Variable Temperature Spectroscopic Ellipsometry as a Tool for Insight into the Optical Order in the P3HT:PC70BM and PC70BM Layers

Two combined ellipsometric techniques—variable angle spectroscopic ellipsometry (VASE) and variable temperature spectroscopic ellipsometry (VTSE)—were used as tools to study the surface order and dielectric properties of thin films of a poly(3-hexylthiophene-2,5-diyl) (P3HT) mixture with a fullerene...

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Bibliographic Details
Published in:Polymers 2023-09, Vol.15 (18), p.3752
Main Authors: Hajduk, Barbara, Jarka, Paweł, Bednarski, Henryk, Tański, Tomasz
Format: Article
Language:English
Subjects:
Annealing
Approximation
Butyric acid
Dielectric films
Dielectric properties
Effective medium theory
Electrical conductivity
Ellipsometry
Fullerenes
Mixtures
Morphology
Photovoltaic cells
Physical properties
Polymers
Saturated fatty acids
Spectroellipsometry
Temperature
Thickness
Thin films
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Summary:Two combined ellipsometric techniques—variable angle spectroscopic ellipsometry (VASE) and variable temperature spectroscopic ellipsometry (VTSE)—were used as tools to study the surface order and dielectric properties of thin films of a poly(3-hexylthiophene-2,5-diyl) (P3HT) mixture with a fullerene derivative (6,6-phenyl-C71-butyric acid methyl ester) (PC70BM). Under the influence of annealing, a layer of the ordered PC70BM phase was formed on the surface of the blend films. The dielectric function of the ordered PC70BM was determined for the first time and used in the ellipsometric modeling of the physical properties of the P3HT:PC70BM blend films, such as their dielectric function and thickness. The applied ellipsometric optical model of the polymer–fullerene blend treats the components of the blend as a mixture of optically ordered and disordered phases, using the effective medium approximation for this purpose. The results obtained using the constructed model showed that a layer of the ordered PC70BM phase was formed on the surface of the layer of the polymer and fullerene mixture. Namely, as a result of thermal annealing, the thickness of the layer of the ordered fullerene phase increased, while the thickness of the underlying material layer decreased.
ISSN:2073-4360
2073-4360
DOI:10.3390/polym15183752