Performance Of Dye Solar Cells Research Articles

Computational studies of the influence of auxiliary acceptors in the D-A'-π-A structure of organic dyes on the photovoltaic performance of dye solar cells.

A series of five organic dyes (Mi, i = 1-5) of the D-A'-π-A structure were designed based on reference dye (Ref), and the influence of different auxiliary acceptors (A') on their efficiency in dye-sensitized solar cells (DSSC). Was studied theoretically using density functional theory (DFT) and time-dependent DFT (TD-DFT) methods. In this context, the electronic structures, optical properties, and the parameters influencing the power conversion efficiency (PCE), such as light harvesting efficiency (LHE), electron injection driving force (∆Ginject.), and open circuit photo-voltage (VOC), have been evaluated and discussed.The modification of the auxiliary acceptor (A') in the D-A'-π-A structure of the designed organic dyes has the advantage of significantly decreasing the band gap, which leads to the broadening of the absorption band that is red-shifted and improves the photovoltaic characteristics compared to Ref. Theoretical results reveal that M1, and M5 can be used as excellent sensitizer candidates for DSSC applications.

Preparation and Performance of ZnO and ZnO/MnO<sub>2</sub> Nanostructures as Anode Electrodes in DSSCs

Nanoparticles and nanocomposites prepared by the hydrothermal method (ZnO, ZnO/MnO2) were used to build dye-sensitized solar cells (DSSCs), which were used as photoelectrodes using two natural dyes as the absorbent media: red (Hibiscus sabdariffa) and green (Apium graveolens). The results showed the efficiency of the green dye in DSSCs is superior to the red dye in terms of conversion efficiency (η). The purpose of the study is to improve the performance of dye solar cells. The properties of nanomaterials were studied by X-ray diffraction (XRD), scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM) for the analysis of ZnO NPs and ZnO/MnO2, whereas the sizes of the prepared materials are within the size of 1–100 nm. The solar cell parameters were obtained from simple (I-V) measurements for nanomaterials prepared using two-dye DSSCs where Isc represents the short circuit current through the solar cell when the voltage across the solar cell is zero, and Voc represents the open circuit voltage across the solar cell and is the maximum voltage available from the solar cell. The photoelectrochemical properties of the two dye DSSCs in this study were calculated at 22.53 mW/cm2 of the light intensity.

Predictive Modeling of Dye Solar Cell Degradation

Degradation of dye solar cell performance based on the early changes in electrolyte color is predicted, allowing to estimate the lifetime of the dye solar cells even before their efficiency declines. Previous predictive models commonly rely on regression analysis of the predicted parameter; thus, they are unable to capture degradation before a significant decrease in performance. Degradation tests, even when accelerated, may take thousands of hours. As such, recognizing degradation trends early can lead to rewarding cuts in the duration of solar cell development pipelines. With accurate lifetime predictions, researchers can steer materials research to reach longer lifetimes in shorter cycles. The predictive power of our model relies on color changes in the electrolyte that directly correlate with the concentration of tri‐iodide charge carriers within it, the loss of which is the predominant degradation mechanism for most liquid‐electrolyte dye solar cells. By linking the physical mechanisms inside the cell, which eventually start to degrade the performance of dye solar cells, an early prediction of the lifetime can be made even when the device performance still appears stable. It is exemplified with dye solar cells that integrating architecture‐specific knowledge on degradation mechanisms has potential to improve lifetime predictions for photovoltaics.

Effect of dye absorption time on performance of ZnO, TiO2 and ‎SnO2 nanoparticle photo-anodes in dye sensitized solar cell

Interior design, engineering, and the configuration of materials used in photo‏-‏anode systems play ‎key roles in the photovoltaic performance of dye solar cells.‎‏ ‏In this study, the photo-anodes of dye sensitized ‎solar cells were fabricated based on TiO2, ZnO and SnO2 nanoparticles separately using doctor Blade method ‎on the transparent conductive oxide as substrates, then sensitized with N719 dye. Due to the fact that the dye ‎plays the role of photon absorption, different photo‏-‏anode oxides were placed in a N719 dye solution over a ‎different time period.‎‏ ‏Based on current-voltage curve, efficiency parameter, short-circuit current density, ‎open circuit voltage, and fill factor of the cells were obtained. The results of current-voltage characterization ‎indicate that the best time for the N719 dye loading for the TiO2 and SnO2 layers is 20 h and for the ZnO layer ‎is 1 h.‎‎

Polyaniline (PANI)/reduced graphene oxide (rGO) composite as a counter electrode for dye solar cells.

Polyaniline (PANI)-reduced graphene oxide (rGO) based transparent counter electrodes have been fabricated for dye sensitized solar cells as an alternative to the expensive platinum (Pt) counter electrodes. Here, the graphene oxide (GO) added during the polymerization of PANI will subsequently reduce to rGO. The concentration of graphene oxide (GO) was varied in PANI matrix to optimize the performance of dye solar cell (DSC). With 1% GO addition in PANI, 9.68% current density was increased, consequently, 13.9% photocurrent density was found to be increased as compared to pure PANI. Electrochemical impedance spectroscopy (EIS) disclosed that the incorporation of 1% GO in PANI caused the double-layer capacitance to increase by 10 times compared to pure PANI. This implies that graphene is capable of enhancing the specific surface area and catalytic capacity of PANI. Optical transparency of PANI-1% GO counter electrode was found to be ∼67% between the wavelengths of 500 to 600 nm. Such transparency enables the construction of bifacial DSCs. Although the photo conversion efficiency (PCE) of DSC with PANI-1% GO counter electrode is still not comparable to the one with Pt counter electrode but it is sufficient to be considered as the replacement as it exhibits good photovoltaic performance and optical characteristics together with an exceptionally low cost material.

Applications of Taguchi Method for Optimization of Dye Solar Cell Design

This paper addresses the optimal Dye Solar Cell (DSC) design considering parameters namely TiO2 thickness, surface area, iodide concentration in electrolyte and TiO2 passivation layer thickness as they have influence on DSC performance. It aims to do the research of the practical use of Taguchi method in the optimization of DSC design in order to improve the performance of DSC. This work highlight on the integration of Taguchi method with simulation which showed that the optimal design of DSC is 10 μm thickness of TiO2, 90m2/g of TiO2 photoelectrode surface area, 1 M iodide concentration in electrolyte and two layers with 20 nm thickness of TiO2 passivation layer with efficiency of 4.59165. All the features of the Taguchi-based optimization were also discussed. © 2017, Penerbit Universiti Kebangsaan Malaysia. All rights reserved.

Tuning flat band potential of TiO2 using an electrolyte additive to enhance open circuit voltage and minimize current loss in dye sensitized solar cells

Electrolyte is an important component of dye sensitised solar cells (DSSC). Its composition, in particular, additives controls the energetic at the TiO2/dye/electrolyte interface, influencing the performance of dye solar cell. We report here for the first time the use of 8-Hydroxyquinoline (8HQ) as an electrolyte additive to replace costly, volatile 4-tert-butyl pyridine (TBP). Due to its unique structural feature containing hydroxyl and amine group, 8HQ results in remarkable difference in the energy band alignment at the TiO2/dye/electrolyte interface with respect to that of TBP, as revealed by photocurrent density and Mott-Schottky analysis. Apart from this band shift, 8HQ is very effective in suppressing back electron transfer resulting in enhancement in open circuit voltage. Compared to TBP, additive 8HQ resulted in ∼22% increase in Jsc, with minor loss in Voc (∼5.8%) and 15% increase in photoconversion efficiency with N3 dye. Overall, we found that 8HQ is a highly effective additive in tailoring the TiO2/dye/electrolyte interface which results in superior performance of dye sensitized solar solar cells as compared to cells with TBP as the additive.

Maximized performance of dye solar cells on plastic: a combined theoretical and experimental optimization approach

Maximizing the performance of dye solar cells on plastic using a combined theoretical and experimental optimization approach.

Simulation on the Performance of Dye Solar Cell Incorporated with TiO2Passivation Layer

Dye Solar Cell (DSC) has started to gain interest in the recent years for practical application because of its ecofriendly, low cost, and easy fabrication. However, its efficiency is still not as competitive as the conventional silicon based solar cell. One of the research efforts to improve the efficiency of DSC is to use the passivation layer in between the photoelectrode material and the conductive oxide substrate. Thus, the objective of this simulation study is to investigate the effect of passivation layer on the performance of DSC. Properties from literatures which are based on physical work were captured as the input for the simulation using process, ATHENA, and device, ATLAS, simulator. Results have shown that the addition of two-20 nm TiO2passivation layers on DSC can enhance the efficiency by 11% as the result of less recombination, higher electron mobility, and longer electron lifetime.

Multidirectional Light‐Harvesting Enhancement in Dye Solar Cells by Surface Patterning

One dimensional gratings patterned on the surface of nanocrystalline titania electrodes are used as a light harvesting strategy to improve the overall performance of dye solar cells under both frontal and rear illumination conditions. A soft‐lithography‐based micromoulding approach is employed to replicate a periodic surface relief pattern onto the surface of the electrode, which is later sensitized with a dye. As the patterned surface acts as an optical grating both in reflection and transmission modes, its effect is to increase the light path of diffracted beams within the absorbing layer when it is irradiated either from the electrode or the counter electrode for a broad range of angles of incidence on each surface. Full optical and photovoltaic characterization demonstrates not only the optical quality of the patterned surfaces but also the multidirectional character of the enhancement of light harvesting and conversion efficiency. The approach herein presented thus permits to preserve the operation of the cell when irradiated from its two faces while increasing its overall power conversion efficiency. This feature is a key advantage over other light harvesting efficiency enhancing methods, such as the deposition of a back diffuse scattering layer, in which the performance of the cell under illumination from one of its sides is enlarged at the expense of reducing the output under reverse irradiation conditions.

Modified Polyol-Mediated Synthesis of Doped TiO<sub>2</sub> Nanoparticles as the Photoanode in Dye Solar Cells (DSCs)

Synthesis of nanoscale TiO2 exhibiting specific properties of electron or ion conductivity is critical to improve the performance of dye solar cells (DSC). This paper presents the modified polyol-mediated synthesis of doped TiO2 nanoparticles. TiO2 samples were doped with cobalt (Co) and nickel (Ni) and the effects of calcination temperature (550 °C and 650 °C) on the crystallinity of pure samples were investigated. X-ray diffraction (XRD) analysis was used to determine the effect of dopant in lattice structure. The morphology and Crystal structure of TiO2 samples and their chemical analysis was conducted using scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectrometer respectively. Results show agglomeration of spherical particles in all doped samples. Crystal structure in the doped samples reveals modified phases and major crystal phase identical to anatase. It is observed that the molar ratio of water to metal can control the nucleation and growth and prevents significant agglomeration of nanoparticles. More effective doping was recorded for samples with 0.5 % concentration. Effective hydroxyl group is detected in both 0.5% Ni and Co promising good photocatalytic material. SEM images of 0.2% Ni-doped sample shows smallest average particle size.

Effect of Reflective Platinum Film on the Performance of Flexible Dye Solar Cell (DSC)

Robust and flexible dye solar cell (DSC) made up of nanocrystalline TiO2 encapsulated in polyethylene naphthalate (PEN) substrate will be able to fulfill the demand for indoor power applications as it has lower energy and manufacturing cost, produces electricity in low light conditions even under artificial light. The fabrication using PEN substrate has the advantage of scalability and compatible with the roll to roll manufacturing method. This paper reports the study on the effect of platinum film reflectance on the counter electrode to the DSC performance and efficiency. The reflective counter electrode uses the commercially available Pt/Ti PEN film with 100% reflectance properties. The transparent counter electrode with 20.9% reflectance is prepared using pre-treated indium doped tin oxide (ITO). The platinum film is sintered at 170°C followed by direct heat of 150°C to achieve a good bonding between the ITO and the deposited platinum film. Both cells uses TiO2 coated ITO PEN as the working electrode. The DSC test cell with reflective counter electrode increases the cell efficiency compared to the non-reflective counter electrode as there is a higher light spectrum response on the reflective DSC cell.

Improved performance of dye solar cells using nanocarbon as support for platinum nanoparticles in counter electrode

Carbon nanoparticles (CNPs) were used to support platinum nanoparticles as counter electrodes in dye-sensitized solar cells (DSCs). Carbon nanoparticles provided larger effective surface area and better exposure of Pt nanoparticles resulting in very efficient electrocatalytic performance as counter electrode. DSCs fabricated using such counter electrode showed enhanced efficiency owing to lower series resistance and higher fill factor as a result of reduced charge transfer resistance. The overall power conversion efficiency of the DSC devices using these CNP/Pt counter electrodes reached 8.12% as compared to 7.49% for reference platinum counter electrode DSCs under 1sun illumination.

Effect of electrolyte bleaching on the stability and performance of dye solar cells

Degradation of dye solar cells (DSCs) under severe ageing conditions may lead to loss of the tri-iodide in the electrolyte - a phenomenon known as electrolyte bleaching. Monitoring changes in the tri-iodide concentration as a result of degradation mechanisms and understanding their causes and effects are fundamental for improving the long-term stability of DSCs. In this contribution a strongly accelerated ageing test (1 Sun visible light, 1.5 Suns UV light, T = 110 °C for 12 h) was performed on DSCs in a double-sealed masterplate configuration to purposely induce severe electrolyte bleaching, and its effects on the performance and stability of DSCs with different initial tri-iodide concentrations [I3(-)]0 were investigated. The cells with low [I3(-)]0 suffered a severe loss in short circuit current density JSC (up to 85%). Also a significant loss of open circuit voltage VOC was observed and this loss was proportional to [I3(-)]0 with the highest VOC drop observed with the highest [I3(-)]0. Non-destructive analysis techniques based on the limited current density, JSCvs. light intensity, and photographic image analysis, were used to quantify the [I3(-)] loss, which was found to be ca. 50 mM and independent of [I3(-)]0. Quantitative model based VOC analysis in terms of changing [I3(-)] revealed that the degradation responsible for the VOC drop was dominated by an unknown mechanism that is unrelated to [I3(-)]0. The methods and results reported here help separating and identifying different degradation mechanisms related to electrolyte bleaching in DSCs.

Formulations and processing of nanocrystalline TiO2 films for the different requirements of plastic, metal and glass dye solar cell applications

We carried out a systematic study on the effect of nanocrystalline TiO2 paste formulations and temperature treatment on the performance of dye solar cells (DSCs) over a large temperature range, to provide useful information for the fabrication of both plastic and metal flexible devices. We compared conventional screen-printable and binder-free TiO2 pastes with a new formulation which includes hydroxylethyl cellulose (HEC), enabling the study of the effect of organic materials in the TiO2 layer in the whole 25–600 ° C temperature range. Differently from the binder-free formulations where the device efficiency rose monotonically with temperature, the use of cellulose binders led to remarkably different trends depending on their pyrolysis and decomposition thresholds and solubility, especially at those temperatures compatible with plastic foils. Above 325 ° C, where metal foil can be used as substrates, the efficiencies become similar to those of the binder-free paste due to effective binder decomposition and inter-nanoparticle bonding. Finally, we demonstrated, for the first time, that the simultaneous application of both temperature (110–150 ° C) and pressure (100 MPa) can lead to a large improvement (33%) compared to the same mechanical compression method carried out at room temperature only.

Spectral sensitization of TiO2 by new hemicyanine dyes in dye solar cell yielding enhanced photovoltage: Probing chain length effect on performance

New hemicyanine dyes having indole nucleus with different alkyl chain length were synthesized and characterized using 1H NMR and mass spectroscopy. These dyes were used to sensitize the TiO2 film in dye sensitized solar cell. Nanocrystalline dye solar cells were fabricated and characterized using various electrochemical techniques. It has been found that the alkyl chain length present in the dye molecules greatly affects the overall performance of dye solar cell. Molecules having longer alkyl chain are having better sensitizers which enhance Voc to significant extent. Chain length dependent performance was further investigated using Tafel polarization and impedance method. Hemicyanine dye having hexyl chain has outperformed by attaining 2.9% solar to electricity conversion efficiency.

Analysis of the Origin of Open Circuit Voltage in Dye Solar Cells.

Changes in the composition of the electrolyte are known to affect the parameters that determine the performance of dye solar cells. This paper describes a robust method for the analysis of the photovoltage in dye solar cells. The method focuses on the study of recombination resistance and chemical capacitance of TiO2 obtained from impedance spectroscopy. Four dye solar cells with electrolytes producing known effects on photovoltage behavior have been studied. Effects of conduction band shifts and changes in recombination rate in the photovoltage have been evaluated quantitatively.

Effect of Diffuse Light Scattering Designs on the Efficiency of Dye Solar Cells: An Integral Optical and Electrical Description

Herein, we present an integral optical and electrical theoretical analysis of the effect of different diffuse light scattering designs on the performance of dye solar cells. Light harvesting efficiencies and electron generation functions extracted from optical numerical calculations based on a Monte Carlo approach are introduced in a standard electron diffusion model to obtain the steady-state characteristics of the different configurations considered. We demonstrate that there is a strong dependence of the incident photon to current conversion efficiency, and thus of the overall conversion efficiency, on the interplay between the value of the electron diffusion length considered and the type of light scattering design employed, which determines the spatial dependence of the electron generation function. Other effects, like the influence of increased photoelectron generation on the photovoltage, are also discussed. Optimized scattering designs for different combinations of electrode thickness and electron diffusion length are proposed.

Effect of molecular filtering and electrolyte composition on the spatial variation in performance of dye solar cells

It is demonstrated that the molecular filtering effect of TiO 2 has a significant influence on dye solar cell (DSC) performance. As electrolyte is injected to a DSC, some of the electrolyte components adsorb to the surface TiO 2 (here 4- tert-butylpyridine and 1-methyl-benzimidazole) and accumulate near the electrolyte filling hole resulting in varying electrolyte composition and performance across the cell. The spatial performance distribution was investigated with a new method, the segment cell method. Not only is the segmented cell method simple and cheap when compared to the only other method for examining spatial variation (photocurrent mapping), it also has the major advantage of allowing the spatial variation in all other operating parameters to be assessed. Here the molecular filtering effect was to influence the cell performance in case of all the five studied electrolytes causing up to 35% losses in efficiency. Raman spectra indicated that the loss in photocurrent in the electrolyte filling was in correlation with the loss of thiocyanate ligands suggesting that dye regeneration may also be a significant factor in addition to electron injection in some of the cells. There were also shifts in the absorption spectra the photoelectrodes which further supported changes in the thiocyanate ligands. Besides absorption changes, there were additional shifts in the IPCE spectra which may relate to deprotonation of the dye. The efficiency losses were reduced to ∼10% with contemporary electrolyte compositions.

In situ image processing method to investigate performance and stability of dye solar cells

A simple and non-destructive method is introduced using image processing to investigate changes in the performance of the dye solar cells (DSCs). The main principle is based on the fact that the most important DSC components (dye, electrolyte, catalyst) have a specific color which often changes as result of degradation. Here the imaging technique is demonstrated in the case of exposing DSCs on very harsh conditions (85 °C temperature and UV + Visible light). The aging of the cells was recorded with a color sensitive camera in a well regulated setup and the photographs were processed using image analysis techniques. A key factor in making the imaging method quantitative and suitable for aging studies is color calibration which is explained in detail. The image analysis of different cell configurations revealed that the bleaching reactions of the electrolyte were related to reactions between TiO2 and the electrolyte. The dye layer on the TiO2 was shown slow down the degradation. Furthermore the comparison of image analysis and current–voltage curves indicated that the performance degradation of the cells was only partly due to loss of tri-iodide. The loss of photocurrent and photovoltage was apparently largely due to the harmful effect of the by-products of the bleaching and/or the degradation of the dye. In addition, a small recovery effect due to the generation of tri-iodide under reverse bias condition was seen in both image analysis and electrical measurements.