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Context: The world's energy and environmental requirements are changing due to rapid population growth and industrial growth, and solar cells can be used to meet these demands. Dye-sensitized solar cells (DSSCs) are solar cells in which energy conversion occurs via a process similar to photosynthesis in plants. DSSC development is still in its infancy. DSSCs can operate under cloudy conditions and indirect sunlight and have attracted considerable attention due to their low cost and high efficiency. We designed two metal-free TPA-based dyes (Dye2 and Dye3) based on the reference dye Mg207 (Dye1) by increasing the donor strength of the molecule, as such dyes have shown enhanced efficiency in DSSCs. Moreover, the triphenylamine (TPA) moiety has been demonstrated to be a good donor that prevents charge recombination. Intramolecular charge transfer (ICT) from the donor to acceptor moiety was found in the sensitizers, and electrons were promoted to the conduction band (CB) of the TiO2 semiconductor. The negative binding energy of the dye@TiO2 clusters indicated that dye adsorption on the semiconductor surface was stable. The double donor increased the electron injection and electronic coupling constants in Dye2 and Dye3, indicating that these newly designed dyes have superior charge injection capacity. Accordingly, the efficiencies of DSSCs with Dye2 and Dye3 were 9.77% and 9.62%, respectively, and substitution with the TPA unit at the -R1 and -R2 positions in Dye1 resulted in better power conversion compared to the parent compound (9.09%). Increased donor strength improved photovoltaic performance by increasing current density and light-harvesting efficiency. This is a good molecular design approach for preparing targeted donor- π -acceptor (D- π -A) organic dyes with high DSSC efficiency. Methods: To predict the charge transport and optoelectronic characteristics of the TPA dyes, quantum chemical calculations were carried out using Gaussian16. The ground-state (S0) optimized geometries of the sensitizers were computed by utilizing DFT at the B3LYP/6-31G** level. The absorption spectra (λ max) were computed by employing TD-DFT with various functionals (B3LYP, PBE1PBE, CAM-B3LYP, and BHandHLYP) in the gas and solvent (DCM) phases. Among the studied functionals, BHandHLYP was found to be best at successfully reproducing the experimental data. Thus, the absorption spectra of the newly designed dyes and dye@TiO2 were calculated at the BHandHLYP/6-31G** level. The dye@TiO2 cluster optimizations were carried out at the B3LYP/6-31G**(LANL2DZ) level. [ABSTRACT FROM AUTHOR]

Context: A series of five organic dyes (Mi, i = 1–5) of the D-A'-π-A structure were designed based on reference dye (Ref), and the influence of different auxiliary acceptors (A') on their efficiency in dye-sensitized solar cells (DSSC). Methods: Was studied theoretically using density functional theory (DFT) and time-dependent DFT (TD-DFT) methods. In this context, the electronic structures, optical properties, and the parameters influencing the power conversion efficiency (PCE), such as light harvesting efficiency (LHE), electron injection driving force (∆Ginject.), and open circuit photo-voltage (VOC), have been evaluated and discussed. The modification of the auxiliary acceptor (A') in the D-A'-π-A structure of the designed organic dyes has the advantage of significantly decreasing the band gap, which leads to the broadening of the absorption band that is red-shifted and improves the photovoltaic characteristics compared to Ref. Theoretical results reveal that M1, and M5 can be used as excellent sensitizer candidates for DSSC applications. [ABSTRACT FROM AUTHOR]

Context: This research aims to investigate the potential of pyrazine-based small donor moieties as donor–acceptor switches for optical and photovoltaic applications. The designed organic dyes have a high light harvesting efficiency (LHE) and can potentially generate significant electrical energy. Methods: The study focuses on understanding the structural and electronic properties of these dyes through the analysis of dihedral angles, bond lengths, and energies of frontier molecular orbitals The UV–Vis spectroscopy parameters of the designed organic dyes revealed their absorption characteristics, including transition energies, wavelengths (λmax), and oscillator strengths (f). The photovoltaic properties of the developed organic dyes show a range of values: a range of 0.95–0.99 for LHE and a range of 1.77–33.02 W for maximum power output (Pmax) with the highest value for dye DDP5. For their stabilization energies, their natural bond orbitals had values ranging from 0.56 to 128.48 kcal/mol, their E(j)E(i) values from 0.22 to 1.29 a.u, and their Fi,j values from 0.024 to 0.213 kcal/mol. Out of all dyes, the DDP5 produced highest push–pull effect and can be good choice for further studies. The design of these novel organic materials for effective and economical solar energy conversion will be aided by evaluating the potential of 5,10-diphenyl-5,10-dihydrophenazine as a donor moiety and determining the structure–property correlations controlling the photovoltaic performance of the compounds. [ABSTRACT FROM AUTHOR]

Context: In this work, we designed ten new organic phenothiazine dyes bridged by different πi-spacers (PTZ1-PTZ10) of D-π-A type based on the synthesized dye CC202-III for their efficacy in dye-sensitized solar cells (DSSC) applications. To learn how various π-spacers affect their performance in DSSCs, these isolated dyes and dye-cluster systems have had their geometries, electronic structures, absorption spectra, dipole moments, and molecular electrostatic potential examined and talked about. Additionally, a number of quantization parameters that affect power conversion efficiency (PCE), including light collection efficiency (LHE), reorganization energy (λtotal), vertical dipole moment (μnormal), strength electron injection driving force (ΔGinject), regeneration driving force (ΔGreg), excited state lifetime (τ), and open circuit voltage (VOC), were calculated in order to identify the organic dyes that would be best suited for DSSC applications. Calculated results revealed that the designed dyes PTZ3, PTZ4, PTZ5, and PTZ10 exhibit a lower energy gap among all dyes compared to the corresponding CC202-III. Additionally, PTZ3, PTZ4, PTZ5, PTZ7, PTZ8, PTZ9, and PTZ10 exhibit significant red-shifted absorption spectra compared to the other dyes with a larger oscillator strength, which improves the photocurrent density of the devices. The findings thus imply that bridge modification is a workable tactic to raise DSSC effectiveness. Method: We used density functional theory (DFT) and time-dependent DFT (TD-DFT) methods to study the electronic and photovoltaic properties of the dyes designed (PTZ1–PTZ10) to assess their effectiveness in DSSCs. DFT and TD-DFT simulations are theoretically used to deeply analyze key characteristics of all organic dyes that affect open-circuit voltage (VOC) and short-circuit current (JSC) to identify structure–property relationships. [ABSTRACT FROM AUTHOR]

Context: Dye-sensitized solar cells (DSSCs) have displayed huge potential in inexpensive, efficient, and clean solar energy technology. In this work, seven new dyes with the structure D-A'-A were designed in which the thiophene in the reference dye was replaced by auxiliary acceptors (A'). These dyes consist mainly of a pyranylidene-based electron donor D and the cyanoacrylic acid moiety as acceptor A. A computational investigation was carried out on the effect of various auxiliary acceptors A' on the efficiency of D-A'-A dyes in isolation and after binding to the semiconductor TiO2. Optimized structures, geometrical, optoelectronic, and photovoltaic parameters were calculated to predict promising dyes for potential use as solar cell sensitizers, including band gap (Egap), natural bond orbital (NBO) analysis, nonlinear optical properties (NLO), UV–Vis absorption spectra, maximum absorption wavelength (λmax), reorganization energy (λtotal), light-harvesting efficiency (LHE), electron injection driving force (ΔGinject) and open-circuit photovoltage (VOC). The results of this study revealed that all designed dyes, compared to the reference dye, are characterized by small Egap and λtotal values as well as large λmax, in addition to significant NLO properties and large adsorption energy (Eads). Therefore, all studied dyes can be used as sensitizers in DSSC. Methods: Using Density Functional Theory (DFT) approaches with the B3LYP functional and the 6-31G(d,p) basis set, all ground state geometries of the isolated dyes were fully optimized. Time-Dependent Density Functional Theory (TD-DFT) method using the CAM-B3LYP/6-31G(d,p)/IEF-PCM level was applied to simulate the UV–visible absorption properties. All isolated dye calculations were performed using the Gaussian 09 software package. DFT calculations have been carried out with the DMol3 package included in Materials Studio for simulating the adsorption of the investigated dyestuff on the TiO2 surface of anatase (101), using the generalized gradient corrected approximation (GGA) approach of the Perdew-Burke-Ernzerhof (PBE) functional with the basic set of digital double polarisation (DNP). To study the optical performance of dye@TiO2 the PBE/DNP method present in DMol3 was applied. [ABSTRACT FROM AUTHOR]

Context: The organic solar cells (OSCs) are being developed with the goal of improving their photovoltaic capabilities. Here, utilizing computational methods, six new nonfullerene acceptors (NFA) comprising dyes (A1–A6) have been created by end-group alterations of the Y123 framework as a standard (R). Methods: The DFT-based investigations at B3LYP/6-31G + (d,p) level were applied to evaluate their properties. The planar geometries associated with these structures, which lead to improved conjugation, were validated by the estimation of molecular geometries. Dyes A1–A6 have shorter Egap than R, according to a frontier molecular orbital (FMO) investigation, which encourages charge transfer in them. The dyes with their maximum absorption range were shown by optical properties to be 692–711 nm, which is significantly better than R with its 684 nm range. Their electrostatic and Mulliken charge patterns provided additional evidence of the significant separation of charges within these structures. All the dyes A1–A6 had improved light harvesting efficiency (LHE) values as compared to Y123, highlighting their improved capacity to generate charge carriers by light absorption. With the exception of dye A4, all newly developed dyes might have a superior rate of charge carrier mobility than R, according to reorganization energies λre. Dyes A3 and A4 had the greatest open-circuit voltage (Voc). Dye A3 exhibited improvement in all of its examined properties, making it a promising choice in DSSC applications. [ABSTRACT FROM AUTHOR]

Context: Since 1991 when Grätzel et al. improved the conversion efficiency of dye-sensitized solar cells to 7.1% by applying nano technology as the first time, the researches on dye-sensitized solar cells have received widely attentions. The organic dye without precious metals has a lower cost, which is easily to get synthesized and its structure is easily decorated, owing a higher photoelectric conversion efficiency at the same time. Therefore, in recent years, the organic dye has attracted people's attentions more and more. In order to better understand the relationship between structure and properties of dye molecules, with ZL003 as a prototype, molecular modifications are then made and a scheme, with rigid fused π-bridge comprising electron-rich and deficient segments. The calculated results indicate that the π-bridge containing dithienopyrrolobenzothiadiazole and dipyrrolo-dithienobenzothiadiazole as π-bridge has been demonstrated to be successful to significantly redshift the absorption maximum wavelength, extend the lifetime of the first excited state, and decrease the energy gap between the highest occupied molecule orbital (HOMO) and the lowest unoccupied molecule orbital (LUMO). It is hoped that the calculation result of this paper would provide theoretical basis for the experimental synthesis of more efficient dye molecules. Method: All calculations were performed in Gaussian 09 program package. The ground state geometries (S0) and the first excited state (S1) were optimized using density function theory (DFT) with the hybrid function B3LYP functional, coupled with the 6-31G(d, p) basis set for optimization of molecule ground state conformations. TD-DFT calculations of excited state energies and absorption spectra were performed using MPWPW91 functional combined with the 6–31 + G (d) basis set. [ABSTRACT FROM AUTHOR]

Background: In the present work, DFT and time-dependent DFT calculations were performed to investigate the role of anchoring groups on the photophysical properties and reveal structure-property correlations of triphenylamine (TPA) derivatives. The selected anchoring groups are tetrazole, acrylamide, hydantoin, and rhodanine. Results: Our results show that the different anchoring groups employed alter the planarity, intramolecular charge transfer properties, and HOMO-LUMO gap and hence influence the optoelectronic properties of the dyes. Although all molecules fulfill the basic requirements with suitable energy levels, band gap, absorption, and charge transfer properties, the dye with rhodanine acceptor (TPA4) was the most promising candidate due to its lowest HOMO-LUMO gap, red-shifted highest λmax absorption value, better ICT pattern, low total reorganization energy, and good electron injection properties. Overall, it is anticipated that the results of this investigation will point to new avenues for the experimental fabrication of remarkably effective metal-free organic dyes for solar cell applications. [ABSTRACT FROM AUTHOR]

Context: The improvement of new organic flavone-based donor-spacer-acceptor (D-π-A) type dye molecules of the 3-(4-hydroxypiperidin-2-yloxy)-7-hydroxy-2-(3,4-dihydroxyphenyl)-4H-chromen-4-one (D1), 7-hydroxy-2-(3,4-dihydroxyphenyl)-3-(piperidin-4-yloxy)-4H-chromen-4-one (D2), and 3-((2-aminopyridin-4-yloxy)methoxy)-7-hydroxy-2-(3,4-dihydroxyphenyl)-4H-chromen-4-one (D3) were successfully designed and synthesized for dye-sensitized solar cells (DSSCs). Methods: Here, we discuss the synthesis of flavone compounds as well as their photophysical and electrochemical characterization. Using the Gaussian 09w software, the electronic structures and apsorption spectra have been calculated at the B3LYP, B3PW91, CAM-B3LYP, MPW1PW91, PBEPBE, and ωB97XD theory with the 6-311G(d,p) basis sets. Results: The computed values of the D2 molecule ground state optimized HOMOs-LUMOs energy is well positioned for advantageous charge transfer (CT) into the semiconducting material (TiO2) as well as the electron injection process. With a high power conversion efficiency (PCE) of 3.46% (VOC = 0.718 V, JSC = 7.07 mA cm−2, and FF = 0.68), the D2 compound also demonstrated good photovoltaic (PV) properties. Conclusion: These findings unequivocally demonstrate that altering the D-π-A metal-free organic material electron-withdrawing capacity is a useful strategy for enhancing the optical and electrical characteristics of the organic PV system. [ABSTRACT FROM AUTHOR]

A new photosensitizer 1-WS55 (dyad) based on two dyes with excellent properties, azulenocyanine (1) and WS55, is proposed at the density functional theory level (M06/def2-SVP). 1 is a dye having a broad NIR absorption (~ 1000 nm), and WS55 is a metal-free organic dye that presents a huge photoelectric conversion efficiency (PCE) of 9.5%. The dyad presents a panchromatic absorption along the UV–Vis-NIR region. It exhibits two intense Q bands (880, 926 nm) in the NIR region, one strong band (672 nm) in the visible region, and several bands in 300–600 nm. Charge transfer bands in the dyad from 1 to WS55 were found in the visible region, which favors the adsorption on an anatase TiO2 surface. The interaction energies dyad (dye)-TiO2 were calculated as a periodic system and corrected by the basis set superposition error. These show better adsorption for the dyad than fragments 1 and WS55. The electron injection calculated from the dye (dyad) to TiO2 suggests an efficient solar energy conversion because of ΔGinj > 0.2 eV. Additionally, calculations performed for the reorganization energy of electrons and holes indicate that the dyad presents the highest charge mobility. In summary, the dyad proposed 1-WS55 constitutes an excellent candidate to be used as a potential photosensitizer for the DSSCs. [ABSTRACT FROM AUTHOR]

New dyes were developed and produced utilizing distinct electron donors (phenothiazine and dibenzofuran), a π-spacer, and an electron acceptor of cyanoacetohydrazide, and their structures were studied using FT-IR and NMR spectroscopy. Following the synthesis of dye molecules, the photophysical and photovoltaic characteristics were investigated using experimental and theoretical methods. The photosensitizers have been exposed to electrochemical and optical property experiments in order to study their absorption performance and also molecular orbital energies. The monochromatic optical conversion efficiency of (Z)-N-((5-(10H-phenothiazin-2-yl)furan-2-yl)methylene)-2-cyanoacetohydrazide (PFCH) was found higher than that of (Z)-2-cyano-N′-((5-(dibenzo[b,d]furan-4-yl)furan-2-yl)methylene)acetohydrazide (BFCH), with IPCEs of 58 and 64% for BFCH and PFCH, respectively. According to the photosensitizer molecular energy level diagram, the studied dye molecules have strong thermodynamically advantageous ground and excited-state oxidation potentials for electron injection into the conduction band of titanium oxide. It was observed that the ability to attract electrons correlated favorably with molecular orbital energy. While density functional theory calculations were used to examine molecule geometries, vertical electronic excitations, and frontier molecular orbitals, experimental and computed results were consistent. Natural bond orbital and nonlinear optical properties were also calculated and discussed. [ABSTRACT FROM AUTHOR]

Some novel metal-free 1,2,4-triazole compounds A1-A8, based on the 3,5-bis(2-hydroxyphenyl)-1,2,4-triazole derivatives were examined for photovoltaic properties using density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations to test their suitability as metal-free organic dyes for use in dye-sensitized solar cells (DSSCs). Through deductive logic, the fluorescence emission (Φf) and charge collection (ηc) efficiencies of these compounds as dyes were obtained and used to determine each dye's incident conversion efficiency (IPCE). From the analyses, A2 displayed the highest IPCE value, followed by A6 and A1. This technique is restricted to evaluating compounds for potential metal-free organic dyes only. [ABSTRACT FROM AUTHOR]

The investigation of dye-sensitized solar cells (DSSCs) based on different donor groups linked with cyanoacrylic acid electron acceptor by Selenophene as π-bridged (D-π-A) was performed based on density functional theory (DFT) time-dependent DFT (TDDFT). Different functional were tested W97XD, PBEPBE, CAM-B3LYP, and B3PW91, and compared with experimental results of the reference D1. The theoretical results with CAM-B3LYP functional at 6-311G (d,p) basis sets were capable of predicting the absorption maximum that has been reported experimentally. Calculations were made to establish the conformational orientation of the cyanoacrylic acid group and evaluate the effect of changing donor units' on the electronic properties of the ground state. Structural and electronic properties, along with the photovoltaic properties, were investigated. The LUMO and HOMO energy levels of these dyes can positively affect the process of electron injection and dye regeneration. Light-harvesting efficiency (LHE), injection driving force (ΔGinject), and total reorganization energy (total) were also discussed. To further support the previous proprieties, electronic excited state energies were obtained by TDDFT// CAM-B3LYP/6-311G(d,p) calculations. The calculated results of these dyes reveal that D8 dye possessing triphenylamine donor unit has the best electronic, optical properties, and photovoltaic parameters. [ABSTRACT FROM AUTHOR]

In the present work, the structural and electronic properties of the D-D′-π-A organic dye with two donors have been calculated theoretically by DFT/time-dependent DFT method. In order to prove their efficiency as sensitizers, a comparative study was performed with a series of D-π-A architecture with one donor. The results of light-harvesting efficiency (LHE), open circuit voltage (Voc), free energy injection (∆Ginj), free energy dye regeneration∆Greg,excited-state lifetimes for the two series reveal that the D-D′-π-A dyes are promising for the design of new sensitive dyes in solar cells. [ABSTRACT FROM AUTHOR]

The molecular structure, UV-visible spectra, and optical properties of D-π-A conjugated organic dye molecules (Disperse Red 1 (DR1) and Disperse Red 73 (DR73)) were analyzed using density functional theory (DFT) and time-dependent density functional theory (TD-DFT) and compared with azobenzene molecule to study the effect of donor and acceptor substituents on the molecular properties. The performance of DFT functionals is investigated using B3LYP hybrid functional and three long-range corrected functionals (CAM-B3LYP, LC-ω PBE, and ω B97XD) in conjunction with 6-31G(d,p) basis set. Using TD-DFT, we calculate the vertical excitation energies and transition dipole moment values for 100 excited states. These values were further utilized to calculate frequency dependent polarizability under sum-over-states (SOS) formalism and refractive index of these molecular systems. We observe that for azobenzene and DR1 molecules, ω B97XD predicted wavelengths corresponding to peak absorbance closest to the experimental results, while for DR73 molecule, B3LYP gave better prediction. Large polarizability response is also observed for these molecules (DR1 and DR73) in comparison to parent azobenzene structure due to charge transfer between donor and acceptor groups. For DR1 and DR73 molecules, αxx component of polarizability dominates in contrast to azobenzene where αyy dominates. The HOMO → LUMO transition during excitation contributes to the peak molecular response in simulated UV-visible spectra. The high polarizability response of selected D-π-A conjugated molecules in comparison to parent molecule suggests that these molecules are promising candidates for tailor-made photonic and optoelectronic device development. [ABSTRACT FROM AUTHOR]

In this work, we theoretically studied ten organic dyes using the DFT and TD-DFT methods, where triphenylamine was used as the donor for the D1-D5 dyes, while the 2, 6-diphenyl-4H-pyranylidene donor was used for the D6-D10 dyes. Substituents (alkyl and methoxy) were also introduced into these donor groups. These dyes also include 1, 3, 4-oxadiazole and phenyl as a bridge π and cyanoacrylic acid as acceptor. The electronic and optical properties of all dyes have been calculated as EHOMO, ELUMO, EGAP, Voc (the open-circuit photovoltage), λmax, Eex, LHE (the light-harvesting efficiency) and ΔGinj (the free injection energy) in order to compare their performance as DSSC sensitizers. The donor effect of all dyes was discussed on the one hand and on the other hand the effects of the introduction of substituents (alkyl and methoxy) to the donor before and after binding to TiO2 cluster. The results show that the performance of the dyes using 2, 6-diphenyl-4H-pyranylidene as donor has improved compared with the rest of the dyes, which may improve the power conversion efficiency. Therefore, these dyes D6-D10 are good candidates for use as DSSC sensitizers. [ABSTRACT FROM AUTHOR]

We present a computational density functional theory study of the potential to improve the solar absorbance of small organic dyes featuring a phenothiazine donor and an acceptor moiety that combines a thiophene unit and a cyanoacrylic group. We consider different conjugation orders and functional groups on and around the thiophene unit, including electron-donating and electron-withdrawing moieties (H, F, CH, CF, and CN). We predict that by combining change of conjugation order and functionalization with electron withdrawing CN groups, it must be possible to decrease the excitation energy by up to 60 % vs. the parent dye (which would correspond to a redshift of the absorption peak maximum from 450 nm to 726 nm), effectively enabling red light absorption with small dyes. The contraction of the band gap is mostly due to the stabilization of the LUMO (by up to 1.8 eV), so that-in spite of the kinetic redundancy of the parent dye with respect to the conduction-band minimum of TiO-care must be taken to ensure efficient injection when using the dyes in dye-sensitized solar cells. By studying 50 dyes, of which 44 are new dyes that are studied for the first time in this work, we identify parameters (such as charges, dihedral angles between donor and acceptor groups, bond length alternation) which can serve as predictors of the band gap. We find that bond length alternation or dihedral angles are not good predictors, while the charge on the thiophene unit is. [ABSTRACT FROM AUTHOR]

The metal-free organic dye sensitizer 2,3′-diamino-4,4′-stilbenedicarboxylic acid has been investigated for the first time for dye-sensitized solar cell applications. Density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations (performed using the hybrid functional B3LYP) were carried out to analyze the geometry, electronic structure, polarizability, and hyperpolarizability of 2,3′-diamino-4,4′-stilbenedicarboxylic acid used as a dye sensitizer. A TiO cluster was used as a model semiconductor when attempting to determine the conversion efficiency of the selected dye sensitizer. Our TD-DFT calculations demonstrated that the twenty lowest-energy excited states of 2,3′-diamino-4,4′-stilbenedicarboxylic acid are due to photoinduced electron-transfer processes. Moreover, interfacial electron transfer between a TiO semiconductor electrode and the dye sensitizer occurs through electron injection from the excited dye to the semiconductor's conduction band. Results reveal that metal-free 2,3′-diamino-4,4′-stilbenedicarboxylic acid is a simple and efficient sensitizer for dye-sensitized solar cell applications. [ABSTRACT FROM AUTHOR]

We report a DFT, TDDFT and DFTB investigation of the performance of two donor-π-acceptor (D-π-A)-type organic dyes bearing different electron-withdrawing groups (EWG) for dye-sensitized solar cells (DSSCs) to evaluate which EWG is better for an acrylic acid acceptor, i.e., Cyano (-CN) or o-nitrophenyl ( o-NO-Ph). A series of theoretical criteria applied successfully in our previous work to explain the different performance of organic dyes related to open-circuit photovoltage ( V) and short-circuit current density ( J) were used to evaluate the performance of the dyes with just different EWG. Our calculated results reveal that dye 2 with o-NO-Ph has a larger vertical dipole moment, more electrons transferred from the dye to the semiconductor and a lower degree of charge recombination, which could lead to larger V; while the larger driving force and comparable light harvesting efficiency could lead to higher J , highlighting the potential of o-NO-Ph as an EWG in an acrylic acid acceptor. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

In Ti0 nanostructured dye-sensitized solar cells indole based organic dyes D149, D205 exhibits greater power conversion efficiency. Such organic dye molecules are easily undergone for aggregation. Aggregation in dye molecules leads to reduce electron transfer process in dye-sensitized solar cells. Therefore, anti-aggregating agents such as chenodeoxycholic acid are commonly added to organic dye solution in DSSCs. Studying aggregation of such dye molecules in the absence of semiconductors gives a detailed influence of anti-aggregating agents on dye molecules. Atomistic level of molecular dynamics (MD) simulations were performed on aggregation of indole type dye molecules D149, D205 and D205-F with anti-aggregating agent chenodeoxy cholic acid using AMBER program. The trajectories of the MD simulations were analyzed with order parameters such as radial atom pair distribution functions g(r), diffusion coefficients and root mean square deviations values. MD results suggest that addition of chenodeoxy cholic acid to dyes significantly reduces structural arrangement and increases conformational flexibility and mobility of dye molecules. The influence of semi-perfluorinated alkyl chains in indole dye molecules was analyzed. The parameters such as open-circuit voltage (V) and power conversion efficiency (η) of dye-sensitized solar cells are corroborated with flexibility and diffusion values of dye molecules. [ABSTRACT FROM AUTHOR]

Organic dyes have great potential for its use in solar cells. In this recent work, the molecular structure and properties of Dye 7 were obtained using density functional theory (DFT) and different levels of calculation. Upon comparing the molecular structure and the ultraviolet visible spectrum with experimental data reported in the literature, it was found that the M05-2X/6-31G(d) level of calculation gave the best approximation. Once the appropriate methodology had been obtained, the molecule was characterized by obtaining the infrared spectrum, dipole moment, total energy, isotropic polarizability, molecular orbital energies, free energy of solvation in different solvents, and the chemical reactivity sites using the condensed Fukui functions. [ABSTRACT FROM AUTHOR]

In this paper, we present a series of sensitizers to shed light on the influence of π-spacers on the performance of dye-sensitized solar cells. We have accurately calculated key properties in energy conversion, including sunlight absorption, electron injection, electron/hole reorganization energy, ionization potential (IP) and electronic affinity (EA). We chose a series of donor-π-acceptor dyes based on methyl-indole-carbazole as the electron donor group and cyano-acrylic acid as an acceptor with various π-conjugated systems. The results obtained show that, with incorporation of the thieno(3,4-b)pyrazine in the two π-spacer parts, D4 may be the best candidate among the dyes studied, due to its many advantages such as low gap energy, red-shift absorption spectra, large ΔGInj, low hole/electron reorganization energies, low IP and high EA, which indicate its better optoelectronic properties, which present more balanced transport rates and provide good injection ability. Graphical abstract Absorption spectra in gaz phase, obtained by CAM-B3LYP/6-31G(d,p) with solar spectrum. [ABSTRACT FROM AUTHOR]

In this work, we carried out a theoretical study in which DFT and TD-DFT calculations of a series of six new organic dyes that incorporate N,N-alkylamine as an electron donor and a cyanoacrylic acid group as an electron acceptor and anchoring group were performed. In each dye, the donor and the acceptor were bridged by six different π-conjugated spacers consisting of an auxiliary donor group (3,4-ethylenedioxythiophene, EDOT) or an auxiliary acceptor group (benzothiadiazole, BTZ or diketopyrrolopyrrole, DPP) that was linked to either thiophene or phenyl. EHOMO, ELUMO, Egap, λmax, Eex, the open-circuit photovoltage (Voc), the light-harvesting efficiency (LHE), and the free injection energy (ΔGinject) were calculated for all of the dyes to compare their photovoltaic performance. The effects of the incorporation of an additional acceptor group (DPP or BTZ) or an additional donor group (EDOT) into the π-bridge on the geometry, electronic structure, and photovoltaic performance of each designed dye were explored. The study shows that modifying the dye skeleton can greatly improve the performance of the dye and increase its power conversion efficiency. It also reveals that all of the studied dyes are promising candidates for an effective DSSC sensitizer, especially those that include the acceptor group DPP in the π-bridge. [ABSTRACT FROM AUTHOR]