Correlation of spatially resolved photoluminescence and viscoelastic
mechanical properties of encapsulating EVA in differently aged PV modules
--------------------Supporting Information-------------------Photoluminescence
Spatial intensity images
Figure 1: Spectrally integrated photoluminescence intensity of the heat aged modules a) A-H and b) B-H. The color scale is
the same as in the article.
Figure 2: Spectrally integrated photoluminescence intensity of the reference modules, a) A-ref b) B-ref.
Spectral data
Figure 3: Spectra of the A-H specimen, a) measurement data, b) normalized spectra.
Figure 4: Spectra of the spectra of the B-H specimen, a) measurement data, b) normalized spectra.
Figure 5: Spectra of the spectra of the B-DH specimen, a) measurement data, b) normalized spectra.
Dynamic mechanical characterization
Reference modules
Figure 6: Temperature dependence of modulus for the a) A-ref specimen and b) the B-ref specimen. The strong increase in
storage modulus starting at about 150°C for the A-ref samples indicates that crosslinking occurs during the measurement.
The A-ref samples differ with respect to the qualitative shape of the curve of the temperature
dependence of the storage modulus from the samples from the aged specimens: The A-ref samples
show considerable post-crosslinking, indicated by the increase in modulus at about 150°C, which is a
clear sign of a crosslinking process during the measurement. In contrast to the A specimen the samples
from the B-ref module show no such signs. The consequence of this observation is, that the absolute
values of storage modulus and tan δ in the molten state are not comparable for the aged and the
reference samples of the A specimens.
Spatially averaged storage modulus at 40°C
Storage modulus at 40°C
Storage modulus [MPa]
4
3.5
3
2.5
2
1.5
1
0.5
0
A-ref
A-H
A-DH
B-ref
B-H
B-DH
B-UV
Figure 7: Storage modulus at 40°C averaged for all DMA measurements of a specimen. The error bars indicate the standard
deviation of all samples taken from the module.
The storage modulus at 40°C shows no systematic dependence on the location, thus the statistical
error for the storage modulus at 40°C in Figure 7 was set as the standard deviation of all values across
the specimen. The reference specimens, H and DH aged specimens do not deviate in storage modulus
at ambient temperature outside this error. Only the value of the UV specimen indicates a decrease
outside the error margin compared to the other modules.
Spatial distribution of DMA data
Figure 8: Values for storage modulus at 100°C with a fit according to equation 4 of the article. a) Heat aged specimens, b)
Damp-heat aged specimens.
Table of fit values for Luminescence and DMA data
A-H
A-DH
L-H
L-DH
Luminescence
a
b
5785
11010
6645
14950
2500*
2620
3000*
2320
β
0,57
0,82
0,34
0,3
Tan δ @ 100°C
a
b
0,163
0,059
0,165
0,027
0,15*
0,033
0,165
0,02
β
1,28
0,81
0,33
0,34
Storage modulus @ 100°C
a
b
β
0,468
0,14
0,89
0,486
0,1
1,24
0,425* 0,06
0,3
0,42*
0,05
0,27
Table 1: Complete set of fitted parameters according to Equation 6 of the article, based on the data of luminescence intensity,
tan δ and storage modulus at 100°C. Values with asterix* were held fixed for fitting.
UV influence
Spatial photoluminescence intensity image
Figure 9: Spectrally integrated photoluminescence intensity of the B-UV specimen. The color scale was extended to account
for the higher luminescence intensity. The cell itself is not visible. The luminescent plateau is about 4 mm from the cell edge.
The anomalies visible outside of the cell area are due to the clamping in the UV chamber. The dashed rectangle indicates the
location of sample extraction.
Dynamic mechanical characterization
Figure 10: Temperature scans of tan δ for all B-UV samples.
Figure 11: Comparison of the shape of the DMA curves of a) storage modulus and b) tan δ for the H and UV aged B-specimen
at the edge of the cell (0.5 cm) and in the center (7.0 cm).
Figure 12: Values for a) storage modulus and b) tan δ at 100°C for all B specimens.