Dyes For Dye-sensitized Solar Cells Research Articles

Adamantyl Side Chains as Anti-Aggregating Moieties in Dyes for Dye-Sensitized Solar Cells.

Designing and evaluating novel dye concepts is crucial for the development of the field of dye‐sensitized solar cells (DSSCs). In our recent report, the novel concept of tethering the anti‐aggregation additive chenodeoxycholic acid (CDCA) to dyes for DSSC was introduced. Based on the performance improvements seen for this modification, the aim of this study is to see if a simplified anti‐aggregation unit could achieve similar results. The following study reports the synthesis and photovoltaic characterization of two novel dyes decorated with the steric ethyladamantyl moiety on the π‐spacer, and on the triarylamine donor. This modification is demonstrated to be successful in increasing the photovoltages in devices employing copper‐based electrolytes compared to the non‐modified reference dye. The best photovoltaic performance is achieved by a device prepared with the adamantyl decorated donor dye and CDCA, this device achieves a power conversion efficiency of 6.1 % (Short‐circuit current=8.3 mA cm−2, Open‐circuit voltage=1054 mV, Fill factor=0.69). The improved photovoltaic performance seen for the adamantyl decorated donor demonstrate the potential of ethyladamantyl side chains as a tool to ensure surface protection of TiO2.

The effect of conjugated groups for favourable molecular planarity and efficient suppression of charge recombination simultaneously of phenothiazine-based organic dyes for dye-sensitized solar cells

With the view to the poor coexistence between promoting molecular planarity towards improving the intramolecular charge transfer (ICT) effect and preventing charge recombination for dyes in Dye-sensitized solar cells (DSSCs). A novel 2-phenothiazine-amine-based organic dye PTZ-10 is synthesized and applied in DSSCs. The extra benzene and ethynyl conjugated groups are inserted as the isolation groups between the 2-phenothiazine-amine donor and benzothiadiazole auxiliary acceptor to obtain PTZ-17 in order to probe the possibility of reaching the aim of suppressing the charge recombination and strengthening molecular planarity synchronously in a better degree. Our photophysical measurement, electrochemical test and theoretical calculation demonstrate that the introduction of ethynyl and benzene is beneficial to the improvement of ICT effect and the inhibition of charge recombination, which can also be confirmed by the photovoltaic property and EIS study. Therefore, higher short-circuit photocurrent density (Jsc) and the open-circuit voltage (Voc) are exhibited in devices based on PTZ-17, along with the higher photoelectric conversion efficiency (PCE) up to 4.24 % relative to that of 3.37 % in PTZ-10. We demonstrated that the incorporation of different sizes of conjugated groups is a promising candidate to fine-tune the structure-performance of dye molecules in the development of DSSCs’ materials.

A Theoretical Evaluation of the Efficiencies of Metal-Free 1,3,4-Oxadiazole Dye-Sensitized Solar Cells: Insights from Electron–Hole Separation Distance Analysis

Herein, some novel metal-free 1,3,4-oxadiazole compounds O1–O7 were evaluated for their photovoltaic properties using density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations to determine if they can serve as metal-free organic dyes in the use of dye-sensitized solar cells (DSSCs). To understand the trends in the relative efficiencies of the investigated compounds as dyes in DSSCs, their electron contributions, hole contributions, and electron–hole overlaps for each respective atom and fragment within the molecule were analyzed with a particular focus on the electron densities on the anchoring segments. As transition density matrices (TDM) provide details about the departure of each electron from its corresponding hole during excitations, which results in charge transfer (CT), the charge separation distance (Δr) between the electron and its corresponding hole was studied, in addition to the degree of electron–hole overlap (Λ). The latter, single-point excitation energy of each electron, the percentage electron contribution to the anchoring segments of each compound, the incident-photon-conversion-efficiency (IPCE), charge recombination, light harvesting efficiency (LHE), electron injection (Φinj), and charge collection efficiency (ncollect) were then compared to Δr to determine whether the expected relationships hold. Moreover, parameters such as diffusion constant (Dπ) and electron lifetime (t), amongst others, were also used to describe electron excitation processes. Since IPCE is the key parameter in determining the efficiency, O3 was found to be the best dye due to its highest value.

Photovoltaphores: pharmacophore models for identifying metal-free dyes for dye-sensitized solar cells

Dye-sensitized solar cells (DSSCs) are cost-effective, sustainable, and versatile electricity producers, allowing them to be incorporated into a variety of devices. In this work, we explore the usage of pharmacophore modeling to identify metal-free dyes for DSSCs by means of virtual screening. Pharmacophore models were built based on experimentally tested sensitizers. Virtual screening was performed against a large dataset of commercially available compounds taken from the ZINC15 library and identified multiple virtual hits. A subset of these hits was subjected to DFT and time-dependent-DFT calculations leading to the identification of two compounds, TSC6 and ASC5, with appropriate molecular orbitals energies, favorable localization, and reasonable absorption UV–vis spectra. These results suggest that pharmacophore models, traditionally used in drug discovery and lead optimization, successfully predicted electronic properties, which are in agreement with the theoretical requirements for sensitizers. Such models may therefore find additional usages as modeling tools in materials sciences.

Kajian sifat listrik bayam merah dan daun kelor sebagai fotosensitizer pada DSSC solar cell

DSSC (Dye Sensitized Solar Cell) uses dye as a sensitizer material which is used as an electron donor to TiO2 nanoparticles and uses an electrolyte as an electron transport medium. One of the dye extracts of purple spinach and moringa leaves used as a photosensitizer is chlorophyll extract or anthocyanin. The nature of chlorophyll which is able to absorb light is a function of the dye in DSSC. Making Moringa leaf and red spinach leaf dye after being blended, dried and ground into powder. Then the Moringa leaf powder was mixed with 70% ethanol with the ratio of Moringa leaves and ethanol, namely 1:2, 1:3, and 1:4. Meanwhile, red spinach leaf powder was mixed with ethanol solution in a ratio of 1:3. DSSC fabrication shows that the voltage, current, and power produced increases with the increasing amount of ethanol used, namely 1.879 mW, 1.573 mW, and 1.98 mW. Meanwhile, red spinach leaves mixed with ethanol in a ratio of 1:3 showed that the results were higher than Moringa leaves. So from the results of DSSC Solar Cell fabrication using Moringa leaves and red spinach leaves, it shows that there is light absorption from these materials and an increase in the conductive properties of Moringa and red spinach DSSCs.

Synthetic Efforts to Investigate the Effect of Planarizing the Triarylamine Geometry in Dyes for Dye-Sensitized Solar Cells.

The geometry of a dye for dye-sensitized solar cells (DSSCs) has a major impact on its optical and electronic properties. The dye structure also dictates the packing properties and how well the dye insulates the metal–oxide surface from oxidants in the electrolyte. The aim of this work is to investigate the effect of planarizing the geometry of the common triarylamine donor, frequently used in dyes for DSSC. Five novel dyes were designed and prepared; two employ conventional triarylamine donors with thiophene and furan π-spacers, two dyes have had their donors planarized through one sulfur bridge (making two distinct phenothiazine motifs), and the final dye has been planarized by forming a double phenoxazine. The synthesis of these model dyes proved to be quite challenging, and each required specially designed total syntheses. We demonstrate that the planarization of the triarylamine donor can have different effects. When planarization was achieved by a 3,7-phenothiazine and double phenoxazine structures, improved absorption properties were noted, and a panchromatic absorption was achieved by the latter. However, an incorrect linking of donor and acceptor moieties has the opposite effect. Further, electrochemical impedance spectroscopy revealed clear differences in charge recombination depending on the structure of the dye. A drawback of planarized dyes in relation to DSSC is their low oxidation potentials. The best photovoltaic performance was achieved by 3,7-phenothazine with furan as a π-spacer, which produces a power conversion efficiency of 5.2% (Jsc = 8.8 mA cm–2, Voc = 838 mV, FF = 0.70).

Expanding π-bridge and introducing auxiliary acceptor for realizing panchromatic absorption of the phenothiazine dyes in dye-sensitized solar cells

Dyes with panchromatic absorption of the solar radiation is crucial for the photovoltaic performances of dye-sensitized solar cells (DSSCs). In this paper we have constructed four phenothiazine dyes (PS1, PS2, PID1 and PID2), and applied to fabricate the DSSCs. Some important results have been found: (I) PID1 and PID2 with isoindigo as auxiliary acceptor successfully achieve nearly panchromatic absorption. (II) thieno[3,2-b]thiophene is a better π-bridge than 2,2′-bithiophene in terms of facilitating the intramolecular transport of photoexcited electrons, reducing the dye aggregation and improving the photovoltaic properties of DSSCs; (III) it is surprised that PID1 and PID2 exhibit broader absorption spectra, but achieve lower conversion efficiencies than PS2 with thieno[3,2-b]thiophene as π-bridge; (IV) The low device efficiencies of the isoindigo-based dyes might be due to the strong electron-withdrawing ability of isoindigo moiety, affecting the electron transport. These findings suggest that it might be an effective way to realize panchromatic absorption of the organic dyes by introducing isoindigo as an auxiliary acceptor, and a balanced perspective on the molecular design of dye is necessary to improve the performance of DSSCs.

Effect of π-Spacer Length in Novel Xanthene-Linked l-(D−π–A)2-Type Dianchoring Dyes for Dye-Sensitized Solar Cells

Effect of π-Spacer Length in Novel Xanthene-Linked <scp>l</scp>-(D−π–A)₂-Type Dianchoring Dyes for Dye-Sensitized Solar Cells

Effect of carboxylic acid and cyanoacrylic acid as anchoring groups on Coumarin 6 dye for dye-sensitized solar cells: DFT and TD-DFT study

Starting with Coumarin-6 dye, two novel D-π-A organic dyes C6X and C6N have been designed by attaching carboxylic acid and cyanoacrylic acid groups as anchoring groups to Coumarn-6 dye, respectively, to understand their potential use in dye-sensitized solar cells (DSSCs). The electronic structure and photophysical and photovoltaic properties of the novel designed dyes were studied using density functional theory DFT and time-dependent density functional theory TD-DFT with the Becke3-Parameter-Lee–Yang–Parr (B3LYP) functional and the 6-31G (d, p) basis set. Optimized structure and electronic properties (highest occupied molecular orbital energy (EHOMO), lowest unoccupied molecular orbital (ELUMO), and energy difference (Eg) between HOMO and LUMO) were calculated showing that C6N has the smallest band gap with the larger absorption region. Density of states (DOS), molecular electrostatic potential (MEP), natural bond orbital (NBO) analysis, non-linear optical (NLO) properties, UV–vis spectra, as well as some crucial parameters affecting the photovoltaic performance of DSSCs, such as light-harvesting efficiency (LHE), electron injection driving force (ΔGinject), dye regeneration driving force(ΔGreg), and the excited state life time(τe), were calculated to study the effect of the anchoring group on the DSSC performance. Additionally, the adsorption of C6X and C6N dyes on the TiO2 anatase (101) surface and the mechanism of electron injection were also investigated using a dye–(TiO2)9 cluster model using TD-B3LYP calculation. The calculated adsorption energies of the dyes suggest a strong adsorption of dyes to a TiO2 surface. The results show that C6N may be theoretically a good candidate as sensitizer of DSSC application.

Effect of the TiO2 surface modification with 3-glycidyloxypropyltrimethoxysilane on the aggregation of cresyl violet: Application to a dye-sensitized solar cell

Dye aggregation is a typical phenomenon occurring in dye-sensitized solar cells (DSSCs), which causes a decrease in the electron injection efficiency from the photoexcited dye to titanium dioxide (TiO2). As this results in a decrease in the photovoltaic performance, it cannot be ignored in the study of DSSCs. This paper reports a DSSC involving a TiO2 electrode chemically modified by cresyl violet (CV) covalently attached to 3-glycidyloxypropyltrimethoxysilane (GPTMS). The aim of the study is to understand the influence of silane coupling agents (SCAs) on dye aggregation. Aggregation of CV occurring on the TiO2 surface was prevented by GPTMS treatment on the TiO2 surface. This result was revealed by the decreased absorption intensity of the dimeric band observed in the total transmittance spectra. Density functional theory calculations and fluorescence decay curve measurements indicated that the CV covalently attached to GPTMS acts as a photosensitizing dye in DSSCs. As a result, the photovoltaic performance of DSSCs containing CV was enhanced by preventing its aggregation upon GPTMS treatment onto the TiO2 surface (7-fold increase: 0.0020%–0.014%). We concluded that TiO2 surfaces treated with SCAs can help to prevent dye aggregation, and therefore, enhance the photovoltaic performance of DSSCs.

Optical and electronic properties of the natural Alizarin dye: Theoretical and experimental investigations for DSSCs application

Optical properties of Alizarin dye for dye-sensitized solar cells were performed experimentally using transmittance and photoluminescence spectroscopies and confirmed theoretically using the density functional theory. The solvent effect of photoluminescence measurement was observed, and the strongest luminescence was 1.4E7 CPS at 437 nm. A widely investigated transmittance, focusing our attention on its optical properties in the visible and near-infrared regions. Broad absorbance from 400 nm to 600 nm was shown with two maximum peaks. The electronic properties such as HOMO and LUMO levels were computed via Gaussian software, as well as the estimation of the key photovoltaic parameters such as ΔGinject, ΔGreg, |VRP |, LHE, τ and Voc equal to −1.96 eV, 1.64 eV, 1.22 eV, 0.21, 11.39 ns and 1.26 V, respectively. The theoretical absorbance calculations of Alizarin dye are in good agreement with the experimental measurement, with a shift of 9 nm for the first absorbance peak and 2 nm for the second peak. The experimental and computational results confirm that Alizarin dye can be applied as a potential sensitizer for dye-sensitized solar cells.

Fabrication and characterization of highly efficient dye-sensitized solar cells with composited dyes

As a representative of the next-generation solar cells, dye-sensitized solar cells (DSSCs) offer the efficient and ease of implementation of new technology for future energy supply. Herein, four commercially available dyes including, curcumin (C), betanin (B), crystal violet (CV), and methylene blue (MB), and their compositions were used as sensitizers for fabrication of titanium oxide photo-anode based DSSCs. All dyes were fully characterized using absorption and emission spectroscopy. Both DFT and TDDFT studies were also carried out to probe the electronic structure of these dyes. The power conversion efficiencies of each DSSCs prepared using the individual and composited dyes were measured and compared. Particularly, this is the first study to combine four different dyes for DSSCs, leading to a remarkable increase of power conversion efficiency. The DSSCs with combined curcumin, betanin, crystal violet, and methylene blue (in ratio 1:1:1:1 respectively) in ethanol exhibited the highest power conversion efficiency of 3.63%.

Effect of Exchange–correlation Functionals on Ground State Geometries, Optoelectronic and Charge Transfer of Triphenylamine-based Dyes

The importance of the Density Functional Theory (DFT) calculation approach lies in their ability to provide a highly accurate prediction of structural and optoelectronic properties. However, the traditional methods of DFT failed to predict optoelectronic properties satisfactorily. Therefore, it will be necessary to examine methods containing different percentages of Hartree-Fock exchange and correlation in order to find the most suitable functionals. DFT and Time-Dependent-DFT (TD-DFT) calculations was carried out using four different functionals approximations incorporating a different amount of Hartree Fock exchange (B3LYP, BHandHLYP, CAM-B3LYP and LCωPBE), in order to evaluate their accuracies to predict the geometrical, optoelectronic and charge transfer properties of four triphenylamine-based dyes for Dye-Sensitized Solar Cells (DSSCs) applications. The functional hybrid B3LYP was the best among adopted functional that reproduced the geometrical, optoelectronic and charge transfer properties. On the other hand, it has been shown that the Hartree-Fock exchange percentage for BHandHLYP, significantly improved TD-DFT results in the case of organic dyes. Moreover, the corrected long-range functionals (CAM-B3LYP and LC-wPBE) present valuable tools for giving results of comparable precision with experimental optical data. In terms of the choice of the most appropriate functional for computational calculation, the obtained results can be useful for future DSSC applications. DOI: http://dx.doi.org/10.17807/orbital.v14i1.1682

DFT Study of bis(1,10-phenanthroline)copper complexes: Molecular and electronic structure, redox and spectroscopic properties and application to Solar Cells

A density functional theory study (DFT) on the geometry, electronic structure and properties of a series of [Cu(phen)2]n+ complexes (n = 1 and 2, and phen = differently substituted phenanthroline ligands), is presented. The DFT study determined various properties of the complexes to be used either as dyes or as redox mediators in dye-sensitized solar cells (DSSCs). The calculated properties, namely absorption wavelength, light harvesting efficiency, excited state lifetime and driving force for electron injection, and the regeneration of these complexes, are favourable for these complexes to be used as dyes in DSSCs. However, the calculated electron transfer distance is small, implying excitation would result in a serious intramolecular electron recombination and low efficiency electron injection into the semiconductor. The redox properties of these complexes compare well with the redox reaction of the iodide/triiodide (I−/I3−) redox mediator which is generally being used in DSSCs. Relationships obtained between experimental redox potentials and DFT calculated energies can be used to design and fine-tune complexes with a desired redox potential, as required for a redox mediator in DSSCs.

Effects of different anchoring groups in phenothiazinyl-benzothiadiazolyl dyes for dye-sensitized solar cells

In this work, we synthesize two new dyes with phenothiazine (PTZ) as π-bridge, benzothiadiazole (BTD) as acceptor moiety, and rhodanine-3-acetic acid (-RA) / cyanoacrylic acid (-CA) as anchoring group. In combination with a previously reported one with anchoring group of carboxylic acid (-CH), the effects of the three anchoring groups on material properties and the performance of dye-sensitized solar cells (DSSCs) are investigated. It is found that in terms of anchoring group for DSSC dye, the moiety features of electron-pulling ability, the spatial stretching, as well as its conjugation to the main molecular axis should be considered simultaneously. When attached over a para-phenyl group to a phenothiazinyl-benzothiadiazolyl dye, among the three commonly used anchoring groups of -RA, -CA and -CH, the last one is the best, with which the CBPTZ-BTD1 based DSSC exhibits the highest power conversion efficiency of 6.69%, mainly due to the highest dye loading, open-circuit voltage, and rather high fill factor.

Indoline-Based Donor-π-Acceptor Visible-Light Responsive Organic Dyes for Dye-Sensitized Solar Cells: Co-sensitization with Squaraine Dye for Panchromatic IPCE Response

Indoline-Based Donor-π-Acceptor Visible-Light Responsive Organic Dyes for Dye-Sensitized Solar Cells: Co-sensitization with Squaraine Dye for Panchromatic IPCE Response

Molecular design of benzo[c][1,2,5]thiadiazole or thieno[3,4-d]pyridazine-based auxiliary acceptors through different anchoring groups in D-π-A-A framework: A DFT/TD-DFT study

Based on density functional theory (DFT) and time-dependent DFT (TD-DFT) methods, a novel series of D-π-A-A porphyrin sensitizers adsorbed on the TiO2 cluster has been investigated. The D-π-A-A configurations contained a donor of iminodibenzyl, π-linker of Zn-porphyrin, and two kinds of auxiliary acceptors (labeled as BT and TP), as well as five types of anchoring groups. The ground-state geometries, electronics, optics, and charge transfer properties of all free dyes including injection driving force (ΔGinj), regeneration energy (ΔGreg), and light-harvesting efficiency (LHE) were calculated. Additionally, reorganization energy (λtotal), electron affinity (EA), and ionization potential (IP) were also reported to confirm the transport properties of the designed dye. Furthermore, the interfacial system of dye@(TiO2)48 was further discussed to reveal the complexation energy of the system by considering the adsorption energy (Eads) between dyes and (TiO2)48. The results showed that the insertion of different auxiliary acceptors in the D-π-A-A motif and variations in the anchoring groups resulted in red-shift absorption along with the increase in photovoltaic properties. These results suggested that BT with the rhodanine-3-acetic acid group (BT4) and BT with 2-(1,1-dicyanomethylene)rhodanine group (BT5) and TP with the same rhodanine-3-acetic acid and 2-(1,1-dicyanomethylene)rhodanine groups (TP4 and TP5) had shown better properties among other candidates for DSSCs. BT4-BT5 and TP4-TP5 had pronounce effect on optical and charge transfer properties by showing small HOMO-LUMO gaps, red-shifted spectra (λmax), greater LHE and ICT characters, and maximum-negative Eads. Thus, our theoretical investigation using these auxiliary moieties can be helpful for the precise structural modifications and design for developing efficient dyes in dye-sensitized solar cells (DSSCs).

Lewis Acid–Lewis Base Interactions Promote Fast Interfacial Electron Transfers with a Pyridine-Based Donor Dye in Dye-Sensitized Solar Cells

Lewis Acid–Lewis Base Interactions Promote Fast Interfacial Electron Transfers with a Pyridine-Based Donor Dye in Dye-Sensitized Solar Cells

Light Absorption Enhancement Using Graphene Quantum Dots and the Effect of N-719 Dye Loading on the Photoelectrode of Dye-Sensitized Solar Cell (DSSC)

Graphene quantum dots (GQDs) is used to enhance light absorption in the visible region of DSSC by sensitising method. The used of GQDs in photoelectode may effect the N-719 dye loading on photoelectrode and the study is done by ultraviolet spectroscopy (Uv-Vis). Initially, the TiO2 photoelectrode films is sensitised in ∼5 nm GQDs to overcome TiO2 photoelectrode drawback such as random electron transport and short-circuit current. Then, photoelectrode films is sensitised in N-719 dye to excite the electrons in TiO2 film. PG 7.5 adsorbed only 0.103 x 10-7 mol cm-2 N719 dye while PT at 0.527 x 10-7 mol cm-2. The pristine TiO2 photoelectrode (PT) adsorbed more than 80.4% of N-719 dye compared to PG 7.5 photoelectrode and other TiO2-GQDs photoeletrodes (PG 2.5, PG 5.0 and PG 10). As a result, the used of GQDs for TiO2 photoelectrode is reduced the intake of expensive N-719 dye for DSSCs. This happened because some of the functional groups in the GQDs solution such as hydroxyl and carboxyl groups are biocompatible with TiO2 which allows more adsorption sites of GQDs onto TiO2 surface. Thus, after GQDs molecules were occupied on the TiO2 surface, not many sites were available for N719 dye molecule. Therefore, it might reduce the N719-dye intake in the DSSC device, which can reduce the fabrication cost of DSSC and give good impact on environment.

Effect of the Ancillary Ligand on the Performance of Heteroleptic Cu(I) Diimine Complexes as Dyes in Dye-Sensitized Solar Cells.

A series of heteroleptic Cu(I) diimine complexes with different ancillary ligands and 6,6′-dimethyl-2,2′-bipyridine-4,4′-dibenzoic acid (dbda) as the anchoring ligand were self-assembled on TiO2 surfaces and used as dyes for dye-sensitized solar cells (DSSCs). The binding to the TiO2 surface was studied by hard X-ray photoelectron spectroscopy for a bromine-containing complex, confirming the complex formation. The performance of all complexes was assessed and rationalized on the basis of their respective ancillary ligand. The DSSC photocurrent–voltage characteristics, incident photon-to-current conversion efficiency (IPCE) spectra, and calculated lowest unoccupied molecular orbital (LUMO) distributions collectively show a push–pull structural dye design, in which the ancillary ligand exhibits an electron-donating effect that can lead to improved solar cell performance. By analyzing the optical properties of the dyes and their solar cell performance, we can conclude that the presence of ancillary ligands with bulky substituents protects the Cu(I) metal center from solvent coordination constituting a critical factor in the design of efficient Cu(I)-based dyes. Moreover, we have identified some components in the I–/I3–-based electrolyte that causes dissociation of the ancillary ligand, i.e., TiO2 photoelectrode bleaching. Finally, the detailed studies on one of the dyes revealed an electrolyte–dye interaction, leading to a dramatic change of the dye properties when adsorbed on the TiO2 surface.