Optical absorption spectroscopy and electronic properties of D-A dyes and chlorophyll derivatives for co-sensitization in DSSCs.

The photophysical and photochemical processes of the experimental dyes ZS11 and ZS12 containing phenyl-cyanoacrylic acid (PCA) and ethynyl-PCA (EPCA) group were studied by DFT and TD-DFT systems to develop their applications in solar cells. First, their geometry, absorption spectra, chemical reaction parameters, electron transfer and dye activity were systematically studied. The photoelectric conversion efficiency (PCE) was predicted, and it was found that the PCE of ZS12 (9.974 %) was higher than ZS11 (7.171 %), which was consistent with the experimental trend (the PCE of ZS12 is 10.4 ± 0.3 % and the PCE of ZS11 is 9.0 ± 0.3 %). Secondly, the dye was co-sensitized with the chlorophyll derivative CHL-1c, and the co-sensitization system's interaction force, excited state characteristics, electron transfer mechanism and electron transfer rates were studied. The results show that the JSC of all co-sensitive systems (the JSC of ZS12-CHL is 22.363 mA/cm2 and the JSC of ZS11-CHL is 23.978 mA/cm2) is significantly higher than that of monomers (the JSC of ZS12 is 16.112 mA/cm2 and the JSC of ZS11 is 11.051 mA/cm2). It can be inferred that the optoelectronic performance of co-sensitizing systems is better than that of monomers. This study demonstrates that the use of dye molecules co-sensitized with chlorophyll derivatives can enhance DSSC performance from multiple perspectives, providing insights for further improvements.

Development of dye-sensitized solar cells using pigment extracts produced by Talaromyces atroroseus GH2.

The identification of more efficient, clean, secure, and competitive energy supply is necessary to align with the needs of sustainable devices. For this reason, a study for developing innovative dye-sensitized solar cells (DSSCs) based on microbial pigments is reported starting from Talaromyces atroroseus GH2. The fungus was cultivated by fermentation and the extracellular pigment extract was characterized by HPLC-DAD-ESI-MS analyses. The most abundant compound among the 22 azaphilone-type pigments identified was represented by PP-O. The device's behavior was investigated in relation to electrolyte and pH for verifying the stability on time and the photovoltaic performance. Devices obtained were characterized by UV-vis measurements to verify the absorbance intensity and transmittance percentage. Moreover, photovoltaic parameters through photo-electrochemical measurements (I-V curves) and impedance characteristics by Electrochemical Impedance Spectroscopy (EIS) were determined. The best microbial device showed a short-circuit current density (Jsc) of 0.69 mA/cm2, an open-circuit photo-voltage (Voc) of 0.27 V and a Fill Factor (FF) of 0.60. Furthermore, the power conversion efficiency (PCE) of the device was 0.11%. Thus, the present study demonstrated the potential of microbial origin pigments for developing DSSCs.

Amphiphilic Graft Copolymers as Templates for the Generation of Binary Metal Oxide Mesoporous Interfacial Layers for Solid-State Photovoltaic Cells.

The binary metal oxide mesoporous interfacial layers (bi-MO meso IF layer) templated by a graft copolymer are synthesized between a fluorine-doped tin oxide (FTO) substrate and nanocrystalline TiO2 (nc-TiO2). Amphiphilic graft copolymers, Poly(epichlorohydrin)-graft-poly(styrene), PECH-g-PS, were used as a structure-directing agent, and the fabricated bi-MO meso IF layer exhibits good interconnectivity and high porosity. Even if the amount of ZnO in bi-MO meso IF layer increased, it was confirmed that the morphology and porosity of the bi-MO meso IF layer were well-maintained. In addtion, the bi-MO meso IF layer coated onto FTO substrates shows higher transmittance compared with a pristine FTO substrate and dense-TiO2/FTO, due to the reduced surface roughness of FTO. The overall conversion efficiency (η) of solid-state photovoltaic cells, dye-sensitized solar cells (DSSCs) fabricated with nc-TiO2 layer/bi-MO meso IF layer TZ1 used as a photoanode, reaches 5.0% at 100 mW cm-2, which is higher than that of DSSCs with an nc-TiO2 layer/dense-TiO2 layer (4.2%), resulting from enhanced light harvesting, good interconnectivity, and reduced interfacial resistance. The cell efficiency of the device did not change after 15 days, indicating that the bi-MO meso IF layer with solid-state electrolyte has improved electrode/electrolyte interface and electrochemical stability. Additionally, commercial scattering layer/nc-TiO2 layer/bi-MO meso IF layer TZ1 photoanode-fabricated solid-state photovoltaic cells (DSSCs) achieved an overall conversion efficiency (η) of 6.4% at 100 mW cm-2.

Computational studies of the influence of auxiliary acceptors in the D-A'-π-A structure of organic dyes on the photovoltaic performance of dye solar cells.

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.

Preparations of MgO Nanoparticles by a Poly(acrylic acid)s Template-Assisted Method and Photovoltaic Performances of Dye-Sensitized Solar Cells based on MgO lnterlayer.

Magnesium oxide (MgO) nanoparticles are commonly used to enhance the reactivity and performance of devices and systems in various applications, primarily due to the heat-resistance, binding, and alkaline properties of MgO. However, most of the methods used to synthesize MgO nanoparticles suffer from nonuniform particle size distributions that make it difficult to manufacture stable particles. In this study, uniform magnesium oxide (MgO) nanoparticles were developed for TiO2 photoelectrodes of dye-sensitized solar cells (DSSCs) to enhance their interfacial resistances. The uniform MgO nanoparticles were synthesized from MgO 93% using a poly(acrylic acid) template-assisted method. The particle size and crystalline structure of MgO nanoparticles were characterized by NANOPHOX particle size analysis, transmission electron microscopy, and X-ray diffraction. Multilayered TiO2 photoelectrodes containing interlayers of MgO nanoparticles were fabricated as photoelectrodes for DSSC devices, and their photovoltaic performances were investigated. When the MgO interlayer was introduced into the multilayered TiO2 photoelectrode, it not only increased the photocurrent value of the DSSC device but also improved its power conversion efficiency. The DSSC device containing the MgO interlayer and the scattering layer exhibited an open-circuit voltage of 0.74 V, a short-circuit current density of 14.60 mA/cm2, and a fill factor of 0.64 under a photointensity of 100 mW/cm2 at AM 1.5, resulting in an overall solar energy conversion efficiency of 6.94%. The application of an MgO interlayer in a DSSC device exhibited improved conductivity, charge transfer ability, and excellent device performance.

A Recent Review of Electrospun Porous Carbon Nanofiber Mats for Energy Storage and Generation Applications.

Electrospun porous carbon nanofiber mats have excellent properties, such as a large surface area, tunable porosity, and excellent electrical conductivity, and have attracted great attention in energy storage and power generation applications. Moreover, due to their exceptional properties, they can be used in dye-sensitized solar cells (DSSCs), membrane electrodes for fuel cells, catalytic applications such as oxygen reduction reactions (ORRs), hydrogen evolution reactions (HERs), and oxygen evolution reactions (OERs), and sensing applications such as biosensors, electrochemical sensors, and chemical sensors, providing a comprehensive insight into energy storage development and applications. This study focuses on the role of electrospun porous carbon nanofiber mats in improving energy storage and generation and contributes to a better understanding of the fabrication process of electrospun porous carbon nanofiber mats. In addition, a comprehensive review of various alternative preparation methods covering a wide range from natural polymers to synthetic carbon-rich materials is provided, along with insights into the current literature.

Rational modification of TiO2 photoelectrodes with spinel ZnFe2O4 and Ag-doped ZnFe2O4 nanostructures highly enhanced the efficiencies of dye sensitized solar cells.

To develop effective photoelectrode nanomaterials for dye-sensitized solar cells (DSSCs), spinel ZnFe2O4 (2.5, 5, 7.5, 10 wt%) and Ag-doped ZnFe2O4 (AgxZn1-x/2Fe2O4, x = 0.1, 0.2, 0.3, 0.4 mmol) nanomaterials were added into the TiO2 photoanodes. It was found that the DSSC fabricated with TiO2 + 5 wt% ZnFe2O4 exhibited the most improved efficiency of 3.89 % among the ZnFe2O4 containing devices. Furthermore, the power conversion efficiency (PCE) values were boosted when the Ag+ cations were doped into the ZnFe2O4 crystalline lattice. The greatest PCE = 5.75 % was achieved for the solar cell assembled using TiO2 + 5 wt% Ag0.2Zn0.90Fe2O4 photoanode indicating 47.81 % improved performance relative to that of the reference DSSC containing TiO2 + 5 wt% ZnFe2O4 photoelectrode. The electrochemical impedance spectra (EIS) approved that the DSSC with the TiO2 + 5 wt% Ag0.2Zn0.90Fe2O4 photoelectrode nanomaterial had the lowest charge transfer resistance but the greatest e-h recombination resistance at the interfaces of photoanode/dye/electrolyte. Hence, it had the quickest electron transport rate, and the greatest electron collecting efficiency in addition to the highest dye loading capacity and least photoluminescence (PL) intensity (charge recombination) which were all prominently beneficial for improvement of the DSSC performance.

Spectroscopic Behaviour of Copper(II) Complexes Containing 2-Hydroxyphenones.

Theoretical investigations by density functional theory (DFT) and time-dependent DFT (TD-DFT) methods shed light on how the type of ligand or attached groups influence the electronic structure, absorption spectrum, electron excitation, and intramolecular and interfacial electron transfer of the Cu(II) complexes under study. The findings provide new insight into the designing and screening of high-performance dyes for dye-sensitized solar cells (DSSCs).

Investigating Tungsten Sulfide as a Counter Electrode Material in Dye-Sensitized Solar Cells.

With the recent interest in renewable energy sources, dye-sensitized solar cells (DSSCs) have received a great deal of attention as a cheaper and more sustainable alternative to silicon-based solar cells. In a DSSC, the counter electrode performs the catalytic reduction of the electrolyte and electron collection. To perform this function adequately, platinum is the preferred material currently. To reduce the dependence of the DSSC on such an expensive material, alternatives such as activated carbon (AC) and two-dimensional transition metal dichalcogenides, and more specifically, tungsten sulfide (WS2), were considered. AC has shown great potential as a material for counter electrodes, whereas WS2 has unique physiochemical properties which warrant its exploration as an energy material. In this article, we synthesized and evaluated the performance of DSSCs with AC, WS2, and AC/WS2 composite counter electrodes. It was demonstrated that the performance of the WS2/AC composite counter electrode with a 1:2 ratio of WS2 to AC shows the highest performance with an efficiency of 6.25%.

Influence of thickness and morphology of MoS2 on the performance of counter electrodes in dye-sensitized solar cells.

Non-platinum electrodes for photoelectric devices are challenging and attractive to the scientific community. A thin film of molybdenum disulfide (MoS2) was prepared on substrates coated with fluorine-doped tin oxide (FTO) to substitute the platinum counter electrode (CE) for dye-sensitized solar cells (DSSCs). Herein, we synthesized layered and honeycomb-like MoS2 thin films via the cyclic voltammetry (CV) route. Thickness and morphology of the MoS2 thin films were controlled via the concentration of precursor solution. The obtained results showed that MoS2 thin films formed at a low precursor concentration had a layered morphology while a honeycomb-like MoS2 thin film was formed at a high precursor concentration. Both types of MoS2 thin film were composed of 1T and 2H structures and exhibited excellent electrocatalytic activity for the I3 -/I- redox couple. DSSCs assembled using these MoS2 CEs showed a maximal power conversion efficiency of 7.33%. The short-circuit value reached 16.3 mA·cm-2, which was higher than that of a conventional Pt/FTO CE (15.3 mA·cm-2). This work reports for the first time the possibility to obtain a honeycomb-like MoS2 thin film morphology by the CV method and investigates the effect of film structure on the electrocatalytic activity and photovoltaic performance of CEs for DSSC application.

1,2,4-Triazine-based Materials: Spectroscopic Investigation, DFT, NBO, and TD-DFT Calculations as Well As Dye-sensitized Solar Cells Applications.

In this manuscript, we report four series for 1,2,4-triazine derivatives as dye-sensitized solar cells (DSSCs). Density functional theory (DFT) methods via utilizing Becke's three-parameter functional and LeeeYangeParr functional (B3LYP) level with 6-31G (d, p) basis set to investigate their modeling molecular structures. Optimized molecular structures for studied molecular structures are obtained using the DFT/B3LYP/6-31G (d, p) method. In addition, the time-dependant density functional theory (TD-DFT) is used to study the optoelectronic properties and absorption spectra using DFT/CAM-B3LYP/ 6-31G + + (d, p) level in the Gaussian 09 program. The highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO), energy gap (Eg), light harvest efficiency (LHE), and open-circuit voltage (Voc) of the studied molecular structures are calculated and illustrated. These properties indicate that these molecular modeling structures as good candidates for utilization in organic DSSCs.

Photovoltaic Performances of Dye-Sensitized Solar Cells Based on Modified Polybutadiene Matrix Electrolytes by Sol-Gel Process.

A new type of polymer matrix electrolyte based on modified polybutadiene (modified PB) was developed for dye-sensitized solar cells (DSSCs) to improve their stability. The modified PB was fabricated by cross-linking the reaction of polybutadiene with siloxane groups as a substitute sol-gel process. A DSSC device using the modified PB matrix electrolyte showed an open-circuit voltage of 0.64 V, a short-circuit current density of 15.00 mA/cm2, and a fill factor of 0.58 under photointensity of 100 mW/cm2 at AM 1.5, consequently leading to an overall solar energy conversion efficiency of 5.49%. The DSSC device using the modified PB matrix electrolyte improved the conductivity, and the charge transfer ability showed the outstanding stability of the device.

Quasi-Solid-State SiO2 Electrolyte Prepared from Raw Fly Ash for Enhanced Solar Energy Conversion.

Quasi-solid-state electrolytes in dye-sensitized solar cells (DSSCs) prevent solvent leakage or evaporation and stability issues that conventional electrolytes cannot; however, there are no known reports that use such an electrolyte based on fly ash SiO2 (FA_SiO2) from raw fly ash (RFA) for solar energy conversion applications. Hence, in this study, quasi-solid-state electrolytes based on FA_SiO2 are prepared from RFA and poly(ethylene glycol) (PEG) for solar energy conversion. The structural, morphological, chemical, and electrochemical properties of the DSSCs using this electrolyte are characterized by X-ray diffraction (XRD), high-resolution field-emission scanning electron microscopy (HR-FESEM), X-ray fluorescence (XRF), diffuse reflectance spectroscopy, electrochemical impedance spectroscopy (EIS), and incident photon-to-electron conversion efficiency (IPCE) measurements. The DSSCs based on the quasi-solid-state electrolyte (SiO2) show a cell efficiency of 5.5%, which is higher than those of nanogel electrolytes (5.0%). The enhancement of the cell efficiency is primarily due to the increase in the open circuit voltage and fill factor caused by the reduced electron recombination and improved electron transfer properties. The findings confirm that the RFA-based quasi-solid-state (SiO2) electrolyte is an alternative to conventional liquid-state electrolytes, making this approach among the most promising strategies for use in low-cost solar energy conversion devices.

Robust design of D-π-A model compounds using digital structures for organic DSSC applications.

New D-π-spacer-A model compound dye sensitizers (or dyes) are developed using digital structures for organic dyes sensitized solar cells (DSSCs) applications. Based on our previous studies, the model D-π-spacer-A dyes contain building blocks of a di(p-carboxy)-phenylamine as the electron donor and a perylene monoimide as the electron acceptor. The new D-π-spacer-A dyes are constructed through variations of a set of three model π-spacer units, fluorene, 3,4-ethylenedioxythiophene and thiophene. The new dyes are presented by digital structures of π(ijk) in a digital control Π-matrix. If the chromophore database of the π-units is arranged in a defined manner, the new dyes are therefore designed through selecting of the set of three integers (ijk). Properties such as the UV-vis spectra which are calculated using the time-dependent density functional theory (TD-DFT) determine if the new compounds are suitable for organic solar cell purposes. The same strategy can be applied to donors and acceptors in the D-π-spacer-A model compound in order to robust design and build new organic dyes for DSSCs. The digital structures of the organic compounds enhance the machine driven structure-property relationship establishment once the database is sufficiently comprehensive. The present study demonstrates that new compounds obtained through mixing the π-spacer units of fluorene, 3,4-ethylenedioxythiophene and thiophene, e.g. π121 and π211, result in better dyes in DSSC applications. The concise digital structures of the new dyes are able to achieve a more robust design of the organic dyes and other materials.

Theoretical Analysis on Heteroleptic Cu(I)-Based Complexes for Dye-Sensitized Solar Cells: Effect of Anchors on Electronic Structure, Spectrum, Excitation, and Intramolecular and Interfacial Electron Transfer.

Two groups of heteroleptic Cu(I)-based dyes were designed and theoretically investigated by density functional theory (DFT) and time-dependent DFT (TD-DFT) methods. Different anchors were integrated into the dye skeleton to shed light on how the type of anchor influenced the electronic structure, absorption spectrum, electron excitation, and intramolecular and interfacial electron transfer of dyes. The results indicated that, compared with other dyes, the dyes with cyanoacrylic acid and nitric acid exhibited more appropriate electron distributions in frontier molecular orbitals (FMOs), lower HOMO (the highest occupied molecular orbital) -LUMO (the lowest unoccupied molecular orbital) energy gaps, broader absorption spectral ranges as well as improved spectral characteristics in the near-infrared region and better intramolecular electron transfer (IET) characteristics with more electrons transferred to longer distances, but smaller orbital overlap. Among all the studied Cu(I)-based dyes, B1 and P1 (with cyanoacrylic acid anchoring group) exhibited the best interface electronic structure parameters with a relatively short electron injection time (τinj) and large dipole moment (µnormal), which would have a positive effect on the open-circuit photovoltage (Voc) and short-circuit current density (Jsc), resulting in high power conversion efficiency (PCE) of dye-sensitized solar cells (DSSCs). Our findings are expected to provide a new insight into the designing and screening of high-performance dyes for DSSCs.

Sol-Gel Chemistry: From Molecule to Functional Materials.

Through this Special Issue, you will discover the potentiality of inorganic polymerization (sol-gel process) which is a unique and versatile way for the preparation of materials [...].

Theoretical study of T shaped phenothiazine/carbazole based organic dyes with naphthalimide as π-spacer for DSSCs.

Eight novel T shaped phenothiazine/carbazole based organic dyes with naphthalimide as π-spacer were designed, and the geometries, electronic structures, and optical features of these isolated dyes and dye-(TiO2)9 systems were investigated with density functional theory (DFT) and time dependent density functional theory (TD-DFT) calculations. Some quantify factors influencing the energy conversion efficiency (PCE) such as the light harvesting efficiency (LHE), electron injection driving force (ΔGinject) and dye regeneration driving force (ΔGreg) were also calculated for dye-sensitized solar cells (DSSCs) applications. It is found that these dyes show a good performance of electron injection and dye regeneration owing to the proper value of ΔGinject and ΔGreg. The optimized geometries of the non-planar molecular configuration of donor and the planar structure of the naphthalimide conjugated bridge are beneficial to efficient intramolecular charge transfer and the suppression of molecular aggregation. The properties about the electronic structure and absorption spectra indicate that replacement of benzene with thiophene unit near to cyanoacetic acid acceptor can generate more efficient conjugation effect and achieve red shift of absorption spectra, resulting a higher Jsc and Voc in DSSCs device. The theoretical results reveal that DTPH2, DTPH4, DTCA2 and DTCA4 would be used as potential sensitizers for DSSCs applications.

Methodologies in Spectral Tuning of DSSC Chromophores through Rational Design and Chemical-Structure Engineering.

The investigation of new photosensitizers for Grätzel-type organic dye-sensitized solar cells (DSSCs) remains a topic of interest for researchers of alternative solar cell materials. Over the past 20 years, considerable and increasing research efforts have been devoted to the design and synthesis of new materials, based on "donor, π-conjugated bridge, acceptor" (D-π-A) organic dye photosensitizers. In this paper, the computational chemistry methods are outlined and the design of organic sensitizers (compounds, dyes) is discussed. With reference to recent literature reports, rational molecular design is demonstrated as an effective process to study structure-property relationships. Examples from established organic dye sensitizer structures, such as TA-St-CA, Carbz-PAHTDDT (S9), and metalloporphyrin (PZn-EDOT), are used as reference structures for an examination of this concept applied to generate systematically modified structural derivatives and hence new photosensitizers (i.e., dyes). Using computer-aided rational design (CARD), the in silico design of new chromophores targeted an improvement in spectral properties via the tuning of electronic structures by substitution of molecular fragments, as evaluated by the calculation of absorption profiles. This mini review provides important rational design strategies for engineering new organic light-absorbing compounds towards improved spectral absorption and related optoelectronic properties of chromophores for photovoltaic applications, including the dye-sensitized solar cell (DSSC).

Effect of Nitrogen Cation as "Electron Trap" at π-Linker on Properties for p-Type Photosensitizers: DFT Study.

On the basis of thieno(3,2-b)thiophene and dithieno[3,2-b:2',3'-d]thiophene (T2 and T3 moieties) as π-linker, the A, D and S series dyes were designed to investigate the effect of the introducing N+ as an "electron trap" into T2 and T3 on the properties of the dyes. The optimized structures, electronic and optical properties were investigated by the density functional theory (DFT) and time-dependent DFT (TD-DFT). The results show that the properties of the dyes are sensitive to the N+ position in π-linkers. D series dyes with electron-withdrawing units located near the donor have better properties than the corresponding A series with the electron-withdrawing units located near the acceptor. For A and D series, the N+ modified dye named T2N+1-d displays the largest red shift of the UV-vis absorption, the maximum integral values of the adsorption-wavelength curves over the visible light, the highest light harvesting efficiency (LHE, 0.996), and the strongest adsorption energy (-44.33 kcal/mol). T2N+1-d also has a large driving force of hole injection (ΔGinj, -0.74 eV), which results in a more efficient hole injection. Bearing a lengthier π-linker than T2N+1-d, the properties of T2N+1-s are further improved. T2N+1-d moiety or its increased conjugated derivatives may be a promising π-linker.

Effect of thienyl units in cyanoacrylic acid derivatives toward dye-sensitized solar cells.

A series of heterocyclic donor-acceptor systems were synthesized and well characterized by using 1H, 13C NMR, FT-IR, and elemental analysis. They were designed to investigate the effect of thiophene and cyanoacrylic acid number units on the thermal, optical, electrochemical and finally photovoltaic properties of dye-sensitized solar cells prepared with the selected compounds. The effect of chemical structure on their properties was demonstrated. They showed the beginning of thermal decomposition between 230 and 270 °C. The compounds absorbed the radiation in the range of 300-500 nm or 200-400 nm. They were electrochemically active and varied in energy band gap from 3.40 to 1.58 eV. Additionally, their optimized geometry, HOMO-LUMO levels, ionization potential, and electron affinity were evaluated using density functional theory. The photovoltaic devices based on TiO2 sensitized with the obtained molecules exhibited low power conversion efficiency, which was the highest for the device containing the symmetrical molecule with bithiophene structure. Under co-sensitization, the cell made of the same compound gave significant enhancement of efficiency of 6.3% being higher to that of the individual device prepared from dye N719 (5.75%). Moreover, the effects of immersion time of TiO2 electrode in the dye solution and co-sensitization methods were tested. The surface morphology of photoanode was investigated using atomic force microscopy.