The estimation of PV-modules lifetime facilitates the further development and helps to lower risks for producers and
investors. One base for this extensive testing work is the knowledge of the degradation kinetics of encapsulating polymer
materials. Besides ethylen-vinylacetate copolymer (EVA), which is the prevalent material for encapsulation, new
materials like Poly-Vinyl-Butyral (PVB), and thermoplastic Poly-Urethan (TPU) become available and need the
assessment of their properties and the durability impact. In this context is it very important to identify the extent of
degradation caused by different parameters in order to identify the determining factor of polymer degradation as well as
potential interactions between different degradation processes.
To simulate long time degeneration processes accelerated aging under damp-heat and high-UV conditions was
performed on different EVA, TPU, and PVB samples. In this paper we report first results on measuring fluorescence
spectra from different encapsulation materials after accelerated ageing in dependence on time and aging procedure. Our
investigations clearly demonstrate that it is possible to follow damp-heat and UV induced aging processes of different
polymers used in PV-modules as encapsulation materials by luminescence detection.
The developments in porphyrin chemistry over the last decades give great advantages for the practical use of
porphyrin-based compounds. The properties of these compounds can be systematically tuned by rational utilization of
substituents on meso- and/or β-positions as well as by using different metal atoms in the center of the tetrapyrrole
Recently we prepared novel mono- and bis-functionalized cycloketo-porphyrins (CKPors). In this work the results
of detailed spectroscopic investigations of these compounds are presented. It was found that a seven-membered ketone
exocycle remarkably influences the photophysical properties of the CKPor systems. For mono-functionalized CKPors it
results in strongly enhanced probability of intersystem crossing S1 → T1 with an ISC quantum yield up to 90%.
Moreover, the absorption of all CKPors undergoes a bathochromic shift and the Q-bands extinction is above two times
higher compared to that of H2TPP, what makes these compounds promising candidates for use as photosensitizers in
photodynamic therapy of tumors.
For the first time two NH-tautomers of nonsymmetrical CKPors were experimentally resolved at room
temperature using optical spectroscopic methods. It was found that the concentration of tautomer A with a lower
frequency of the S0,0 → S1,0 transition is higher than that one of tautomer B at room temperature, and becomes dominant
with cooling down. In contrast - and as it is expected - only one optical active species was observed for non-symmetrical
CKPor with a central Zn(II) atom as well as for symmetrical bis-CKPor.
The photophysical properties of DAB-dendrimers from 1st to 4th generation as well as Diaminohexane - all
substituted with the in maximum achievable quantity of pheophorbide a (Pheo) molecules were studied in comparison
with a novel hexapyropheophorbide a - fullerene hexaadduct (FHP6) and a fullerene [6:0]-hexaadduct which carries
twelve pyropheophorbide a units (FHP12) using both steady-state and time-resolved spectroscopic methods. It was
found that neighboring dye molecules covalently linked to one DAB- or fullerene moiety due to the length and high
flexibility of carbon chains could stack with each other. This structural property is the reason for the possibility of
formation different types of energy traps, which were resolved experimentally. The dipole-dipole resonance F&diaero;rster
energy transfer between the dye molecules coupled to one complex caused a very fast and efficient delivery of the
excitation to a trap. As result the fluorescence as well as the singlet oxygen quantum yields of the different complexes
were reduced with increasing number of dye molecules per complex. Nevertheless in every case the singlet oxygen
generation was less influenced then the fluorescence quantum yield, exposing the complex to a non-negligible amount of
excited oxygen in the singlet state. While the fullerene complexes turned out to be stable under these conditions, the
DAB-dendrimer-backbones were completely fragmented to small rudiments carrying just one or a small number of dye