Applications of microwave reflectance methods to the study of p-Si in fluoride solutions

Cass, Michael; Duffy, Noel W.; Kirah, Khaled; Peter, Laurence M.; Pennock, S.R.; Ushiroda, Shin; Walker, Alison B.

doi:10.1016/s0022-0728(02)01141-5

Cited by 11 publications

(9 citation statements)

References 34 publications

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“…technique, have been applied to the characterization of many different semiconductor materials, [5][6][7] as well as in the study of electrochemical [8][9][10][11][12][13][14][15] and solid state junctions. 16 More recently, TRMC has been employed to investigate organic photovoltaic systems 17 and mesoporous films of TiO 2 (bare and sensitized) in the absence of electrolyte and conducting substrate.…”

Section: Microwave Reflectance Methods Including the Time-resolved Mmentioning

confidence: 99%

“…We have demonstrated the utility of the dielectric stack approach previously in microwave reflectance studies of the silicon/electrolyte interface. 11,13,14 The reflectance is calculated using values of the relative permittivity of the TiO 2 layer corresponding to dark and illuminated conditions (the permittivity values for the other components of the cell are given in Table 1 Table 1 for permittivity values and Supporting Information for further details. The calculated reflectance change is negative for the stack configuration used.…”

Section: Reflectance Calculationsmentioning

confidence: 99%

“…Under illumination at open circuit, the increment in concentration of trapped electrons, dn t , in the energy interval E T to E T + dE T , is given by the product of the Fermi Dirac distribution f FD (E T ) and the trap distribution g(E T ). For an exponential trap distribution, it follows that (11) where N T,0 is the total trap concentration and T 0 is an effective temperature describing the trap distribution. The perturbation of ε r by trapped electrons is found by integrating the product of the derivatives in equations 10 and 11 over the energy range E F,redox to E C .…”

Section: Perturbation Of the Permittivity Due To Changes In Trapped Ementioning

confidence: 99%

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In Situ Detection of Free and Trapped Electrons in Dye-Sensitized Solar Cells by Photo-Induced Microwave Reflectance Measurements

et al. 2012

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In order to study the behavior of photoinjected electrons in dye-sensitized solar cells (DSC), steady-state microwave reflectance measurements (33 GHz, Ka band) have been carried out on a working cell filled with electrolyte. The experimental arrangement allowed simultaneous measurement of the light-induced changes in microwave reflectance and open circuit voltage as a function of illumination intensity. In addition, frequency-resolved intensity-modulated microwave reflectance measurements were used to characterize the relaxation of the electron concentration at open circuit by interfacial transfer to tri-iodide ions in the electrolyte. The dependence of the free and trapped electron concentrations on open circuit voltage were derived, respectively, from conductivity data (obtained by impedance spectroscopy) and from light-induced near IR transmittance changes. These electron concentrations were used in the fitting of the microwave reflectivity response, with electron mobility as the main variable. Changes in the complex permittivity of the mesoporous films were calculated using Drude–Zener theory for free electrons and a simple harmonic oscillator model for trapped electrons. Comparison of the calculated microwave reflectance changes with the experimental data showed that the experimental response arises primarily from the perturbation of the real component of the complex permittivity by the high concentration of trapped electrons present in the DSC under illumination. The results suggest that caution is needed when interpreting the results of microwave reflectance measurements on materials with high concentrations of electron (or hole) traps, since an a priori assumption that the microwave response is solely determined by changes in conductivity (i.e., by free electrons) may be incorrect. The intensity-modulated microwave reflectance measurements showed that relaxation of the free and trapped electron concentrations occurs on a similar time scale, confirming that the free and trapped electron populations remain in quasi-equilibrium during the decay of the electron concentration.

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Section: Microwave Reflectance Methods Including the Time-resolved Mmentioning

confidence: 99%

Section: Reflectance Calculationsmentioning

confidence: 99%

Section: Perturbation Of the Permittivity Due To Changes In Trapped Ementioning

confidence: 99%

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In Situ Detection of Free and Trapped Electrons in Dye-Sensitized Solar Cells by Photo-Induced Microwave Reflectance Measurements

et al. 2012

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“…The combination of photocurrent and M w allows, for instance, the separate assessment of the charge transfer and surface recombination rate. This can be used to analyze the photoelectrochemical behavior of semiconductors with well -known solid -state properties, such as silicon [49] , and will be presented in Section 2.2.4 . In the situation shown in Figure 2.4 for L p = 20 µ m, the small integral excess carrier profi le and the small slope of ∆ p ( x ) at x = W (small current) show that, in this condition, the recombination processes dominate.…”

Section: Excess Minority Carrier Profi Lesmentioning

confidence: 99%

Tailoring of Interfaces for the Photoelectrochemical Conversion of Solar Energy

Lewerenz

2010

Advances in Electrochemical Sciences and Engineering

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IntroductionIn the search for terrestrially applicable carbon -neutral energy sources, photoelectrochemical systems exhibit several advantageous features: examples are the facilitated junction formation at the electrolyte interface, the scalability typically achieved by self -organized processes at the solid -liquid boundary [1, 2] , lowtemperature processing, and the in situ preparation and optimization of specifi c interface conditions [3,4] . In addition, photoelectrochemical solar cells can operate in the photovoltaic [5 -9] as well as in the photoelectrocatalytic [10 -14] mode. The latter is of particular importance because global energy consumption is clearly dominated by the use of fuels compared to electricity [15] . Due to stability issues when operating a solar cell at a reactive phase boundary, such as a semiconductor -electrolyte contact, photovoltaic electrochemical solar cells have technologically not been realized despite the existence of systems that have demonstrated extended stability under operation [4,7] . As limited thermodynamic stability is also a factor for solar fuel generating devices, a general strategy is needed for the future implementation of photoelectrochemical solar energy conversion systems.At the present stage of the fi eld, a multifaceted approach appears mandatory which focuses on fundamental research regarding charge and excitation energy transfer [16 -18] , materials development, particularly in conjunction with the developments in nanoscience [19 -23] , and control of interface behavior [24 -26] . This latter aspect will be the focus of the present chapter.Besides the investigation of fundamental properties of the solid -liquid interface, the situation with a rapidly deteriorating atmospheric situation [27] also demands the use of rational screening methods for the identifi cation and examination of novel photoactive materials, material combinations, and composites [28 -30] . It is obvious that a large -scale and international research and development effort is 2 Advances in Electrochemical Science and Engineering. Edited

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“…14 In the recent past a number of other groups have started to apply microwave or high frequency reflectometry in combination with conventional electrochemical methods in order to get more information about the complex charge carrier kinetics at semiconductor/electrolyte interfaces. [15][16][17][18] The photoinduced microwave reflection signal is proportional to the integrated excess charge carrier profile. 19,20 For given boundary conditions at the front and rear face, the sta-tionary profile is correlated to the surface concentration of excess carriers as outlined in.…”

Section: Introductionmentioning

confidence: 99%

Surface state capture cross sections at Si/electrolyte interfaces determined by combined microwave reflection/photocurrent measurements

Wünsch

Alonso-Vante

Tributsch

2003

Phys. Chem. Chem. Phys.

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Applications of microwave reflectance methods to the study of p-Si in fluoride solutions

Cited by 11 publications

References 34 publications

In Situ Detection of Free and Trapped Electrons in Dye-Sensitized Solar Cells by Photo-Induced Microwave Reflectance Measurements

In Situ Detection of Free and Trapped Electrons in Dye-Sensitized Solar Cells by Photo-Induced Microwave Reflectance Measurements

Tailoring of Interfaces for the Photoelectrochemical Conversion of Solar Energy

Surface state capture cross sections at Si/electrolyte interfaces determined by combined microwave reflection/photocurrent measurements

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