Dye Sensitized Solar Cells

We report the effect of microwaves sintering on the crystal domain and electrical properties of TiO 2 nanoparticles. Commercially available TiO 2 nanoparticles of 25 nm size were coated on ITO (indium tin oxide) substrates, which were then sintered at 450 °C employing microwave and conventional sintering approaches. The structural properties of the sintered coatings were examined using atomic force microscopy (AFM), scanning electron microscope (SEM), X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDS), whereas the charge transfer properties were investigated using electrochemical impedance spectroscopy (EIS). Structural analysis reveals that the microwave sintering of TiO 2 -coated substrates results in the formation of more ordered crystal structure as compared to the conventionally sintered samples. Nyquist plots demonstrate the improved charge transfer characteristics of TiO 2 nanoparticles in microwave-sintered layers. Also, the application of the microwave-sintered TiO 2 -coated ITO substrates as photoanode in dyesensitized solar cells (DSSCs) confirms superior electrical properties compared to conventionally sintered samples.

A n-type nanostructured PbS thin films were prepared by chemical bath deposition onto flat Silicon (Si) and Silicon nanowires (SiNWs) which were derived from electroless etching of Si substrates. The morphological characterization was carried out by scanning electron microscopy (SEM), while the optical properties were studied using Ultraviolet-Visible Spectroscopy (UV-Vis). The catalytic activity was studied by linear sweap voltammetry (LSV) in dark and under white light irradiation using potentiostat station. Cyclic voltammetry in presence and without purging CO 2 was also conducted. The LSV investigations showed the coupling effect between PbS thin films and Si for the rising and transport of the charge carriers. The results showed a higher photocatalytic activity toward CO 2 reduction of PbS/SiNWs compared to Silicon substrate without any surface modification and sensitization. The electrode based on PbS/SiNWs/Si could efficiently be used as photocathode for the PEC reduction of CO 2 to Methanol.

Una de las tecnicas para hacer sintesis de nanoparticulas bimetalicas es por medio de la Ablacion laser pulsado en medio liquido (PLAL) siendo esta una de las tecnicas mas utilizadas y apropiadas para la obtencion de nanoparticulas (NPs) y evitar la via quimica La tecnica PLAL llega a ser muy versatil debido a la simplicidad de su manejo y manipulacion, tambien esta tecnica llega a proporcionarle al nanocoloide ciertas propiedades que al momento de hacer deposicion electroforetica (EPD) puedan ser depositadas en un sustrato conductor. Al igual que la tecnica (PLAL), la deposicion electroforetica es muy sencilla y rapida, lo que posibilita la deposicion de NPs bimetalicas en sustratos conductores. Este proyecto de tesis a nivel de maestria se centro en la operacion de ambas tecnicas, senalando que para la tecnica PLAL se uso un laser Nd: YAG, de 532 nm, con una energia de ~380 mJ. Dicha ablacion se realizo en diferentes medios liquidos como: acetona, alcohol isopropilico y alcohol et...

Resumen En el presente trabajo se abordará el estudio de materiales luminiscentes a base de óxido de hafnio impurificado con elementos de tierras raras. Se desea estudiar específicamente la influencia del tamaño de partícula en las propiedades luminiscentes con la finalidad de mejorar sus propiedades ópticas y la eficiencia luminosa. Para lograr esto, se aplicarán las metodologías clásicas de síntesis en dispersión coloidal bajo diferentes condiciones buscando poder controlar el tamaño de partícula, la dispersión de tamaños así como la morfología del material.

For the past decade, much attention was focused on polysaccharide natural resources for various purposes. Throughout the works, several efforts were reported to prepare new function of chitosan by chemical modifications for renewable energy, such as fuel cell application. This paper focuses on synthesis of the chitosan derivative, namely, O-nitrochitosan which was synthesized at various compositions of sodium hydroxide and reacted with nitric acid fume. Its potential as biopolymer electrolytes was studied. The substitution of nitro group was analyzed by using Attenuated Total Reflectance Fourier Transform Infra-Red (ATR-FTIR) analysis, Nuclear Magnetic Resonance (NMR) and Elemental Analysis (CHNS). The structure was characterized by X-ray Diffraction (XRD) and its thermal properties were examined by using differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). Whereas, the ionic conductivity of the samples was analyzed by electrochemical impedance spectroscopy (EIS). From the IR spectrum results, the nitro group peaks of O-nitrochitosan, positioned at 1646 and 1355 cm -1 , were clearly seen for all pH media. At pH 6, O-nitrochitosan exhibited the highest degree of substitution at 0.74 when analyzed by CHNS analysis and NMR further proved that C-6 of glucosamine ring was shifted to the higher field. However, the thermal stability and glass transition temperatures were decreased with acidic condition. The highest ionic conductivity of O-nitrochitosan was obtained at ~10 -6 cm -1 . Overall, the electrochemical property of new O-nitrochitosan showed a good improvement as compared to chitosan and other chitosan derivatives. Hence, O-nitrochitosan is a promising biopolymer electrolyte and has the potential to be applied in electrochemical devices.

Material parameter variations are one of the main contributors affecting the performance of solar cell devices, thus, Taguchi design is employed to optimize the material parameters in attaining maximum power conversion efficiency (PCE). This paper discusses the optimal modelling of the Perovskite solar cell (PSC) with graphene oxide (GO) hole transport layer (HTL) using L32 (2 8) Taguchi design. The device simulation is conducted using a solar cell capacitance simulator (SCAPS), whereas the L32 (2 8) Taguchi design is used for device optimization. The final results reveal that the L32 (2 8) Taguchi design has significantly optimized the device parameters in which FTO thickness, FTO donor concentration, TiO2 thickness, TiO2 donor concentration, CH3NH3PbI3-xClx thickness, CH3NH3PbI3-xClx donor concentration, GO thickness and GO acceptor concentration are predictively set to 0.1 µm, 1 x 10 20 cm-3 , 0.03 µm, 1 x 10 20 cm-3 , 0.9 µm, 1 x 10 20 cm-3 , 0.03 µm and 1 x 10 20 cm-3 correspondingly. Analysis of variance (ANOVA) reveals that the CH3NH3PbI3-XClX thickness is the most dominant input parameter affecting the PCE of the device. The optimized input parameters yield the maximum attainable PCE of 35.91% with a signal-to-noise ratio (SNR) of 31.11 dB.

Zinc Oxide (ZnO) and ZnO/ multiwalled carbon nanotubes (MWCNTs) nanocomposites were prepared by direct blending procedure. The pure ZnO and ZnO/MWCNTs nanocomposite films were coated on Indium Tin Oxide (ITO) coated glass substrate by doctor blade method followed by annealing. The MWCNTs were functionalized by mixed acid treatment before incorporation into ZnO matrix and the presence of the carboxylic group was confirmed by Fourier Transform Infrared Spectra (FTIR). Electrical properties of these films were investigated by means of Current-Voltage (I-V) characteristics. Structural, Morphological and optical properties of the nanocomposite films were examined by means of X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscope (FE-SEM) and UV-Vis spectroscopy respectively. The incorporation of functionalized MWCNTs (f-MWCNTs) in ZnO matrix provides better separation of ZnO particles and hence prevents aggregation. SEM analysis confirms the increase in porosity of the ZnO films after incorporation of MWCNTs which enhances the absorption of light in photoanode of solar cells. It makes these films a better candidate for use as working electrode for Dye Sensitized Solar Cells (DSSCs).

A model that can be used to interpret the response of a dye-sensitized photo electrode to intensity-modulated light (intensity modulated voltage spectroscopy, IMVS and intensity modulated photo-current spectroscopy, IMPS) is presented. The model is based on an equivalent circuit approach involving a transmission line with both an electrical and an ionic branch. An analytical expression including a term from the passive electrochemical impedance of the network, and a term accounting for the photo generation in the electrode is found. From this model IMVS and IMPS responses as well as iV curves can be calculated and used to optimize the photo electrode with respect to thickness and density. The result is mathematically equivalent to the usual approach for IMVS and IMPS modelling based on diffusion equations describing the transport of electrons in the semiconductor and on charge accumulation in traps, although these assumptions are not included in the transmission line model. The diffusion-like behaviour shows up as a consequence of the topology of the coupling between transport processes rather than as an inherent property of the electron transport itself. In this model electron trapping occurs because of electrostatic interactions between electrons in the semiconductor and ions in the electrolyte.

ABSTRACT
Recently, a new generation of photovoltaic solar cell materials has been
developed. Featuring special characteristics such as a high absorption
coefficient, an ideal band gap, high defect tolerance, and a long carrier diffusion length. These advancements have led to experimental improvements in the performance of both organic and inorganic hybrid lead/tin halide perovskite solar cells. However, to complete the photovoltaic process, suitable electrodes and transport materials are essential. This is due to the phenomena of charge carrier separation, transportation, and charge collection at the interfaces between layers. As a result, the power conversion efficiency (PCE) has improved from 3.9% to 33.6%. This book chapter focuses on the progress made in enhancing hybrid perovskite solar devices, emphasising the role of charge generation through the photovoltaic effect and the stability of charge using conjugated polymers.

Perovskite solar cells (PSCs) have rapidly emerged as frontrunners in next-generation photovoltaics due to their high-power conversion efficiency (PCE), low-cost solution processability, and tunable optoelectronic properties. However, their commercialization remains limited by challenges such as poor long-term stability, defect-induced recombination, and scalability barriers. Multifunctional additives have shown great promise by enhancing crystallization, passivating defects, and improving the environmental and thermal stability of PSCs. This review covers multifunctional additives incorporated both into perovskite precursor solutions and at the interfaces between perovskite and charge transport layers, addressing their roles in both regular (n-i-p) and inverted (p-in) device architectures. Special emphasis is placed on mitigating both intrinsic and extrinsic degradation under harsh conditions, which is crucial for real-world applications. We also highlight additive strategies for flexible, large-area, and tandem PSCs, along with considerations of trade-offs and scalability, providing strategic insights toward commercial viability.

Herein, using DFT + U calculations, this study investigates the structural, optical, and magnetic properties of Ce-doped ZnS, with a focus on bandgap engineering and the induction of ferromagnetic states. Our theoretical analysis indicates that Ce doping substantially alters the electronic structure of ZnS, reducing its bandgap from 3.37 eV in the pure material to 2.8 eV at a 12% doping level. This bandgap reduction is attributed to the formation of localized Ce-4f states within the gap, which enable sub-bandgap optical transitions, as demonstrated by increased absorption in both the infrared and visible spectra. Additionally, the incorporation of Ce 3+ ions introduces ferromagnetic states due to the partially filled 4f-orbitals, breaking time-reversal symmetry and enabling spin-dependent functionality. By precisely controlling Ce doping, the optical and magnetic properties of ZnS can be finely tuned, making it a promising material for advanced applications such as light-emitting diodes, phosphors, infrared detectors, and spintronic devices. This study offers a comprehensive examination of the effects of Ce doping in ZnS and underscores its potential in next-generation optoelectronic and spintronic technologies.

Industrial activities are the major factor causing the water pollution and degradation of the environment around us. Sugar industry play important role in economic development of country but the effluent releases from the industry posses water pollution and causes health hazards. In this study, Pseudomonas fluorescens strain MK5 was isolated from sugar mill effluent and identified in the basis of morphological, cultural, biochemical characteristics and 16S rRNA analysis. Free and immobilized cells of Pseudomonas fluorescens strain MK5 was employed for bioremediation of sugar mill effluent and their Physico-chemical variance were analyzed. Results showed that the effluent physical and chemical properties were changed in the remediated sample. Better results were also observed in effluent sample treated with immobilized cells rather than free cells.

Zinc oxide nanostructures exhibit unique properties which make them suitable for dye-sensitized solar cell applications. Their specific properties such as appropriate optical properties, proper energy band gap and high electron transfer characteristics have motivated researchers to use them in the fabrication of dye-sensitized solar cell photo-anodes. In the present study, the effect of thickness on the performance of a new ZnO photo-anode has been studied. All the photovoltaic parameters of the cells fabricated using N719 ruthenium dye were measured. SEM technique was utilized to determine the thickness and the UV-Visible method was used to study the transparent properties of the photo-anodes. Electrochemical impedance spectroscopy technique was employed to determine the appropriate equivalent circuit for studying the electron transfer mechanisms in all the fabricated cells. The results demonstrated that the ZnO thickness is a critical parameter for providing either sufficient resi...

Metal nanoparticles (NPs) introduced in sensitive places in Dye Sensitized Solar Cells (DSSCs) has demonstrated superior performance due to surface plasmon resonance effect. Herein, a systematic investigation by introducing plasmonic silver nanoparticles (AgNPs) in the photoanode of DSSCs with Zinc oxide (ZnO) is investigated. The broadening of the absorption band in the visible region is made possible using the natural pigments betanins. The combined effect of UV-visible absorption spectroscopy, XRD technique, SEM and solar simulator were used to explore the surface plasmon resonance effect. The ZnO photoanode without Ag-NPs shows a Power Conversion Efficiency (PCE) of 0.156 %, Current Density (Jsc) of 0.477 mAcm -2 , Open Circuit Voltage (Voc) of 0.762 V and Fill Factor (FF) of 0.431. On coating AgNPs on the pristine photoanode, the PCEs were improved significantly as compared with the pure ZnO based device. The AgNPs were deposited in cycles (2 cycles, 4 cycles and 6 cycles). The device with 2 cycles of Ag NPs, shows a PCE of 0.373 % which demonstrates an enhancement of ∼2.39 times to that of the prestine device. Also depositing 4 cycles of AgNPs results to PCE of 0.290 % which shows a leading of 0.134 % ahead of the reference PCE. With 6 cycles of AgNPs deposited on the photoanode of bare ZnO NPs, it results to PCE of 0.244%, FF of 0.592, Jsc of 0.572 mAcm -2 and Voc of 0.722 V which also shows an enhancement of ∼ 1.56 times, ∼ 1.37 times and ∼1.20 times in PCE, FF and Jsc over the device lacking AgNPs. These results show significant increment in performances of all the devices with silver inclusion. The performance is attributed to the reduced recombination of electron-hole pairs due to the Ag-ZnO junction and the generation of intense electric fields at the immediate vicinity of the sensitizer, resulting in enhanced light absorption.

This work was aimed to extract, prepare and use dyes from bark of Syzygium guineense as photosensitizer for dye sensitized solar cell. The extraction processes were takes place in presence of acetone, ethanol and water as solvent. The photoelectron-chemical performance of the DSSCs based on the acetone extract showed Voc of 0.36 V, FF of 0.546, Jsc of 1.57 mA cm -2 and a power conversion efficiency of 0.319% under the sunlight illumination of 100 mW cm -2 and active area of 1 cm 2 . The J-V curves were plotted according to collected data of DSSCs by using Extech Multimeter, and electrical circuit with resisters made from wood board. The acetone extract of day from bark of Syzygium guineense offered the highest conversion efficiency than ethanol and water extracts. Generally, the dye extracted from bark of Syzygium guineense as natural photosensitizer could be a possible alternative for the production of low cost and environment friendly DSSCs.

The basic concept for efficiency improvement in dye-sensitized solar cells (DSSC) is limiting the electron-hole recombination. One way to approach the problem is to improve the photogenerated charge carriers lifetime and consequently reduce their recombination probability. We are reporting on a facile posttreatment of the mesoporous photoanode by using a colloidal solution of TiO 2 nanoparticles. We have investigated the outcome of the different sintering temperature of the posttreated photoanodes on their morphology as well as on the conversion efficiency of the DSSC. The DSSCs composed of posttreated photoanodes at 450 ∘ C showed an increase in 𝐽 SC and consequently an increase in efficiency of 10%. Investigations were made to determine the electron recombination via the electrolyte by the OCVD technique. We found that the posttreatment has the effect of reducing the surface trap states and thus increases the electron lifetime, which is responsible for the increase of the overall cell efficiency.

Capture and conversion of sunlight into the storable energy carrier H 2 can be achieved through photoelectrochemical water splitting using light-absorbing cathodes and anodes bearing H 2 and O 2 evolving catalysts. Here, we report on the development of a dye-sensitised p-type nickel oxide (NiO) photocathode with a hexaphosphonated Ru(2,2 0 -bipyridine) 3 based dye (RuP3) and a tetraphosphonated molecular [Ni(P 2 N 2 ) 2 ] 2+ type proton reduction catalyst (NiP) for the photoreduction of aqueous protons to H 2 . A layer-by-layer deposition approach was employed, using Zr 4+ ions to link the phosphonate units in RuP3 and NiP in a supramolecular assembly on the NiO photocathode. This approach keeps the dye in close proximity to the catalyst and semiconductor surface, but spatially separates NiP from NiO for advantageous electron transfer dynamics. The NiO|RuP3-Zr 4+ -NiP electrodes generate higher photocurrents and are more stable than photocathodes with RuP3 and NiP co-immobilised on the NiO surface in the absence of Zr 4+ cations linking dye and catalyst. The generation of H 2 with the NiO|RuP3-Zr 4+ -NiP hybrid electrode in pH 3 aqueous electrolyte solution during irradiation with a UV-filtered solar light simulator (l > 400 nm, 100 mW cm À2 , AM1.5G) has been confirmed by gas chromatography at an underpotential of 300 mV (E appl ¼ +0.3 V vs. RHE), demonstrating the potential of these electrodes to store solar energy in the chemical bond of H 2 .

Dye-sensitized solar cells (DSSCs) have garnered considerable attention due to their cost-efficiency, expandability, and potential for renewable energy production using small-scale materials and natural organic dyes in harnessing solar radiation for power generation. In this study, Red Dragon fruit (Hylocereus polyrhizus) extract (RDFD) was used as a dye sensitizer for Cu@TiO2 photoanode with waste chicken feather biocarbon as a counter electrode. Scanning electron microscopy with energy-dispersive X-ray spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and ultraviolet–visible spectroscopy were used to characterize the photoanode in terms of its surface morphology and elemental composition, crystalline phases, functional groups with bond formation, and optical properties, respectively. Comparative experiments were conducted to assess the effects of varying TiO2:Cu mass ratios on the photovoltaic parameters namely short-circuit current density (Jsc), open-circuit voltage (Voc), fill factor (FF), and cell efficiency (ɳ). The highest comparative photovoltaic performance with Jsc = 0.958 mA∙cm–2, Voc = 785.630 mV, FF = 0.669, and ɳ = 0.503% was achieved at annealing temperature (AnT) = 350 °C, annealing time (AT) = 1 h, and dye-soaking time (DST) = 1 h using 63.5 μm TCu1.5 photoanode. Parametric analysis was further carried out to investigate the influence of AnT, AT, and DST on the photovoltaic parameters. Cell efficiency optimization using Box-Behnken design of response surface methodology showed a remarkable ɳ = 2.19% at AnT = 418.53 °C, AT = 1.98 h, and DST = 1.03 h. The results of this study confirmed the successful integration of Cu@TiO2 photoanode and RDFD sensitizer and thus marked substantial advancement in sustainable energy solutions by creating unparalleled and eco-conscious photovoltaic devices.

Since 1991, dye-sensitized solar cells (DSSCs) have emerged as a potential alternative to conventional silicon photovoltaics for conversion of solar energy to electric power, due to their advantages of costeffectiveness, sustainability and ease of fabrication among others. As the functioning of DSSCs depends on the sum of the functions of individual components, effective understanding and optimization of these components is important for the optimization of the device itself. Therefore, this review focuses on the recent developments made in the fabrication of two particular components of DSSCs, viz. photoanode and counter electrode.

Upon cathodizing a conducting substrate in O2 saturated aqueous mixed solution of ZnCl2 and eosinY, ZnO/eosinY nano-hybrid films with high crystallinity, high transparency and grain boundary-free nano-porous structure are deposited. By soaking the films in soft alkaline solution, eosinY is completely removed without any change in film thickness. By re-loading various dyes onto the surface of these films, highly transparent ZnO films with various colors are easily obtained. The ZnO films thus loaded with various dyes are effectively applied to flexible and colorful dye-sensitized solar cells. Owing to superior properties of the films obtained under optimized conditions, the incident photon to current conversion efficiencies of the solar cells re-loaded with some kinds of organic dyes amount to 90 ％. Solar-to-electrical energy conversion efficiency of the DSSC employing D149 dye (Mitsubishi Paper Mills Limited) amount to 5.6 ％ under illumination of AM1.5 simulated sun light (100 mW cm -2 ). Efficient flexible colorful solar cells by using ITO-coated PET film substrates have been fabricated. Novel application of our plastic solar cells such as wearable solar cells and the solar powered functional traffic signs has been proposed.

This review paper provides a general overview of Organic Solar Cells (OSCs), more precisely their instability and commercialization challenges. The discussion begins by situating OSCs in the context of the global field of renewable energy, where their unique strengths of flexibility, low cost, and semi-transparency are brought out. Despite significant advances made, with power conversion efficiencies (PCEs) over 20% under laboratory conditions, the biggest challenge for wide-scale commercialization remains poor device stability and scalability. This report outlines the historical evolution of photovoltaic technologies, recent development of OSC efficiency and material advancement, specifically non-fullerene acceptors and ternary blends, and comparison with other generations of PV. Technical challenges are highlighted centrally, including intrinsic material instability, environmental degradation under oxygen, water, light, and heat, mechanical stress, and production bottlenecks. Solutions proposed and existing are presented, e.g., cutting-edge material engineering, optimization of device structure like inverted geometry, new processing ideas, and encapsulation technologies. Notably, the synergistic effect of optimizing the active layer thickness on stability and cost-effectiveness is discussed. Finally, the paper outlines critical directions for further study, such as the need for standardized test procedures, further material development, and an integrated methodology to accelerate the commercial readiness of OSC technology.

Sol-gel synthesis was used to develop a new hybrid photoanode material, a spherical zinc stannate/tin oxide nanorod named ZSTP. The subsequent step involves doping ZSTP with silver using a precursor called silver nitrate. The undoped sample was labelled as ZSTP, whereas silver-doped composites containing 1, 2, and 3 wt% silver were labelled as ZSTP-Ag1, ZSTP-Ag2 and ZSTP-Ag3 respectively. The pattern of powder X-ray diffraction (PXRD) with 2θ values of 26.52 and 33.84 confirms the orthorhombic structure of ZSTP and silver-doped samples. In the FT-IR spectra of the ZSTP and their silver-doped samples, the stretching frequency for Zn-O-Sn is observed at 1100 and 1464 cm-1. In addition, the surface-adsorbed Ag peaks at 1384 cm-1. The XPS spectra of ZSTP-Ag3 confirms the existence and structure of SnO and Ag. Examining the morphology with a scanning electron microscope (SEM) and transmission electron microscope (TEM) reveals a porous structure with adsorbed Ag on the surface. Doped silver appears as tiny spherical particles on the surfaces, whereas SnO nanorod zinc stannate appears as spherical particles in the TEM image. In-depth optical experiments were conducted to evaluate the characteristics of hybrid composites for DSSC applications. It was explored how the dye aggregates on the surface of silver-doped ZSTP. On the basis of the energy levels of their conductance bands, the electron transfer kinetics and energy transfer mechanism were predicted. Under a conventional one-sun illumination condition, the output photocurrent and photovoltage of these DSSC materials are evaluated. ZSTP-Ag3 offered the highest PCE at 1.38%. Due to the role of Ag2O in electron transfer, silver doped samples based devices offer a high FF (0.7) and steady photovoltage. Using the photovoltage decay curve, the recombination time (τ rec) and rate (k rec) were calculated to confirm a slower rate of recombination. Using simulated results, the overall performance of the DSSC is compared and validated.

For developing efficient DSCs, anchoring moieties need to be understood in detail with respect to a particular dye. Herein, we have synthesized new Zn-thienyl porphyrin dyes based on pyridyl and hydroxyphenyl anchors and compared with traditional carboxyphenyl anchoring group. The effect of such variation in anchoring groups was investigated with UV-vis and fluorescence spectroscopy as well as electrochemical studies. The hydroxyphenyl appended dye showed higher molar extinction coefficient and red shifted emission bands. Both pyridyl and hydroxyphenyl dyes showed adsorption over TiO 2 semiconductor. The dye loading amount was found to be greater for carboxyphenyl dye due to stronger bidendate coordination of the carboxy group, as revealed by FT-IR studies. The electrochemical potentials were found to be strongly influenced by the anchoring functionality and all the dyes showed positive driving force for electron injection to the conduction band of TiO 2 and regeneration of oxidized dye by the redox electrolyte. DSC devices were fabricated for each of the dyes and characterized well. Hydroxyphenyl dye showed higher V oc as a result of lower back reactions. Transient photovoltage decay measurments indicated lower recombination rate in hydroxyphenyl and pyridyl than the carboxyphenyl anchored thienyl porphyrins offering potential for further dye optimization.

Three-dimensional mesoporous TiO 2-Ni-MOF composite aerogels were synthesized via sol-gel route and used as photoanode materials for quasi-solid dye-sensitized solar cell (QSDSC) applications. The assessment of their photovoltaic performance revealed an enhancement compared to pure aerogel-based QSDSCs; the maximum photo-conversion efficiency of the fabricated photoanode was 8.846% for 0.5% composite aerogel, which is ~30% higher than that of pure aerogel-based ones (6.805%). The achievement of other key factors required for efficiency enhancement such as increased photocurrent density, reduced charge-transfer resistance, and suppressed electron recombination was confirmed by photocurrent density-applied voltage curves and electrochemical impedance measurements. The surface area of the composite aerogels ranged between 269 and 233 m 2 g-1 , which make them promising candidates for high-efficiency QSDSCs.

Sulfur-doped mesoporous TiO 2 aerogels were synthesized by the sol-gel method. The synthesized composite aerogels were characterized by powder X-ray diffraction, Fourier Transform Infrared spectroscopy, Scanning Electron Microscopy, and UV-Visible Spectroscopy. Their photovoltaic performances were evaluated as photoanode material in quasi-solid dye-sensitized solar cells (QSDSC) using photocurrent density-photovoltage (J-V) curve, electrochemical impedance spectra analysis (EIS) such as Nyquist plot and Bode plot, and transient measurements of photocurrent/photovoltage. The obtained photovoltaic results revealed that all synthesized sulfur-doped TiO 2 aerogel-based QSDSC devices show enhanced performance than the device based on pure TiO 2 aerogel. Maximum power conversion efficiency (PCE) of 3.42% was achieved with 20% of the sulfur-doped TiO 2 aerogel-based device which is higher than that of the device based on pure TiO 2 aerogel (2.46%). The efficiency enhancement is due to reduced bandgap, increased photocurrent density, low charge-transfer resistance (R ct), and suppressed recombination reactions. Further, the photostability and reproducibility of the fabricated devices were studied by transient measurements of photocurrent response and photovoltage decay curves.

A novel approach for modifying zinc stannate nanomaterials involves using a bio-extract derived from the leaves of Hibiscus rosa-sinensis. Ag nanomaterial and biomolecule sensitization was conducted in a single pot. The composite materials of Ag and biomolecules were characterized using powder X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy analysis to determine their structural aspects. Based on the PXRD results, it was determined that the composites exhibit a face-centered cubic structure. The observed frequencies of C-H and Sn-O stretching in the FT-IR spectra indicate the existence of biomolecules within the composite material. Furthermore, the X-ray photoelectron spectroscopy findings validate the coordination of zinc and tin within the zinc stannate compound with biomolecules while indicating silver's presence on the surface. Scanning electron microscopy and transmission electron microscopy techniques have revealed the material's porous characteristics and reduction in size of the zinc stannate particles. In addition, the results demonstrated the spherical morphology of the silver particles that have undergone doping. Surface agglomeration and optical characteristics were investigated using UV-Vis spectroscopy. The observed phenomenon exhibits pronounced particle agglomeration resulting from biomolecules on the surface. In addition, the emergence of an additional absorption band at approximately 453 nm can be attributed to silver's surface plasmon resonance effect. The obtained J-V curve for all samples demonstrates the observed enhancements, resulting from incorporating Ag and biomolecules. The enhancements observed in the simulation results were further confirmed through the validation process, which demonstrated the extended absorption and surface plasmon resonance effect.

Counter electrode is one of the key components in
the fabrication of dye-sensitized solar cell (DSSC). It is mainly
used to complete the electrical circuit of a solar cell as well as
to reduce tri-iodide to iodide at the interface of fluorine-doped
tin oxide/electrolyte. Platinum (Pt) is the conventional counter
electrode for DSSCassembly.Inrecenttimes, lots of research work
hasbeencarriedouttoreplace(Pt)withlowcostcarbonelectrodes.
In this article, as an alternative to platinum, graphite which is a
cost-effective carbon material is used as counter electrode material
forDSSC.ADSSCwasfabricatedusingtitaniaaerogelphotoanode,
graphite counterelectrode, gel polymerelectrolyte, porphyrin, and
N719dyesensitizers. The photocurrent density-voltage (J–V)plots
of the fabricated DSSC were measured at one sun illumination.
The photocurrent conversion efficiency of graphite-based DSSC
was comparable with that of platinum-based DSSC for the N719
dye. The electron transfer process in graphite-based DSSC was ex
plained based on the photo-physical parameters such as relaxation
time (τn) and diffusion time (τd) measurements. The J–V curves
were simulated using a MATLAB program to compare with the
experimental measurements. There is a good agreement between
The simulated and experimental results.

CdS and CdSe quantum dot-sensitized solar cells (QDSSCs) were used for the study of determining the optimum preparation parameters that could yield the best solar cell performance. The quantum dots (QDs) were coated on the surface of mesoporous TiO 2 layer deposited on FTO substrate using the successive ionic layer adsorption and reaction (SILAR) method. In this method the QDs are allowed to grow on TiO 2 by dipping the TiO 2 electrode successively in two different solutions for predetermined times. This method allows the fabrication of QDs in a facile way. Three preparation parameters that control the QD fabrication were investigated: concentration of precursor solutions, number of dipping cycles (SILAR cycles), and dipping time in each solution. CdS based QDSSC showed optimum performance when the QDs were prepared from precursor solutions having the concentration of 0.10 M using 4 dipping cycles with the dipping time of 5 minutes in each solution. For CdSe QDSSC, the optimum performance was achieved with QDs prepared from 0.03 M precursor solutions using 7 dipping cycles with 30 s dipping time in each solution. The QDs deposited on TiO 2 surface were characterized using UV-vis absorption spectroscopy, FESEM, and TEM imaging.

A unique, hierarchically structured, aggregated TiO 2 nanowire (A-TiO 2 -nw) is prepared by solvothermal synthesis and used as a dualfunctioning photoelectrode in dye-sensitized solar cells (DSSCs). The A-TiO 2 -nw shows improved light scattering compared to conventional TiO 2 nanoparticles (TiO 2 -np) and dramatically enhanced dye adsorption compared to conventional scattering particles (CSP). The A-TiO 2 -nw is used as a scattering layer for bilayer photoelectrodes (TiO 2 -np/A-TiO 2 -nw) in DSSCs to compare the cell performance to that of devices using state-ofthe-art photoelectrode architectures (TiO 2 -np/CSP). The DSSCs fabricated using bilayers of TiO 2 -np/A-TiO 2 -nw show improved power conversion efficiency (9.1%) and current density (14.88 mA cm -2 ) compared to those using single-layer TiO 2 -np (7.6% and 11.84 mA cm -2 ) or TiO 2 -np/CSP bilayer structures (8.7% and 13.81 mA cm -2 ). The unique contribution of the A-TiO 2 -nw layers to the device performance is confirmed by studying the incident photon-to-current efficiency. The enhanced external quantum efficiencies at approximately 520 nm and 650 nm clearly reveal the dual functionality of A-TiO 2 -nw. These unique properties of A-TiO 2 -nw may be applied in other devices utilizing light-scattering n-type semiconductor.

221 of the semiconductor takes place. In following, the oxidized dye molecules are regenerated by means of the electron donation from the redox couple in the electrolyte; usually Iˉ/I 3 ˉ or Co 2+ /Co 3+ . Finally, the reduction of the oxidized electrolyte component occurs at the counter electrode and permits the reversible device operation. It can be seen that the power-generation process would never work properly unless it employs a suitable initiator, e.g. a dye molecule. There are some criterions to employ an ideal sensitizer in the DSC [1], like:

Quantum dots have attracted extreme attention due to their excellent optical performance. This study insight optoelectronic performance of the Ag doped CdS passivated CuInSe 2 quantum sensitized solar cell. CuInSe 2 quantum dots (CISe QDs) of 6 nm were synthesized by simple thermolysis method, followed by 3-merceptopropinic acid (MPA) ligand exchange process. Additionally, titanium dioxide nanoflowers (TiO 2 NFs) were prepared by hydrothermal method. In-situ Chemical bath deposition (CBD) technique was adopted for CISe QDs sensitization, followed by co-sensitization of Ag doped CdS (Ag-CdS) layer through successive ionic layer adsorption and reaction (SILAR) method. Co-sensitization of Ag-CdS layer remarkably elevates the absorption spectra, which increase carrier generation in the quantum dots sensitized solar cells (QDSSCs). High charge transfer rate and plasmonic effect of Ag incorporated CdS nanoparticles result in the suppression of electron-hole recombination, which is confirmed by the high open circuit voltage (V oc ) 640 mV of CISe/Ag-CdS compare to 510 mV of CISe solar cell. The fabricated CISe/Ag-CdS novel structure device show significantly improved optoelectronics properties, with highest power conversion efficiency (PCE) 3.34% of CISe/Ag-CdS co-sensitized solar cells.

This study explores the effects of magnesium (Mg) and lanthanum (La) doping on the performance of dye-sensitized solar cells (DSSCs) utilizing TiO 2(98%)-ZrO 2(2%) (TZ, TZM, and TZL) photoanodes. The photoanodes were fabricated using a spin-coating sol-gel method, followed by calcination at 400°C. The structural, morphological, crystallographic, and optical properties of the proposed photoanode composites were characterized by X-ray diffraction, transmission electron microscopy, and ultraviolet-visible spectroscopy. The crystallite sizes of the synthesized thin films varied from 21.16 to 59.04 nm for the TZ, TZM, and TZL compositions. The current-voltage measurements of DSSCs based on TZL8 photoanode, cobalt sulfide-doped graphene counter electrode, and N719 dye revealed the highest efficiency of nearly 5.052%. The assembled DSSCs exhibited an open-circuit voltage of 0.74 V, a short-circuit current density of 9.964 mA/cm 2 , and a fill factor of 0.685. The enhancement in open-circuit voltage and short-circuit current density could be attributed to the improved electronic and microstructures of the proposed photoanodes.

TiO 2 and Ni-doped TiO 2 thin films have been prepared by sol-gel dip coating method. X-ray diffraction studies show that TiO 2 and Ni-doped nanocrystalline TiO 2 thin films are of anatase phase. The surface morphology of CdS quantum dot sensitized TiO 2 thin film and CdS quantum dot sensitized Ni-doped TiO 2 thin film were analysed by scanning electron microscopy. The absorption edge of TiO 2 thin films shift towards longer wavelengths (i.e. red shifted) with Ni doping, which greatly enhances the light absorption of TiO 2 in the visible region. The power conversion efficiency of CdS quantum dot sensitized Ni-doped TiO 2 (CdS QDS-NT) based solar cell exhibited an efficiency of 1.33%, which is higher than that of CdS quantum dot sensitized TiO 2 (CdS QDS-T) (0.98%) solar cells.

Semiconductor-based metal oxide gas detector of five mixed Z:S from zinc chloride salt (0,25,50,75,100%) ratios with tin chloride salt, were fabricated on glass substrate by a spray pyrolysis technique with thickness were about ( 0.2 ±0.05 µm) using water soluble as precursors at a substrate temperature 500 Cº±5, 0.05 M ,and their gas sensing properties toward (CO 2 , NO 2 and SO 2 gas at different concentration (10,100,1000 ppm) in air were investigated at room temperature which related with the petroleum industry. Furthermore structural and morphology properties was inspecting. Experimental results show that the mixing ratio affect the composition of formative oxides (ZnO,Zn 2 SnO 4 ,Zn 2 SnO 4 +ZnSnO 3 ,ZnSnO 3 , SnO 2 ) ratios mentioned in the above respectively, and related with the sensitivity of the tested oxidation gases.

Herein, we report the synthesis and characterization of metal complexes of Fe(III), Co(II), and Cu(II) with SALPHEN (N,N-bis(salicylimine)-o-phenyldiammine) and their potential application as sensitizers in dyesensitized solar cells (DSSCs). The high thermal stability up to 550 1C observed for these compounds suggests that they may be possible candidates for the fabrication of solar cell devices without pyrolysis or thermo-oxidative degradation during the solar cell operation. The photovoltaic parameters of SALPHEN and its metal complexes were investigated experimentally, and it was observed that the metal ion coordination generally enhanced the power conversion efficiency (Z) where the maximum Z of 46.2% was obtained for the Co(II) complex due to its high molar extinction coefficient and enhanced charge transfer by improved p-conjugation and electron-withdrawing capability. In the theoretical calculations, the B3LYP functional was employed to compute the ground-state geometries and the frontier molecular orbitals for all the complexes. The ground-state and excited-state energy transfer, which specifically contribute to the light harvesting properties of SALPHEN and its metal complexes, were analyzed using the functionals with corrected dispersion CAM-B3LYP/dgdzvp basis set (double zeta) and functional (B3PW91, B3P86/6-311++G(d,p) basis set (triple-zeta)). It was observed that the HOMOs of the metal complexes were localized on the d orbitals with p(SALPHEN nitrogen and O À atoms) orbital character, whereas their LUMOs have p*(O À ) orbital character. The light-harvesting efficiency (LHE) was analyzed using the theoretically obtained band-gap values for SALPHEN and its metal complexes. In general, metal ion chelation showed increased charge transfer transitions in both the ground and excited states. Moreover, the charge density difference in each compound was observed through three-dimensional (3D) visualization of its electron density isosurface (contour 0.05 e Å À3 ), which supports understanding the mechanism involved in the energy transfer.

In this study, the effects of surface treatments of working anode with co-adsorbents such as chenodeoxycholic acid (CDCA) and TiCl 4 over efficiency and other photovoltaic parameters of dye-sensitized solar cell (DSSC) have been observed. The DSSC based on natural dye quercetin as sensitizer using quasi-solid polymeric electrolyte was fabricated. The improvement in power conversion efficiency () from 0.13% to 0.35% was well justified by increment in various photovoltaic parameters such as open circuit voltage (V oc ), short circuit density (I sc ) and fill factor (FF). The overall increment in power conversion efficiency after CDCA + TiCl 4 treatment was found to be around three times of the efficiency of untreated device. The use of polymeric electrolyte system consisting of I -/I 3 -redox moieties imparts stability to the devices, which is essential for the commercial potential.

Crystalline titanium oxide films with a thickness of 0.09–0.55 μm were prepared at temperatures below 500 °C by CVD using a mixture of titanium tetrachloride (TiCl4), carbon dioxide (CO2), and hydrogen (H2) as reactants. Film thickness decreased with increasing substrate temperature and CO2/H2 input. Nanosized microstructure was obtained at high CO2/H2 input due to the growth retardation of reacted HO‐TiCl3* by the unreacted TiCl4 and CO2. That film composition, i.e., the O/Ti ratio, increased with temperature and the CO2/H2 input can be explained by growth kinetics. Unlike film thickness, internal film stress increased with increasing substrate temperature. Adhesion was controlled by compressive internal stress due to the weak bonding between film and substrate. Two growth mechanisms are proposed to explain the tensile and compressive stress states in films produced by CVD. The adsorption‐controlled reaction has a film in compressive stress that increases with an increase in temper...

Dye-sensitized solar cells produce saturation of electrons and holes when exposed to high-intensity UV photons. These photon energies do not match the bandgap of the semiconductor materials, which not only degrades the dye and electrolyte but also disrupts the electron kinetics. In this work, graphene oxide (GO) was incorporated into TiO 2 to form a composite photoanode structure. The results indicated that a composite photoanode based on GO/TiO 2 enhanced the power conversion efficiency of a solid-state dye-sensitized solar cell (ss-DSSC) by 62% compared to that of pure TiO 2 . This enhancement is attributed to the high conductivity of graphene oxide. Further improvement in device performance was obtained by plasmonic luminescent down-shifting (LDS), where the UV region of the solar spectrum is shifted hundreds of nanometers. The multifunctional LDS coating layer was fabricated with a composite of ZnSe quantum dots and Ag nanoparticles. The experimental results demonstrated the ability of LDS to absorb photons at wavelengths below 400 nm and re-emit them at longer wavelengths (above 400 nm), where the cell has better photovoltaic response. When compared to a bare ss-DSSC, the power conversion efficiency (PCE) is enhanced by 37.62% for cells with a Ag/ZnSe coating layer. Moreover, the LDS-coated device exhibits 16.45% increased photon-to-current conversion efficiency compared to the LDS-free device for wavelengths lower than 500 nm. The 240-h aging tests confirmed that the LDS-coated ss-DSSC retained $ 83% of its original PCE value. This potential LDS coating layer not only leads to excellent device stability but also improves the cell performance, which increases the market value of the ss-DSSCs.

Light-driven water oxidation is an essential step for conversion of sunlight into storable chemical fuels. Fujishima and Honda reported the first example of photoelectrochemical water oxidation in 1972. In their system, TiO2 was irradiated with ultraviolet light, producing oxygen at the anode and hydrogen at a platinum cathode. Inspired by this system, more recent work has focused on functionalizing nanoporous TiO2 or other semiconductor surfaces with molecular adsorbates, including chromophores and catalysts that absorb visible light and generate electricity (i.e., dye-sensitized solar cells) or trigger water oxidation at low overpotentials (i.e., photocatalytic cells). The physics involved in harnessing multiple photochemical events for multi-electron reactions, as required in the four-electron water-oxidation process, has been the subject of much experimental and computational study. In spite of significant advances with regard to individual components, the development of highly ...

Linkers that favor rectification of interfacial electron transfer are likely to be required for efficient photo‐driven catalysis of multi‐electron reactions at electrode surfaces. Design principles are discussed, together with the synthesis and characterization of a specific pair of molecular linkers, related by inversion of the direction of an amide bond in the heart of the molecule. The linkers have a terpyridyl group that can covalently bind Mn as in a well‐known water oxidation catalyst and an acetylacetonate group that allows attachment to TiO2 surfaces. The appropriate choice of the sense of the amide linkage yields directionality of interfacial electron transfer, essential to enhance electron injection and slow back‐electron transfer. Support comes from electron paramagnetic resonance and terahertz spectroscopic measurements, as well as computational modeling characterizing the asymmetry of electron transfer properties.

Si 3 N 4 /MoS 2 nanocomposite has been fabricated through a solvothermal process and Mixed with polystyrenesulfonate-doped poly (3, 4-ethylenedioxythiophene) to prepare (Si 3 N 4 /MoS 2 -PEDOT: PSS) as a counter electrode (CE) for bifacial dye-sensitized solar cells (DSSCs). The electrochemical studies confirm that Si 3 N 4 / MoS 2 -PEDOT: PSS CEs exhibits higher catalytic activity compared with pristine Si 3 N 4 /MoS 2 and PEDOT: PSS. The DSSCs with 5% Si 3 N 4 /MoS 2 -PEDOT: PSS composite CE achieves conversion efficiency (PCE) of 7.16%, which is comparable to that of the conventional platinum CE (7.50%) and better than those of the pristine Si 3 N 4 / MoS 2 (3.80%) or PEDOT: PSS (4.20%) CEs. Owing to the optical transparency of Si 3 N 4 /MoS 2 -PEDOT: PSS composite CEs, bifacial DSSCs based on 5% Si 3 N 4 /MoS 2 -PEDOT: PSS CE yield 2.03% PCE from rear irradiation. The simple preparation method, high catalytic activity and electrochemical stability demonstrate that Si 3 N 4 / MoS 2 -PEDOT: PSS can be used a transparent CE in bifacial DSSCs.