On The Scalability of Dye-Sensitized Solar Cells : Effect of Photoelectrode Area on the Photovoltaic and Charge Transport Parameters
0
Citation
0
Reference
20
Related Paper
Abstract:
This study is aimed to provide new insights on the scalability of dye-sensitized solar cells (DSCs). The DSCs of electrode area up to ~2 cm2 were fabricated using commercially available P25 TiO2 particles, N3 dye, and iodide/triiodide electrolyte and evaluated using voltage - current and electrochemical impedance spectroscopic measurements. The photovoltaic conversion efficiency follows a biexponential decay, the main contributor to which is the short circuit current density(JSC). Interesting features were observed in the electrochemical impedance spectra and charge transport parameters in the devices as the photoelectrode areas are increased. Results show that electrons from an area above a threshold are not collected due to varied choice of diffusion pathways. Furthermore, this study identify that area of the photoelectrode for reporting the efficiency needs to be fixed at ~0.5 cm2 for 25 nm TiO2 particles because below which it strongly vary. On the other hand, the study provides opportunities to build high efficiency dye-sensitized solar cells using the current choice of materials.Keywords:
Triiodide
Open-circuit voltage
Cite
We report the full electrical characterization of a dye-sensitized solar cell (DSSC), in which the photovoltaic (PV) effect can be observed, under a radiation field closely resembling the AM 1.5 solar spectrum, together with an estimation of the variation of the determined parameters in the 300-400K temperature ranges, based on the electrical model and theoretical estimation techniques. The current-voltage characteristic serves as both a proof-of-existence for the PV effect and a source for electrical parameter extraction. The devices exhibits promising efficiency and fill factors if operated at convenient temperatures.
Cite
Citations (2)
The rapid development of industries that use fossil fuels produces negative impacts on the environment. For the first time in human history, CO2 levels in the atmosphere have doubled compared to the ice age. Renewable energy is one solution to reduce dependence on fossil fuels. One source of renewable energy is solar energy. This energy can be utilized using the Dye-Sensitized Solar Cell. DSSC is environmentally friendly, low cost, and can be grown on elastic thin films. DSSC consists of four main components, one of which is photoanode. Photoanode serves as a medium for photogeneration of electrons to produce an electric current. For better performance, DSSC was analytically modeled by several previous researchers. But only on macro parameters such as working temperature, solar intensity, and electron lifetime. It is necessary to make variations on the photoanode semiconductor material and nanostructure parameters to optimize DSSC performance. There are three best variations in a photoanode semiconductor material such as TiO2, ZnO, Nb2O3. Further modeling of nanostructures photoanode constituent particles uses the constant overlap method. This modeling can describe nanostructural parameters such as diffusion coefficient, absorption coefficient, and porosity to describe J-V characteristics of DSSC. The simulation is done after the modeling results agreed well with the experimental results based on the reference. Simulation results illustrate the value of sunlight penetration depth that affects the short circuit current density. The short circuit current is proportional to the absorption coefficient and the diffusion coefficient. 0.41 porosity is the optimum value that produces maximum power. Photoanode semiconductor material based on the J-V characteristics of the best is TiO2, ZnO, Nb2O3.
Cite
Citations (6)
In this paper the optical and electrical simulation of the organic solar cells are represented. It is shown that the results of optical simulation are consistent with previously calculated ones. Due to interference, the peak amplitude of wave and its position change within the structure and cause the exciton generation to oscillate inside the active layer. Electrical simulation of devices is done and it is seen that the solar cell fill factor decreases with enhancing the thickness due to the increased serial resistance. For the thickness of 90nm the fill factor of solar cell is 75% however by increasing the thickness to the 320nm it decreases to 42%. The effect of active layer thickness on the short circuit current and efficiency in organic solar cells is studied. Comparing our results with experimental data confirms that the model is well simulated the behavior of the Bulk Heterojunction Solar Cells. According to the obtained results from simulations, despite of the increased photon absorption, the power conversion efficiency is reduced by increasing the thickness due to the low mobility of organic materials and non-geminate recombination.
Active layer
Equivalent series resistance
Cite
Citations (10)
The dependence of photocurrent and photovoltage of dye-sensitized solar cell on the incident light intensity were investigated based on the electron continuity diffusion equation. For the first time a model was presented for power loss of series resistance in dye-sensitized solar cell, and were simulated the influence of the active-area width of nanoporous film, the effect of special contact resistance on the photo-electric conversion efficiency, as well as the silver impedance in lager-scale solar cells with active area greater than 1 cm2 under different illuminations. It was found that the efficiency strongly depends on the width of active area and the silver impedance under strong illumination, nevertheless, this dependence is not obvious under poor illumination.
Equivalent series resistance
Photocurrent
Nanoporous
Cite
Citations (4)
The tandem pn-type dye-sensitized solar cells (pn-DSCs) have received much attention in the field of photovoltaic technologies because of their great potential to overcome the Shockley-Queisser efficiency limitation that applies to single junction photovoltaic devices. However, factors governing the short-circuit current densities (Jsc) of pn-DSC remain unclear. It is typically believed that Jsc of the pn-DSC is limited to the highest one that the two independent photoelectrodes can achieve. In this paper, however, we found that the available Jsc of pn-DSC is always determined by the larger Jsc that the photoanode can achieve but not by the smaller one in the photocathode. Such experimental findings were verified by a simplified series circuit model, which shows that a breakdown will occur on the photocathode when the photocurrent goes considerably beyond its threshold voltage, thus leading to an abrupt increase in Jsc of the circuit. The simulation results also suggest that a higher photoconversion efficiency of the pn-DSCs can be only achieved when an almost equivalent photocurrent is achieved for the two photoelectrodes.
Photocathode
Photocurrent
Tandem
Cite
Citations (5)
Organic solar cells have the potential to be portable power sources that are light-weight, flexible, and inexpensive. However, the highest power conversion efficiency for organic solar cells to date is ~8%, and most high-efficiency solar cells have an area of less than 1 cm². This thesis advances the field of organic solar cells by studying the physics and engineering of the devices to understand the reverse saturation current, which is related to efficiency, and the effects of area scaling.
The most commonly accepted models to describe the physics of organic photovoltaic devices are reviewed and applied to planar heterojunction solar cells based on pentacene / C60 as a model system. The equivalent circuit model developed for inorganic solar cells is shown to work well to describe the behavior of organic devices and parameterize their current-voltage characteristics with five parameters. Changes in the parameters with different material combinations or device structures are analyzed to better understand the operation of the presented organic solar cells. A one-dimensional diffusion model for the behavior of excitons and treatment of the organic layers as planes is demonstrated to adequately model the external quantum efficiency and photocurrent in pentacene / C60 solar cells.
The origin of the open-circuit voltage is studied using cells with different electrodes and different donor materials. While changing the electrodes does not affect open-circuit voltage, it is greatly modified by changes in the donor. Tests with additional semiconductors show the change in open-circuit voltage is not consistent from donor to donor as the acceptor is varied, suggesting a more complex relation than just the difference in energy levels. Study of the temperature dependence of the equivalent circuit parameters shows that the reverse saturation current, which has a significant role in determining the open-circuit voltage, has a thermally activated behavior. From this behavior, the reverse saturation current is related back to charge transfer at the donor / acceptor heterojunction to suggest that both the effective energy barrier presented by the energy levels and the electronic coupling are important in determining the reverse saturation current and open-circuit voltage. This marks a shift from just considering a built-in voltage or the energy levels to also considering the electronic coupling of the donor and acceptor materials. Temperature-dependent performance characteristics are also used to show key differences between organic and inorganic devices.
Finally, the effect of area scaling is explored with pentacene / C60 solar cells having areas of 0.11, 7, and 36.4 cm². Analysis with the equivalent circuit model shows that performance decreases as area increases because of an increasing series resistance presented by the transparent electrode. A metal grid, to provide low resistance pathways for current, fabricated on top of the transparent electrode is proposed to reduce the effective resistance. The grid is unique in…
Photocurrent
Organic semiconductor
Open-circuit voltage
Hybrid solar cell
Pentacene
Cite
Citations (9)
Many studies reported that dye-sensitized solar cells have more significant capacitance characteristics than the silicon solar cell. In this study, it was found the capacitance characteristics of dye-sensitized solar cell changes with the imposed bias voltage. The bias voltage is indispensable in the standard measurement for the conversion efficiency of dye-sensitized solar cell. The influence of changed capacitance during the measurement on the conversion efficiency of dye-sensitized solar cells was investigated. The analysis on the EIS spectra and equivalent circuit shows that the capacitance of dye-sensitized solar cells is small and the deviation cell I-V characteristics from the steady-state value is minor when the applied bias is small; while under a condition with a large applied bias, the capacitance characteristics of dye-sensitized solar cell grew rapidly and the I-V characteristics deviated from the steady-state value significantly increased. This phenomenon is helpful for the accurate measurement of the quantum conversion efficiency and photoelectric conversion efficiency of dye-sensitized solar cells.
Quantum Efficiency
Open-circuit voltage
Cite
Citations (3)
Efficiency estimations of organic solar cells are observed to be dependent on the dimensions of electrode defining the active area. We address this issue and explore the manner in which efficiency scales in polymer solar cells by studying these devices as a function of electrode area and incident beam size. The increase in efficiency for smaller active areas can be explained by the reduced electrical resistive loss, the enhanced optical effects, and the finite additional fraction of photogenerated carriers in the vicinity of the perimeter defined by the metal electrode
Resistive touchscreen
Cite
Citations (97)
Dye-sensitized solar cells (DSSC) are rapidly becoming an advantageous option for solar energy harvesting. In order to optimize DSSC performance and durability, a deeper understanding of properties is required, and detailed investigations over each device component must be conducted. This paper focuses on DSSC performance as a function of TiO 2 layer thickness. Monte Carlo simulations of free electron diffusion through several widths of TiO 2 were executed, which allowed the calculation of device performance parameters, such as maximum power yield, fill-factor, and power-conversion efficiency, as functions of TiO 2 layer thickness.
Cite
Citations (1)
Open-circuit voltage
Equivalent series resistance
Halogen lamp
Cite
Citations (10)