Page 218 - Mirjam-Theelen-Degradation-of-CIGS-solar-cells
P. 218
Chapter 7
Figure 7.1
Copper, indium, gallium, selenium and sodium concentration profiles perpendicularly to the grain boundary interface in a
CIGS layer on the end of the three stage coevapouration process [9].
7.1.2 Sodium introduction
Sodium can be applied in various ways: When soda lime glass is used as a substrate,
sodium and potassium are often supplied during the growth process by diffusion
from the substrate through the molybdenum back electrode into the CIGS layer. For
substrates that do not contain the required amount of sodium or for more controlled
sodium addition, alternative methods such as deposition of a sodium containing back
contact layer (Mo:Na) or the use of NaF as sodium source. The latter can be used by
deposition of a precursor layer, co-evapouration during the CIGS growth process or
evapouration of NaF after the CIGS growth in a post-deposition treatment (PDT) [8].
In this case, the sodium and potassium have only been obtained from the soda lime
glass substrates.
This study focuses on the impact of damp heat and illumination on unencapsulated
CIGS solar cells with high and low concentrations of the alkali elements. The impact of
these elements on the stability performance of the solar cells is evaluated. The mech-
anisms which might be responsible for the degradation of CIGS solar cells under si-
multaneous damp heat and illumination conditions are proposed.
7.2 Experimental
CIGS solar cells were deposited as described in chapter 3.2. Alkali-rich solar cells
were produced following the standard deposition procedure, while alkali-poor solar
216
Figure 7.1
Copper, indium, gallium, selenium and sodium concentration profiles perpendicularly to the grain boundary interface in a
CIGS layer on the end of the three stage coevapouration process [9].
7.1.2 Sodium introduction
Sodium can be applied in various ways: When soda lime glass is used as a substrate,
sodium and potassium are often supplied during the growth process by diffusion
from the substrate through the molybdenum back electrode into the CIGS layer. For
substrates that do not contain the required amount of sodium or for more controlled
sodium addition, alternative methods such as deposition of a sodium containing back
contact layer (Mo:Na) or the use of NaF as sodium source. The latter can be used by
deposition of a precursor layer, co-evapouration during the CIGS growth process or
evapouration of NaF after the CIGS growth in a post-deposition treatment (PDT) [8].
In this case, the sodium and potassium have only been obtained from the soda lime
glass substrates.
This study focuses on the impact of damp heat and illumination on unencapsulated
CIGS solar cells with high and low concentrations of the alkali elements. The impact of
these elements on the stability performance of the solar cells is evaluated. The mech-
anisms which might be responsible for the degradation of CIGS solar cells under si-
multaneous damp heat and illumination conditions are proposed.
7.2 Experimental
CIGS solar cells were deposited as described in chapter 3.2. Alkali-rich solar cells
were produced following the standard deposition procedure, while alkali-poor solar
216
