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Variable Temperature Spectroscopic Ellipsometry as a Tool for Insight into the Optical Order in the P3HT:PC70BM and
Barbara Hajduk1, Paweł Jarka2, Henryk Bednarski1
1Centre of Polymer and Carbon Materials, Polish Academy of Sciences, 34 Marie Curie-Skłodowska Str., 41-819 Zabrze, Poland.
Polymers
|September 28, 2023
Summary
Annealing poly(3-hexylthiophene-2,5-diyl) (P3HT) and PC70BM blend films created an ordered PC70BM surface layer. This study determined the dielectric function of this ordered phase for the first time.
Area of Science:
- Materials Science
- Optoelectronics
- Polymer Science
Background:
- Polymer-fullerene blends are crucial for organic electronics.
- Understanding thin film morphology and dielectric properties is key to device performance.
- Previous studies lacked detailed surface phase characterization.
Purpose of the Study:
- To investigate the surface ordering and dielectric properties of P3HT:PC70BM blend films.
- To determine the dielectric function of the ordered PC70BM phase.
- To develop an ellipsometric model for analyzing blend film physical properties.
Main Methods:
- Utilized variable angle spectroscopic ellipsometry (VASE) and variable temperature spectroscopic ellipsometry (VTSE).
- Developed an optical model treating blend components as ordered and disordered phases using effective medium approximation.
- Applied thermal annealing to induce surface phase ordering.
Main Results:
- Confirmed the formation of an ordered PC70BM phase on the blend film surface after annealing.
- Determined the dielectric function of the ordered PC70BM phase.
- Observed an increase in ordered fullerene phase thickness and a decrease in underlying layer thickness upon annealing.
Conclusions:
- Ellipsometry is effective for characterizing polymer-fullerene blend thin films.
- Thermal annealing promotes surface segregation of the ordered PC70BM phase.
- The determined dielectric function aids in accurate physical property modeling of P3HT:PC70BM blends.
