Defects in Cu(In,Ga)Se 2 chalcopyrite semiconductors: A comparative study of material properties, defect states, and photovoltaic performance

Qing Cao, Oki Gunawan, Matthew Copel, Kathleen B. Reuter, S. Jay Chey, Vaughn R. Deline, David B. Mitzi

Research output: Contribution to journalArticle

Abstract

Understanding defects in Cu(In,Ga)(Se,S) 2 (CIGS), especially correlating changes in the film formation process with differences in material properties, photovoltaic (PV) device performance, and defect levels extracted from admittance spectroscopy, is a critical but challenging undertaking due to the complex nature of this polycrystalline compound semiconductor. Here we present a systematic comparative study wherein varying defect density levels in CIGS fi lms were intentionally induced by growing CIGS grains using different selenium activity levels. Material characterization results by techniques including X-ray diffraction, scanning electron microscopy, transmission electron microscopy, secondary ion mass spectrometry, X-ray photoelectron spectroscopy, and medium energy ion scattering indicate that this process variation, although not significantly affecting CIGS grain structure, crystal orientation, or bulk composition, leads to enhanced formation of a defective chalcopyrite layer with high density of indium or gallium at copper antisite defects ((In, Ga) Cu) near the CIGS surface, for CIGS films grown with insufficient selenium supply. This defective layer or the film growth conditions associated with it is further linked with observed current-voltage characteristics, including rollover and crossover behavior, and a defect state at around 110 meV (generally denoted as the N1 defect) commonly observed in admittance spectroscopy. The impact of the (In, Ga) Cu defects on device PV performance is also established.

Original languageEnglish (US)
Pages (from-to)845-853
Number of pages9
JournalAdvanced Energy Materials
Volume1
Issue number5
DOIs
StatePublished - Oct 1 2011
Externally publishedYes

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Materials properties
Semiconductor materials
Defects
Selenium
Spectroscopy
Gallium
Indium
Defect density
Crystal microstructure
Film growth
Current voltage characteristics
Secondary ion mass spectrometry
Crystal orientation
chalcopyrite
Copper
X ray photoelectron spectroscopy
Scattering
Ions
Transmission electron microscopy
X ray diffraction

ASJC Scopus subject areas

  • Renewable Energy, Sustainability and the Environment
  • Materials Science(all)

Cite this

Defects in Cu(In,Ga)Se 2 chalcopyrite semiconductors : A comparative study of material properties, defect states, and photovoltaic performance. / Cao, Qing; Gunawan, Oki; Copel, Matthew; Reuter, Kathleen B.; Chey, S. Jay; Deline, Vaughn R.; Mitzi, David B.

In: Advanced Energy Materials, Vol. 1, No. 5, 01.10.2011, p. 845-853.

Research output: Contribution to journalArticle

Cao, Qing ; Gunawan, Oki ; Copel, Matthew ; Reuter, Kathleen B. ; Chey, S. Jay ; Deline, Vaughn R. ; Mitzi, David B. / Defects in Cu(In,Ga)Se 2 chalcopyrite semiconductors : A comparative study of material properties, defect states, and photovoltaic performance. In: Advanced Energy Materials. 2011 ; Vol. 1, No. 5. pp. 845-853.
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