Theory of the impedance of charge transfer via surface states in dye-sensitized solar cells

Bisquert, Juan

doi:10.1016/j.jelechem.2010.01.007

Cited by 94 publications

(78 citation statements)

References 38 publications

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“…15 In the following, we present a simple model that allows prediction of the voltammetry plots in the presence of a monoenergetic level of surface states with a pretreatment done under illumination at a voltage above the onset voltage. The model, which is based on a previous model developed by Bisquert,29 allows prediction of the voltammetry patterns reported in the present study and, in general, in the measurement of solar water splitting semiconductor films.…”

Section: Irect Transformation Of Solar Energy Into Chemical Energymentioning

confidence: 99%

“…29 The general solution of the above set of equations can be obtained numerically, but it is useful to distinguish between different physical cases. In the model of Figure 3, we will consider that charge transfer from the traps is slow enough compared to the velocity of trap charging so that a capacitance peak can be observed.…”

Section: Irect Transformation Of Solar Energy Into Chemical Energymentioning

confidence: 99%

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Interpretation of Cyclic Voltammetry Measurements of Thin Semiconductor Films for Solar Fuel Applications

Bertoluzzi

Badia-Bou

Fabregat‐Santiago

et al. 2013

J. Phys. Chem. Lett.

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A simple model is proposed that allows interpretation of the cyclic voltammetry diagrams obtained experimentally for photoactive semiconductors with surface states or catalysts used for fuel production from sunlight. When the system is limited by charge transfer from the traps/catalyst layer and by detrapping, it is shown that only one capacitive peak is observable and is not recoverable in the return voltage scan. If the system is limited only by charge transfer and not by detrapping, two symmetric capacitive peaks can be observed in the cathodic and anodic directions. The model appears as a useful tool for the swift analysis of the electronic processes that limit fuel production. SECTION:Energy Conversion and Storage; Energy and Charge Transport D irect transformation of solar energy into chemical energy by hydrogen production through water splitting with semiconductor materials in a photoelectrochemical cell constitutes an attractive solution to our energy needs. However, despite the intense efforts carried out in the last decades, no single material has been identified satisfying all of the efficiency, stability, and cost conditions needed for industrial deployment of this technology. 1−4 Hematite (α-Fe 2 O 3 ) has emerged as a promising candidate 5−9 due to its abundance in the earth crust, visible light absorption, and good stability in the harsh environmental conditions needed for operation, although the obtained solarto-fuel efficiencies still remain low for commercial exploitation. One of the main causes of the low performance of hematite is related to the large overpotentials required for water oxidation (around 500 mV), and surface treatments have proven to enhance notably water splitting performances. 10−12 It has been suggested that the reasons for these large overpotentials are related to sluggish hole transfer to the electrolyte 13,14 and to the existence of traps in the bulk and at the semiconductor/ electrolyte interface, 15−17 leading to high recombination. 18,19 Clearly, the separation of the different processes that constitute the oxidative current and the identification of the main kinetic bottlenecks are complex tasks. Therefore, the accurate interpretation of the results provided by characterization techniques constitutes a key tool to rationalize materials development and device optimization. Recently, we have proposed a simple physical model that allows the interpretation of impedance spectroscopy (IS) spectra for water splitting applications. 20 In this model, we have considered a monoenergetic level of surface states where both electron and holes can recombine or transfer from/to the solution.In the present study, we propose a complementary simple model to predict the curves obtained by cyclic voltammetry (CV). This characterization technique allows a quick test of the faradic behavior associated with charge transfer and the capacitive behavior associated with the separated modes of carrier storage, which depend on the thermodynamics and kinetics of the system at stake. 21 ...

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Section: Irect Transformation Of Solar Energy Into Chemical Energymentioning

confidence: 99%

Section: Irect Transformation Of Solar Energy Into Chemical Energymentioning

confidence: 99%

Interpretation of Cyclic Voltammetry Measurements of Thin Semiconductor Films for Solar Fuel Applications

Bertoluzzi

Badia-Bou

Fabregat‐Santiago

et al. 2013

J. Phys. Chem. Lett.

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“…[30][31][32] It can be clearly observed that the two fabrication procedures yield values of C µ and R rec that are similar, confi rming their equivalent photovoltaic performance. In particular R rec , which is inversely proportional to the recombination current between photoextracted electrons and the I − wileyonlinelibrary.com represents a very relevant limiting mechanism affecting the extracted photocurrent.…”

Section: Analysis Of Photovoltaic Performance Charge Collection Effimentioning

confidence: 69%

“…In particular R rec , which is inversely proportional to the recombination current between photoextracted electrons and the I − wileyonlinelibrary.com represents a very relevant limiting mechanism affecting the extracted photocurrent. [30][31][32] Moreover, from a linear fi t (in semilogarithmic scale) of the two data sets, we extracted the same slope β L = β C = 0.49, which falls in a range (i.e., 0.4 < β < 0.7) for which device performance is not strongly affected by recombination mechanisms. [ 33 ] An insight in the charge transport properties of the nc-TiO 2 fi lms is obtained by calculating the lifetime τ = R rec C µ (see Figure 6 a), the diffusion coeffi cient of electrons D e = δ 2 /( R T C µ ) (see Figure 6 b), and the electron diffusion length L n = sqrt( D e τ ), which is the characteristic length electron diffuses into the nc-TiO 2 before it recombines.…”

Section: Analysis Of Photovoltaic Performance Charge Collection Effimentioning

confidence: 99%

Taking Temperature Processing Out of Dye‐Sensitized Solar Cell Fabrication: Fully Laser‐Manufactured Devices

Mincuzzi

Vesce

Schulz-Ruhtenberg

et al. 2014

Advanced Energy Materials

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a light-absorbing dye, an electrolyte and a platinized conductive top substrate.Different from more established photovoltaic technologies, standard, industrial, reliable, highly automated, and effi cient fabrication procedures have yet to be fully defi ned and integrated for DSCs. Most fabrication steps currently entail the use of printing processes (such as screen printing of the nc-TiO 2 and Pt precursor layers) and of high temperature treatments in ovens to fi re the nc-TiO 2 and Pt precursor fi lms at 400-550 °C. Alternative low-tempteature approaches suitable for plastic substrates have been intensively studied and reported in the literature. [8][9][10][11][12] The nc-TiO 2 fi lm sensitization is usually achieved by soaking the fi lms in a dye solution, and devices are sealed by means of a thermoplastic gasket (heated and pressed at around 100 °C) followed by electrolyte injection.Lasers have recently started to be utilized in DSCs processing. [13][14][15][16][17][18] In particular, we have reported an effi cient, effective, scalable, and low embodied energy sintering procedure for the nc-TiO 2 fi lm. [19][20][21] Here we demonstrate that all the primary DSC manufacturing steps that required temperature treatments and in particular, sintering of the TiO 2 fi lm, curing of the Pt precursor, and device sealing, can be successfully and effi ciently carried out via laser assisted processes controlled by means of raster scanning systems (RSLSs). We believe this to be the fi rst demonstration of a device which is also effi cient and durable, where absolutely no temperature treatments were applied (all replaced by laser processing) together with a method for the defi nition of the cell pattern. The new processes were introduced while maintaining an uncompromising level of performance (6% conversion effi ciency) and durability (lifetime), the same as devices manufactured by conventional processes.We developed laser fabrication processes for the 1) patterning of the active layer, 2) sintering of the TiO 2 layer, 3) curing of the Pt precursor catalyst, and 4) encapsulation via a perimeter thermoplastic gasket. We present each of these developments here. Results and Discussion Laser-Patterning and Laser-Sintering of nc-TiO 2 FilmsAn important feature of DSC technology consists in the use of printing/masking procedures to defi ne the main active Pt and

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“…Electrochemical impedance spectroscopy (EIS) [7,[33][34][35] is an experimental method that used to scrutinize the DSSCs operation as well as intensity-modulated photocurrent/photovoltage spectroscopy (IMPS/IMVS) [36][37][38][39][40][41]. The EIS method can be used to measure the internal impedance of electrochemical system over a range of frequencies [42][43][44][45][46][47][48]. Therefore, this method is helpful to understand the transport properties of the injected electrons and recombination phenomena in mesoscopic titania electrode in the DSSCs.…”

Section: Introductionmentioning

confidence: 99%

Modified multistep electrophoretic deposition of TiO2 nanoparticles to prepare high quality thin films for dye-sensitized solar cell

2012

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In this study, a modified procedure is introduced which consists of multistep process for improving the structure of mesoporous TiO 2 films. The films were prepared by electrophoretic deposition (EPD) on FTO (FSnO 2 coated glass). It is shown that high quality TiO 2 film can be produced by multistep EPD method. The effect of EPD time on the thickness and density of the films have been investigated. The performance of dye-sensitized solar cells (DSSCs) that were fabricated by improved layer are tested under AM 1.5 simulated sunlight. Finally, the structure and effective parameters of DSSCs that were fabricated by one step and multistep EPD are investigated precisely, using electrochemical impedance spectroscopy.

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Theory of the impedance of charge transfer via surface states in dye-sensitized solar cells

Cited by 94 publications

References 38 publications

Interpretation of Cyclic Voltammetry Measurements of Thin Semiconductor Films for Solar Fuel Applications

Interpretation of Cyclic Voltammetry Measurements of Thin Semiconductor Films for Solar Fuel Applications

Taking Temperature Processing Out of Dye‐Sensitized Solar Cell Fabrication: Fully Laser‐Manufactured Devices

Modified multistep electrophoretic deposition of TiO2 nanoparticles to prepare high quality thin films for dye-sensitized solar cell

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