Photoelectrochemical Investigations of Passive Films on Titanium Electrodes

Leitner, Klaus; Schultze, J.W.; Stimming, Ulrich

doi:10.1149/1.2108969

Cited by 120 publications

(60 citation statements)

References 22 publications

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“…The accuracy of the estimation, although not verified here by an independent measurement, corresponds to an anodic growth rate of 3 ± 0.5 nm·V -1 , which is fairly consistent to the rate of 2.5 nm·V -1 reported for anodic titanium oxide films grown potentiostatically at similar conditions [8].…”

Section: Estimation Of Thin Film Thicknesssupporting

confidence: 87%

Characterization of Thin Films by Low Incidence X-Ray Diffraction

Bouroushian¹,

Kosanovic²

2012

CSTA

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Glancing Angle X-ray Diffraction (GAXRD) is introduced as a direct, non-destructive, surface-sensitive technique for analysis of thin films. The method was applied to polycrystalline thin films (namely, titanium oxide, zinc selenide, cadmium selenide and combinations thereof) obtained by electrochemical growth, in order to determine the composition of ultra-thin surface layers, to estimate film thickness, and perform depth profiling of multilayered heterostructures. The experimental data are treated on the basis of a simple absorption-diffraction model involving the glancing angle of X-ray incidence.

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Section: Estimation Of Thin Film Thicknesssupporting

confidence: 87%

Characterization of Thin Films by Low Incidence X-Ray Diffraction

Bouroushian¹,

Kosanovic²

2012

CSTA

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“…Therefore, as will be discussed below in more detail, the determination of the conduction band edge often translates into the measurement of the position of the quasi-Fermi level of electrons. Once this is known, the position of the valence band edge can be simply calculated by adding the value of bandgap energy, that is, typically determined by optical [128,[141][142][143][144][145][146][147][148][149][150][151] or photoelectrochemical methods [152][153][154][155][156].…”

Section: Theory and Fundamental Conceptsmentioning

confidence: 99%

(Photo)electrochemical Methods for the Determination of the Band Edge Positions of TiO₂‐Based Nanomaterials

Beránek

2011

Advances in Physical Chemistry

340

183

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TiO 2 -based nanomaterials play currently a major role in the development of novel photochemical systems and devices. One of the key parameters determining the photoactivity of TiO 2 -based materials is the position of the band edges. Although its knowledge is an important prerequisite for understanding and optimizing the performance of photochemical systems, it has been often rather neglected in recent research, particularly in the field of heterogeneous photocatalysis. This paper provides a concise account of main methods for the determination of the position of the band edges, particularly those suitable for measurements on nanostructured materials. In the first part, a survey of key photophysical and photochemical concepts necessary for understanding the energetics at the semiconductor/solution interface is provided. This is followed by a detailed discussion of several electrochemical, photoelectrochemical, and spectroelectrochemical methods that can be applied for the determination of band edge positions in compact and nanocrystalline thin films, as well as in nanocrystalline powders.

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“…E g varies for the anatase phase between 3.2 eV [14], 3.46 eV [21], 3.5±3.7 eV [22] and 3.98 eV [23] depending on the preparation conditions and measurement techniques. For example, PC measurements on por-TiO 2 give usually E g 3.2 eV [14] while photoelectrochemical investigations on thin anatase electrodes give 3.15±3.3 and 3.5±3.7 eV for indirect and direct bandgap analysis, respectively [24]. The absorption spectra of anatase single crystals contain Urbach tails even at very low temperature and the optical gap is 3.42 or 3.46 eV depending on the polarization [21].…”

Section: Resultsmentioning

confidence: 99%

Porous TiO2: Electron Transport and Application to Dye Sensitized Injection Solar Cells

Dittrich

2000

phys. stat. sol. (a)

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Porous TiO 2 (anatase, rutile) belongs to the class of materials with very low drift mobility of electrons (10 ± ±4 ±10 ± ±7 cm/Vs). The drift mobility is limited by traps being responsible for the slow interparticle charge transfer. The deep traps are generated at the TiO 2 surface in oxygen deficient atmosphere and should be avoided in dye sensitized injection solar cells since they increase the saturation current. Another group of defects is related to disorder in the bulk TiO 2 . The disorder is much stronger for anatase than for rutile. The respective optical bandgap of the undisturbed anatase is 3.45 eV. The disorder related defects do not limit the efficiency of the dye sensitized injection solar cell. The current dependent barrier height has been shown to be important as a limiting factor for the energy conversion efficiency in dye sensitized injection solar cells at moderate light intensity.Introduction Nanoporous semiconductors belong to the class of materials with very low drift mobilities (m) of charge carriers. For example, m is in the order of 10 ± ±4 ±10 ± ±1 and 10 ± ±4 ±10 ± ±6 cm 2 /Vs for electrons in nanoporous Si [1] and porous TiO 2 [2], respectively, what is lower by four to six orders of magnitude than m for the single crystalline Si and TiO 2 [3], an overview of electron Hall mobilities is given in [4]. The main reasons for the strong decrease of m are the complex network of a nanoporous structure, see e.g.[5] and the huge internal surface area of a porous semiconductor, see e.g. [6] which may lead to hopping transport on a fractal [7] or trap limited transport [8]. However, the microscopic picture of the charge transport is more complicated, especially in the presence of injected carriers of charge.The electronic transport in porous semiconductors is extremely sensitive to adsorbed molecules which change the distribution of electronic states. This bears a large potential for applications in sensors, especially for porous metal oxides, see e.g. [9,10]. The electronic states below the bandgap are not well investigated in porous metal oxides and their nature is not well understood up to now. Metal oxides are very sensitive to nonstoichiometry. A deficit of oxygen causes n-type doping (high temperature (T), low partial pressure of oxygen (p O 2 )) while additional incorporation of oxygen into the metal oxide leads to p-type doping, see e.g. [11]. TiO 2 is of n-type [12]. By using reduction and oxidation reactions one can reversibly cycle or refresh the electronic properties of metal oxides.TiO 2 is a wide bandgap semiconductor (E g 3.06 eV for the rutile phase [13]) and it can be easily produced as a nanocrystalline powder. (TiO 2 nanoparticles are widely used, for example, in white paint.) These two properties make TiO 2 nanoparticles quite interesting for application in dye sensitized injection solar cells, the so-called ªGra È tzelcellsº [14]. The idea of the injection solar cell is the separation in space of the steps of

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Photoelectrochemical Investigations of Passive Films on Titanium Electrodes

Cited by 120 publications

References 22 publications

Characterization of Thin Films by Low Incidence X-Ray Diffraction

Characterization of Thin Films by Low Incidence X-Ray Diffraction

(Photo)electrochemical Methods for the Determination of the Band Edge Positions of TiO₂‐Based Nanomaterials

Porous TiO2: Electron Transport and Application to Dye Sensitized Injection Solar Cells

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Photoelectrochemical Investigations of Passive Films on Titanium Electrodes

Cited by 120 publications

References 22 publications

Characterization of Thin Films by Low Incidence X-Ray Diffraction

Characterization of Thin Films by Low Incidence X-Ray Diffraction

(Photo)electrochemical Methods for the Determination of the Band Edge Positions of TiO2‐Based Nanomaterials

Porous TiO2: Electron Transport and Application to Dye Sensitized Injection Solar Cells

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Product

Resources

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(Photo)electrochemical Methods for the Determination of the Band Edge Positions of TiO₂‐Based Nanomaterials