Sensitizers For Dye-sensitized Solar Cells Research Articles

Flavonoid from Hedera helix fruits: A promising new natural sensitizer for DSSCs

Owing to their lower cost, simplicity of manufacture, environmental friendliness, and accessibility of raw materials, natural dyes emerge as the most viable substitute for dye-sensitized solar cells (DSSCs). However, the photovoltaic performance of DSSCs based on natural dyes stays behind that of their metal-based counterparts. This can be partially overcome when appropriate chemical additives are present in the redox electrolyte employed in DSSCs based on natural dyes. To determine the ideal additives for DSSCs based on natural dye extracted from Hedera helix fruits, including flavonoid pigments, we thoroughly compare the actions of 1-butyl-3-methylimidazolium iodide, guanidinium thiocyanate, and tert-butylpyridine additives in ionic liquid-based redox electrolytes. These additives suppress undesirable charge recombination and parasitic resistance effects, achieving a more significant enhancement of open-circuit voltage (Voc) of 130 mV and fill factor (FF) of 30 % compared to their counterparts. Utilizing prepared electrolyte solutions in DSSCs also presents an outstanding increase in the efficiency of the devices, from 0.75 % to 1.17 % (∼56 % improvement), which outperforms other natural dye sources containing flavonoid pigments as well. The experimental findings provided in this study demonstrate that the development of electrolytes tailored for natural dyes can lead to greater power conversion efficiency.

Investigation of the effect of a nitro group as an anchor group in dye-sensitized solar cells

As a result of the increasing in the world population, the development of technology to meet increasing energy needs and to find other energy resources is one of the biggest tests for society. Triphenylamine and its derivatives attract the attention of researchers due to their many applications such as in solar cells, electronics, and medicine. The nitro group, an electron-accepting chromophore, is a good candidate for D–π–A sensitizers for dye-sensitized solar cells. In this study, the power conversion efficiency of an anchor nitro group in dye-sensitized solar cells and the synthesis of new compounds containing a donor triphenylamine unit, functionalized with a nitro group as an anchor group and possessing a π-conjugated structure are investigated. The structures of the compounds are determined by FTIR, UV-Vis spectrometry, NMR, and MS. Considering the photovoltaic performance of the produced dye-sensitized solar cell devices, the anchor group, and its acceptor effect, it is observed that the efficiency increases, in the order, F2 < F1. The highest power conversion efficiency value of 0.45% was obtained with the F1-based dye-sensitized solar cell under amplitude modulation irradiation (100 mW cm−2). From the obtained results, it can be seen that an increase in the number of electron-donor groups located close to the anchor group increases the power conversion efficiency.

Geminal-Based Strategies for Modeling Large Building Blocks of Organic Electronic Materials.

We elaborate on unconventional electronic structure methods based on geminals and their potential to advance the rapidly developing field of organic photovoltaics (OPVs). Specifically, we focus on the computational advantages of geminal-based methods over standard approaches and identify the critical aspects of OPV development. Examples are reliable and efficient computations of orbital energies, electronic spectra, and van der Waals interactions. Geminal-based models can also be combined with quantum embedding techniques and a quantum information analysis of orbital interactions to gain a fundamental understanding of the electronic structures and properties of realistic OPV building blocks. Furthermore, other organic components present in, for instance, dye-sensitized solar cells (DSSCs) represent another promising scope of application. Finally, we provide numerical examples predicting the properties of a small building block of OPV components and two carbazole-based dyes proposed as possible DSSC sensitizers.

Fabrication of dye-sensitized solar cells with the dyeing industrial effluent

Dye-Sensitized Solar Cell (DSSC) is the upcoming future technology in the consumption of solar energy. Even though DSSC has been researched for decades, it is in recent times that scientists developed this technology. The economic, eco-friendly and effective dye to be used as sensitizer in DSSC is still the target of the research community across the world. As an attempt in achieving this target, two textile dye (Blue and Green) effluents from the small-scale industries have been employed as sensitizer for DSSC. These dyes were the mixture of the chemicals ((H5G) and combination of H5G and H7GL) with soda ash (Na2CO3) and salt (NaOH) in required amount of water. It was observed that the DSSC made with the blue and green dye exhibited an efficiency of 0.054% and 0.015% respectively. This study revealed that these effluents can be turned into beneficial output when used as sensitizer in DSSC.

A Green Approach to Natural Dyes in Dye-Sensitized Solar Cells.

Solar cells are pivotal in harnessing renewable energy for a greener and more sustainable energy landscape. Nonetheless, eco-friendly materials for solar cells have not been as extensive as conventional counterparts, highlighting a significant area for further investigation in advancing sustainable energy technologies. This study investigated natural dyes from cost-effective and environmentally friendly blueberries and mulberries. These dyes were utilized as alternative sensitizers for dye-sensitized solar cells (DSSCs). Alongside the natural dyes, a green approach was adopted for the DSSC design, encompassing TiO2 photoanodes, eco-friendly electrolytes, and green counter-electrodes created from graphite pencils and candle soot. Consequently, the best-optimized dye sensitizer was mulberry, with an output power of 13.79 µW and 0.122 µW for outdoor and indoor environments, respectively. This study underscored the feasibility of integrating DSSCs with sensitizers derived from readily available food ingredients, potentially expanding their applications in educational kits and technology development initiatives.

A DFT Study of Solvent and Substituent Effects on the Adsorptive and Photovoltaic Properties of Some Selected Porphyrin Derivatives for DSSC Application.

A DFT/TD-DFT method was employed to study the effects of structural modification and solvent variation on the solubility, adsorptive, and photovoltaic properties of six porphyrins (A-F) obtained by structurally modifying two literature porphyrins A and D. The properties of interest were studied in vacuum, acetonitrile (AcCN), dichloromethane (DCM), dimethyl sulphoxide (DMSO), and ethanol (EtOH) for possible application of the molecules as sensitizers in dye-sensitized solar cells (DSSCs). Electronic absorption properties of the molecules were computed via potential energy surface scan, and thermodynamic data were obtained by DFT calculations in the selected media. Solubility properties of the molecules were mostly enhanced with DMSO as the solvent. The adsorptivity of the molecules onto mesoporous titanium (IV) oxide surface were predicted to be enhanced in the presence of DMSO. Most of the molecules were found to exhibit their highest photovoltaic activity measured in terms of the incidentphoton conversion efficiency (IPCE) in AcCN and DCM, rather than in DMSO due to its high viscosity and the ability to use its oxygen to form the catenating O-Ti4+ bond with the Ti4+ of the TiO2, causing inhibition of electron movement on the semiconductor surface. In general, the computed photovoltaic (PV) properties were found to be enhanced with -CO2H group as the substituent, and in AcCN or DCM as the solvent.

Electronic effect of substituent groups on the oxidation and reduction of bis(2,2′:6′,2″-terpyridine)ruthenium

A series of bis(tpy)ruthenium(II) (tpy = differently substituted 2,2′:6′,2″-terpyridine) were prepared. The substituents were chosen to range from electron donating (pyrrolidinyl, hydroxy, tert-butyl, methoxy, phenyl) to electron withdrawing (Cl, Br). Electrochemistry results show that the complex with the most electron donating group in the series, [Ru(4′-(N-pyrrolidinyl)-2,2′:6′,2″-terpyridine)2]2+, oxidizes at 0.363 V vs the redox couple of ferrocene (Fc/Fc+). The oxidation of [Ru(4′-chloro-2,2′:6′,2″-terpyridine)2]2+, containing the electron withdrawing chlorine group, is much higher, 0.992 V vs Fc/Fc+. Theoretical density functional theory calculations confirmed that the oxidation and reduction of bis(tpy)ruthenium(II) are metal and ligand based, respectively. Graphs comparing the experimentally measured redox potentials and theoretically calculated energies, charges, potentials and various global and local reactivity parameters, all show linear relationships associated with the donating/withdrawing nature of the substituents as quantified by Hammett constants. All these relationships may be utilized to quantify the electronic influence of substituent groups on the redox chemistry of bis(tpy)ruthenium(II) complexes. Linear relationships obtained may also be utilized in the design of bis(tpy)ruthenium(II) type of molecules with a required oxidation or reduction potential. DFT calculations also indicate the potential utilization of these complexes as dye sensitizers in dye-sensitized solar cells.

Solar cells based on doubly concerted companion dyes with the efficiencies modulated by inserting an ethynyl group at different positions

To develop efficient sensitizers for dye-sensitized solar cells (DSSCs), we recently reported doubly concerted companion (DCC) dye XW83 with a wrapped porphyrin sub-dye unit linked to an organic sub-dye unit through a flexible chain, which exhibits panchromatic absorption and excellent anti-aggregation ability. To further improve the absorption, we herein report XW87 and XW88 by inserting an ethynyl group into the organic sub-dye unit of XW83 near the donor and acceptor, respectively. For the corresponding organic dyes Z3 and Z4, the introduced ethynyl group improves their absorption, but induces aggravated charge recombination, leading to lowered power conversion efficiencies (PCEs). Similar to the organic dyes, the introduced ethynyl group improves the absorption of DCC dyes XW87 and XW88 as well. In addition, the ethynyl group near the acceptor of the organic sub-dye unit can be well protected by the long wrapping chains from the porphyrin unit. As a result, XW88 affords the highest JSC (21.84 mA/cm2), VOC (782 mV) and PCE (12.2%) among the DCC dyes. These results provide an effective method for developing efficient DSSC dyes by inserting an ethynyl group at a suitable position of a DCC dye.

Exploring the impact of structural rigidification of amino-substituted bio-inspired flavylium dyes in DSSCs

Sharing with anthocyanins the 2-phenyl-1-benzopyrylium structural motif, flavylium derivatives are strongly colored bio-inspired dyes that have been explored in dye-sensitized solar cells (DSSCs). Following on the fact that the most efficient flavylium-based dyes for DSSCs require amine electron-donating groups, a diethylamino group and the corresponding rigidified julolidine group were introduced in the benzopyrylium core. This structural variation was combined with another structural parameter – increased planarization of the flavylium ring system – to yield four flavylium derivatives all with a catechol anchoring group. The several pKa values of the new dyes and the UV–vis absorption data at different pH values and upon adsorption to TiO2 (corroborated by TD-DFT calculations) demonstrate a stronger delocalization of the nitrogen lone pair in the julolidine systems when compared to the diethylamino ones, reflecting the stronger electron-donating ability of the former. However, the julolidine-based dyes resulted in a decrease in all DSSC parameters, with efficiencies of 0.6% vs. 2.3% for the diethylamino devices. Discarding eventual increased self-aggregation processes of the more planar julolidine derivatives through studies with a de-aggregating agent (CDCA), and determining comparable dye loadings for all dyes, the presence of increased back-electron transfer processes for the julolidine-based compounds is advanced to explain their lower efficiencies. Rigidification of the flavylium dyes by bridging the benzopyrylium and the phenyl rings is demonstrated by higher fluorescence quantum yields and by electrochemical data and leads to a slight increase in the efficiency of the respective DSSCs. The results contribute to consolidate the potential of flavylium dyes as sensitizers for DSSCs.

Development of new co-sensitizer based squaraine dyes for enhancing the performance of DSSC

The conversion of near-infrared (NIR) light into electricity is a crucial goal for advancing the capabilities of dye-sensitized solar cells (DSSC). In order to achieve this, two novel squaraine dyes, namely SQI-P and SQI-H, were synthesized and employed as NIR sensitizers in DSSC. These dyes were constructed with a conjugated indoline donor on both sides of the squaraine core, and a long pendant group on the N-position. The strongly donating indoline with phenyl bis-carboxylic anchor groups located in the N-position resulted in a high molar extinction coefficient and a broad absorption spectrum that extended into the NIR region. The experimental results showed that SQI-P/SQI-H sensitizer exhibits strong absorption in the NIR region, improved electron injection efficiency, and excellent photostability. After optimizing the co-sensitized DSSC, the combination of the NIR-absorbing squaraine based-indoline with SQI-P produced a high photocurrent output of 22.3 mA/cm2 at an efficiency of 4.8%. This achievement represents a breakthrough for DSSCs and paves the way for a more efficient future of DSSCs in the NIR region.

Novel quinoline-based sensitizers coupled with diethylenetriamine as a new co-adsorbent to improve photovoltaic performance of dye-sensitized solar cells

Two novel metal-free dyes with 2-ethylhexyloxy substituted triphenylamine as the donor, quinoline as the π-conjugated bridge, benzothiadiazole (BIM27) and N-propylbenzotriazole (BIM28) as the auxiliary acceptors and cyanoacrylic acid as the anchoring group were synthesized and used as the sensitizers for dye-sensitized solar cells (DSSCs). It was found that BIM 27 exhibits anti-aggregation ability, whereas BIM28 forms the undesired aggregates. Therefore, chenodeoxycholic acid (CDCA) and diethylenetriamine (DETA) molecules were employed as the co-adsorbents to suppress the dye aggregation of BIM28. The DSSC with DETA exhibited a highest power conversion efficiency (PCE) of 3.89%, a remarkable improvement of 25% compared with 3.11% of the cell fabricated without co-adsorbent, exceeding that of the benchmark CDCA-based cell (3.57%) under AM 1.5G conditions. The small DETA can effectively insert between the bulky dye molecules compared to the large CDCA, resulting a more compact dye packing on TiO2, able to less charge recombination. The results demonstrate that DETA may be more efficient for co-adsorption of the bulky dyes.

Blueberries as a Source of Energy: Physical Chemistry Characterization of Their Anthocyanins as Dye-Sensitized Solar Cells’ Sensitizers

This work aimed to show the possibility of applying anthocyanins extracted from blueberries following a straightforward path as potential impregnation dyes in dye-sensitized solar cells (DSSCs), particularly in the presence of co-adsorbents, such as silver nanoparticles, as an alternative in order to profit from large amounts of discarded fruits. Following a simple procedure, anthocyanins (mainly delphinidin-3-glucoside) were obtained from blueberries (Southern Highbush type). Complete characterization was carried out in order to prove the utility of delphinidin-3-glucoside as a sensitizer in DSSCs. The analyzed anthocyanin is suitable for sensitizing because of its high molar absorptivity values within the visible region of the light spectra, the adsorption ability to a FTO/TiO2 electrode (FTO, fluorine-doped tin oxide) as confirmed by Fourier transform infrared (FTIR) as well as thermogravimetry coupled to differential scanning calorimetry (TG-DSC), a potential oxidation value near 1 V, and adequate thermal as well as light stabilities. Moreover, the cell’s conversion efficiency is improved in the presence of silver nanoparticles, reaching 0.24% (nearly a 25% increase). The sum of all these characteristics points to the application of delphinidin-3-glucoside as a sensitizer in DSSCs, offering a technological use with potential interest for countries where agricultural production offers an abundant origin of extraction.

Exploring Different Designs in Thieno[3,4-b]pyrazine-Based Dyes to Enhance Divergent Optical Properties in Dye-Sensitized Solar Cells

Two novel organic sensitizers for Dye-Sensitized Solar Cells (DSSC), called TP1 and TP2, based on the electron-poor thieno[3,4-b]pyrazine (TPz) π-bridge and the electron-rich N,N-bis(4-(hexylthio)phenyl)aniline (TPA) were designed following two different approaches: the classical D-A-π-A design and a symmetric structure with double anchoring functions. Both compounds were prepared exploiting short synthetic pathways based on direct arylation strategies and possibly one-pot desymmetrization. The two novel dyes displayed opposite optical properties: a broad and intense light absorption over the entire visible spectrum for TP1, and a localized absorption that peaked in the center of the visible region for TP2, resulting in a pitch-dark coloration and a green tone, respectively. When assembling the photovoltaic devices, different electrolyte compositions were explored to enhance the optical properties of the dyes. Power conversion efficiencies as high as 5.2% under full sun intensity were recorded for small test devices. The composition of the light transmitted through the TP2-containing transparent DSSC fits well with the human eye sensitivity spectrum, thus fulfilling the transparency requirements for building-integrated photovoltaics (BIPV).

Molecular engineering of auxiliary acceptor for the development of efficient organic D-A-π-A sensitizers

Molecular structure is vitally important for the selective optimization of energy level and improving the interfacial charge transfer performance of dye-sensitized solar cells (DSSCs). With appropriate auxiliary acceptor, the organic sensitizer owing D-A-π-A structure can act as a promising efficient sensitizer for DSSCs. Herein, considering the conjugated π-system and electron-withdrawing capability, dyes CS-71 and CS-72 were designed and synthesized with naphthothiadiazole and naphthobisthiadiazole units as the auxiliary acceptors, respectively, while the benzothiadiazole unit was applied as the auxiliary acceptor for the reference dye CS-70. The structure-activity relationship between the molecular structure characteristics, including steric hindrance, π-conjugation system, and electron-withdrawing capability of the auxiliary acceptors, and the properties of the dye are systematically investigated. Ascribed to the extended auxiliary acceptor moieties, CS-71 and CS-72 obtained obvious downward shift LUMO levels accompanying with the HOMO levels remaining unchanged, with respect to the reference dye CS-70. Owing to the shrinked energy gap, their absorption spectra were also significantly bathochromic shifted, resulting in the effectively broadened light-harvesting region. Combining the improved charge injection process, cell devices sensitized by CS-72 achieves an optimal PCE of 7.17%, presenting us a promising way to obtain highly efficient organic sensitizer in the future.

New D−A propeller system with pyridine core for co-sensitization in dye sensitized solar cells

In this study, a propeller-type molecule with a pyridine core (D) was designed and synthesized. Photophysical and electrochemical studies, along with theoretical DFT simulations, indicated that the molecule has suitable light absorption properties and frontier molecular orbital levels for usage as a sensitizer in dye-sensitized solar cells (DSSCs). Meanwhile, the standard dye Z-907 was chosen to investigate the effect of the synthesized molecule as a co-adsorbent dye on DSSCs. Intriguingly, when compared to the D and Z907-based devices, the performance of the co-sensitized Z907 + D cell exhibited an increase in photocurrent (JSC), photo-voltage (VOC), and, as a result, total power conversion efficiency (PCE).

Optical absorption and photoluminescence properties of Cucurbita maxima dye adsorption on TiO2 nanoparticles

Dye-sensitised solar cells (DSSCs) are 3rd generation photovoltaic device that imitate photosynthesis in plants. The fundamental concept of a DSSCs is that the photoanode is covered by the dye as a sensitiser. Natural dyes from plant-based extracts have gained attention as alternatives to toxic and expensive commercial dye sensitisers. Various studies have been conducted on the use of natural plant dye extracts for DSSCs . However, more fundamental studies on their adsorption on TiO2 photoanode nanoparticles are still not well understood. In this study, we investigated the crystal structure, optical absorption, and photoluminescence properties of TiO2, Cucurbita maxima, and Cucurbita maxima dyes adsorbed on TiO2 nanoparticles as potential materials for DSSCs. Raman spectra confirmed the anatase phase of the TiO2 nanoparticles. The particle size of 12 ± 2 nm was confirmed through the transmission electron microscope. The optical absorption properties of Cucurbita maxima show two distinct absorption bands: blue visible (450–500 nm) and red visible (635–674 nm). The photoluminescence spectra of the dye extract and its adsorption onto the TiO2 nanoparticles showed two prominent peaks in the blue and red regions of the electromagnetic spectrum. No significant peak is observed in the green region of the electromagnetic spectrum. These studies shed more light on the fundamental properties of chlorophyll adsorption on TiO2 nanoparticles and their optical and photoluminescence properties for applications as sensitisers in DSSCs.

Prickly Pear Fruit Extract: Capping Agent for the Sol–Gel Synthesis of Discrete Titanium Dioxide Nanoparticles and Sensitizer for Dye-Sensitized Solar Cell

Plant extracts have been utilized as an ecofriendly natural reducing agent for the synthesis of nanomaterials, including metal oxides. Prickly pear (opuntia) fruit extract (PPE) was used as a reducing agent for the sol–gel synthesis of titanium dioxide nanoparticles (TiO2 NPs) and as a sensitizer for the TiO2 NPs photoanode used in dye-sensitized solar cells (DSSCs). Ultraviolet-visible and infrared spectra, X-ray diffraction patterns, and scanning electron microscopic images were confirmed in the formation of semiconducting TiO2 NPs with the predominate size of ~300 nm. The use of PPE rendered discrete TiO2 NPs, whereas the typical synthesis without PPE resulted TiO2 aggregates. TiO2 NPs had a tetragonal crystalline structure, and their grain size was varied with respect to the concentration of PPE. The size of TiO2 crystallites was found to be 20, 19, 15, and 10 nm when the volume percentage of PPE was 0.2, 0.4, 0.6, and 0.8%, respectively. TiO2 NPs obtained using PPE were coated on indium-doped tin oxide substrates and sensitized with natural dye made up of PPE and synthetic dyes, namely rose Bengal (RB) and eosin yellow (EY). The photoanode fabricated with dye-sensitized TiO2 NPs was subjected to current–voltage response studies. The maximum power-conversion efficiency, 1.4%, was recorded for photoanodes sensitized with PPE dye, which is considerably higher than that for RB (1.16%) or EY (0.8%). Overall, the above findings proved that PPE can be used as a potential reducing/capping agent and TiO2 sensitizer for DSSC applications.

Role of Pi-Electron Density at the Interface of Small Molecule-Sensitized Solar Cells

Conventional dye-sensitized solar cells (DSSCs) involving charge-transfer interfaces face charge injection losses and offsets for TiO2-sensitizer band alignment. The direct charge-transfer mechanism in DSSCs with catechol (CT, 1,2-benzenediol)-based compounds minimizes the injection losses and eliminates band alignment issues, although the photovoltaic performance of the corresponding device is very poor due to the ultrafast (picosecond) recombination of photoexcited electrons. Just as in a natural photosystem, structural selectivity toward inhibition of this recombination needs to be defined. The interfacial electron density and back electron transfer kinetics at the molecular sensitizer–TiO2 interface play a significant role in the overall energy conversion efficiency. Herein, we identified, for the first time, that the π-electron cloud at the sensitizer–TiO2 interface facilitates the degree of recombination. Comparative density functional theory analyses confirmed that these electron clouds act as large recombination sites. Luminol (LM) and isoluminol (ILM) were employed as “small molecule” sensitizers without the cloud, having a secondary amine linker, which increased the photoenergy conversion efficiency of the single-step sensitization-based photovoltaic cell (type-II DSSC) by reducing the recombination. The device with LM exhibited a power-conversion efficiency (PCE) of ca. 1.11% (representing 363% improvement when compared to CT), the highest ever reported in this category. This understanding is insightful for the design of novel small molecular sensitizers for future DSSCs.

Synthesis and Photovoltaic Properties of Simple Fluorene-Based Triphenylamine Metal-Free Organic Sensitizers for Dye-Sensitized Solar Cells

Synthesis and Photovoltaic Properties of Simple Fluorene-Based Triphenylamine Metal-Free Organic Sensitizers for Dye-Sensitized Solar Cells

Effect of Gel Electrolyte, Paste and Electrode on the Efficiency of Dye-Sensitized Solar Cell using Schiff Base Dye Compound

The low cost and ease of production have led to widespread adoption of dye-sensitized solar cells (DSSCs). Therefore, this study aims to synthesize Schiff base compounds from salicylaldehyde and ethylenediamine as a sensitizer in DSSC. The Shiff base compound was synthesized using the condensation method with mol ratio of 1:1 and the results showed yellow crystals with a yield of 81.14%. Furthermore, the UV-Vis spectrometer analysis showed that the Schiff base compound has bathochromic shift with a maximum wavelength change from 324 and 328 nm to 335 nm with transition n→π, while the IR spectrum at wavenumber of 1610 cm-1 indicated the presence of an azomethine group (–C=N–). The TG-DTA analysis showed a mass loss stage of the Schiff base molecule at 97.2% in the temperature range of 180-300 ºC. Based on UV-Vis, IR and TG-DTA data, the synthesized Schiff base has the potential to be used as a sensitizer in DSSC. The fabrication was then carried out using two variations of semiconductor namely TiO2 and ZnO, three variations of PEG gel electrolyte with 0.05 M, 0.1 M and 0.15 M, as well as three counter electrodes including graphite from a pencil, candle flame and a combination of both. Based on the results, DSSC based on TiO2 semiconductor with 0.15 M PEG gel electrolyte and candle flame counter electrode produced the highest efficiency of 0.29 % with maximum voltage (Vmax) of 370 mV and maximum current strength (Imax) of 0.8 mA.