Behavior Of Dye-sensitized Solar Cells Research Articles

A novel thermoelectrical model for dye-sensitized solar cells for consideration of the effects of solar irradiation, wavelength, and surface temperature

The present study aims to provide an innovative model to simulate the behavior of dye-sensitized solar cells, considering their advantages and the emerging technology of cells. The new model uses carrier particle continuity equations and the Butler-Volmer equation to examine the effects of solar radiation, wavelength, and temperature on cell performance. Power Conversion Efficiency (PCE) is studied for sunny and cloudy days (7 am to 6 pm) based on input and output power. Parametric changes, including fill factor, open circuit voltage, and short circuit, are calculated in this regard. The good agreement observed between the outcomes of previous studies and the results obtained here emphasizes the reliability of the proposed model. As a striking novelty, the impact of transparent conductive oxide (TCO) recombination current on cell performance parameters is also examined using the Butler-Volmer equation under normal and diffuse radiation (low light). The results reveal that the effect of recombination current is more significant for diffuse radiation conditions than the clear sky (sunny day). For example, the efficiency and voltage drop are higher for the cloudy mode. The sunny weather has a reduction of about 0.2 % in efficiency, while the same state for the cloudy weather is about 1.8 %.

Development of Y2O3: Ho3+/Yb3+ Upconverting Nanophosphors for Enhancing Solar Cell Efficiency of Dye-Sensitized Solar Cells

Light scattering behavior of dye-sensitized solar cells (DSSCs) containing Y <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> : Ho <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> /Yb <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> upconverting (UC) nanophosphor has been studied. To study the influence of UC nanophosphors on photovoltaic performance of DSSCs, UC nanophosphors have been introduced into the TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> film to form the hybrid film. The electron ejection ability, current density (JSC ), open-circuit voltage (VOC ), and power conversion efficiency (PCE) of DSSCs have been determined. The enhancement of about 31% and 30% for JSC and PCE in DSSCs hybrid film compared with that of DSSCs TiO2 film has been observed due to improved near infrared to visible light harvesting properties of UC nanophosphors.

Direct Comparison of Electron Transport and Recombination Behaviors of Dye-Sensitized Solar Cells Prepared Using Different Sintering Processes

Flexible dye-sensitized solar cells on plastic substrates have achieved a conversion efficiency of 8.6% with the hot compression technique (<150 °C). However, the value of efficiency is only 70% of that achieved using glass substrates with high-temperature sintering technique (500 °C). Investigating the origin of this difference is a critical step for further improving the performance of plastic dye-sensitized solar cells. In this study, an optimized ternary viscous titania paste without the addition of organic binders enables the fabrication of efficient dye-sensitized solar cells with a low-temperature process. Therefore, the electron-transport behavior of dye-sensitized solar cells can be directly compared with those prepared with the high-temperature sintering technique. In addition to the structural and optical differences, the hot compressed photoanode of dye-sensitized solar cells have an electron diffusion coefficient that is 2 times smaller and a recombination time that is 6 times shorter than th...

Effect of Extraction Time and Concentration of Crocus sativus on Behavior of Dye-Sensitized Solar Cells

Different concentrations of saffron (Crocus sativus) spice in ethanol have been used as dye material in dye-sensitized solar cells (DSSCs). The photovoltaic system prepared by adding one gram of saffron spice powder in 50-mL ethanol for 7 days showed the best efficiency (η) of 0.11% with short-circuit current density (J sc) of 0.50 mA cm−2, open-circuit voltage (V oc) of 0.39 V, and fill factor (FF) of 0.56. Increasing extraction time to 60 days witnessed the increase in J sc to 0.72 mA cm−2, V oc to 0.44 V, and FF to ~0.90. The efficiency increased by ~86%. Charge transfer resistance was lowest and J sc was highest in DSSCs with highest efficiency.

Effect of casting condition on the porosity of polymer membrane and its impact on the photoelectrochemical behavior of dye-sensitized solar cells

The present study demonstrates the effect of casting conditions (relative humidity and temperature) on morphology of poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) membranes prepared from solution of the co-polymer in tetrahydrofuran (solvent) and water (non-solvent and pore former). Membranes with thicknesses of 4–6 μm have been obtained by doctor blade casting under different conditions. High-temperature cast membranes yield less porous membranes. Low-temperature casting results in a maximum of 52 % (surface) porosity of membranes. High relative humidity (80 %) during casting results in bigger pore size in membrane than low relative humidity. Membranes containing liquid electrolyte have been subjected to testing in dye-sensitized solar cells as quasi-solid electrolytes. A maximum photo-conversion efficiency of 2.5 % for 1 cm2 active area has been achieved in membrane-based cells as compared to 2.8 % for cells having liquid electrolyte. High-temperature cast membranes result in poor performance due to hindrance in the charge transport.

Influence of 4-tert-butylpyridine/guanidinium thiocyanate co-additives on band edge shift and recombination of dye-sensitized solar cells: experimental and theoretical aspects

The co-additives of 4-tert-butylpyridine (TBP) and guanidinium thiocyanate (GuSCN) in electrolytes can prominently affect the photovoltaic behavior of dye-sensitized solar cell (DSSC) due to their advantages fitting with energy levels and charge transfer. Mott-Schottky analysis is used to quantify the TiO2 band edge movement to clarify the change of open-circuit voltage. The corresponding kinetic investigations are carried out using cyclic voltammetry, electrochemical impedance spectroscopy, intensity modulated photocurrent/photovoltage spectroscopy and charge extraction. Theoretically, the density functional theory (DFT) method is performed to explore the details of the adsorption, including the interacting energy, Fermi energy and frontier orbitals properties. The results show that the frontier orbitals between TBP and TiO2 are sufficiently overlapped to induce the negative shift of Fermi energy, increasing the open-circuit voltage. The Gu(+) cations can be tightly absorbed on TiO2 surface to by electrostatic attraction form a passivated layer due to the Coulomb attraction, depressing the recombination rate and improving the short-circuit photocurrent. The different proportion of TBP and GuSCN would produce a competitive effect, which would be caused by their volume and electrostatic effect. The photovoltaic performance might be as a result of a synergistic effect of co-additives. DSSC based on the optimal molar ratio (9: 1) of TBP and GuSCN achieves its optimized short-circuit current density of 13.74 mA cm(-2), open-circuit voltage of 0.74 V, fill factor of 0.70 and overall efficiency of 7.12%. (C) 2015 Elsevier Ltd. All rights reserved.

Modulation of photovoltaic behavior of dye-sensitized solar cells by electron donors of porphyrin dyes and cosensitization

Abstract Porphyrin dyes have received great attention due to their excellent photovoltaic performance in dye-sensitized solar cells (DSSCs). In this work, dyes XC1 – XC3 were synthesized by introducing various numbers of bis(4-methoxyphenyl)amino and p -hexyloxyphenyl groups to porphyrin meso -positions. The XC1 molecule contains two p -hexyloxyphenyl groups, and its DSSCs showed the power conversion efficiency of 4.81%. For XC2 and XC3 , the replacement of p -hexyloxyphenyl with diphenylamino groups can effectively enhance the light harvesting around 500 nm. However, the highest occupied molecular orbitals (HOMOs) were elevated too much, which suppressed the dye regeneration processes, leading to low cell efficiencies of 2.51% and 1.27% for XC2 , and XC3 , respectively. To further improve the cell performance, an anthracene derivative C1 was used as the cosensitizer for XC1 , which increased both the J sc and V oc values, with an improved efficiency of 5.75%.

Consistent static and small-signal physics-based modeling of dye-sensitized solar cells under different illumination conditions

A numerical device-level model of dye-sensitized solar cells (DSCs) is presented, which self-consistently couples a physics-based description of the photoactive layer with a compact circuit-level description of the passive parts of the cell. The opto-electronic model of the nanoporous dyed film includes a detailed description of photogeneration and trap-limited kinetics, and a phenomenological description of nonlinear recombination. Numerical simulations of the dynamic small-signal behavior of DSCs, accounting for trapping and nonlinear recombination mechanisms, are reported for the first time and validated against experiments. The model is applied to build a consistent picture of the static and dynamic small-signal performance of nanocrystalline TiO2-based DSCs under different incident illumination intensity and direction, analyzed in terms of current-voltage characteristic, Incident Photon to Current Efficiency, and Electrochemical Impedance Spectroscopy. This is achieved with a reliable extraction and validation of a unique set of model parameters against a large enough set of experimental data. Such a complete and validated description allows us to gain a detailed view of the cell collection efficiency dependence on different operating conditions. In particular, based on dynamic numerical simulations, we provide for the first time a sound support to the interpretation of the diffusion length, in the presence of nonlinear recombination and non-uniform electron density distribution, as derived from small-signal characterization techniques and clarify its correlation with different estimation methods based on spectral measurements.

Electrochemical Characterization of the Dye-Sensitized Solar Cells

Dye-Sensitized Solar cells (DSSC) has had considerable interest to be a promising solar energy conversion device. In order to improve the performance and long term stability of the DSSC, it is essential to understand the characteristics of DSSC. Various electrochemical experiments were conducted to evaluate DSSC characteristics. Variation in internal interfaces and/or components of DSSC due to exposure time, light intensity and ambient temperature were monitored. Different illumination conditions affected open circuit voltage, short circuit current and fill factor. Change in behavior of DSSC was observed when test conditions were switched from open circuit voltage conditions to potential cycling conditions. Electrochemical impedance spectroscopy (EIS) was selected to scrutinize the interfacial charge transfer resistance variation. Equivalent circuit model for EIS results illustrated that charge transfer resistance at Pt counter electrode was mainly affected by both Voc conditions and potential scanning with same irradiation intensity in the aging study.

The degradation of dye sensitized solar cell in the presence of water isotopes

The effects of water content on the degradation behavior of dye-sensitized solar cells were studied by adding water isotopes (H 2O, D 2O, and H 2 18O) to the electrolytes. Time-dependent photovoltaic performance of the water-added DSSCs was monitored accompanied with the diffuse-reflectance infrared Fourier transform (DRIFT) technique and electrochemical impedance spectroscopy (EIS) measurement. DRIFT technique was utilized to study the chemical reactions that occurred on the working electrodes (TiO 2). EIS was implemented to evaluate the effects of the charge-transfer resistance at the interfaces between TiO 2/dye/electrolyte. Results show that the degradation rates of the cells in presence of water isotopes were in the order of H 2O>D 2O>H 2 18O. In addition, the values of open-circuit voltage ( V oc) and fill factor (FF) for the water-added cells increased within first 12 h sun irradiation. However, their short-circuit current ( J sc) and efficiency ( η) decreased during the sun irradiation. Moreover, a new peak assigned to LiNCS was noticed after soaking in water-added electrolytes for 48 h, attributing to the interaction of lithium ions with free thiocyanate ions from the dye.

Optically Transparent Cathode for Dye-Sensitized Solar Cells Based on Graphene Nanoplatelets

Commercial graphene nanoplatelets in the form of optically transparent thin films on F-doped SnO(2) (FTO) exhibited high electrocatalytic activity toward I(3)(-)/I(-) redox couple, particularly in electrolyte based on ionic liquid (Z952). The charge-transfer resistance, R(CT), was smaller by a factor of 5-6 in ionic liquid, compared to values in traditional electrolyte based on methoxypropionitrile solution (Z946). Optical spectra and electrochemical impedance confirm that the film's absorbance scales linearly with R(CT)(-1). Electrocatalytic properties of graphene nanoplatelets for the I(3)(-)/I(-) redox reaction are proportional to the concentration of active sites (edge defects and oxidic groups), independent of the electrolyte medium. Dye-sensitized solar cell (DSC) was assembled with this material as a cathode. Semitransparent (>85%) film of graphene nanoplatelets presented no barrier to drain photocurrents at 1 Sun illumination and potentials between 0 and ca. 0.3 V, but an order of magnitude decrease of R(CT) is still needed to improve the behavior of DSC near the open circuit potential and, consequently, the fill factor. We predict that the graphene composite is a strong candidate for replacing both Pt and FTO in cathodes for DSC.

Sol–gel hydrothermal synthesis of bismuth–TiO 2 nanocubes for dye-sensitized solar cell

Bismuth–TiO 2 nanocubes were synthesized via a facile sol–gel hydrothermal method with titanium tetraisopropoxide as the precursor. The influence of the bismuth on the size, morphology, crystallinity and optical behavior of TiO 2 nanocubes were investigated. The samples were characterized by X-ray diffraction analysis (XRD), transmission electron microscopy (TEM), energy dispersive X-ray (EDX), field emission scanning electron microscopy (FESEM) and UV–visible spectroscopy (UV–vis). Photovoltaic behavior of dye-sensitized solar cells (DSSCs) fabricated using Bi–TiO 2 nanocubes was studied. The DSSCs had an open-circuit voltage ( V oc ) of 590 mV, a short-circuit current density ( J sc ) of 7.71 mA/cm 2, and the conversion efficiency ( η) of 2.11% under AM 1.5 illumination, a 77% increment as compared to pure TiO 2 nanocubes.

The effects of shell characteristics on the current-voltage behaviors of dye-sensitized solar cells based on ZnO/TiO2 core/shell arrays

The ZnO/TiO2 core/shell structure was formed through deposition of a TiO2 coating layer on the hydrothermally fabricated ZnO nanorod arrays through radio frequency magnetron sputtering. The effects of the TiO2 shell’s characteristics on the current-voltage behaviors of the core/shell-based dye-sensitized solar cells (CS-DSSC) were investigated. As the rates of injection, transfer, and recombination of electrons of such CS-DSSC were affected significantly by the crystallization, morphology, and continuity of the TiO2 shells, the photovoltaic efficiency was accordingly varied remarkably. In addition, the efficiency was further improved by enhancing the surface area in the core/shell electrode.

Application of finite-difference time domain to dye-sensitized solar cells: The effect of nanotube-array negative electrode dimensions on light absorption

We examine the light absorbing behavior of dye-sensitized solar cells (DSCs) having cathodes (negative electrodes) comprised of highly ordered TiO 2 nanotube arrays using the electromagnetic computational technique, finite-difference time domain (FDTD). The highly ordered nanotube arrays, grown using anodic oxidation of titanium foils or thin films, feature an open end with the other end fixed on a dense oxide layer (barrier layer). The numerical simulation model is comprised of nanotube arrays on a transparent conducting glass substrate under front-side illumination. In the FDTD analysis, a transverse electromagnetic (TEM) wave is incident onto a N719 dye-coated nanotube array initially passing through the barrier layer; light that emerges from the nanotubes is reflected by a perfectly conducting layer (perfect electric conductor—PEC) boundary that simulates the effect of the DSC platinum counter electrode. An observation plane placed between the electromagnetic source and DSC detects the intensity of both the incident wave and the wave returning back from the DSC structure. The absorbance and transmittance spectra are determined in the wavelength range 300–700 nm as a function of nanotube-array dimensions including length, pore size, barrier layer thickness, and surface roughness while keeping the wall thickness constant at 12 nm. The validity of the computational simulations is experimentally verified. A significant increase in the light absorption by the dye-coated nanotubes was observed for increasing nanotube length; smaller pore sizes, and increased surface roughness. Changes in the barrier layer thickness had a negligible effect on the absorbance spectrum. Our efforts demonstrate FDTD to be a broadly applicable technique capable of guiding design of an optimal DSC architecture.

Short-Circuit Current Density Behavior of Dye-Sensitized Solar Cells

Short-circuit current densities (Jscs) were measured on two kinds of dye-sensitized solar cells (DSCs). The dependences of Jsc on the diffusion coefficient of I3- and the cell gap are discussed using relevant model equations for the DSC. In the lower diffusion coefficient region, the DSC operates under an I3- diffusion-limiting condition and, under this condition, narrowing the cell gap is a simple and effective way to increase the Jsc. The Jsc of a gel-type polymeric-electrolyte-based DSC with a cell gap of 20 µm is verified to be equal to that of a liquid electrolyte-based DSC.

Property Influence of Polyanilines on Photovoltaic Behaviors of Dye-Sensitized Solar Cells

The influence of polyanilines (PANIs) as hole conductors on the photovoltaic behaviors of dye-sensitized solar cells is studied. The current-voltage (I-V) characteristics and the incident photon to current conversion efficiency (IPCE) curves of the devices are determined as the function of different conductivities and morphologies of PANIs. The results show that the conductivity of PANIs affects the performance of the devices greatly, and PANI with the intermediate conductivity value (3.5 S/cm) is optimum. In addition, the effects of both the film formation property and the cluster size of polyanilines on the photovoltaic behaviors of the devices are also discussed.