Evolution of Electronic Properties of (Cu(In,Ga)Se2 (CIGS)-Based Solar Cells During a 3-Stage Growth Process: Preprint

Research output: Contribution to conferencePaper

Abstract

We investigated the electronic properties of ZnO/CdS/CIGS /Mo/SLG polycrystalline thin-film solar cells with compositions ranging from Cu-rich to In(Ga)-rich by deep-level transient spectroscopy (DLTS) and capacitance-voltage (C-V) measurements. This compositional change represents the evolution of the film during growth by the 3-stage process. Two sets (four samples each) of CIGS thin films wereprepared with Ga/(In+Ga) ratios of~0.3 (low Ga) and~0.6 (high Ga). The Cu/(In+Ga) ratio ranges from 1.24 (Cu-rich) to 0.88 (In(Ga)-rich). The films were treated with NaCN to remove the Cu2-xSe phase where needed. Key results include: (1) For low-Ga devices, DLTS data show that acceptor-like traps dominate in samples where CIGS grains do not go through the Cu-rich to In(Ga)-rich transition,whereas donor-like traps dominate in In(Ga)-rich samples. Therefore, we see a clear transformation of defects from acceptor-like to donor-like traps. The activation energies of these traps range from 0.12 to 0.63 eV. We also observed that NaCN treatment eliminates a deep minority trap in the In(Ga)-rich devices, (2) For high-Ga devices, only majority-carrier traps were detected. These trapsagain range from shallow to deep, (3) The carrier concentration around the junction and the density of traps decrease as the CIGS becomes more In(Ga)-rich.
Original languageAmerican English
Number of pages9
StatePublished - 2003
Event2003 Materials Research Society Spring Meeting - San Francisco, California
Duration: 21 Apr 200325 Apr 2003

Conference

Conference2003 Materials Research Society Spring Meeting
CitySan Francisco, California
Period21/04/0325/04/03

NREL Publication Number

  • NREL/CP-520-33949

Keywords

  • acceptor-like traps
  • capacitance voltage (CV)
  • deep level transient spectroscopy (DLTS)
  • polycrystalline
  • PV
  • solar cells
  • thin films

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