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

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

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18 Citations (Scopus)


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
Issue number19
Publication statusPublished - 1994

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

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