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Temperature dependency of the electrical parameters of CIGS solar cells
0.02 SLG Au
PI
Temperature coefficient n (/ o C) -0.01
0.01
SLG In
0.00
-0.02
-0.02 0.00 0.02 0.04 0.06
2 o
Figure 4.6 Temperature coefficient J sc (mA/cm / C)
The relationship between the temperature coefficients of the ideality factor and of the short circuit current density.
short circuit current with a temperature increase. This is expected since the band gap
energy E (T) decreases slightly with temperature and more photons therefore have
g
enough energy to create electron hole pairs leading to a higher J . This has a minor
ph
positive effect on the efficiency of the cell [20].
However, this is not the case for all samples: the short circuit current density of
the cells on SLG declined with strongly varying numbers, which can be as low as
dJ sc =-0.019 mA/cm /°C. This negative temperature dependency for the J of CIGS
2
dT sc
modules was also detected in another study, giving dJ sc = -0.007 mA/cm / C [1].
2 o
dT
It is proposed [19] that the negative temperature coefficient for the SLG samples is
caused by enhanced recombination. When the electrical parameters influencing this
factor are compared between the PI and SLG samples, the strongest effect can probably
be seen in the evolution of the ideality factor. The temperature coefficients of the short
circuit current density and the ideality factor are shown in Figure 4.6. This figure shows
that the samples with a positive trend for the ideality factor have a negative trend for the
current density. This can be explained by the fact that a higher ideality factor negatively
impacts the current density, since every inefficient recombination corresponds to an
electron which will not contribute to the output current.
Additionally to this clear trend of the ideality factor, it was also concluded that for
the PI samples that the photocurrent and saturation current densities have different
trends with temperature than the SLG samples. The PI samples have shown an
119
0.02 SLG Au
PI
Temperature coefficient n (/ o C) -0.01
0.01
SLG In
0.00
-0.02
-0.02 0.00 0.02 0.04 0.06
2 o
Figure 4.6 Temperature coefficient J sc (mA/cm / C)
The relationship between the temperature coefficients of the ideality factor and of the short circuit current density.
short circuit current with a temperature increase. This is expected since the band gap
energy E (T) decreases slightly with temperature and more photons therefore have
g
enough energy to create electron hole pairs leading to a higher J . This has a minor
ph
positive effect on the efficiency of the cell [20].
However, this is not the case for all samples: the short circuit current density of
the cells on SLG declined with strongly varying numbers, which can be as low as
dJ sc =-0.019 mA/cm /°C. This negative temperature dependency for the J of CIGS
2
dT sc
modules was also detected in another study, giving dJ sc = -0.007 mA/cm / C [1].
2 o
dT
It is proposed [19] that the negative temperature coefficient for the SLG samples is
caused by enhanced recombination. When the electrical parameters influencing this
factor are compared between the PI and SLG samples, the strongest effect can probably
be seen in the evolution of the ideality factor. The temperature coefficients of the short
circuit current density and the ideality factor are shown in Figure 4.6. This figure shows
that the samples with a positive trend for the ideality factor have a negative trend for the
current density. This can be explained by the fact that a higher ideality factor negatively
impacts the current density, since every inefficient recombination corresponds to an
electron which will not contribute to the output current.
Additionally to this clear trend of the ideality factor, it was also concluded that for
the PI samples that the photocurrent and saturation current densities have different
trends with temperature than the SLG samples. The PI samples have shown an
119
