Dye-sensitized solar cells (DSCs) offer the possibilities to design solar cells with a large flexibility in shape, color, and transparency. DSC research groups have been established around the worl ...

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Dye-Sensitized Solar Cells

Electrochemical impedance spectroscopy (EIS) has been performed to investigate electronic and ionic processes in dye-sensitized solar cells (DSC). A theoretical model has been elaborated, to interpret the frequency response of the device. The high-frequency feature is attributed to the charge transfer at the counter electrode while the response in the intermediate-frequency region is associated with the electron transport in the mesoscopic TiO2 film and the back reaction at the TiO2/electrolyte interface. The low-frequency region reflects the diffusion in the electrolyte. Using an appropriate equivalent circuit, the electron transport rate and electron lifetime in the mesoscopic film have been derived, which agree with the values derived from transient photocurrent and photovoltage measurements. The EIS measurements show that DSC performance variations under prolonged thermal aging result mainly from the decrease in the lifetime of the conduction band electron in the TiO2 film.

Electrochemical Impedance Spectroscopic Analysis of Dye-Sensitized Solar Cells

Organometal trihalide perovskite based solar cells have exhibited the highest efficiencies to-date when incorporated into mesostructured composites. However, thin solid films of a perovskite absorber should be capable of operating at the highest efficiency in a simple planar heterojunction configuration. Here, it is shown that film morphology is a critical issue in planar heterojunction CH3NH3PbI3-xCl x solar cells. The morphology is carefully controlled by varying processing conditions, and it is demonstrated that the highest photocurrents are attainable only with the highest perovskite surface coverages. With optimized solution based film formation, power conversion efficiencies of up to 11.4% are achieved, the first report of efficiencies above 10% in fully thin-film solution processed perovskite solar cells with no mesoporous layer. © 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim.

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Morphological control for high performance, solution-processed planar heterojunction perovskite solar cells

This review describes recent advances in electrochemical impedance spectroscopy (EIS) with an emphasis on its novel applications to various electrochemistry-related problems. Section 1 discusses the development of new EIS techniques to reduce measurement time. For this purpose, various forms of multisine EIS techniques were first developed via a noise signal synthesized by mixing ac waves of various frequencies, followed by fast Fourier transform of the signal and the resulting current. Subsequently, an entirely new concept was introduced in which true white noise was used as an excitation source, followed by Fourier transform of both excitation and response signals. Section 2 describes novel applications of the newly developed techniques to time-resolved impedance measurements as well as to impedance imaging. Section 3 is devoted to recent applications of EIS techniques, specifically traditional measurements in various fields with a special emphasis on biosensor detections.

Electrochemical Impedance Spectroscopy

Influence of electrolyte in transport and recombination in dye-sensitized solar cells studied by impedance spectroscopy

Internal resistance in a dye-sensitized solar cell (DSC) was investigated using electrochemical impedance spectroscopy measurements. Four resistance elements were observed in the impedance spectra, and their dependencies on the applied bias voltage were characterized. It is found that the resistance element related to charge transport at the TiO2/dye/electrolyte interface displays behavior like that of a diode, and the series resistance elements largely correspond to the sum of the other resistance elements. An equivalent circuit for DSCs is proposed based on these results.

Modeling of an equivalent circuit for dye-sensitized solar cells

Modeling of an equivalent circuit for dye-sensitized solar cells : improvement of efficiency of dye-sensitized solar cells by reducing internal resistance

Iconographies supplémentaires de l'article : Modeling of an equivalent circuit for dye-sensitized solar cells: improvement of efficiency of dye-sensitized solar cells by reducing internal resistance

Quasi-solid state dye-sensitized solar cells were fabricated using an oligomer having three polymerizable reactive groups. Only 7% polymer concentration in the polymer electrolyte is found enough to form a stable quasi-solid structure and a three-dimensional polymer network structure is proposed. Conductivity measurement of the polymer electrolyte in different organic solvents shows that the ionic conductivity increases with decreasing the viscosity of the solvent and a high ionic conductivity of 9 mS/cm is observed for the polymer electrolyte composition of 0.2 M DMPII, 0.5 M LiI, 0.05 M I2 in the mixed solvent of ethylene carbonate and γ-butyrolactone (30:70 v/v). A short circuit photocurrent density of 14.8 mA/cm2, an open circuit voltage of 0.78 V, a fill factor of 0.70 and an overall conversion efficiency of 8.1% under AM1.5 irradiation (100 mW/cm2) was observed when fabricated a quasi-solid state dye-sensitized solar cells using these high conducting polymer electrolyte. The quasi-solid cells with the polymer electrolyte show higher open circuit voltage than that of the liquid cells that may be due to the suppression of the back electron transfer between the conduction band of the TiO2 electrode and the triiodide ion in the electrolyte.

Highly efficient quasi-solid state dye-sensitized solar cell with ion conducting polymer electrolyte

A photovoltaic cell comprises: an anode electrode including a conductive support and a porous semiconductor layer; a photosensitive dye; a charge transport layer; and a counter electrode support, wherein the anode electrode has the property of causing cathode luminescence having a luminous peak wavelength in a visible region and shows a haze rate H of 60% or more at a wavelength in the visible region.

Takehito Mitate

Papers

Modeling of an equivalent circuit for dye-sensitized solar cells

Modeling of an equivalent circuit for dye-sensitized solar cells : improvement of efficiency of dye-sensitized solar cells by reducing internal resistance

Iconographies supplémentaires de l'article : Modeling of an equivalent circuit for dye-sensitized solar cells: improvement of efficiency of dye-sensitized solar cells by reducing internal resistance

Highly efficient quasi-solid state dye-sensitized solar cell with ion conducting polymer electrolyte

Photovoltaic cell including porous semiconductor layer, method of manufacturing the same and solar cell