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Chapter 2
Abstract
As Cu(In,Ga)Se (CIGS) photovoltaic technology matures to production on an industrial
2
scale, its long-term stability becomes increasingly important: the electric yield and thus
the revenue of a PV system depend on both the initial conversion efficiency as well as its
development over time. Increasing the long term stability of CIGS modules by understand -
ing and lowering the degradation of this PV technology is therefore a key strategy for mar -
ket success of this technology. Furthermore, increasing the long-term stability of solar cell
materials allows to lower the demands and thus the cost of barriers within CIGS modules.
In this review chapter, the result of an extensive literature on the stability of CIGS solar cells
and modules is presented. This review focuses on the behaviour of unencapsulated CIGS
solar cells and (mini)modules when exposed to different accelerated lifetime tests, like el-
evated temperature and humidity. The changes in electrical and physical performance
due to these tests, as well as the chemical reactions that are causing these changes, are
described.
Additionally, the influence of these accelerated lifetime tests on the individual layers of
the CIGS solar cell has been summarised. In the following chapters, the stability of both
the transparent conducting ZnO:Al front contact and the molybdenum back contact, as
well as on the CIGS and buffer layers is discussed. Stability issues related to the design of
CIGS modules, like the application of grid structures and monolithic interconnection, are
presented as well.
26
Abstract
As Cu(In,Ga)Se (CIGS) photovoltaic technology matures to production on an industrial
2
scale, its long-term stability becomes increasingly important: the electric yield and thus
the revenue of a PV system depend on both the initial conversion efficiency as well as its
development over time. Increasing the long term stability of CIGS modules by understand -
ing and lowering the degradation of this PV technology is therefore a key strategy for mar -
ket success of this technology. Furthermore, increasing the long-term stability of solar cell
materials allows to lower the demands and thus the cost of barriers within CIGS modules.
In this review chapter, the result of an extensive literature on the stability of CIGS solar cells
and modules is presented. This review focuses on the behaviour of unencapsulated CIGS
solar cells and (mini)modules when exposed to different accelerated lifetime tests, like el-
evated temperature and humidity. The changes in electrical and physical performance
due to these tests, as well as the chemical reactions that are causing these changes, are
described.
Additionally, the influence of these accelerated lifetime tests on the individual layers of
the CIGS solar cell has been summarised. In the following chapters, the stability of both
the transparent conducting ZnO:Al front contact and the molybdenum back contact, as
well as on the CIGS and buffer layers is discussed. Stability issues related to the design of
CIGS modules, like the application of grid structures and monolithic interconnection, are
presented as well.
26
