Understanding the Defect Physics in Polycrystalline Photovoltaic Materials

Yanfa Yan, K. M. Jones, C. S. Jiang, X. Z. Wu, R. Noufi, M. M. Al-Jassim

Research output: Contribution to journalArticlepeer-review

48 Scopus Citations

Abstract

We use the combination of high-resolution electron microscopy and density-functional theory to study the atomic structure and electronic effects of structural defects, such as lamellar twins, stacking faults, and double-positioning twin boundaries in polycrystalline photovoltaic materials such as Si, CdTe, and CuInSe2. We find that individual lamellar twins and stacking faults do not create deep levels in all these materials. However, areas with high density of these defects can form buried wurtzite layers that introduce a barrier to the majority carriers. Double-positioning twin boundaries, which contain dislocation cores, create deep levels in Si and CdTe. Surprisingly, however, they do not create deep levels in CuInSe2. These results may explain the fact that Si and CdTe solar cells usually require special passivation, whereas CuInSe2 solar cells do not. Our further study on the passivation effects indicates that grain boundaries in Si cannot be passivated completely by H alone. On the other hand, grain boundaries in CdTe can be passivated well by Cl and I.

Original languageAmerican English
Pages (from-to)25-32
Number of pages8
JournalPhysica B: Condensed Matter
Volume401-402
DOIs
StatePublished - 2007

NREL Publication Number

  • NREL/JA-520-41893

Keywords

  • CdTe
  • CuInSe
  • Density-functional theory
  • Electron microscopy
  • Grain boundaries
  • Photovoltaic
  • Si

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