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 were prepared 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 Cu 2-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 traps again 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 language | American English |
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Pages | 255-260 |
Number of pages | 6 |
DOIs | |
State | Published - 2003 |
Event | Compound Semiconductor Photovoltaics: Materials Research Society Symposium - San Francisco, California Duration: 22 Apr 2003 → 25 Apr 2003 |
Conference
Conference | Compound Semiconductor Photovoltaics: Materials Research Society Symposium |
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City | San Francisco, California |
Period | 22/04/03 → 25/04/03 |
Bibliographical note
For preprint version including online full-text document, see; NREL/CP-520-33949.NREL Publication Number
- NREL/CP-520-33084