Aggregation-Tuned Charge Transport and Threshold Voltage Modulation in Poly(3-hexylthiophene) Field-Effect...

Area of Science:

• Organic Electronics
• Materials Science
• Polymer Physics

Background:

• Poly(3-hexylthiophene) (P3HT) is a key organic semiconductor used in electronic devices.
• Film morphology significantly impacts the performance of P3HT-based field-effect transistors (FETs).
• Understanding structure-property relationships is crucial for optimizing P3HT device design.

Purpose of the Study:

• To investigate the thickness-driven optimum in aggregation structure and charge transport of sonicated P3HT FETs.
• To elucidate the relationship between film thickness, molecular ordering, and device performance.
• To guide the rational design of P3HT devices for applications like photovoltaics and sensing.

Main Methods:

• Fabrication and characterization of P3HT FETs with varying film thicknesses.
• Photoluminescence (PL) spectroscopy to analyze aggregate formation and interchain coupling.
• X-ray diffraction (XRD) to assess crystalline structure and lamellar ordering.
• Absorption spectroscopy and Spano model analysis for interchain order evaluation.

Main Results:

• Mobility peaks at film thicknesses of approximately 10-20 nm.
• This optimum correlates with minimum photoluminescence vibronic ratio (indicating strong H-aggregate coupling) and sharpened XRD peaks.
• Optimal mobility arises from a balance between intrachain planarity (J-aggregates) and interchain connectivity (H-aggregates).
• Excessive thickness leads to over-aggregation, increased trap states, and reduced device performance, evidenced by a sharp rise in threshold voltage.

Conclusions:

• Film thickness is a critical parameter for optimizing charge transport in P3HT FETs.
• An optimal balance of polymer aggregation structures (H- and J-aggregates) is essential for high mobility.
• Solution processing techniques like sonication and precise thickness control can tune P3HT device performance for specific applications.