Material Property Changes in Defects Caused by Reverse Bias Exposure of CIGS Solar Cells
article
Partial shading of Cu(In,Ga)Se2 modules can lead
to the formation of reverse bias induced wormlike defects. These
wormlike defects act as local shunts and permanently decrease
module output. A good understanding of the formation and propagationmechanisms
of these defects is needed in order tomitigate the
negative effects, or to prevent these defects from forming. In this
article, wormlike defects were formed on small nonencapsulated
cells by exposing them to reverse bias conditions. Scanning electron
microscopy-energy-dispersive X-ray spectroscopy measurements
showed a rearrangement of elements: Indium, gallium, and copper
were replaced by cadmium, whereas selenium was replaced
by sulfur in the area around the defect. Moreover, additional
electronic-defect levels were found in that area with spectrally
resolved photoluminescence spectroscopy. Based on the material
changes in the area close to the wormlike defects, a propagation
mechanism is proposed. The model assumes a chemical reaction
as the driving force for propagation instead of melting because of
ohmic heating
to the formation of reverse bias induced wormlike defects. These
wormlike defects act as local shunts and permanently decrease
module output. A good understanding of the formation and propagationmechanisms
of these defects is needed in order tomitigate the
negative effects, or to prevent these defects from forming. In this
article, wormlike defects were formed on small nonencapsulated
cells by exposing them to reverse bias conditions. Scanning electron
microscopy-energy-dispersive X-ray spectroscopy measurements
showed a rearrangement of elements: Indium, gallium, and copper
were replaced by cadmium, whereas selenium was replaced
by sulfur in the area around the defect. Moreover, additional
electronic-defect levels were found in that area with spectrally
resolved photoluminescence spectroscopy. Based on the material
changes in the area close to the wormlike defects, a propagation
mechanism is proposed. The model assumes a chemical reaction
as the driving force for propagation instead of melting because of
ohmic heating
Topics
TNO Identifier
875665
Source
IEEE Journal of Photovoltaics, 9(6), pp. 1-5.
Pages
1-5
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