Further mechanistic studies of n-type Si photoelectrodes: Behavior in contact with methanol-dimethylferrocene+/0 and in contact with aqueous electrolytes

Amit Kumar, Nathan S Lewis

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Abstract

Mechanistic studies of n-Si photoelectrodes have been conducted using aqueous and nonaqueous electrolytes. In contact with the CH3OH-dimethylferrocene (Me2Fc)+/0 electrolyte, the dark current and open-circuit voltage (Voc) were not dependent on acceptor concentration for [Me2Fc+] ≤ 0.010 M and were only weakly dependent on acceptor concentration for [Me2Fc+] ≥ 0.010 M. For [Me2Fc+] between 0.3 mM and 0.050 M, the temperature dependence of Voc indicated that bulk-diffusion/recombination was the rate-limiting recombination process. In all of these experiments, conventional Shockley diode theory provided an excellent description of the solid/liquid junction properties. In a related set of experiments, HF-etched n-Si photoelectrodes ((100)- and (111)-oriented samples) and n-Si samples that had been metalized by several different methods all showed passivation in contact with Fe(CN)6 3-/4- (aq) or Br2/Br- (aq) electrolytes. For several metalized Si samples, etches that had been reported to produce metal islands on the Si surface instead yielded Si surfaces free of metal. All Si samples that had been metalized by filament evaporation yielded I-V behavior in contact with the CH3OH-Me2Fc+/0 redox system that was characteristic of a pinned surface Fermi level, even for coverages of metal as low as 9 Å. This indicates that proposed metal-insulator-semiconductor junctions with anomalously high barrier heights are difficult to obtain by such metalization and etching methods.

Original languageEnglish
Pages (from-to)7021-7028
Number of pages8
JournalJournal of Physical Chemistry
Volume95
Issue number18
Publication statusPublished - 1991

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Electrolytes
Methanol
methyl alcohol
Metals
electrolytes
Semiconductor junctions
nonaqueous electrolytes
metals
semiconductor junctions
Dark currents
MIS (semiconductors)
Open circuit voltage
dark current
Fermi level
open circuit voltage
Passivation
passivity
Fermi surfaces
Etching
filaments

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

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title = "Further mechanistic studies of n-type Si photoelectrodes: Behavior in contact with methanol-dimethylferrocene+/0 and in contact with aqueous electrolytes",
abstract = "Mechanistic studies of n-Si photoelectrodes have been conducted using aqueous and nonaqueous electrolytes. In contact with the CH3OH-dimethylferrocene (Me2Fc)+/0 electrolyte, the dark current and open-circuit voltage (Voc) were not dependent on acceptor concentration for [Me2Fc+] ≤ 0.010 M and were only weakly dependent on acceptor concentration for [Me2Fc+] ≥ 0.010 M. For [Me2Fc+] between 0.3 mM and 0.050 M, the temperature dependence of Voc indicated that bulk-diffusion/recombination was the rate-limiting recombination process. In all of these experiments, conventional Shockley diode theory provided an excellent description of the solid/liquid junction properties. In a related set of experiments, HF-etched n-Si photoelectrodes ((100)- and (111)-oriented samples) and n-Si samples that had been metalized by several different methods all showed passivation in contact with Fe(CN)6 3-/4- (aq) or Br2/Br- (aq) electrolytes. For several metalized Si samples, etches that had been reported to produce metal islands on the Si surface instead yielded Si surfaces free of metal. All Si samples that had been metalized by filament evaporation yielded I-V behavior in contact with the CH3OH-Me2Fc+/0 redox system that was characteristic of a pinned surface Fermi level, even for coverages of metal as low as 9 {\AA}. This indicates that proposed metal-insulator-semiconductor junctions with anomalously high barrier heights are difficult to obtain by such metalization and etching methods.",
author = "Amit Kumar and Lewis, {Nathan S}",
year = "1991",
language = "English",
volume = "95",
pages = "7021--7028",
journal = "Journal of Physical Chemistry",
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T1 - Further mechanistic studies of n-type Si photoelectrodes

T2 - Behavior in contact with methanol-dimethylferrocene+/0 and in contact with aqueous electrolytes

AU - Kumar, Amit

AU - Lewis, Nathan S

PY - 1991

Y1 - 1991

N2 - Mechanistic studies of n-Si photoelectrodes have been conducted using aqueous and nonaqueous electrolytes. In contact with the CH3OH-dimethylferrocene (Me2Fc)+/0 electrolyte, the dark current and open-circuit voltage (Voc) were not dependent on acceptor concentration for [Me2Fc+] ≤ 0.010 M and were only weakly dependent on acceptor concentration for [Me2Fc+] ≥ 0.010 M. For [Me2Fc+] between 0.3 mM and 0.050 M, the temperature dependence of Voc indicated that bulk-diffusion/recombination was the rate-limiting recombination process. In all of these experiments, conventional Shockley diode theory provided an excellent description of the solid/liquid junction properties. In a related set of experiments, HF-etched n-Si photoelectrodes ((100)- and (111)-oriented samples) and n-Si samples that had been metalized by several different methods all showed passivation in contact with Fe(CN)6 3-/4- (aq) or Br2/Br- (aq) electrolytes. For several metalized Si samples, etches that had been reported to produce metal islands on the Si surface instead yielded Si surfaces free of metal. All Si samples that had been metalized by filament evaporation yielded I-V behavior in contact with the CH3OH-Me2Fc+/0 redox system that was characteristic of a pinned surface Fermi level, even for coverages of metal as low as 9 Å. This indicates that proposed metal-insulator-semiconductor junctions with anomalously high barrier heights are difficult to obtain by such metalization and etching methods.

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