Microelectrical Characterizations of Junctions in Solar Cell Devices by Scanning Kelvin Probe Force Microscopy

C. S. Jiang, A. Ptak, B. Yan, H. R. Moutinho, J. V. Li, M. M. Al-Jassim

Research output: Contribution to journalArticlepeer-review

17 Scopus Citations

Abstract

Scanning Kelvin probe force microscopy was applied to the microelectrical characterizations of junctions in solar cell devices. Surface Fermi-level pinning effects on the surface potential measurement were avoided by applying a bias voltage (Vb) to the device and taking the Vb-induced potential and electric field changes. Two characterizations are presented: the first is a direct measurement of Bi-induced junction shift in GaInNAs(Bi) cells; the second is a junction-uniformity measurement in a-Si:H devices. In the first characterization, using Bi as a surfactant during the molecular beam epitaxy growth of GaInNAs(Bi) makes the epitaxial layer smoother. However, the electrical potential measurement exhibits a clear Bi-induced junction shift to the back side of the absorber layer, which results in significant device degradation. In the second characterization, the potential measurement reveals highly non-uniform electric field distributions across the n-i-p junction of a-Si:H devices; the electric field concentrates much more at both n/i and i/p interfaces than in the middle of the i-layer. This non-uniform electric field is due possibly to high defect concentrations at the interfaces. The potential measurements further showed a significant improvement in the electric field uniformity by depositing buffer layers at the interfaces, and this indeed improved the device performance.

Original languageAmerican English
Pages (from-to)952-957
Number of pages6
JournalUltramicroscopy
Volume109
Issue number8
DOIs
StatePublished - 2009

NREL Publication Number

  • NREL/JA-520-43804

Keywords

  • Atomic force microscopy
  • Microscopic methods
  • Specifically for solid interfaces and multilayers

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