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Stability of Cu(In,Ga)Se 2 Solar Cells
The encapsulation materials and humidity barriers impacted the stability of solar cells
significantly. Samples with water barriers with a higher WVTR retain their efficiency
longer than samples with low WVTR. EVA was often the encapsulation material with
the least positive impact, potentially due to the formation of acetic acid, which can
lead to the dissolution of ZnO:Al.
2.5 Degradation from the module perspective
According to the focus of this review chapter, the previous sectins have described the
material degradation happening within the individual layers within CIGS solar cells
and modules. However, some issues specific for CIGS modules do also influence the
degradation. These issues have to be discussed as well since module producers use
various CIGS specific techniques in order to make modules from large area CIGS solar
cell stacks. These techniques can be separated into two categories:
1. Monolithic integration by scribing – this leads to cells of typically 5 to 10 mm
width (Figure 2.13 en chapter 2.5.1).
2. Large area deposition of metallic grids, normally followed by cutting into
smaller cells that are interconnected (width and length of one cell typically 10
to 200 mm (chapter 2.5.2).)
In this chapter, the available but limited knowledge about the impact of these tech-
niques on CIGS module reliability is presented.
R S
G SH R S
R C
P1 P2 P3
Front contact: Buer Back contact:
TCO molybdenum
Front contact: Absorber: Substrate
i-ZnO CIGS
Figure 2.13:
A monolithic interconnect structure for CIGS modules. Functional parts that may degrade and thereby lead to a reduction in
conversion efficiency are indicated. This figure is based on reference [27].
77
The encapsulation materials and humidity barriers impacted the stability of solar cells
significantly. Samples with water barriers with a higher WVTR retain their efficiency
longer than samples with low WVTR. EVA was often the encapsulation material with
the least positive impact, potentially due to the formation of acetic acid, which can
lead to the dissolution of ZnO:Al.
2.5 Degradation from the module perspective
According to the focus of this review chapter, the previous sectins have described the
material degradation happening within the individual layers within CIGS solar cells
and modules. However, some issues specific for CIGS modules do also influence the
degradation. These issues have to be discussed as well since module producers use
various CIGS specific techniques in order to make modules from large area CIGS solar
cell stacks. These techniques can be separated into two categories:
1. Monolithic integration by scribing – this leads to cells of typically 5 to 10 mm
width (Figure 2.13 en chapter 2.5.1).
2. Large area deposition of metallic grids, normally followed by cutting into
smaller cells that are interconnected (width and length of one cell typically 10
to 200 mm (chapter 2.5.2).)
In this chapter, the available but limited knowledge about the impact of these tech-
niques on CIGS module reliability is presented.
R S
G SH R S
R C
P1 P2 P3
Front contact: Buer Back contact:
TCO molybdenum
Front contact: Absorber: Substrate
i-ZnO CIGS
Figure 2.13:
A monolithic interconnect structure for CIGS modules. Functional parts that may degrade and thereby lead to a reduction in
conversion efficiency are indicated. This figure is based on reference [27].
77
