### Abstract

Current density vs potential, open-circuit voltage vs temperature, and differential capacitance vs potential measurements have been used to show that n-GaAs and n-Al_{x}Ga_{1-x}As electrodes exhibit partial Fermi level . pinning in contact with CH_{3}CN over a wide range of redox potentials. Despite a change of over 1.2 V in redox potential of the solution, the open-circuit voltage only changed by ∼300 mV. The slope of the open-circuit voltage vs redox potential of the solution was typically 0.33-0.44. Differential capacitance vs potential data also yielded a barrier height change of less than 300 mV for over 1.2 V change in the redox potential of the solution. The dependence of the current density vs potential behavior of n-GaAs/CH_{3}CN-ferricenium-ferrocene^{+/0} on variables such as the illumination intensity, dopant density of the semiconductor, concentration of redox acceptor in the solution, crystal face, electrolyte, and cell temperature was evaluated. The resultant kinetic data indicate that surface-state recombination is the dominant recombination mechanism at these interfaces, which are capable of producing an open-circuit voltage of 0.83 V at a short-circuit current density of 20 mA cm^{-2}, as well as energy conversion efficiencies of > 10%. X-ray photoelectron spectroscopy investigation of n-GaAs confirmed surface changes were induced by electrochemical operation of n-GaAs electrodes in CH_{3}CN-cobaltocenium-cobaltocene^{+/0} electrolyte. The presence of Fermi level pinning and the existence of changes in n-GaAs and n-Al_{x}Ga_{1-x}As electrode surfaces when these electrodes are in contact with CH_{3}CN-cobaltocenium-cobaltocene^{+/0} electrolyte complicates the extraction of k_{et} values from the steady-state current density vs potential behavior of n-GaAs or n-Al_{x}Ga_{1-x}As/CH_{3}CN contacts.

Original language | English |
---|---|

Pages (from-to) | 5436-5447 |

Number of pages | 12 |

Journal | Journal of Physical Chemistry B |

Volume | 104 |

Issue number | 23 |

Publication status | Published - Jun 15 2000 |

### Fingerprint

### ASJC Scopus subject areas

- Physical and Theoretical Chemistry
- Engineering(all)

### Cite this

*Journal of Physical Chemistry B*,

*104*(23), 5436-5447.

**Photoelectrochemical behavior of n-GaAs and n-AlxGa1-xas in CH3CN.** / Casagrande, Louis G.; Juang, Agnes; Lewis, Nathan S.

Research output: Contribution to journal › Article

*Journal of Physical Chemistry B*, vol. 104, no. 23, pp. 5436-5447.

}

TY - JOUR

T1 - Photoelectrochemical behavior of n-GaAs and n-AlxGa1-xas in CH3CN

AU - Casagrande, Louis G.

AU - Juang, Agnes

AU - Lewis, Nathan S

PY - 2000/6/15

Y1 - 2000/6/15

N2 - Current density vs potential, open-circuit voltage vs temperature, and differential capacitance vs potential measurements have been used to show that n-GaAs and n-AlxGa1-xAs electrodes exhibit partial Fermi level . pinning in contact with CH3CN over a wide range of redox potentials. Despite a change of over 1.2 V in redox potential of the solution, the open-circuit voltage only changed by ∼300 mV. The slope of the open-circuit voltage vs redox potential of the solution was typically 0.33-0.44. Differential capacitance vs potential data also yielded a barrier height change of less than 300 mV for over 1.2 V change in the redox potential of the solution. The dependence of the current density vs potential behavior of n-GaAs/CH3CN-ferricenium-ferrocene+/0 on variables such as the illumination intensity, dopant density of the semiconductor, concentration of redox acceptor in the solution, crystal face, electrolyte, and cell temperature was evaluated. The resultant kinetic data indicate that surface-state recombination is the dominant recombination mechanism at these interfaces, which are capable of producing an open-circuit voltage of 0.83 V at a short-circuit current density of 20 mA cm-2, as well as energy conversion efficiencies of > 10%. X-ray photoelectron spectroscopy investigation of n-GaAs confirmed surface changes were induced by electrochemical operation of n-GaAs electrodes in CH3CN-cobaltocenium-cobaltocene+/0 electrolyte. The presence of Fermi level pinning and the existence of changes in n-GaAs and n-AlxGa1-xAs electrode surfaces when these electrodes are in contact with CH3CN-cobaltocenium-cobaltocene+/0 electrolyte complicates the extraction of ket values from the steady-state current density vs potential behavior of n-GaAs or n-AlxGa1-xAs/CH3CN contacts.

AB - Current density vs potential, open-circuit voltage vs temperature, and differential capacitance vs potential measurements have been used to show that n-GaAs and n-AlxGa1-xAs electrodes exhibit partial Fermi level . pinning in contact with CH3CN over a wide range of redox potentials. Despite a change of over 1.2 V in redox potential of the solution, the open-circuit voltage only changed by ∼300 mV. The slope of the open-circuit voltage vs redox potential of the solution was typically 0.33-0.44. Differential capacitance vs potential data also yielded a barrier height change of less than 300 mV for over 1.2 V change in the redox potential of the solution. The dependence of the current density vs potential behavior of n-GaAs/CH3CN-ferricenium-ferrocene+/0 on variables such as the illumination intensity, dopant density of the semiconductor, concentration of redox acceptor in the solution, crystal face, electrolyte, and cell temperature was evaluated. The resultant kinetic data indicate that surface-state recombination is the dominant recombination mechanism at these interfaces, which are capable of producing an open-circuit voltage of 0.83 V at a short-circuit current density of 20 mA cm-2, as well as energy conversion efficiencies of > 10%. X-ray photoelectron spectroscopy investigation of n-GaAs confirmed surface changes were induced by electrochemical operation of n-GaAs electrodes in CH3CN-cobaltocenium-cobaltocene+/0 electrolyte. The presence of Fermi level pinning and the existence of changes in n-GaAs and n-AlxGa1-xAs electrode surfaces when these electrodes are in contact with CH3CN-cobaltocenium-cobaltocene+/0 electrolyte complicates the extraction of ket values from the steady-state current density vs potential behavior of n-GaAs or n-AlxGa1-xAs/CH3CN contacts.

UR - http://www.scopus.com/inward/record.url?scp=0033706013&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0033706013&partnerID=8YFLogxK

M3 - Article

VL - 104

SP - 5436

EP - 5447

JO - Journal of Physical Chemistry B

JF - Journal of Physical Chemistry B

SN - 1520-6106

IS - 23

ER -