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Hologram quantitative structure-activity relationship guided in silicon molecular design of phenothiazine dye sensitizers for dye-sensitized solar cells
The effects of climate change are becoming increasingly clear, and the urgency of solving the energy and resource crisis has been recognized by politicians and society. One of the most important solutions is sustainable energy technologies. The problem with the state of the art, however, is that production is energy-intensive and non-recyclable waste remains after the useful life. For monocrystalline photovoltaics, for example, there are recycling processes for glass and aluminum, but these must rather be described as downcycling. The semiconductor material is not recycled at all. Another promising technology for sustainable energy generation is dye-sensitized solar cells (DSSCs). Although efficiency and long-term stability still need to be improved, the technology has high potential to complement the state of the art. DSSCs have comparatively low production costs and can be manufactured without toxic components. In this work, we present the world’ s first experiment to test the recycling potential of non-toxic glass-based DSSCs in a melting test. The glass constituents were analyzed by optical emission spectrometry with inductively coupled plasma (ICP-OES), and the surface was examined by scanning electron microscopy energy dispersive X-ray (SEM-EDX). The glass was melted in a furnace and compared to a standard glass recycling process. The results show that the described DSSCs are suitable for glass recycling and thus can potentially circulate in a circular economy without a downcycling process. However, material properties such as chemical resistance, transparency or viscosity are not investigated in this work and need further research.
Acrylamide is probably carcinogenic to humans (International Agency for Research on Cancer, group 2A) with major occurrence in heated, mainly carbohydrate-rich foods. For roasted coffee, a European Union benchmark level of 400 µg/kg acrylamide is of importance. Regularly, the acrylamide contents are controlled using liquid chromatography combined with tandem mass spectrometry (LC–MS/MS). This reference method is reliable and precise but laborious because of the necessary sample clean-up procedure and instrument requirements. This research investigates the possibility of predicting the acrylamide content from proton nuclear magnetic resonance (NMR) spectra that are already recorded for other purposes of coffee control. In the NMR spectrum acrylamide is not directly quantifiable, so that the aim was to establish a correlation between the reference value and the corresponding NMR spectrum by means of a partial least squares (PLS) regression. Therefore, 40 commercially available coffee samples with already available LC–MS/MS data and NMR spectra were used as calibration data. To test the accuracy and robustness of the model and its limitations, 50 coffee samples with extreme roasting degrees and blends were additionally prepared as the test set. The PLS model shows an applicability for the varieties Coffea arabica and C. canephora, which were medium to very dark roasted using drum or infrared roasters. The root mean square error of prediction (RMSEP) is 79 µg/kg acrylamide (n = 32). The current PLS model is judged as suitable to predict the acrylamide values of commercially available coffee samples.
Metal oxide nanoparticles prepared by biological route using green plant parts as a template are eco-friendly as well as yield good results than the conventional methods. This present study focusses on biosynthesis and characterization of TiO2 NPs using root extract of Kniphofia schemperi for dye-sensitized solar cells. TiO2 NPs were synthesized using 0.25 M titanium tetra butoxide in the presence of root extract of Kniphofia schemperi with the volume ratios. The analysis result revealed that the synthesized TiO2 NPs were thermally stable above 500°C and have spherical morphology, with the average crystalline size of 11.7, 8.3, and 8.6 nm, and band gap energy of 3.35 eV, 3.33 eV, and 3.36 eV, respectively, for the TiO2 NPs prepared at the volume ratios of 2 : 3, 1 : 1, and 3 : 2. Biosynthesized TiO2 NPs were used as photoanode in dye-sensitized solar cells (a device used for converting absorbed light into electricity). Solar cell devices were fabricated using roots of Kniphofia schemperi sensitizer in the presence of TiO2 NPs biosynthesized within (2 : 3, 1 : 1, and 3 : 2) volume ratio, which showed power conversion efficiency of 0.039%, 0.117%, and 1.3%. Incident photon to current conversion efficiency (IPCE) analysis using TiO2 (2 : 3, 1 : 1, and 3 : 2) photoelectrodes showed 6.64%, 2.66%, and 18%. Among the biosynthesized TiO2 different volume ratios, TiO2 (3 : 2) NPs showed relatively maximum solar cell efficiency and IPCE value due to its uniform spherical shape that enables to absorb large dye molecules on its surface, and this intern improves device efficiency.
Boron-dipyrromethene (BODIPY) is one promising class of sensitizers for dye-sensitized solar cells (DSSCs) due to unique merits of high absorption coefficient and versatile structural modification capability. However, such derivatives usually suffer from limited power conversion efficiencies (PCEs) because of narrow light absorption band and low electron injection. To aid the discovery of BODIPY sensitizers, we employ an inverse design method to design efficient sensitizers by integrating data mining and first-principle techniques. We establish robust data-mining models using genetic algorithm and multiple linear regression, where the features are filtered from 5515 descriptors and their meanings are explicitly explored for next inverse designs. Based on the features’ understanding, we design candidates NH1-6 and predict their PCEs, demonstrating remarkable enhancements (58% maximum) compared to previous works. Furthermore, their optoelectronic properties including maximum absorption wavelengths, oscillator strengths, bandgaps, transferred charges, charge transferred distances, TiO2 conduction band shifts, short-circuit currents and electron injection efficiencies simulated via first-principle calculations indicate significant increasements (93nm, 122.41%, 23.70%, 36.36%, 471.17%, 63.64%, 28.55%, 107.86% maximum), which testifies the corresponding highly predicted PCEs and may overcome BODIPY dyes’ shortcomings. The as-designed BODIPY sensitizers can be promising candidates for DSSCs, and such method could help accelerate the discovery of other energy materials.
The development of highly efficient dye‐sensitized solar cells (DSSCs) is greatly hindered by the lack of a reliable and understandable quantitative structure‐property relationship (QSPR) model. Herein, an accurate, robust and interpretable QSPR model is established by combining the machine learning technique and computational quantum chemistry, and perform virtual screening with this model as well as the assessment of synthetic accessibility to search new efficient and synthetically accessible organic dyes for DSSCs. Finally, 8 promising organic dyes with high power conversion efficiency and synthetic accessibility are screened out from ∽10000 candidates. Meanwhile, the interpretability of our model is used for deducing reasonable chemical rules for high‐performance organic dyes, which are expected to contribute to further innovations for the practical applications of DSSCs.
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The quantitative structure–property relationship (QSPR) models for predicting the octane number (ON) of toluene primary reference fuel (TPRF; blends of n-heptane, isooctane, and toluene) was investigated. The electrotopological state (E-state) index of TPRF components was computed and weight-summed to generate the quantitative descriptor of TPRF samples. The partial least squares (PLS) technique was used to build up the regression model between the ON and weight-summed E-state index of the investigated samples. The QSPR models for the research octane number (RON) and motor octane number (MON) of TPRF were built. The prediction performance of the obtained PLS models was assessed by the external test set validation and leave-one-out cross-validation. The validation results demonstrate that the proposed PLS models are feasible for predicting the ON, both RON and MON, of TPRF. In addition, several other QSPR models for the ON of TPRF were developed by employing the stepwise regression and Scheffé polynomials methods, and the prediction performance of these models were compared with that of the PLS models. The comparison result shows that the proposed PLS models are slightly better than multiple linear regression models and Scheffé models. It is demonstrated that the combination of the E-state index and PLS is an easy-to-use and promising method for studying and forecasting the ON of TPRF.
The initial charge separation process in Dye Sensitized Solar Cells (DSSC) is crucial to their efficiency. An interesting strategy is to employ D-π-A (donor-π-acceptor) dyes, since the push-pull effect may avoid charge recombination instead of electron transfer to the semiconductor. In this work, we propose a method to design a photosensitizer based exclusively on quantum mechanics calculations. Our analysis focused on the influence of (i) different donor groups and (ii) conformational contributions, on electronic properties aiming to enhance the push-pull effect and the alignment with the CB. Based on this study, we propose a new dye, CAHM1, where the selected substituent have a donor character and, at the same time, enable a twisted geometry that enhances charge separation of the first excited state. The system is characterized by a marked push-pull effect, as well as, presents absorption spectrum and LUMO energy in a suitable region for DSSC devices.
Dye-sensitized solar-cell (DSSC) systems have been investigated by calculating light-absorption and electron-injection processes of the LD13 ([5,15-bis(2,6-(1,1-dimethylethyl)-phenyl)-10-4-dimethylaminophenylethynyl-20-4-carboxy phenylethynyl porphyrinato]zinc-(II)) and YD2-o-C8 ([5,15-bis(2,6-dioctoxyphenyl)-10-(bis(4-hexylphenyl)amino-20-4-carboxyphenylethynyl)porphyrinato]zinc-(II)) dyes adsorbed on a TiO2 cluster simulating the semiconductor. The binding energy of the dyes with the TiO2 clusters has been calculated at the density functional theory (DFT) level using the B3LYP and CAM-B3LYP functionals. The electronic excitation energies have been calculated at the time-dependent DFT (TDDFT) level for the dyes in the gas and solvent phase employing the B3LYP, CAM-B3LYP and BHLYP functionals. The calculated excitation energies have been compared to values obtained at the algebraic diagrammatic construction through second order (ADC(2)) level of theory. The TDDFT calculations with the B3LYP in tetrahydrofuran solvent with the dye and dye–TiO2 models yield excitation energies that agree well with the transitions in the experimental absorption spectra. Changes in the free energy for electron injection support the better performance of the dyes on the TiO2 clusters.
Advances in solar cell technology require designing of new organic dye sensitizers for dye-sensitized solar cells with high power conversion efficiency to circumvent the disadvantages of silicon-based solar cells. In silico studies including quantitative structure-property relationship analysis combined with quantum chemical analysis were employed to understand the primary electron transfer mechanism and photo-physical properties of 273 arylamine organic dyes from 11 diverse chemical families explicit to iodine electrolyte. The direct quantitative structure-property relationship models enable identification of the essential electronic and structural attributes necessary for quantifying the molecular prerequisites of 11 classes of arylamine organic dyes, responsible for high power conversion efficiency of dye-sensitized solar cells. Tetrahydroquinoline, N,N′-dialkylaniline and indoline have been least explored classes under arylamine organic dyes for dye-sensitized solar cells. Therefore, the identifi
Solar cells that operate efficiently under indoor lighting are of great practical interest as they can serve as electric power sources for portable electronics and devices for wireless sensor networks or the Internet of Things. Here, we demonstrate a dye-sensitized solar cell (DSC) that achieves very high power-conversion efficiencies (PCEs) under ambient light conditions. Our photosystem combines two judiciously designed sensitizers, coded D35 and XY1, with the copper complex Cu(II/I)(tmby) as a redox shuttle (tmby, 4,4′,6,6′-tetramethyl-2,2′-bipyridine), and features a high open-circuit photovoltage of 1.1 V. The DSC achieves an external quantum efficiency for photocurrent generation that exceeds 90% across the whole visible domain from 400 to 650 nm, and achieves power outputs of 15.6 and 88.5 mW cm–2 at 200 and 1,000 lux, respectively, under illumination from a model Osram 930 warm-white fluorescent light tube. This translates into a PCE of 28.9%.
Post silicon solar cell era involves light-absorbing dyes for dye-sensitized solar systems (DSSCs). Therefore, there is great interest in the design of competent organic dyes for DSSCs with high power conversion efficiency (PCE) to bypass some of the disadvantages of silicon-based solar cell technologies, such as high cost, heavy weight, limited silicon resources, and production methods that lead to high environmental pollution. The DSSC has the unique feature of a distance-dependent electron transfer step. This depends on the relative position of the sensitized organic dye in the metal oxide composite system. In the present work, we developed quantitative structure-property relationship (QSPR) models to set up the quantitative relationship between the overall PCE and quantum chemical molecular descriptors. They were calculated from density functional theory (DFT) and time-dependent DFT (TD-DFT) methods as well as from DRAGON software. This allows for understanding the basic electron transfer mechanism along with the structural attributes of arylamine-organic dye sensitizers for the DSSCs explicit to cobalt electrolyte. The identified properties and structural fragments are particularly valuable for guiding time-saving synthetic efforts for development of efficient arylamine organic dyes with improved power conversion efficiency.
Dye-sensitized solar cells have gained widespread attention in recent years because of their low production costs, ease of fabrication and tunable optical properties, such as colour and transparency. Here, we report a molecularly engineered porphyrin dye, coded SM315, which features the prototypical structure of a donor-π-bridge-acceptor and both maximizes electrolyte compatibility and improves light-harvesting properties. Linear-response, time-dependent density functional theory was used to investigate the perturbations in the electronic structure that lead to improved light harvesting. Using SM315 with the cobalt(II/III) redox shuttle resulted in dye-sensitized solar cells that exhibit a high open-circuit voltage VOC of 0.91 V, short-circuit current density JSC of 18.1 mA cm(-2), fill factor of 0.78 and a power conversion efficiency of 13%.
In order to increase electron-donating ability of the donor part of the organic dye, the two phenothiazine groups as additional electron donors are introduced into a triphenylamine unit to form a starburst donor-donor (2D) structure in this paper. Three new organic dyes (WD-6, WD-7 and WD-8) containing this starburst 2D structure and 2-cyanoacetic acid acceptor linked by various conjugated linkers (benzene, thiophene, and furan) have been designed, synthesized and applied in dye-sensitized solar cells (DSSCs). The introduction of phenothiazine group with a butterfly conformation in triphenylamine donor part has a good influence on preventing the molecular [small pi]-[small pi] aggregation due to the starburst 2D structure of the organic dye. The conjugated linker effects on the photophysical, electrochemical and photovoltaic properties of these organic dyes were investigated in detail. The DSSCs made with these organic dyes displayed remarkable overall conversion efficiencies, ranging from 4.90-6.80% under an AM 1.5 solar condition (100mW cm-2). The best performance was found in organic dye WD-8, in which a furan group was the conjugated linker. It displayed a short-circuit current (Jsc) of 14.40 mA cm-2, an open-circuit voltage (Voc) of 675 mV, and a fill factor (ff) of 0.70, corresponding to an overall conversion efficiency of 6.80%. The different photovoltaic behaviors of the solar cells based on these organic dyes were further elucidated by the electrochemical impedance spectroscopy.
The study was aimed to design fluoroquinolone (FQ) substitutes, improve the biological metabolism and concentration ability of fluoroquinolones (FQs) drug from the perspective of source control, and provide theoretical support for alleviating the potential environmental risks of FQs. First, the 3D-QSA²R model of the bidirectional selective effect of FQs was constructed, and 122 norfloxacin (NOR) substitutes were designed. Then, the biological metabolism and concentration of the 3D-QSAR models, two environmental friendliness evaluation models, and the pharmacokinetics (ADMET) and toxicokinetics (TOPKAT) models were used for screening, evaluation, and verification. Moreover, three environment-friendly NOR substitutes (N-039, N-068, and N-120) with enhanced bidirectional selectivity, improved functional properties and reduced human health and ecological risk were screened. Finally, the simulation of the metabolic pathways of the three molecules in fish was established. Meanwhile, their metabolic capacity in organisms of different trophic levels in the food chain (algae → shrimp → fish → human) was evaluated. Additionally, based on molecular docking, molecular dynamics (MD) simulation, and notability analysis, it was found that van der Waals force was the dominant factor in the enhancement of the bio-metabolism of FQs, NOR substitutes entered the catalytic active sites of metabolic enzymes more easily than NOR, and more hydrogen bonds and hydrophobic bonds were formed to improve the metabolic transformation ability of molecules in aquatic organisms.
The rapid use of fossil fuels has led to quick industrialization, swift economic growth, improved living standards, a high release of greenhouse gas, and fast exhaustion of fuel resources, which is a big threat to the environment and climate changes. To keep the planet green, dye-sensitized solar cells (DSSCs) have attracted much attention as the third-generation solar cells. This article documented an extensive study on the efficient use of natural dyes (Portulaca grandiflora, pereskia bleo, and alternanthera ficoidea), mesoporous TiO 2 photoanode, a carbon cathode, and conductive layers to improve efficiency of DSSCs at ambient conditions. All of the conductive/TiO 2 /natural dyes display enhanced structural, optical, and electrical properties. X-ray diffraction studies of conductive/TiO 2 layers represent the tetragonal structure which is buttressed by the SEM imaging, whereas organic dyes are amorphous in nature. The integrated conductive/TiO 2 /natural dye films have good sensitization in the visible spectrum (380-750 nm) and possess a bandgap falling (1.25-1.50 eV) and high refractive index while the maximum optical conductivity is observed in pereskia bleo. On the other hand, alternanthera ficoidea and portulaca grandiflora exhibit higher electrical conductivity (7.5 × 10 12 Scm − 1) and optical electronegativity (1.777). The TiO 2 photoanodes at a conductive layer thickness of 3886.8 nm with iodide/tri-iodide redox liquid electrolyte generated current densities of 0.071-0.106 mAcm − 2 under AM 1.5 illumination. Furthermore, the short-circuit photocurrent density (J SC), open-circuit voltage (V OC), fill factor (FF), and the corresponding photon-to-current conversion efficiency (η) estimated from the J-V characteristic curves with an effective area of 1 cm 2 calculated for pereskia bleo DSSC are J SC = 0.106 mAcm − 2 , V OC = 0.023 V, FF = 45, and η = 0.11%. This study will open up a new door to fabricate highly efficient solar cells by modifying different parameters (photoanode, conductive layer, hybrid active layer, or different electrolyte) that can achieve meaningful success in photovoltaic industries.
Quantitative structure-activity relationship models on the gas chromatographic retention index of the 38 volatile fragrance compounds of Liliumspp were investigated and established by comparative molecular field analysis (CoMFA) and comparative molecular similarity index (CoMSIA) methods. The robustness and predictive performance of the developed models were assessed using external test set validation and leave-one-out cross validation. Further, the effects of the molecular structure on the gas chromatographic retention indices of these compounds were intuitively studied in light of the three-dimensional contour maps of molecular fields provided by the developed CoMSIA and CoMFA models. The validation results demonstrated that both the models could accurately predict the retention indices of the investigated components. The influence of the molecular structure on the retention indices could be reasonably explained by these models. Moreover, the prediction accuracy of the CoMSIA model was slightly higher than that of the CoMFA model. Obviously, the proposed CoMSIA model is more promising for the analysis of the volatile fragrance compounds of Lilium spp.
The present chapter reports a partial least squares (PLS)-regression-based chemometric model for the carbazole class of dyes used in dye-sensitized solar cells (DSSCs) to predict the absorption maxima (λmax) values. Quantitative prediction of the λmax values can be an important criterion for molecular design of new dye molecules. We have used only 2D descriptors for the model development purpose as the quantum chemical and electrochemical analyses are time consuming. The developed model was validated extensively using internationally acceptable statistical and validation parameters. A seven-descriptor PLS model with one latent variable (LV) was developed. The statistical results suggested that the model was statistically significant. The majority of the descriptors involved in the model are easily interpretable 2D atom pair descriptors. The model suggests that presence of nitrogen and sulfur atoms at the topological distance of 8, presence of nitrogen and oxygen atoms at the topological distance of 4, higher frequency of oxygen and sulfur atoms at the topological distance of 5, higher frequency of two nitrogen atoms at the topological distance of 5, presence of two oxygen atoms at the topological distance of 4, presence of carbon atoms connected with three aromatic bonds, and presence of two sulfur atoms at the topological distance of 4 in the dye molecules shifted the λmax value toward the longer wavelength. From the information obtained from the model, it has also been suggested that highly conjugated π-systems shift the λmax values toward the longer wavelength. Finally, it can be concluded that the identified features from the PLS model for the carbazole derivatives may be employed for the design and development of new carbazole dyes and to predict λmax values before they are synthesized.
Platinum is commonly used as a catalyst to regenerate the redox mediator in Dye-Sensitized Solar Cells (DSSCs). This work intends to replace the expensive and rare platinum with conventional and economical materials. Nanocomposites of Multi-walled Carbon Nanotubes (MWCNTs) and TiO2 can be used as active catalyst materials for the counter-electrode of DSSC. In these composites, MWCNTs provide catalytic properties, and TiO2 acts as a binder. The interaction between MWCNTs and TiO2 has been investigated by Transmission Electron Microscopy (TEM). It has been observed that DSSCs photovoltaic performance significantly depends on the concentration of MWCNTs in nanocomposites. The amount of MWCNTs has been optimized for the best performance of DSSC. The solar cell assembled with 4%MWCNTs catalyst material showed an efficiency of 8.81%, comparable to Pt-based device (9.40%), fabricated under analogous environment.
Dye-sensitized solar cells (DSSCs) are an efficient and versatile method of transforming the clean and most plentiful energy resources available. DSSC is translucent to some extent and relatively inexpensive than the traditional solar cell. Thus, it may be a possible source of electricity for the future. But other things need to be focused on before it is considered a viable commercial product. The review discusses these facets and the numerous changes the DSSC has experienced in the recent years. Photoelectric conversion systems struggle to fulfil the specifications of constant power output owing to the erratic and unstable characteristics of the solar radiation. With the evolution of rechargeable electric energy storage systems (ESSs), the integration of a DSSC and ESSs has developed into a promising approach to solve this issue. Here, we describe the working principle, recent progress of DSSCs, including photoanodes, sensitizers, electrolytes, and counter electrodes, and the use of DSSCs in energy storage, targeting DSSC and supercapacitor (SC) integrated devices. The future prospects for highly effective, reliable DSSC and DSSC-SC development have also been highlighted.
Partial least squares, as a dimension reduction technique, has become increasingly important for its ability to deal with problems with a large number of variables. Since noisy variables may weaken estimation performance, the sparse partial least squares (SPLS) technique has been proposed to identify important variables and generate more interpretable results. However, the small sample size of a single dataset limits the performance of conventional methods. An effective solution comes from gathering information from multiple comparable studies. Integrative analysis has essential importance in multidatasets analysis. The main idea is to improve performance by assembling raw data from multiple independent datasets and analyzing them jointly. In this article, we develop an integrative SPLS (iSPLS) method using penalization based on the SPLS technique. The proposed approach consists of two penalties. The first penalty conducts variable selection under the context of integrative analysis. The second penalty, a contrasted penalty, is imposed to encourage the similarity of estimates across datasets and generate more sensible and accurate results. Computational algorithms are developed. Simulation experiments are conducted to compare iSPLS with alternative approaches. The practical utility of iSPLS is shown in the analysis of two TCGA gene expression data.
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%.
A series of D-A-π-A organic dyes are taken into consideration to study the influence of different internal acceptor
groups and thiophene based π-spacers on their efficiency in dye-sensitized solar cells (DSSCs). Density functional
theory (DFT) and time-dependent density functional theory (TDDFT) methods are used for investigating the
electronic excitations along with their geometrical and charge transport properties. HOMO, LUMO energy levels
and HOMO-LUMO energy gap helped in the understanding of energy levels appropriate for electron injection,
electron transfer and dye regeneration. Thereafter, the calculations for short circuit current density (JSC) were
performed by considering injection driving force (ΔGinj), dye regeneration energy (ΔGreg) and light-harvesting
efficiency (LHE). In addition to this, charge transport properties like electron reorganization energy (λe), hole
reorganization energy (λh), electron affinity (EA) and ionization potential (IP) are also reported. The results show
that the insertion of internal acceptor in D-π-A system and variation in the length of π-spacer results in red-shifted
absorption along with improved photovoltaic properties. Hence, the main purpose of this present study is to
provide a theoretical background for proper designing and structural modifications in the development of efficient
dyes in dye-sensitized solar cells (DSSCs).
The D–D––A framework based dyes are competent to lower the aggregation and reduce the charge recombination inherently due to their 3D structure. Seven D−D−π−A-based N,N′-dialkyl/diphenyl-aniline (NDI) dyes designed and investigated using cluster and periodic Density Functional Theory (DFT) approaches to evaluate their prospect of application in the future dye-sensitized solar cells (DSSCs). The critical parameters related to short-circuit photocurrent density 〖(J〗_SC) and open-circuit voltage 〖(V〗_OC) of considered dyes such as the driving force of electro injection (〖∆G〗_Inject), the spontaneity of dye regeneration (∆G_Reg), exciton binding synergy (E_b), charge transfer length (d_CT), reorganization energy (λ_Total), the shift of CB of TiO2 (〖∆E〗_CB), projected density of states (PDOS) and chemical reactivity parameters were computed. Computed results implied that the fused--conjugation bridge, along with benzothiadiazole (BTD) unit, improves the absorption spectrum and charge separation d_CT. Also, incorporation of benzene ring lowers λ_Total with balancing its counterparts' reorganization energy. Considering the dye characteristics after electron injection, NDI04 would possess the most stable excited state due to its longer excited-state lifetime, τ_e, with the lowest driving force between excited state oxidation potential (ESOP) and conduction band minimum of TiO2. We found that the presence of benzene ring in fused--conjugation unit increases the light-harvesting by shifting the UV-vis spectrum to a higher wavelength. The value of 〖∆E〗_CB and ∆G_Reg suggests that the NDI04 and NDI10 would be able to suppress the charge recombination and thus enhance V_OC of NDI-based dyes. The outcomes inferred that the new designed NDI04 dye could be the lead candidate for the enhanced NDI-based DSSCs. Our work also provides a rational insight into designing the D–D––A dyes with a fused--conjugation.
A quantitative structure-property relationship (QSPR) study on the critical micelle concentration (CMC) of 120 Gemini surfactants was performed with hologram quantitative structure-activity relationship (HQSAR) technique. In the proposed HQSAR model, three fragment parameters, fragment distinction, fragment size and fragment length, were set to “A, B, C and D”, “7–10” and “307” respectively. Two conventional validation techniques, external test set validation and leave-one-out cross-validation (LOO-CV), were utilized to evaluate the forecasting accuracy of as-proposed model. As the result, the QF32, concordance correlation coefficient, root mean squared error, r¯m2 and Δr m² of external test set validation is 0.9799, 0.9803, 0.1757, 0.9429 and 0.0100, respectively. The root mean squared error, r¯m2 and Δr m² of LOO-CV is 0.2734, 0.9296 and 0.0436, respectively. It is demonstrated that the HQSAR model built in this work is available and accurate for preliminarily studying and predicting the CMC of Gemini surfactants. Moreover, HQSAR is shown to be a promising approach for building up QSPR model in relation to the CMC of Gemini surfactants.
There are many strategies to improve the efficiency of DSSCs, the most impactful way is to promote the effective light capturing, such as widening the spectral absorption range and/or enhancing the spectral absorption intensity. In this paper, we are inspired by Hagfeldt and his coworkers’ work, and designed several spectral-complementary D-π-A dyes for high performance dye-sensitized solar cells. What's more, we studied the designed and the experimental dyes using density functional theory and time-dependent density functional theory. The electronic properties, including frontier molecular orbital, intra-molecular charge transfer, absorption spectra, are investigated. Our results show that the designed dye B1 have the best absorption complementarity with dye XY1, and correspondingly induces higher light-harvesting performance in the range of the solar spectrum. The dye-sensitized solar cells using B1 and XY1 as sensitizers is predicted to be higher performance than the combination of other dyes. Our work is expected to assist to prepare high performance dye-sensitized solar cells.
A series of novel D-A-π-A organic dyes with different π-spacers for dye-sensitized solar cells (DSSCs) are designed based on hetero-tri-arylamine donor-based dye DP2. The key parameters of all the dyes affecting short-circuit current (JSC) and open-circuit voltage (VOC) are theoretically investigated in detail using density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations to reveal structure-property relationships. The theoretical results indicate that extending π-spacer is beneficial to improve light-absorbing capacities with larger responsive range of spectra and molar extinction coefficients (ε). The designed dyes DP2-1–DP2-5 exhibit a good balance in various important properties including light harvesting efficiency (LHE), electronic injection driving force (ΔGinject), regeneration driving force (ΔGreg), reorganization energy (λtotal) and vertical dipole moment (μnormal) and number of photoinjected electrons (nc) compared to reference dye DP2. Among all the designed dyes, DP2-3–DP2-5 containing π-spacers with branched chain exhibit obvious red shifted absorption band, smaller regeneration driving force (ΔGreg) and larger excited state lifetime (τ0). This study is expected to provide new clues for the experimental synthesis of highly efficient metal-free organic dyes for DSSCs.
Seven D-A-π-A based Indoline (IND) dyes that were designed via Quantitative-Structure Property Relationship (QSPR) modeling have been comprehensively investigated using computational approaches to evaluate their prospect of application in future dye-sensitized solar cells (DSSCs). An array of optoelectronic properties of the isolated dye and dyes adsorbed on a TiO2 cluster that simulates the semiconductor were explored by DFT and TDDFT methods. Light absorption spectra, vertical dipole moment, shift of the conduction band (CB) of semiconductor, excited state life time, driving force of electron injection, photostability of the excited state and exciton binding energy were computed. Our study showed that presence of internal acceptor such as pyrido[3,4-b]pyrazine (PP) would influence greater the open circuit voltage (V_OC) , compare to the benzothiadiazole (BTD) moiety. Considering the balance between the V_OC and J_SC along with the all calculated characteristics , the IND3, IND5 and IND10 are the most suited among the designed dyes to be used as potential candidates for the photo efficient DSSCs. The present study provides the results of rational molecular design followed by exploration of photophysical properties to be used as a valuable reference for the synthesis of phot-efficient dyes for DSSCs.
Phthalocyanines (Pcs) are robust and intensely colored macrocycles (blue pigments) with high chemical, thermal and light stability, properties that are of paramount importance for realistic photovoltaic applications. In particular, Pcs have played a very important role in the development of dye-sensitized solar cells (DSSCs), as they are promising candidates for incorporation in these devices. Good efficiencies have been obtained by the use of Pcs as the light harvester, and, most importantly, a number of synthetic strategies have been developed for engineered dyes based on the Pc scaffold, due to the synthetic versatility and robustness of these macrocycles. In this review, recent advances in the use of phthalocyanines as photosensitizers for DSSC applications are presented.
Using the GUSAR 2013 program, we have performed a quantitative analysis of the “structure–power conversion efficiency (PCE)” on the series of 100 methano[60]fullerenes previously tested as acceptor components of bulk-heterojunction polymer organic solar cells (PSCs) utilizing the same donor polymer, viz. poly(3-hexylthiophene). Based on the MNA and QNA descriptors and self-consistent regression implemented in the program, six statistically significant consensus models for predicting the PCE values of the methano[60]fullerene-based PSCs have been constructed. The structural fragments of the fullerene compounds leading to an increase in the device performances are determined. Based on these structural descriptors, we have designed the three methano[60]fullerenes included in the training sets and characterized by poor optoelectrical properties is performed. As a result, two new compounds with potentially moderate efficiency have been proposed. This result opens opportunities of using the GUSAR 2013 program for modeling of the “structure–PCE” relationship for diverse compounds (not only fullerene derivatives).
In order to develop efficient phenothiazine organic dyes for dye-sensitized solar cells (DSSCs), four new phenothiazine organic dyes (W21-24) containing dithieno[3,2-b:2′,3′-d]pyrrole (DTP) units have been designed and synthesized. W21-23 contains diverse DTP blocks on the terminal part of the dyes, which allow us to understand the effect of the DTP substituent on the performance organic dyes. Results reveal that the substituent of DTP unit affects the light harvesting capability of dyes as well as interfacial charge transfer and recombination in devices. In addition, electrochemical, photophysical and photovoltaic performance of W23 have been investigated and compared to those of W24, which has a different conjugation order of phenothiazine and DTP unit. W24 sensitized electrode exhibits a better light absorption due to a strong ICT charge transition and high dye loading amount, which contributes to the higher photocurrent of devices. Particularly, W24 displays a significantly decreased charge recombination rates. Thus, W24 shows the best photovoltaic efficiency of 7.7% under the standard global AM 1.5 solar conditions.
The power conversion efficiency (PCE) of pure polymer solar cells (PSCs) remains low, although significantly higher values could be achieved by using PSCs as carrier donors in conjunction with composite fullerene derivative (FD) acceptors. Significant resources, however, are required to experimentally develop and screen FDs that may serve as efficient acceptors in PSCs. Often, the materials are expensive, the methods are time consuming, and the production processes can generate toxic hazards. As an alternative approach, we introduce a quantitative structure-property relationship (QSPR) model for predicting the PCE of 59 FDs, including both C60 and C70 FDs. The QSPR model enables identification of the essential structural attributes necessary for quantifying the molecular prerequisites of diverse FDs, chiefly responsible for high PCE of PSC acceptors in composition with poly(3-hexylthiophene) (P3HT). The identified properties and structural fragments are particularly valuable for guiding future synthetic efforts for development of FDs with improved power conversion efficiency. Furthermore, a large number of FDs are collected to generate a database. Virtual screening of the database employing the developed QSPR model allows for identification of nine FDs with higher PCE than previously studied FDs.
An N-annulated indenoperylene (NIP) electron-donor decorated with photochemically inactive auxiliary segments is synthesized and further conjugated via ethynyl with electron-acceptor benzothiadiazolylbenzoic acid for a metal-free donoracceptor dye. Without use of any coadsorbate, the judiciously tailored indenoperylene dye achieves a high power conversion efficiency of 12.5% under an irradiance of 100 mW cm-2 AM1.5G sunlight.
In dye-sensitized solar cells (DSSCs), as the excited electrons from dye molecules are injected to the conduction band of semiconductor film through the acceptor moieties, the acceptor groups have significant influences on the photovoltaic properties of the dyes. In this paper, the effects of different acceptor groups (cyanoacetic acid and rhodanine-3-acetic acid) in two phenothiazine-triphenylamine dyes (PTZ-1 and PTZ-2) on the optical, electrochemical properties and photovoltaic performances were studied. In comparison with PTZ-2, the photovoltaic performance of PTZ-1 is significantly improved by replacing rhodanine-3-acetic acid to cyanoacetic acid. The conversion efficiency of solar cell based on the PTZ-1 is increased about 110%. The lower efficiency of solar cell based on PTZ-2 is mainly because the delocalization of the excited state is broken between the 4-oxo-2-thioxothiazolidine ring and the acetic acid, which affects the electron injection from PTZ-2 to the conduction band of TiO2.
THE large-scale use of photovoltaic devices for electricity generation is prohibitively expensive at present: generation from existing commercial devices costs about ten times more than conventional methods1. Here we describe a photovoltaic cell, created from low-to medium-purity materials through low-cost processes, which exhibits a commercially realistic energy-conversion efficiency. The device is based on a 10-µm-thick, optically transparent film of titanium dioxide particles a few nanometres in size, coated with a monolayer of a charge-transfer dye to sensitize the film for light harvesting. Because of the high surface area of the semiconductor film and the ideal spectral characteristics of the dye, the device harvests a high proportion of the incident solar energy flux (46%) and shows exceptionally high efficiencies for the conversion of incident photons to electrical current (more than 80%). The overall light-to-electric energy conversion yield is 7.1-7.9% in simulated solar light and 12% in diffuse daylight. The large current densities (greater than 12 mA cm-2) and exceptional stability (sustaining at least five million turnovers without decomposition), as well as the low cost, make practical applications feasible.
Quantitative structure property relationship (QSPR) studies on per- and polyfluorinated chemicals (PFCs) on melting point (MP) and boiling point (BP) are presented. The training and prediction chemicals used for developing and validating the models were selected from Syracuse PhysProp database and literatures. The available experimental data sets were split in two different ways: a) random selection on response value, and b) structural similarity verified by self-organizing-map (SOM), in order to propose reliable predictive models, developed only on the training sets and externally verified on the prediction sets. Individual linear and non-linear approaches based models developed by different CADASTER partners on 0D-2D Dragon descriptors, E-state descriptors and fragment based descriptors as well as consensus model and their predictions are presented. In addition, the predictive performance of the developed models was verified on a blind external validation set (EV-set) prepared using PERFORCE database on 15 MP and 25 BP data respectively. This database contains only long chain perfluoro-alkylated chemicals, particularly monitored by regulatory agencies like US-EPA and EUREACH. QSPR models with internal and external validation on two different external prediction/validation sets and study of applicability-domain highlighting the robustness and high accuracy of the models are discussed. Finally, MPs for additional 303 PFCs and BPs for 271 PFCs were predicted for which experimental measurements are unknown.
The evaluation of regression QSAR model performance, in fitting, robustness, and external prediction, is of pivotal importance. Over the past decade, different external validation parameters have been proposed: Q(F1)(2), Q(F2)(2), Q(F3)(2), r(m)(2), and the Golbraikh-Tropsha method. Recently, the concordance correlation coefficient (CCC, Lin), which simply verifies how small the differences are between experimental data and external data set predictions, independently of their range, was proposed by our group as an external validation parameter for use in QSAR studies. In our preliminary work, we demonstrated with thousands of simulated models that CCC is in good agreement with the compared validation criteria (except r(m)(2)) using the cutoff values normally applied for the acceptance of QSAR models as externally predictive. In this new work, we have studied and compared the general trends of the various criteria relative to different possible biases (scale and location shifts) in external data distributions, using a wide range of different simulated scenarios. This study, further supported by visual inspection of experimental vs predicted data scatter plots, has highlighted problems related to some criteria. Indeed, if based on the cutoff suggested by the proponent, r(m)(2) could also accept not predictive models in two of the possible biases (location, location plus scale), while in the case of scale shift bias, it appears to be the most restrictive. Moreover, Q(F1)(2) and Q(F2)(2) showed some problems in one of the possible biases (scale shift). This analysis allowed us to also propose recalibrated, and intercomparable for the same data scatter, new thresholds for each criterion in defining a QSAR model as really externally predictive in a more precautionary approach. An analysis of the results revealed that the scatter plot of experimental vs predicted external data must always be evaluated to support the statistical criteria values: in some cases high statistical parameter values could hide models with unacceptable predictions.
With the growth of interest in database searching and compound selection, the quantification of chemical similarity has become an area of intense practical and theoretical interest. One of the most widely used methods of measuring chemical similarity is based on mapping fragments within a molecule as bits within a binary string. We present empirical results which suggest that bit strings provide a nonintuitive encoding of molecular size, shape, and global similarity. Other results, this time statistical in nature, suggest that the observed behavior of bit string-based searches have a large nonspecific component. On this basis, we question whether bit string-based similarity methods possess all the features desirable in a quantitative chemical distance measure or metric and suggest that there are instances when they may not be the most appropriate tool for searching or segregating chemical structures.
The main utility of QSAR models is their ability to predict activities/properties for new chemicals, and this external prediction ability is evaluated by means of various validation criteria. As a measure for such evaluation the OECD guidelines have proposed the predictive squared correlation coefficient Q(2)(F1) (Shi et al.). However, other validation criteria have been proposed by other authors: the Golbraikh-Tropsha method, r(2)(m) (Roy), Q(2)(F2) (Schüürmann et al.), Q(2)(F3) (Consonni et al.). In QSAR studies these measures are usually in accordance, though this is not always the case, thus doubts can arise when contradictory results are obtained. It is likely that none of the aforementioned criteria is the best in every situation, so a comparative study using simulated data sets is proposed here, using threshold values suggested by the proponents or those widely used in QSAR modeling. In addition, a different and simple external validation measure, the concordance correlation coefficient (CCC), is proposed and compared with other criteria. Huge data sets were used to study the general behavior of validation measures, and the concordance correlation coefficient was shown to be the most restrictive. On using simulated data sets of a more realistic size, it was found that CCC was broadly in agreement, about 96% of the time, with other validation measures in accepting models as predictive, and in almost all the examples it was the most precautionary. The proposed concordance correlation coefficient also works well on real data sets, where it seems to be more stable, and helps in making decisions when the validation measures are in conflict. Since it is conceptually simple, and given its stability and restrictiveness, we propose the concordance correlation coefficient as a complementary, or alternative, more prudent measure of a QSAR model to be externally predictive.
This paper deals with the problem of evaluating the predictive ability of QSAR models and continues the discussion about proper estimates of the predictive ability from an external evaluation set reported in Schüürmann G., Ebert R.-U., et al. External Validation and Prediction Employing the Predictive Squared Correlation Coefficient--Test Set Activity Mean vs Training Set Activity Mean. J. Chem. Inf. Model. 2008, 48, 2140-2145 . The two formulas for calculating the predictive squared correlation coefficient Q2 previously discussed by Schüürmann et al. are one that adopted by the current OECD guidelines about QSAR validation and based on SS (sum of squares) of the external test set referring to the training set response mean and the other based on SS of the external test set referring to the test set response mean. In addition to these two formulas, another formula is evaluated here, based on SS referring to mean deviations of observed values from the training set mean over the training set instead of the external evaluation set.
Consensus hologram QSAR model studying on the aqueous hydroxyl radical oxidation reaction rate constants of organic micropollutants
- Jiao
Chemometric modeling of power conversion efficiency of organic dyes in dye sensitized solar cells for the future renewable energy
- Krishna