Experimental measurement of quasi-fermi levels at an illuminated semiconductor/liquid contact

Ming X. Tan, C. N. Kenyon, Nathan S Lewis

Research output: Contribution to journalArticle

18 Citations (Scopus)

Abstract

A novel electrode geometry and contacting procedure has allowed measurement of the quasi-Fermi levels, i.e., the apparent electrochemical potentials, of electrons and holes at an illuminated semiconductor/liquid contact. The key feature of our experiments is the use of a lithographically patterned, high purity (100-400 Ω·cm n-type float zone material), low dopant density Si sample in contact with CH3OH-dimethylferrocene+/0 solutions. The photogenerated carriers can be collected at the back side of the Si sample through a series of diffused n+ and p+ points. The lifetime of photogenerated carriers approaches 2 ms in this sample, indicating that electron-hole recombination is minimized in the bulk of the semiconductor. Furthermore, surface recombination is minimized by use of low saturation current density, ohmic-selective contacts at the back of the sample. The solid/liquid contact also has a low recombination rate. Therefore, the potentials measured at the diffused points yield values for the quasi-Fermi levels of electrons and holes under illumination of the semiconductor/liquid contact. Transient photovoltage measurements have also been performed to confirm quantitatively that the quasi-Fermi levels are flat across the Si samples used in this work.

Original languageEnglish
Pages (from-to)4959-4962
Number of pages4
JournalJournal of Physical Chemistry
Volume98
Issue number19
Publication statusPublished - 1994

Fingerprint

Fermi level
Contacts (fluid mechanics)
Semiconductor materials
Liquids
liquids
Electrons
low density materials
float zones
photovoltages
yield point
Current density
Lighting
Doping (additives)
purity
electrons
Electrodes
illumination
Geometry
current density
saturation

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

Experimental measurement of quasi-fermi levels at an illuminated semiconductor/liquid contact. / Tan, Ming X.; Kenyon, C. N.; Lewis, Nathan S.

In: Journal of Physical Chemistry, Vol. 98, No. 19, 1994, p. 4959-4962.

Research output: Contribution to journalArticle

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AB - A novel electrode geometry and contacting procedure has allowed measurement of the quasi-Fermi levels, i.e., the apparent electrochemical potentials, of electrons and holes at an illuminated semiconductor/liquid contact. The key feature of our experiments is the use of a lithographically patterned, high purity (100-400 Ω·cm n-type float zone material), low dopant density Si sample in contact with CH3OH-dimethylferrocene+/0 solutions. The photogenerated carriers can be collected at the back side of the Si sample through a series of diffused n+ and p+ points. The lifetime of photogenerated carriers approaches 2 ms in this sample, indicating that electron-hole recombination is minimized in the bulk of the semiconductor. Furthermore, surface recombination is minimized by use of low saturation current density, ohmic-selective contacts at the back of the sample. The solid/liquid contact also has a low recombination rate. Therefore, the potentials measured at the diffused points yield values for the quasi-Fermi levels of electrons and holes under illumination of the semiconductor/liquid contact. Transient photovoltage measurements have also been performed to confirm quantitatively that the quasi-Fermi levels are flat across the Si samples used in this work.

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