Dye-sensitized Solar Cells Research Articles

Competition between Transport and Recombination in Dye Solar Cells at Low Light Intensity

The efficiency of electron collection in a dye‐sensitized solar cell (DSC) is determined by a delicate balance between electronic transport and recombination losses caused by electron transfer to dye cations and electron acceptors. While state‐of‐the‐art DSCs have demonstrated quantitative electron collection under standard 1 sun conditions, the nonlinear nature of the trapping/detrapping dynamics in the photoanode with respect to the stored electronic charge can result in suboptimal performance under the low illumination intensity conditions commonly found indoors. Herein, the key factors influencing electron collection in relation to light intensity using impedance spectroscopy and numerical analysis are thoroughly examined. Impedance analysis reveals that the electron diffusion length tends to decrease as the quasi‐Fermi level is lowered, approaching the critical limit (Ln/d ≈ 1) at intensities characteristic of indoor illumination. A range of tert‐butyl pyridine concentrations and different thermal and chemical treatments of the TiO2 are tested, showing that this low intensity limitation is inherent to the multiple‐trapping mechanism that governs the functioning of a DSC. It is concluded that relatively high ideality factors, nonoptimal electrolyte compositions, or small variations in the quality of the TiO2 layer can result in electron collection limitations that are not apparent under 1 sun but become noticeable at low light intensities.

Synthesis of TiO2 nanoparticles by green approach: Application as photoanode for dye-sensitized solar cells

Efficient photoanodes play a central role in the performance of dye-sensitized solar cells. Traditional methods for synthesizing TiO2 often involve chemical processes that can be expensive and environmentally harmful due to the use of toxic and hazardous substances. Therefore in this work, TiO2 nanoparticles (NPs) were synthesized using bio-inspired processing through a hydrothermal procedure using different concentrations of Aloe barbadensis miller leaves extract as the reducing and stabilizing agent. Scanning electron microscopy (SEM), UV–vis spectroscopy (UV), X-ray difraction (XRD), Raman Spectroscopy, transmission electron microscopy (TEM) and Brunauer–Emmett–Teller (BET) analysis were used to characterize as synthesized TiO2 NPs. DSSCs were fabricated employing the prepared TiO2 NPs as photoanodes, and their performance was assessed. DSSC generates JSC of 9.7 mA/cm2, VOC of 0.682 V and efficiency (η) of 4.3 % when 20 mL concentration of extract was used for the synthesis of TiO2 NPs and subsequently their photoanodes.

Microwave-plasma surface modification of nanostructured-polyaniline:graphite composite counter electrode in dye-sensitized solar cells

This work demonstrates microwave plasma surface modifications of nanostructured polyaniline (NPES)-based counter electrodes (CE). Oxidative oxygen (O2) plasma and reductive hydrogen (H2) plasma were used in this study. Optical emission spectra confirm the presence of reactive species in both plasmas through the emissive species, such as O2+, O+, O•, H(nl), and H2 Fulcher-α. Microwave plasma treatment does not affect the surface morphology of NPES composite CE, which conserves its granule nanostructures, as revealed by SEM. The water contact angle measurements demonstrate how the O2 plasma treatment improves surface hydrophilicity, contrary to the H2 plasma treatment. Raman spectroscopy results show significant changes in the intrinsic-oxidation state and the number of semiquinonoid species (SQ) of NPES after plasma treatments, which are represented by the ratios of Raman intensity at 1368–1260 cm−1 and 1624–1583 cm−1, respectively. Generally, O2 plasma treatment increases the intrinsic-oxidation state and SQ number, opposite to the H2 plasma. The optimum condition of microwave plasma-assisted surface modification was attained in one minute of O2 plasma treatment, producing NPES with the highest intrinsic-oxidation state and SQ number. A power conversion efficiency of 3.17 % was obtained by a dye-sensitized solar cell fabricated with a modified CE using a one-minute O2 plasma treatment.

Poly(ethylene glycol)/poly(vinylidene) fluoride/TiO2 nanoparticle composite for sandwiched solid-state dye-sensitized solar cells

Poly(ethylene glycol)/poly(vinylidene) fluoride/TiO2 nanoparticle composite for sandwiched solid-state dye-sensitized solar cells

BODIPY-Based Macrostructures: A Design Strategy toward Enhancing the Efficiency of Dye-Sensitized Solar Cells.

Among the metal-free dyes, boron dipyrromethene (BODIPY) has attracted much attention in the solar cell industry due to its thermal stability and tunable electronic and photophysical properties. However, the low power conversion efficiency of dye-sensitized solar cells based on BODIPY has limited their widespread application. Accordingly, different types of structural modifications have already been proposed to improve the photophysical properties of the BODIPY dyes. In this study, we used the strategy of constructing BODIPY-based covalent macrostructures by integrating two BODIPY subunits via a π-linker in linear and cyclic configurations. To this end, various types of the π-linkers including butadiyne, phenyl, and thiophene derivatives are considered. The structural, electronic, and optical properties as well as the photovoltaic performance of BODIPY dimers are theoretically calculated within DCM solvent. The results indicate that for a given linker, the BODIPY dimers with a linear configuration show better performance as compared to their macrocyclic counterparts. The reason is the enhancement of π-conjugation length, higher light harvesting ability, and proper charge carrier separation in linearly linked BODIPYs. In the cyclic series, the dyes incorporating phenyl linkers exhibit greater power conversion efficiency of up to 9%. For the dyes with a linear configuration, the involvement of a thienyl-thiophene bridge results in lower charge recombination and enhances the efficiency by up to 15%, which are expected to be potential candidates for organic dyes applied in DSSCs.

Design highly effective B or N doped mesoporous carbon fibers catalysts for I3-/I- redox couple regeneration in carbon-based dye-sensitized solar cells

Construction of mesoporous structure and improving the conductivity of carbon counter electrode are feasible paths to enhance the catalytic activity in dye-sensitized solar cells (DSCs) toward the I3-/I- redox couple regenerating (IRR). Herein, mesoporous carbon fiber (PCf) has been first synthesized and the DSCs using PCf counter electrode results in a power conversion efficiency (PCE) of 7.12%, significantly surpassing the PCE of 6.01% generated by the DSCs with carbon fiber (Cf) counter electrode without mesoporous structure. Additionally, doping with heteroatoms B or N can further enhance the catalytic performance of PCf. Consequently, B or N doped Cf (BPCf or NPCf) counter electrode-based DSCs achieve high PCE values of 8.43% and 7.96%, respectively, demonstrating PCE improvements of 40.3% and 32.4%. This enhancement in catalytic activity for IRR in DSCs can be first attributed to the increased specific surface area of Cf which can provide more catalytic activated sites. Meanwhile, the enhanced conductivity of PCf by heteroatoms B or N doping is also an important factor for the improved catalytic activity. This work is expected to provide potential path to enhanced the catalytic activity of carbon counter electrode in DSCs toward IRR.

Ferrocene Appended D-π-A chromophores for Dye-Sensitized Solar Cells: Synthesis, Photophysical, Effect of Co-adsorbent on Photovoltaic Efficiencies and DFT studies

A new ferrocene conjugated donor–π–acceptor type of dyes 1 and 2 were synthesized and characterized using different spectroscopic techniques (FT-IR, NMR, and ESI-mass). The intramolecular charge transfer process of both the dyes were analysed using the solvatochromic method, which reveals positive solvatochromism due to its well stabilization in the excited states than in the ground states. The electrochemical behavior of the dyes 1 and 2 were carried out by the cyclic voltammetric technique, which shows quasi-reversible in nature, and the potentials were further utilized for the band gap calculation with UV–visible data [2.99 eV (1) and 2.88 eV (2)]. The photovoltaic attainments of the dyes 1 and 2 were studied through the dye-sensitized solar cells (DSSCs) in the presence and absence of co-adsorbent like chenodeoxycholic acid (CDCA), which act as an anti-dye aggregation material. The photovoltaic parameters like short circuit current density (Jsc) = 0.067 mA cm2, open circuit voltage (Voc) = 0.444 V, fill factor (FF) = 0.447, and the cell displayed an overall conversion efficiency of 0.013 % for dye 2. In contrast, the power conversion efficiency (PCE) was found to be enhanced to 0.177 % (Jsc = 0.389 mA/cm2, Voc = 0.577 V, FF =0.790), in the presence of chenodeoxycholic acid (CDCA) co-adsorbent. This enhancement in efficiency is due to reduced dye aggregation and increased electron injection in the presence of CDCA. In addition, chromophore 2 has 1.4 times higher efficiencies than 1, attributing to the presence of an additional phenyl group making an efficient intramolecular process of 2. Furthermore, the incident photon to current efficiency (IPCE) and electrochemical impedance spectroscopy (EIS) studies reveal the dye efficiencies were directly proportional to that of the power conversion efficiency (PCE), respectively. Moreover, the electronic structure and electron density distribution analysis were analysed for both dyes 1 and 2 to confirm the intramolecular charge transfer properties using density-functional theory (DFT) and time-dependent density-functional theory (TD-DFT) calculations using the B3LYP/ 6–31+G** level of theory.

Unlocking the potential of anthocyanin-based dye-sensitized solar cells: Strategies for enhancing efficiency, stability, and economic viability

This study investigates the feasibility and potential of anthocyanins as natural dyes in dye-sensitized solar cells (DSSCs). The focus is on the efficiency, stability, and economic viability of using anthocyanins as green alternatives in renewable energy technology. While anthocyanins offer controlled modification of optical properties at a low cost, there are challenges to overcome in achieving high efficiency, long-term stability, and commercial affordability. The study analyzes recent research developments and proposes strategies to enhance efficiency, stability, and economic viability. Optimization techniques, such as dye mixing and co-pigmentation, as well as modifications to dye structure and protective coatings, are explored. Economic considerations, availability, scalability, and innovative approaches like dye engineering and novel device architectures are discussed. The findings highlight the potential of anthocyanin-based DSSCs as a sustainable and economically viable solar energy technology. The study concludes with recommendations for future research to overcome challenges and advance the field of anthocyanin-based DSSCs.

Experimental optical properties explained by density functional theory of the natural red algae for dye-sensitized solar cells application.

The present study investigates the usage of a novel natural dye derived from red algae of Morocco in dye-sensitized solar cells (DSSCs) for the first time. The main pigments responsible for sensitizing the semiconductor TiO2 coatings in the red algae were identified as phycoerythrin, carotenoid, and chlorophyll. The efficiency of a DSSC made from red algae was compared to that of a solar cell made from chlorophyll alone. The photovoltaic performance of the DSSC was evaluated through photocurrent density to photovoltage (J-V) characteristic analysis, and the efficiency was found to be 0.93%. To gain insights into its behavior, the absorbance and photoluminescence in a broad range were studied. Both absorbance and photoluminescence exhibited a broad-spectrum range. Additionally, electronic properties, such as HOMO, LUMO, energy gap, and chemical reactivity parameters, were studied using density functional theory (DFT) calculations.

Oxygen-Vacancy-Mediated Large Binding Energy Exciton Dissociation in Nb3O7(OH) Nanorods with High Electron Mobility for CO2 Photoreduction.

Despite the excellent performance of Nb3O7(OH) in dye-sensitized solar cells and catalysis, its charge separation, transport, and structural properties remain poorly understood. Herein, the Nb3O7(OH) nanorods were prepared, and their structural characteristics, optoelectronic properties, and carrier mobility were also analyzed and investigated through a series of complex characterizations. Theoretical prediction suggested that the exciton binding energy of Nb3O7(OH) could be as high as 100.49 meV. The temperature-dependent photoluminescence (PL) of Nb3O7(OH) nanorods revealed two activation energies, and a higher proportion of long-lived components observed in the photoluminescence decay indicated effective electron trapping. That is, two energy states were present, hindering photogenerated charge recombination and promoting photocatalytic action. Current-voltage characteristics of the Nb3O7(OH) nanorod film were analyzed, revealing an ultrahigh carrier mobility of ∼310 cm2/V·s, ensuring fast and efficient electron transfer. Furthermore, Nb3O7(OH) nanorods were employed to reduce CO2, resulting in the effective production of CO and CH4. Overall, considering the presence of hydroxyl pairs on the surface of Nb3O7(OH), which facilitate the formation of the frustrated Lewis acid-base pairs and the activation of CO2, together with its effective electron trapping and charge transport, give Nb3O7(OH) nanorods a promising potential for CO2 reduction.

Novel Phenothiazine and Coumarin based Sensitizers: Design, Synthesis and Photoelectrochemical Application by Anchoring on CdS Nanowires

Novel metal-free organic dyes (E)-2-cyano-3-(10-(prop-2-yn-1-yl)-10H-phenothiazin-3-yl)acrylic acid (PPC) and (E)-2-cyano-3-(10-((1-((7-methyl-2-oxo-2H-chromen-4-yl)methyl)-1H-1,2,3-triazol-4-yl)methyl)-4a,10a-dihydro-10H-phenothiazin-3-yl)acrylic acid (PCTC) was synthesized and then anchored to 1D cadmium sulfide nanowires (1D CdS NWs) for application in photoelectrochemical dye-sensitized solar cell (DSSC). The 1D CdS nanowires were interconnected into a nanonetwork using solution chemistry in a straightforward and efficient manner. The UV-visible spectroscopy, cyclic voltammetry and density functional theory (DFT) were effectively employed to analyze the characteristics of PPC and PCTC. The sensitizer-anchored CdS nanowires have a broader range of light absorption in the UV-visible spectrum compared to bare CdS nanowires. The complete device has the assembly FTO, compact CdS, CdS nanowires, synthesized dye and counter electrode. In photovoltaic assessment, the PCTC and PPC devices yield 3.19 and 3.04 times, respectively, more efficiency than naked CdS nanowires under conventional sunshine illumination (100 mW/cm2, AM 1.5G). The obtained results provide strong evidence supporting the presence of rising external quantum efficiency (EQE) and show a high level of consistency with the optical tests.

Co-sensitization effect of chlorophyll and anthocyanin on optical absorption properties and power conversion efficiency of dye-sensitized solar cells

Co-sensitization effect of chlorophyll and anthocyanin on optical absorption properties and power conversion efficiency of dye-sensitized solar cells

Structural, electrical, optical, and DFT studies of phenothiazine-based D–π–A frameworks for dye-sensitized solar cell applications

Structural, electrical, optical, and DFT studies of phenothiazine-based D–π–A frameworks for dye-sensitized solar cell applications

Novel approach: Simultaneous application of ionic liquid doped polymer electrolyte in supercapacitor and dye-sensitized solar cells

The present study reports the synthesis, characterization, and application as energy devices of an ionic liquid blended polymer electrolyte film in which the host polymer polyvinyl alcohol (PVA) is mixed with low viscosity ionic liquid (IL) 1-ethyl-3-methylimidazolium thiocyanate. Various characterization tools have been used further to elaborate electrical, structural, and photoelectrochemical properties. X-ray diffraction (XRD) and polarized optical microscope (POM) affirm the reduction of crystallinity of polymer, while Fourier transform infrared spectroscopy (FTIR) shows complexation and composite nature. Electrochemical impedance spectroscopy shows an enhancement in ionic conductivity by IL doping, where the highest conductivity is achieved at 60 wt% of IL concentration with a conductivity value of 6.21 × 10⁻⁴ S/cm. The ionic transference number (tion) and electrochemical stability measurement show the film's predominantly ionic nature and a reasonable stability window. Using maximum conducting film sandwiched between electrodes, we have successfully fabricated two devices, i.e., an electrical double-layer capacitor (EDLC) and a dye-sensitized solar cell (DSSC). The fabricated EDLC capacitor shows a specific capacitance of 125 F/g, while DSSC shows an efficiency of 1.1 % at one sun condition.

Exploring the Role of Central Metals in Bulky Phthalocyanines for Dye-Sensitized Solar Cells.

Two series of metallo-(Zn(II), Mg(II), and Ru(II)) and free-base phthalocyanines (Pcs) with a carboxyl anchoring group and well-established bulky peripheral substituents (either tert-butyl or bulky 2,6-diisopropylphenoxy) were synthesized and tested as sensitizers in dye-sensitized solar cells (DSSCs). The trend of photovoltaic efficiencies (PCEs) for free-base and metallo Pcs followed the order Zn(II)Pc>Mg(II)Pc≫H2Pc ≈ Ru(II)Pc regardless of the peripheral substitution. Higher efficiencies (4.95 versus 3.63 for the Zn(II) derivatives) were achieved with Pcs bearing the bulkier 2,6-diisopropylphenoxy group, indicating a lower aggregation and more suitable HOMO-LUMO levels. Furthermore, these derivatives showed a morelevant influence of the metal on the PCE values (from the highest 4.95 for the Zn(II)Pc to the lowest 0.23 for the Ru(II)Pc. In both series, the best PCEs observed with the Zn(II) derivatives were mainly due to their highest Jsc values. The lowest efficiencies found for the free-bases and Ru(II) derivatives were attributed to a mismatch between their LUMO levels and the conduction band of the TiO2,and lower light-harvesting capabilities, respectively. In conclusion, Zn(II) derivatives are still the best Pc candidates to use as sensitizers in molecular photovoltaics.

A DFT/TD-DFT Study of the Influence of Anchoring Group and Internal Acceptor of Benzocarbazole-based D-A´-π-A Dyes for DSSCs

Great attention is being shifted to Dye-sensitized solar cells because of their structural and electronic tunability, high performance, and low cost compared to conservative photovoltaic devices. In this work, the DFT/B3LYP/6-31G(d,p) and TD-DFT/mPW9PW91/6-31G(d,p) levels of theory are applied to the theoretical study of a new class of benzocarbazole-based D-A´-π-A dyes for their potential use in DSSCs. The influence of the internal acceptor on the optoelectronic properties is studied for the dyes. The optoelectronic and photovoltaic properties as HOMO, LUMO, E<sub>gap</sub> maximum absorption wavelength (λ<sub>max</sub>), vertical excitation energies (E<sub>ex</sub>), oscillator strength (<i>f</i>), light harvesting efficiency (LHE), open circuit voltage (V<sub>oc</sub>), injection force (ΔG<sub>inject)</sub>, were evaluated and discussed in order to compare their performance as DSSC sensitizers. The theoretical results show that all dyes exhibit excellent optoelectronic properties, such as a lower E<sub>gap</sub>(1.733 eV to 2.173 eV), a significant λ<sub>max</sub>(631.48 nm to 754.40 nm), a sufficient value of V<sub>oc</sub> (0.461 V to 0.880 V) and high LHE (0.853 eV to 0.968 eV). In particular M4 with 2,5-dihydropyrrolo [3,4-c]pyrrole-1,4-dithione as auxiliary acceptor has the potential to be used as a sensitizer for DSSCs, due to its red-shifted absorption spectrum (λ<sub>max</sub>= 754.40 nm), and small energy gap (E<sub>gap</sub>=1.733 eV). Indeed, this study may help chemists to synthesize efficient dyes for DSSC.

Dye-sensitized solar cell: Effect of light on N3 dye/BMII electrolyte based architecture

This study evaluates the photovoltaic performance of Dye-Sensitized Solar Cells (DSSCs) for various light conditions. This work focuses on exploring the experimental characteristics of a thin-film solar cell composed of an ITO/TiO2/N3-Dye and BMII electrolyte molecules/Pt/ITO. A meticulous investigation is conducted to understand the impact of different illumination intensities on the efficiency of these solar cells. In the experiments, the power conversion efficiencies (PCE) of the device reached 7.61 % with a maximum open-circuit voltage (Voc) of 0.67 V under 100 mW/cm2 AM 1.5 solar irradiance. The morphology of the TiO2 nanoparticles that have been synthesized for the DSSC were analyzed by Ultraviolet–Visible Spectrometry, X-Ray Diffractometry, as well as Scanning Electron Microscopy and Atomic Force Microscopy. Electrochemical impedance spectroscopy (EIS) parameters and Nyquist plot results showed that a systematic understanding of charge transfer within the DSSC is essential to extract an equivalent circuit model. The results of this study allow optimizing the performance of future DSSCs for sustainable energy systems.

Metal‐Free Organic Dyes for NiO‐Based Dye‐Sensitized Solar Cells: Recent Developments and Future Perspectives

The increasing global demand for energy and growing environmental concerns emphasize the crucial role of solar energy as a sustainable and nondepletable resource. Solar cells, particularly dye‐sensitized solar cells (DSSCs), have gained prominence due to their efficient conversion of solar power, ecofriendly manufacturing processes, and noteworthy stability. Current research in sustainable energy focuses on transitioning from metal‐based to metal‐free organic materials. Tandem solar cells, combining n‐type and p‐type semiconductors sensitized with diverse photoactive dyes, show potential to surpass thermodynamic limits in photon conversion efficiency. Notably, the exploration of n‐type DSSCs as photoanodes in tandem architectures is promising. However, the absence of efficient p‐type photoactive cathodes remains a significant obstacle. Global research efforts are dedicated to addressing charge recombination issues in NiO‐based devices to enhance the efficiency of p‐type DSSCs. The success of any DSSC hinges on the selection of dyes/sensitizers with suitable anchoring groups, wide absorption in the visible–NIR region, and a high extinction coefficient. This article comprehensively reviews advancements in developing highly efficient p‐type sensitizers, emphasizing their pivotal role in unlocking the full potential of tandem solar cells.

A study on using a binder-free TiO2 paste with sodium dodecylbenzene sulfonate addition to improve the performance of low-temperature DSSCs

The utilization of binder-free TiO2 paste allows for the dye-sensitized solar cells (DSSCs) TiO2 electrode fabrication at low temperatures, thus making it a potential material for flexible solar cell devices. However, the physical robustness of formed electrodes using TiO2 paste at low temperatures remains challenging, including issues such as cracking due to film stress and challenges in adjusting the viscosity of the TiO2 paste. In this study, we enhanced the binder-free TiO2 paste performance by incorporating sodium dodecylbenzene sulfonate (SDBS) as an additive for TiO2 electrode precursor solution. It demonstrated that SDBS additives help to relieve internal stress and ultimately enhance the physical and structural characteristics of the films by improving the viscosity in the TiO2 paste and promoting the dispersed pinholes within the TiO2 films. Furthermore, implementing TiO2 paste with varying ratios of SDBS has enabled the fabrication of DSSCs with the highest achieved power conversion efficiency (PCE) of 4.53%, representing an enhancement of nearly 15% compared to TiO2 paste without SDBS. This research presents a practical and effective approach for preparing highly efficient binder-free TiO2 paste.

Investigation of the structural and optoelectronic characteristics in coumarin-based dye-sensitized solar cells, both in isolation and with TiO2 adsorption

In this study, six novel organic dyes derived from coumarin have been formulated by limiting the rotation of bithiophene through the introduction of substituents, namely NCH3, Si(CH3)2, C(CH3)2, C=C(CH3)2, and C=O. Their structural, electronic, photovoltaic, and spectral properties were investigated using density functional theory at the B3LYP/6-31G(d,p) level. Furthermore, the time-dependent DFT (TD-DFT) at TD-BHandH/6-31G(d,p) level method was chosen to calculate the electronic absorption spectra and charge transfer characteristics of the investigated dyes in the chloroform solvent, as well as molecular properties such as geometries parameters, optoelectronic properties, and frontier molecular orbitals. With our studies, we reveal that all the studied dyes show significance in the range of 340.97–610.89 nm, with a band gap in the range of 1.90–2.26 eV, as well as high light capture efficiency (LHE) and significant intramolecular charge transfer (ICT) properties. In addition, we were interested in the energetic, electronic, and absorption studies of dyes linked to the TiO2 semiconductor (Dye@TiO2). All designed dyes exhibit better geometric and optoelectronic properties except for D3, which has the lowest gap energy and extends towards the red. The results reveal that these compounds would be used as potential sensitizers for DSSC applications.