Photoelectrodes In Dye-sensitized Solar Cells Research Articles

Characterization of graphene–TiO2-deposited semi-organic solar cell

High energy supply is critical, particularly in developing countries, to maintain lifestyles as the world's population and technological-economic metropolis grow. Solar photovoltaic cells have been used as an alternative to generate renewable, sustainable, and green energy for the past two decades. In general, the materials employed in the photoanode part are critical to manufacturing high-efficiency solar cells with 14–18% efficiency. A simple and successful method has been discovered for creating a film composed of graphene sheets and 99.8% pure anatase titanium oxide (TiO2) nanoparticles. After sensitization, the films were tested as photoelectrodes for dye-sensitized solar cells. The experimental results show that using an optimized graphene material considerably improves the power conversion efficiency of the cells, resulting in a 45% increase in short-circuit current density ( JSC). This study uses capsician as a bonding agent to enhance the current density of a graphene–TiO2 based semi-organic solar cell. The mechanical and electrical properties of the cell are investigated using a scanning electron microscope, energy dispersive X-ray, and Corescan.

Enhancing Photovoltaic Performance with BaTiO3/MWCNTs Composite Photoelectrodes in Dye-Sensitized Solar Cells

Dye-sensitized solar cells (DSSCs) have attracted renewed research interest as a potential low-cost substitute for conventional silicon photovoltaics. This work aims to improve the photovoltaic performance of the DSSCs by incorporating multi-walled carbon nanotubes (MWCNTs) into the BaTiO3 photoelectrode. The pure BaTiO3 and BaTiO3/MWCNT nanocomposites were sensitized with N719 dye and fabricated into solar cell devices for testing. The structural characterization confirmed the successful formation of the nanocomposite with an optimal dispersion at 6% of MWCNT incorporation, beyond which agglomeration effects manifested. The optical analysis verified the modulation of defect states and bandgap engineering induced by the MWCNT network. The morphological studies revealed irregular nanoparticle clusters with embedded nanotubes. Solar cell testing under AM1.5G-simulated sunlight demonstrated a peak power conversion efficiency of 4.044% for 6% of MWCNT doping, constituting a 6-fold increment versus pure BaTiO3 (0.693%). It originated from the simultaneous enhancements in the open-circuit voltage and short-circuit current enabled by the favorable band structure alterations and percolation-assisted charge transport. However, further increasing MWCNT content deteriorated the device metrics, owing to emerging limitations like trapping. The rational integration of multi-walled carbon nanotubes with lead-free ferroelectric metal oxides can contribute to the development of emerging organic-inorganic hybrid solar platforms.

Charge Transfer Dynamics in Organic-Inorganic Hybrid Heterostructures-Insights by Vibrational-Sum Frequency Generation Spectroscopy.

Organic-inorganic heterostructures play a pivotal role in modern electronic and optoelectronic applications including photodetectors and field effect transistors, as well as in solar energy conversion such as photoelectrodes of dye-sensitized solar cells, photoelectrochemical cells, and in organic photovoltaics. To a large extent, performance of such devices is controlled by charge transfer dynamics at and across (inner) interfaces, e.g., between a wide band gap semiconductor and molecular sensitizers and/or catalysts. Hence, a detailed understanding of the structure-dynamics-function relationship of such functional interfaces is necessary to rationalize possible performance limitations of these materials and devices on a molecular level. Vibrational sum-frequency generation (VSFG) spectroscopy, as an interface-sensitive spectroscopic technique, allows to obtain chemically specific information from interfaces and combines such chemical insights with ultrafast time resolution, when integrated as a spectroscopic probe into a pump-probe scheme. Thus, this minireview discusses the advantages and potential of VSFG spectroscopy for investigating interfacial charge transfer dynamics and structural changes at inner interfaces. A critical perspective of the unique spectroscopic view of otherwise inaccessible interfaces is presented, which we hope opens new opportunities for an improved understanding of function-determining processes in complex materials, and brings together communities who are devoted to designing materials and devices with spectroscopists.

Light absorption enhancement in dye-sensitized solar cells using thin nanostructured photoelectrodes

As thin-film solar cells are the attraction of many research works nowadays, dye-sensitized solar cells (DSSCs) among other types hold the promise of excellent cost/performance ratio because of the relatively low material costs and simple processing conditions. In order to improve its relatively low performance, different approaches are being explored to enhance the photon-to-current conversion efficiency. Notably, one of the most accessible approaches is by modifying the optical characteristics of the photoelectrode of DSSCs to improve light trapping within the cell. Here, we introduce a cost-effective nanopatterning process done on the photo-active TiO2 photoelectrode layer for better light absorption. This simple technique resulted in increased cell short-circuit current density (from 4.664 to 5.963 mA/cm2) which consequently enhanced cell efficiency (from 2.243 to 2.819%). Furthermore, without compromising the absorption significantly, nanopatterned photoelectrodes with a smaller thickness can lead to reduced material costs and possibly allowing the construction of semitransparent cells. This work can contribute to an attainable efficient DSSC manufacturing route for practical applications.

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

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

Photo-electrodes decorated with carbon quantum dots: Efficient dye-sensitized solar cells

In this study, the blue and green carbon quantum dots (CQDs) are synthesized and applied to the photo-electrodes of dye-sensitized solar cells (DSSCs). The DSSCs exhibited high power conversion efficiency because of the conversion of ultraviolet to the visible region in photo-anode, and good catalytic activity in the photo-cathode. The blue color CQDs (BCQDs) and green color CQDs (GCQDs) are synthesized from the citric acid in a single pot process. We examine the influence of both CQDs decorated on photo-anode and photo-cathode and both photo-electrodes on the photovoltaic performance of the DSSCs. Furthermore, the DSSCs are studied by electrochemical impedance spectroscopy, cyclic voltammetry, and Tafel polarization data to study the charge transfer kinetics. The better performance observed from the DSSCs due to enhanced charge carrier collection through the CQDs. The photovoltaic results of DSSCs shown that the best efficiency shown by DSSC, which fabricated by both photo-electrodes decorated by CQDs.

A theoretical exploration of catechol sensitization of C-doped bronze TiO2 surfaces for photochemical systems

Doping with atom impurities is currently an attractive mechanism to enhance the optical absorption capacity of TiO2 and other inorganic oxide semiconductors. In this work, the electronic and optical properties of carbon-doped TiO2(B) (100) ultrathin surfaces were investigated using density functional theory (DFT) calculations, with the aim of evaluating their potential as photoelectrode for dye-sensitized solar cells (DSSCs). Carbon impurities were introduced onto oxygen sites located in the proximity of the surface and catechol was employed as a sensitizer model, focusing our study mainly on the evolution of the semiconductor’s electronic structure. The reduction of the band gap energy resulting from impurity states within the valence band of C-doped TiO2(B) was confirmed. Moreover, our findings suggest that C doping not only induces a stronger interaction between the catechol molecule and the surface but also, could increase the light absorption capacity of the material. Thus, carbon-doped TiO2(B) could act as a promising semiconductor for DSSCs and other photochemical systems.

Enhancing Dye-Sensitized Solar Cell Performance with Different Sizes of ZnO Nanorods Grown Using Multi-Step Growth

In this study, we employed a chemical solution method to grow zinc oxide (ZnO) nanorods on SnO2:F (FTO) substrates as photoelectrodes for dye-sensitized solar cells (DSSCs). The influence of varying ZnO nanorod dimensions on cell performance was investigated. Specifically, we explored the effects of nanorod length and diameter on dye adsorption capacity and photovoltaic conversion efficiency. Characterization techniques such as electrochemical impedance spectroscopy (EIS), X-ray diffraction (XRD), and field-emission scanning electron microscopy (FE-SEM) were utilized to analyze the ZnO nanorods. Our results demonstrate that the sequential growth technique allows for control over the length and diameter of ZnO nanorods, thereby modulating their optoelectronic properties. XRD and FE-SEM analyses revealed that the surface morphology of the ZnO nanorods impacts dye adsorption capacity and photovoltaic conversion efficiency. EIS measurements further indicated a significant influence of dye adsorption on the electron lifetime of ZnO nanorods. Overall, this study highlights the potential of multi-step growth of ZnO nanorods to optimize the performance of dye-sensitized solar cells by tuning their morphology and surface properties.

Investigation on short–circuit current density (Jsc) in the dye-sensitized solar cells by optimizing photoelectrode thickness

The photoelectrode of dye-sensitized solar cells (DSSC) is a vital part that loads the dye, transports the generated photoelectrons to the external load, and serves as an interface between the current collector and the dye. The performance of the DSSCs is highly influenced by the thickness of the photoelectrode. The short-circuit current density (Jsc) of the DSSC increases with thickness and reaches its maximum at a particular thickness, after which Jsc decreases and saturates. A theoretical approach is formulated, using which the optimal thickness required to obtain maximum Jsc for the DSSC is calculated. A novel analytical expression for optimal diffusion length (L0), which is the electron diffusion length required to maximize Jsc is derived. The experimental validation of the simulated results is carried out with DSSCs of varying photoelectrode thickness. These validation results suggest that this theoretical approach to determine the optimal thickness of photoelectrodes enhances the efficiency of dye-sensitized solar cells.

The Addition of C, Zn-C and Sn-C on Anatase Titanium Dioxide (TiO2) for Dye-Sensitized Solar Cells Application

DSSC (dye-sensitized solar cell) is a third-generation photovoltaic technology that can convert solar energy into electric current using a photoelectrochemical mechanism. Photoelectrode is one of the significant elements in DSSC, where photoexcited electrons are generated, and serves as an electron transport medium. Anatase titanium dioxide (TiO2) is often used as photoelectrode material because of its excellent photoactivity, high stability, non-toxicity, environmental friendliness, and low price. Many DSSC modifications have been conducted to overcome the efficiency limitations in DSSC, and one of them is carried out by modifying the TiO2 via doping. In this study, TiO2 doped with C and co-doping with Zn (Zn-C) and Sn (Sn-C) were prepared using sol-gel reactions, and they were subsequently applied and tested as photoelectrode in DSSC. The results showed that undoped and doped TiO2 had a porous spherical morphology with inhomogeneous particle sizes. The addition of C, Zn-C and Sn-C dopants has reduced in the crystallite size and the band gap energy of TiO2. The efficiency of DSSC with undoped TiO2 DSSC was 3.83%, while the best performance was obtained from DSSC C-TiO2 with an efficiency of 4.20%. In contrast, the DSSC with Zn-C-TiO2 and Sn-C-TiO2 co-doping produced unexpectedly lower efficiency of 0.71% and 0.85%, respectively.

Hoisting photovoltaic performance of perovskite BaSnO3 nanoparticles wrapped reduced graphene oxide: Efficient photoelectrode for dye-sensitized solar cell

Inorganic perovskite nanostructure photoanode has a very important role in dye-sensitized solar cells (DSSC),in collecting photogenerated electrons coming from dye sensitizer. The photo-electric-conversion efficiency of photoelectrode is hindered by an effective photogenerated electron hole/pair. To avoid this problem, modification of BaSnO3 perovskite nanoparticles with graphene nanosheets is attempted in our work. Facile one-step synthesis of RGO loaded BaSnO3 (RGO-BaSnO3 NC) was done by simple solution route. As-prepared perovskite composite was studied using characterization techniques namely Raman spectroscopy, high-resolution transmission electron microscopy (HR-TEM) and field emission scanning electron microscopy (FE-SEM). The photovoltaic performances of RGO-BaSnO3 NC-based photoanode in DSSC employing N719 dye, Pt-counter electrode and imidazole-based liquid electrolyte have been studied under standard simulated lighting of 100 mW cm−2. It was found that RGO-BaSnO3 NC showed better dye adsorption to facilitate light harvesting and promoted a proficient electron transport pathway owing to fewer electron trapping sites on the surface than the pristine BaSnO3 NPs surface. The results demonstrate that the fabricated DSSC made with RGO-BNC-based photoanode delivered overall photoelectric conversion efficiency of 5.59 %, which is 32 % higher than that of DSSC fabricated unmodified BaSnO3 photoanode.

Delafossite CuCoO2/ZnO derived from ZIF-8 heterojunctions as efficient photoelectrodes for dye-sensitized solar cells.

To achieve high-performance dye-sensitized solar cells (DSSCs), it is essential to establish new and effective photoelectrode materials. Herein, we report the successful synthesis of heterojunctions including Cu-based delafossite oxide CuCoO2 and ZnO derived from zeolitic imidazolate framework-8 (ZIF-8). The layered polyhedral nanocrystals of CuCoO2 produced through a feasible low temperature hydrothermal process and the faceted nanocrystals of ZnO were achieved by heat treatment of ZIF-8. The composite heterostructures were applied as photoelectrodes in DSSCs assembled using dye N719 and a Pt counter electrode. The physicochemical characteristics (XRD, FESEM, EDAX, mapping, BET, DRS), dye loading, and photovoltaic properties (J-V, EIS, IPCE) of the fabricated materials were studied and fully discussed. Results revealed that addition of CuCoO2 to ZnO significantly improved the Voc, Jsc, PCE, FF, and IPCE. Among all cells, CuCoO2/ZnO (0.1 : 1) showed the best performance (PCE = 6.27%, Jsc = 14.56 mA cm-2, Voc = 687.84 mV, FF = 62.67%, IPCE = 45.22%) and acted as a promising photoanode in DSSCs.

KNbO3 photoelectrode for DSSC: a structural, optical and electrical approach.

In this work, we present the potassium niobate (KNbO3) nanoparticles as a suitable mesoporous photoelectrode for dye-sensitized solar cells (DSSCs). The KNbO3 particles were synthesized by the microwave-assisted hydrothermal method using mild conditions and characterized by SEM, XRD, Raman, and UV-Vis diffuse reflectance. The particles presented a pyramidal tower-like shape with an orthorhombic structure and an indirect bandgap of (3.0 ± 0.1) eV. Dye-sensitized solar cells were assembled using the synthesized KNbO3 nanoparticles, which were deposited as a photoelectrode on a TiO2 recombination charge blocking layer. It is noticeable that the synergistic operation of the TiO2 blocking layer and KNbO3 photoelectrode is essential to achieve photovoltaic behaviour in our solar cells. The short-circuit current density of Jsc = 2.82 mA, open-circuit voltage Voc = 669 mV, fill factor FF = 0.62, and a power conversion efficiency PCE = 1.17%, reports elevated parameters if compared to other DSSCs alternative materials, becoming potassium niobate suitable as photoelectrode.

High performance photoelectrodes prepared using Au@P3HT composite nanoparticles for dye-sensitized solar cells

In this study, gold (Au) and poly(3-hexylthiophene) (P3HT) composite nanoparticles (Au@P3HT) are synthesized and applied to modify the photoelectrodes of dye-sensitized solar cells (DSSCs). The modification is carried out by adsorption of Au@P3HT onto the electrode surface. The experimental results show that the Au@P3HT nanoparticles demonstrate a spherical shape with a mean diameter of 6 nm. The analysis of X-ray photoelectron spectroscopy indicates that the P3HT strongly interact with Au, protecting the Au particles from the corrosion of iodide electrolytes. Scanning electron microscope analysis reveals that the Au@P3HT nanoparticles adsorb strongly and uniformly on the mesoporous TiO2 photoelectrode. The UV–vis absorption spectrum shows that the Au@P3HT-modified photoelectrode can enhance the light absorption in the long wavelength region, attributed to the plasmon resonance effect of Au nanoparticles. It also demonstrates that the modification of Au@P3HT not only improves the incident photon to current conversion efficiency but also increases the recombination resistance at the photoelectrode/electrolyte interface. Therefore, the corresponding cell has higher current density and open-circuit voltage. By way of this method, the DSSC can achieve an energy conversion efficiency of 9.34%. The non-corrosive characteristics of the Au@P3HT-modified electrode against the iodide liquid electrolyte improve the durability of the DSSCs.

Water-Induced Fine-Structure Disorder and Its Effect on the Performance of Photoelectrodes in Dye-Sensitized Solar Cells

Water-Induced Fine-Structure Disorder and Its Effect on the Performance of Photoelectrodes in Dye-Sensitized Solar Cells

Preparation of ZnO compact layer using vacuum ultraviolet for dye-sensitized solar cells

Vacuum ultraviolet (VUV) light with a wavelength of 172 nm has the capacity to convert the oxygen contained metal organic precursor into metal oxide. Here, zinc acetate precursor thin film is directly converted into ZnO thin film by the irradiation of 172 nm VUV light rather than the high temperature sintering. The converting processes were demonstrated by the measurements of FTIR, XRD, SEM and XPS. And then the effect of irradiating time on the morphology, thickness and transparence of the prepared ZnO thin films was discussed. The ZnO thin film was further used as the compact layer in the photoelectrode of dye-sensitized solar cell (DSSC) to suppress the recombination processes of photogenerated electrons on the conducting glass electrode. For the different irradiation times, the photoelectric conversion efficiency of DSSC based on the compact layer prepared by the irradiation for 30 min is the highest reaching 10.27%, which is also higher than that of DSSCs without the compact layer and even with the compact layer prepared by the high temperature sintering. The uniform, dense, pinhole-free and amorphous ZnO thin film on the conducting glass substrate can be successfully prepared using the VUV irradiation technology for the compact layer of DSSCs.

Non-destructive Monitoring of Dye Depth Profile in Mesoporous TiO2 Electrodes of Solar Cells with Micro-SORS.

The dye distribution within a photo-electrode is a key parameter in determining the performances of dye-sensitized photon-to-electron conversion devices, such as dye-sensitized solar cells (DSSCs). A traditional, depth profiling investigation by destructive means including cross-sectional sampling is unsuitable for large quality control applications in manufacturing processes. Therefore, a non-destructive monitoring of the dye depth profile is required, which is the first step toward a non-destructive evaluation of the internal degradation of the device in the field. Here, we present a conceptual demonstration of the ability to monitor the dye depth profile within the light active layer of DSSCs by non-destructive means with high chemical specificity using a recently developed non-destructive/non-invasive Raman method, micro-spatially offset Raman spectroscopy (micro-SORS). Micro-SORS is able to probe through turbid materials, providing the molecular identification of compounds located under the surface, without the need of resorting to a cross-sectional analysis. The study was performed on the photo-electrode of DSSCs. This represents the first demonstration of the micro-SORS concept in the solar cell area as well as, more generally, the application of micro-SORS to the thinnest layer to date. A sample set has been prepared with varying concentrations of the dye and the thickness of the matrix consisting of a titanium dioxide layer. The results showed that micro-SORS can unequivocally discriminate between the homogeneous and inhomogeneous dye depth profiles. Moreover, micro-SORS outcomes have been compared with the results obtained with destructive time-of-flight secondary ion mass spectrometry measurements. The results of the two techniques are in good agreement, confirming the reliability of micro-SORS analysis. Therefore, this study is expected to pave the way for establishing a wider and more effective monitoring capability in this important field.

Light Absorption Enhancement Using Graphene Quantum Dots and the Effect of N-719 Dye Loading on the Photoelectrode of Dye-Sensitized Solar Cell (DSSC)

Graphene quantum dots (GQDs) is used to enhance light absorption in the visible region of DSSC by sensitising method. The used of GQDs in photoelectode may effect the N-719 dye loading on photoelectrode and the study is done by ultraviolet spectroscopy (Uv-Vis). Initially, the TiO2 photoelectrode films is sensitised in ∼5 nm GQDs to overcome TiO2 photoelectrode drawback such as random electron transport and short-circuit current. Then, photoelectrode films is sensitised in N-719 dye to excite the electrons in TiO2 film. PG 7.5 adsorbed only 0.103 x 10-7 mol cm-2 N719 dye while PT at 0.527 x 10-7 mol cm-2. The pristine TiO2 photoelectrode (PT) adsorbed more than 80.4% of N-719 dye compared to PG 7.5 photoelectrode and other TiO2-GQDs photoeletrodes (PG 2.5, PG 5.0 and PG 10). As a result, the used of GQDs for TiO2 photoelectrode is reduced the intake of expensive N-719 dye for DSSCs. This happened because some of the functional groups in the GQDs solution such as hydroxyl and carboxyl groups are biocompatible with TiO2 which allows more adsorption sites of GQDs onto TiO2 surface. Thus, after GQDs molecules were occupied on the TiO2 surface, not many sites were available for N719 dye molecule. Therefore, it might reduce the N719-dye intake in the DSSC device, which can reduce the fabrication cost of DSSC and give good impact on environment.

Enhanced adsorption on TiO2 photoelectrodes of dye-sensitized solar cells by electrochemical methods dye

Dye-adsorption is an important step in the fabrication of dye-sensitized solar cells (DSSCs). The classical dye-adsorption method is performed by spontaneous process and, to obtain the optimal cell efficiencies, about 16–24 h are required, which is considered uneconomical for the mass production of DSSCs. To solve this problem, here, a quick dye adsorption process based on electrochemical methods including cyclic voltammetry, constant potential, and constant current techniques are the first time utilized to prepare photoelectrodes for DSSC applications. To obtain the optimal cell efficiencies, the experimental conditions are regulated. Among these methods, the electrodes prepared using the constant potential methods (3 V and 4 V for 60 and 30 min, respectively) have high performance in DSSCs under room light and one-sun conditions. This method significantly reduces the time for dye adsorption from 16 to 24 h to 30 min or ~ 1 h. The cells using these electrodes have high incident photon to current efficiencies, high recombination resistances, high electron lifetimes, and low dark current densities. Owing to these characteristics, the DSSCs achieve efficiencies as high as 8.27% and 14.49%, respectively, under one-sun and room light conditions. These efficiencies are identical to that of the efficiencies obtain for the cells prepared using the classical adsorption process.

Paste Aging Spontaneously Tunes TiO2 Nanoparticles into Reproducible Electrosprayed Photoelectrodes.

In this study, the spontaneous microstructure tuning of TiO2 was observed by aging the ethanol/water TiO2 paste for up to 20 days at ambient conditions. A dynamic light scattering study reveals that it formed the outstanding reproducible TiO2 microstructure with a ∼200 nm average particle size and stabilizes in 6 to 20 days under an ambient atmosphere. Interestingly, the as-deposited day 15 sample spontaneously changed its crystallinity upon keeping the paste at ambient conditions; meanwhile the day 0 sample showed an amorphous structure. A dense, uniform, and stable TiO2 electrode was cast on a fluorine doped-tin oxide substrate using the electrospray technique. We exploit the spontaneous evolution of the TiO2 nanopowder to revisit the fabrication procedure of the TiO2 photoelectrode for dye-sensitized solar cells (DSSCs). The controlled microstructure TiO2 film was used in DSSCs, which, to the best of our knowledge, achieved the highest power conversion efficiency of 9.65% using N719 dye in sensitizing the TiO2 photoanode.