductivity was exhibited by the eutectic ILs electrolyte {0.50[C2C1im]I:0.50[C4py]I:I2(50 wt%)} at 9.67 mS·cm−1 showing its potential for electrolyte application in DSSC.

High-Efficiency Dye-Sensitized Solar Cells Based on Kesterite Cu2ZnSnSe4 Inlaid on a Flexible Carbon Fabric Composite Counter Electrode.

Composite counter electrodes have been shown to be a practical and effective strategy in dye-sensitized solar cell (DSSC) application. In this work, we designed and prepared a single-crystal Cu2ZnSnSe4 (CZTSe) plate structure on flexible carbon fabric as a DSSC cathode, which combines the best of the two worlds, namely, the superior catalytic activity and hierarchical microstructure of kesterite CZTSe and the high conductivity and expanded framework of carbon fabric. The composite counter electrode presented a power conversion efficiency of 8.45% and a long-term bending reservation. The remarkable device property is due to the high catalytic activity, good adherence to conductive matrix grains, effective electron migration, and quick iodide species diffusion of the novel cathode. Our results suggest that the CZTSe@carbon fabric composite could be a high-efficiency Pt-free cathode in DSSCs.

Enhanced efficiency with CDCA co-adsorption for dye-sensitized solar cells based on metallosalophen complexes

The condensation of 4-diethylaminosalicylaldehyde and 3,5-di-tert-butyl-salicylaldehyde with 3,4-diaminobenzoic acid afforded two salophen type Schiff base ligands, L1 and L2, respectively. Subsequently, their corresponding platinum(II) and zinc(II) salophen complexes (PtL1, PtL2, ZnL1 and ZnL2) were synthesized through the reaction of the two salophen ligands with potassium tetrachloroplatinate(II) and zinc(II) acetate, respectively. The structures of the metallosalophen complexes were characterized by 1H NMR, infrared spectroscopy and high-resolution mass spectrometry. Their photophysical properties and cyclic voltammetry behaviours were investigated in detail. Using these complexes as photosensitizers, the dye-sensitized solar cells (DSSCs) were prepared and inferior performances were recorded due to their planar structures and significant aggregations. Upon the addition of chenodeoxycholic acid (CDCA) as co-adsorbents, the aggregation behaviours could be effectively inhibited and the cell performances could be enhanced with the highest power conversion efficiency up to 2.57% for PtL1. Considering the simplicity in the preparation and the structure variability, these metallosalophen complexes represent a new class of photosensitizers for DSSC applications.

Facile fabrication of reduced graphene oxide counter electrodes by laser engraver for dye-sensitized solar cell applications

Exploring alternative Pt-free counter electrode with low cost and high electrocatalytic activity is always a main focus at the frontier of dye-sensitized solar cells (DSSCs). In this study, a desktop laser engraver was applied to reduce graphene oxide (GO) film on a fluorine-doped tin oxide (FTO) substrate, and the obtained graphene-based material was further used as counter electrode for DSSC. Additionally, this facile laser-scribing method was also adopted to fabricate a prototype of composite electrode via the combination of reduced graphene oxide (RGO) and carbon black (CB) to enhance the specific surface area and active sites. A variety of characterizations including scanning electron microscopy (SEM), Raman spectroscopy, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were conducted to investigate the microstructures and catalytic properties of these carbon electrodes. The findings reveal that both of the DSSCs with laser-scribed carbon electrodes show evidently increasing photovoltaic performance, and the DSSC based on RGO/CB composite electrode even presents a higher power conversion efficiency (PCE) of 4.49%, comparable to 4.14% of the conventional Pt-based DSSC.