Acceptor-Enhanced Local Order in Conjugated Polymer Films

Area of Science:

• Materials Science
• Polymer Chemistry
• Organic Electronics

Background:

• Disorder in conjugated polymers is a significant limitation for their application in organic electronics.
• MEH-PPV is a widely studied conjugated polymer often exhibiting disorder.

Purpose of the Study:

• To investigate the effect of an electronic acceptor, trinitrofluorenone (TNF), on the structural and electronic order of MEH-PPV.
• To explore methods for enhancing the order of conjugated polymers for improved electronic properties.

Main Methods:

• X-ray diffraction (XRD) to analyze structural patterns.
• Surface roughness measurements.
• Low-frequency Raman spectroscopy to assess electronic broadening.
• Photoinduced absorption and surface photovoltage spectroscopy to study electronic states.

Main Results:

• Addition of TNF to MEH-PPV resulted in a highly structured XRD pattern, indicating semicrystalline behavior.
• Increased surface roughness suggested the formation of crystalline nanodomains upon TNF addition.
• Narrowed low-frequency Raman features indicated reduced inhomogeneous broadening.
• Disappearance of photoexcited and dark polymer intragap electronic states was observed.

Conclusions:

• The enhanced order in MEH-PPV/TNF blends is attributed to the formation of a ground-state charge-transfer complex.
• This study demonstrates a viable strategy for increasing the structural order of conjugated polymers using acceptor additives.
• Findings are crucial for controlling structural properties and advancing organic electronic device performance.