Polymer fullerene solution phase behaviour and film formation pathways.

Area of Science:

• Materials Science
• Polymer Chemistry
• Physical Chemistry

Background:

• Polymer/fullerene composites are crucial for organic electronics.
• Controlling thin film morphology is essential for device performance.
• Solution processing offers a versatile method for fabricating these films.

Purpose of the Study:

• To investigate the phase behavior of polymer/fullerene/solvent ternary mixtures.
• To correlate solution phase behavior with the morphology of resulting composite thin films.
• To provide insights for optimizing the solution processing of polymer/fullerene composites.

Main Methods:

• Static and dynamic light scattering to analyze solution phase behavior.
• Atomic force microscopy and light microscopy to characterize film morphology.
• Preparation of films from solutions of varying ages and thermal annealing conditions.

Main Results:

• Solution phase behavior below polymer overlap concentration (c*) is governed by excluded volume and fullerene miscibility.
• Fullerene miscibility significantly influences the degree of polymer/fullerene exclusion.
• Film morphology varies significantly with solution age and thermal history, aligning with predicted phase boundaries.

Conclusions:

• The phase behavior of polymer/fullerene/solvent mixtures dictates thin film morphology.
• Tuning fullerene solubility and solvent asymmetry impacts phase separation and film structure.
• Findings are critical for the rational design of polymer/fullerene composites and organic electronic devices.