Improving the effective photovoltaic performance in dye-sensitized solar cells using an azobenzenecarboxylic acid-based system

Molecular engineering and electrolyte optimization strategies for enhanced performance of Ru(ii) polypyridyl-sensitized DSSCs

Dye-sensitized solar cells (DSSCs) are a leading third-generation solar cell technology due to their low cost, ease of fabrication, and tunable photoelectrochemical properties. Among DSSC components, the photosensitizer plays a crucial role in light absorption and charge generation, with Ru(ii)-polypyridyl complexes standing out due to their superior photostability, broad absorption spectra, and efficient charge injection. This review provides a comprehensive analysis of molecular engineering strategies for Ru(ii)-polypyridyl photosensitizers, emphasizing ligand modifications to design and develop novel Ru(ii) photosensitizers with prolonged excited-state lifetimes, reduced charge recombination, enhanced light-harvesting capabilities, and improved overall solar-to-power conversion efficiency (PCE). In addition, cyclometallated polypyridyl Ru(ii) complexes are explored as promising alternatives to Ru(ii) complexes incorporating labile thiocyanate (SCN) ligands for DSSCs, which offer improved stability. The relationship between the molecular structure of Ru(ii) photosensitizers and their photovoltaic characteristics is analyzed by examining key factors that influence their photovoltaic performance, including light-harvesting efficiency, fine-tuning ground and excited state oxidation potentials (GSOP/ESOP), extending excited state lifetimes, and minimizing charge recombination. Additionally, the impact of co-adsorbents, electrolyte additives, and interfacial engineering on DSSC performance is explored. Emphasis is placed on optimizing redox electrolytes beyond conventional iodide/triiodide (I-/I- 3) systems to minimize energy loss and enhance PCE. By carefully considering those challenges, this review lays the groundwork for the rational design of next-generation DSSCs that are more efficient, stable, and commercially viable.

Porous carbohydrate-graphene aerogels synthesized by green method as electroactive supercapacitor materials

Various graphene derivatives have been known as electrode-active materials for fabricating supercapacitors. Interconnected graphene networks with adjustable porous structures, i.e., 3D graphene aerogels (GAs), can control the restacking of graphene sheets very well and, thus, lead to the enhanced performance supercapacitors. In this study, carbohydrates (sucrose and fructose) were used to make two types of 3D porous carbohydrates-graphene aerogels, sucrose-graphene aerogel (SCR) and fructose-graphene aerogel (FRC). Carbohydrates operate as a cross-linking and reductant agent. Voltammograms of supercapacitor electrodes based on the FRC and SCR indicate a more rectangular shape with a larger area and a superior current than the GA (graphene aerogel without using carbohydrates) electrode. They have better capacitive performance, more electron transportation ability, and higher specific capacitance (CS) values than GA. The supercapacitor electrodes based on FRC, SCR, and GA demonstrate the CS values of 257.2 F g -1, 221.0 F g -1, and 95 F g -1 at ѵ = 10 mV.s-1, respectively. Improvement in the performance of SCR and FRC supercapacitor electrodes, in comparison to GA, is attributed to the porous interconnected feature of their structures and their suitable available surface area, which facilitates electron and ion transportation throughout graphene networks. These supercapacitors also show excellent stability after recording 5000 consecutive voltammograms.

Role of rare-earth oxides, conjugated with T i O 2 , in the enhancement of power conversion efficiency of dye sensitized solar cells (DSSCs)

Different rare-earth (RE) metal-oxides nano-particles (NPs) viz. Samarium (III) oxide (Sm2O3), Neodymium (III) oxide (Nd2O3), and Gadolinium (III) oxide (Gd2O3) were synthesized using co-precipitation route, and investigated by structural, optical, and morphological studies. Findings and supporting studies were presented to understand the role of RE-metal-oxides NPs as photo-anode material for dye sensitized solar cells (DSSCs) applications. Structural analysis of prepared RE-metaloxides, by X-ray diffraction (XRD), reveals the crystalline nature of the particles ranging from 24 to 37 nm. Morphological study by field emission scanning electron microscopy (FESEM) supports the crystalline nature in the nano range of the prepared RE-metal oxides particles. The observed d values of each sample support the growth of Gd2O3, Nd2O3, and Sm2O3 material. The band-gap of prepared material was estimated from the UV-VIS absorption data and Tauc relation. The observed band gap values are 3.55 eV, 3.31 eV, and 3.52 eV for Gd2O3, Nd2O3, and Sm2O3 respectively. These values are reasonably high compare to the bulk values, indicates the nanostructure formation. Optimized RE-metal oxides NPs employed in the form of TiO2 photo anode for the fabrication of DSSCs. FESEM confirms that the Gd2O3-based photo-anode shows more uniform and decent coverage with more porosity on the TiO2. The EIS measurements of prepared DSSCs also supported the improvement in the photovoltaic output for the modified photo-anode devices as cells with modified photo-anode exhibited less charge recombination at the photo-anode/dye/electrolyte interface with increased electron lifetime leading to improved device performance as compared to the unmodified-based DSSCs. The highest efficiency 5.51% was demonstrated byG d 2 O 3 /T i O 2 photo-anode-based DSSCs compare to Sm2O3, and Nd2O3 activated photo-anode.

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 (Ag_xZn_1-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% Ag_0.2Zn_0.90Fe₂O₄ 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% Ag_0.2Zn_0.90Fe₂O₄ 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.

A Fascinating Trip into Iron and Copper Dyes for DSSCs

The production of electricity in a greener and more sustainable way by employing renewable sources is a great challenge in modern times. Photovoltaic systems represent an important possibility because sunlight is the most abundant renewable source. In this review article, recent studies (from 2018 to the present) involving novel iron and copper complexes employed as dyes in Dye-Sensitized Solar Cells (DSSCs) are reported; mono- and bimetallic Fe complexes, Cu-based dyes, and devices presenting both metals are discussed, together with the performances of the DSSCs reported in the papers and the corresponding values of the main parameters employed to characterize such solar cells. The feasibility of DSSCs employing copper and iron dyes, alone or in combination with other earth-abundant metals, is demonstrated. The proper optimization of the sensitizers, together with that of the electrolyte and of the semiconducting layer, will likely lead to the development of highly performing and cheap photovoltaic devices for future applications on a much larger scale.

Preliminary Investigation on Vacancy Filling by Small Molecules on the Performance of Dye-Sensitized Solar Cells: The Case of a Type-II Absorber

The steric shielding offered by sensitizers on semiconducting surfaces as a result of branching in the dyes used offers the less utilization of semiconducting substrate sites during device fabrication in dye-sensitized solar cells (DSSCs). This work proposes a strategy to increase the coverage through the utilization of small molecules which have the ability to penetrate into the sites. The small molecules play the dual role of vacancy filling and sensitization, which can be viewed as an alternative to co-sensitization also. Hence, we show for the first time ever that the co-adsorption of catechol with Z907 as a sensitizer enhances the electron density in the photo-anode by adsorbing on the vacant sites. Catechol was subsequently adsorbed on TiO₂ after Z907 as it has a stronger interaction with TiO₂ owing to its favorable thermodynamics. The reduced number of vacant sites, suppressed charge recombination, and enhanced spectral response are responsible for the improvement in the PCEs. Quantitatively, both organic and aqueous electrolytes were used and the co-sensitized DSSCs had PCE enhancements of 7.2 and 60%, respectively, compared to the control devices.

Influence of concentration of anthocyanins on electron transport in dye sensitized solar cells

The influence of concentration of anthocyanins in dye sensitized solar cells (DSSC) has been investigated, with focus on how concentration influence electron transport. The influence on electron transport was then linked to solar cell performance. Anthocyanins were extracted from fresh flowers of Acanthus pubscenes using methanol acidified with 0.5% trifluoracetic acid, concentrated using a rotary evaporator and partitioned against ethyl acetate. Concentration of the anthocyanins was determined using Keracyanin Chloride as a standard. DSSC were fabricated using Titanium dioxide as anode, anthocyanins as sensitizers and Platinum as counter electrode material. Titanium dioxide was deposited on Fluorine doped Tin oxide glass substrate using slot coating method. Platinum was deposited on FTO glass substrate using a brush previously dipped in plastisol precursor, and annealed at 450⁰C for 20 min to activate Platinum. Dye sensitized solar cells were assembled using anthocyanins at varying concentrations. Performance parameters of the solar cells were measured using a solar simulator which was fitted with digital source meter. Electron transport parameters were studied using electrochemical impedance spectroscopy (EIS). Open circuit voltage, short circuit current and fill factor were observed to increase with concentration of anthocyanins. The increase in solar cell performance was attributed to increase in charge density which led more charges being available for transported to solar cell contacts. The increased charge resulted in a negative shift in Fermi level of electrons in the conduction band of TiO₂. The shift in Fermi level resulted into an increase in open circuit voltage and the overall solar cell performance. EIS studies revealed increase in recombination resistance with concentration of anthocyanins. The increase in recombination resistance was found to be related to increase in electron density, and hence the shift in the Fermi level of electrons in the conduction band of TiO₂.