Expressions for the dark and photocurrent of a semiconductor-electrolyte junction are derived. Charge transfer kinetics, surface recombination, recombination in the space-charge region, and series resistance are discussed in our model. A measurement of the I-V characteristics, both in the dark and under illumination, aids in the estimation of the parameters of the device. The model agrees with the general observed quantum efficiency variation with voltage.
Expressions are derived for the current-voltage characteristics of semiconductor-electrolyte junctions. Charge transfer kinetics, surface recombination, recombination in the quasineutral region and in the depletion region as well as the effect of the incident illumination on the minority carrier distribution in the semiconductor are included in the model. It is shown that surface transfer velocity for minority carriers is a very important parameter that determines the photocurrent of the cell. The dependence of the photoresponse on the light intensity is shown to be a diagnostic tool in determining the efficiency of charge transfer at the surface.
Holograms were written in a short-circuited antireflection-coated crystal of iron-doped lithium niobate, using essentially uniform illumination of the whole crystal to minimize light-envelope space-charge field effects. The results were compared with the predictions of a computer model which allows for space-charge feedback and for the modification of the writing light pattern by interaction with the hologram being written, but which assumes short transport lengths of electrons (on the scale of the hologram grating spacing) for diffusion, drift, and the bulk photovoltaic effect. The measured ’’virtual’’ field Ev to which the bulk photovoltaic effect is equivalent (for these assumptions) was about 45 kV/cm so that the bulk photovoltaic effect, rather than diffusion, dominated the writing process under the above conditions. The development of the diffraction efficiency was consistent with the computed data but the beam coupling (transfer of energy between the writing beams) was much greater than predicted. The observed beam coupling could occur with the drift-equivalent process of the bulk photovoltaic effect if the transport distance in this effect was on the order of 24 nm, which is larger than has been generally considered probable. In repeated write-erase experiments the beam coupling was variable, more so than the diffraction efficiency. The variability is, we believe, due to parasitic holograms such as are involved in the scattering process observed with these crystals and also to residual space-charge fields from repeated write-erase cycles. If the transport length is indeed long, the term καI used to describe the bulk photovoltaic effect (where κ is a parameter specific to a dopant, α is the absorption coefficient, and I is the intensity) is inapplicable to hologram writing conditions since it implies short transport length. A new representation for this bulk photovoltaic effect allowing for an arbitrary transport length is proposed. This representation is shown to introduce a significant phase shift in the refractive-index pattern relative to the light pattern and can thus account for the beam coupling observed.
Articles you may be interested inSurface photovoltage measured capacitance: Application to semiconductor/electrolyte system J.A theoretical treatment of charge transfer via surface states at a semiconductorelectrolyte interface: Analysis of the water photoelectrolysis process A general analysis is given for the effects of illumination and surface recombination on the currents flowing in a semiconductor/conductor junction. The behavior ofthe electron and hole quasi-Fermi levels is examined and it is shown that a priori assumptions about their flatness in the depletion region leads to contradictions in the analysis. The two theories describing currents in a Schottky barrier junction, the thermionic emission theory and the diffusion theory of Shockley are shown to have their parallels in a semiconductor/electrolyte contact. A Shockley-Read-Hall model for surface recombination was employed in the analysis and it was shown that this model reduces to the expression for surface recombination often used in the literature under certain conditions. PACS numbers: 73.40.Mr, 78.20.Jq, 73.30. + y A. No surface recombination In the absence of surface recombination, the electrons and holes are not coupled together because J r = 0 and one obtains J J VIV, J eE,,,IOI/AT = C + lie + Ie , J c +J II e -E, "IOI/A J Je,electrolyte = ( J c ) [ J II (e V I v, -1) + J le ] , J c +J II Jh,electrolyte = [1 + (J p / J" )e V I V,] --I X [Jp(e
Articles you may be interested inThe role of the anion electronegativity in semiconductor-electrolyte and semiconductor-metal junctionsThe superposition principle of currents in a solar cell states that the current flowing in an illuminated device subject to a forward bias V is given by the algebraic sum of the short circuit photocurrent and the current which would flow at bias Vin the dark. We investigate this principle here in detail for the case of semiconductor-electrolyte solar cells. However, the results are also applicable to Schottky-barrier solar cells. It is concluded that the density of photoexcitable surface states and the surface transfer velocity for minority carriers from the semiconductor into the electrolyte are two important parameters that determine the validity of applying the superposition principle as well as in determining the current-voltage (J-V) characteristic of the device.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.