A vector model for analysing the surface photovoltage amplitude and phase spectra applied to complicated nanostructures

Ivanov, Ts.; Donchev, V.; Germanova, K.; Kirilov, K.

doi:10.1088/0022-3727/42/13/135302

Cited by 51 publications

(41 citation statements)

References 24 publications

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“…The downward dip seen in both phase spectra just below the bandgap is from non-linear effects associated with the dramatic rise in absorption coefficient in this energy range. 22,23 We note that the positive sign of this curvature is opposite to what was previously predicted for a p-type semiconductor. 22 However, this is easily explained by the presence of SCR2: Since the frequency dependent data showed that SCR2 dominates the dynamics below bandgap, the curvature in the phase spectra is no longer that of the surface but of the buried interface, which has the opposite effect on the SPS signal as SCR1.…”

Section: Resultscontrasting

confidence: 63%

Reduction of Fermi level pinning and recombination at polycrystalline CdTe surfaces by laser irradiation

Simonds

Kheraj

Palekis

et al. 2015

Journal of Applied Physics

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Laser processing of polycrystalline CdTe is a promising approach that could potentially increase module manufacturing throughput while reducing capital expenditure costs. For these benefits to be realized, the basic effects of laser irradiation on CdTe must be ascertained. In this study, we utilize surface photovoltage spectroscopy (SPS) to investigate the changes to the electronic properties of the surface of polycrystalline CdTe solar cell stacks induced by continuous-wave laser annealing. The experimental data explained within a model consisting of two space charge regions, one at the CdTe/air interface and one at the CdTe/CdS junction, are used to interpret our SPS results. The frequency dependence and phase spectra of the SPS signal are also discussed. To support the SPS findings, low-temperature spectrally-resolved photoluminescence and time-resolved photoluminescence were also measured. The data show that a modest laser treatment of 250 W/cm 2 with a dwell time of 20 s is sufficient to reduce the effects of Fermi level pinning at the surface due to surface defects. V C 2015 AIP Publishing LLC. [http://dx.

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Section: Resultscontrasting

confidence: 63%

Reduction of Fermi level pinning and recombination at polycrystalline CdTe surfaces by laser irradiation

Simonds

Kheraj

Palekis

et al. 2015

Journal of Applied Physics

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“…23,36 When U x is used in the SPV experiments, only the net result of charge carrier transfer properties is recorded, but usually at the same time there could be more than one process which can cause the SPV response, such as the built-in electric field, external bias, or Dember effect driven SPV. In order to analyse such complicated SPV processes, a qualitative vector model has been adopted along with the SPV amplitude (U R ) and phase (j) spectra, 34 in which the SPV signal is represented by a radial vector, i.e., the SPV amplitude is represented by the vector magnitude and the SPV phase is represented by the included angle between the SPV vector and the x-axis. If there are two different processes which can result in an SPV response, these two SPV signals will be added according to the rule of vector addition.…”

Section: Characterizationmentioning

confidence: 99%

Surface photovoltage phase spectra for analysing the photogenerated charge transfer and photocatalytic activity of ZnFe2O4–TiO2 nanotube arrays

Chen

Liu

et al. 2013

Phys. Chem. Chem. Phys.

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The transfer properties of the photogenerated charge carriers in TiO2 nanotube arrays (TNAs) and ZnFe2O4 modified TiO2 nanotube arrays (ZFO-TNAs) were investigated by surface photovoltage phase spectra. The modification of ZnFe2O4 on TNAs will lead to a new process of photogeneration of charge carriers. When irradiated with UV or visible light, before ZnFe2O4 modification photogenerated holes can transfer to the surface of TNAs; while after ZnFe2O4 modification, a process of photogenerated electrons transferring to the surface occurred. The different detected photogenerated charge transfer processes agree well with the photocatalytic reduction of Cr(VI) and the degradation of methyl orange experiments, which confirmed that the photogenerated holes transferring to the surface of the TNAs or ZFO-TNAs were beneficial for the reactions of photocatalytic reduction and electrons transferring to the surface were beneficial for photocatalytic degradation.

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“…Recently, a new method was proposed based on the surface photovoltage to investigate semiconductor structures including structures with quantum wells . The influence of the Dember EMF should be also taken into account.…”

Section: Introductionmentioning

confidence: 99%

Novel approach to the Dember effect

Meriuts

Gurevich

2014

Annalen der Physik

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In this paper it is demonstrated that the precise physical nature of the Dember effect is a concentration gradient of nonequilibrium carriers under nonuniform illumination. We used the fact that any photo-EMF (electromotive force) can only exist in the presence of nonequilibrium charge carriers, when there are two different Fermi quasilevels. That is why the Dember EMF (as the photo-EMF of any nature ) is not identified as a voltage drop arising between the device contacts in open circuit. Moreover, a correct definition of the EMF is only possible if the problem is solved in a closed circuit. It is shown that the Dember EMF does not depend on the difference of electron-to-hole diffusion coefficients and it is not linked to ambipolar diffusion. Additionally, it is found that the sign of the EMF depends on the ratio between the recombination rates on the contacts, which can be detected from the spectral characteristic of the Dember

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A vector model for analysing the surface photovoltage amplitude and phase spectra applied to complicated nanostructures

Cited by 51 publications

References 24 publications

Reduction of Fermi level pinning and recombination at polycrystalline CdTe surfaces by laser irradiation

Reduction of Fermi level pinning and recombination at polycrystalline CdTe surfaces by laser irradiation

Surface photovoltage phase spectra for analysing the photogenerated charge transfer and photocatalytic activity of ZnFe2O4–TiO2 nanotube arrays

Novel approach to the Dember effect

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