Page 131 - Mirjam-Theelen-Degradation-of-CIGS-solar-cells
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Degradation mechanisms of the molybdenum back contact
Table 5.1 Summary of deposition parameters of direct current sputtering of
molybdenum.
Deposition parameters Mo2 Mo10 Mo15 Mo2Se Mo10Se Mo15Se
Argon pressure (mTorr) 2 10 15 2 10 15
Argon flow (sccm) 11 69 110 11 69 110
Current (A) 3.00 3.35 3.55 3.00 3.35 3.55
Selenised no no no yes yes yes
Figure 5.1
The lift-off procedure for the preparation of the 'lift-off' films used for degradation.
at 580 C for 30 minutes, to simulate the MoSe formation that is expected to occur while
o
2
depositing CIGS on top of Mo. This selenisation process offered the same conditions
as during CIGS coevapouration, but without the heating of the metal sources.
5.2.1.2 Lift-off experiment
Before the deposition, the target was pre-sputtered. On both samples, a bottom layer
of molybdenum was first deposited an argon pressure of 25 mTorr. The top layer had
a different sputter pressure for the two samples: The sputter pressure for the dense
sample (´Mo25/2´) was 2mTorr, while the porous sample (´Mo25/15´) was deposited at
15 mTorr. More information about the deposition conditions can be found in Table 5.2 .
The higher sputter pressure for the top layer (Mo25/15) leads to the formation of a film
with more porous structure and therefore a higher sheet resistance [10].
After molybdenum deposition, a CIGS layer was deposited on both types of
molybdenum by a three stage coevapouration process at 580 C [11,12].
o
A piece of soda lime glass was glued on top of the CIGS layer with EPO-TEK 353 ND
o
glue. After the drying of the glue (30 minutes at 120C), the second piece of glass
was used to lift off the CIGS layer. The lift-off process resulted in separate CIGS and
129
Table 5.1 Summary of deposition parameters of direct current sputtering of
molybdenum.
Deposition parameters Mo2 Mo10 Mo15 Mo2Se Mo10Se Mo15Se
Argon pressure (mTorr) 2 10 15 2 10 15
Argon flow (sccm) 11 69 110 11 69 110
Current (A) 3.00 3.35 3.55 3.00 3.35 3.55
Selenised no no no yes yes yes
Figure 5.1
The lift-off procedure for the preparation of the 'lift-off' films used for degradation.
at 580 C for 30 minutes, to simulate the MoSe formation that is expected to occur while
o
2
depositing CIGS on top of Mo. This selenisation process offered the same conditions
as during CIGS coevapouration, but without the heating of the metal sources.
5.2.1.2 Lift-off experiment
Before the deposition, the target was pre-sputtered. On both samples, a bottom layer
of molybdenum was first deposited an argon pressure of 25 mTorr. The top layer had
a different sputter pressure for the two samples: The sputter pressure for the dense
sample (´Mo25/2´) was 2mTorr, while the porous sample (´Mo25/15´) was deposited at
15 mTorr. More information about the deposition conditions can be found in Table 5.2 .
The higher sputter pressure for the top layer (Mo25/15) leads to the formation of a film
with more porous structure and therefore a higher sheet resistance [10].
After molybdenum deposition, a CIGS layer was deposited on both types of
molybdenum by a three stage coevapouration process at 580 C [11,12].
o
A piece of soda lime glass was glued on top of the CIGS layer with EPO-TEK 353 ND
o
glue. After the drying of the glue (30 minutes at 120C), the second piece of glass
was used to lift off the CIGS layer. The lift-off process resulted in separate CIGS and
129
