Thiophene-Thiazole-Based Semiconducting Copolymers for High-Performance Polymer Field-Effect Transistors

Area of Science:

• Materials Science
• Organic Electronics
• Semiconductor Physics

Background:

• Organic field-effect transistors (OFETs) are crucial for flexible electronics.
• Developing novel semiconducting polymers is key to improving OFET performance.
• Controlling thin-film morphology is essential for efficient charge transport.

Purpose of the Study:

• To synthesize and characterize a new donor-acceptor semiconducting copolymer (PQTBTz-TT-C8).
• To investigate the relationship between film morphology (controlled by spin-coating rate) and charge transport properties in OFETs.
• To understand how film thickness influences device performance.

Main Methods:

• Synthesis of PQTBTz-TT-C8 copolymer.
• Fabrication of OFET devices using PQTBTz-TT-C8 as the active layer.
• Grazing incidence X-ray diffraction (GIXRD) for crystallinity analysis.
• Temperature-dependent electrical measurements to determine charge transport properties and density of states (DOS).

Main Results:

• The spin-coating rate significantly influenced the thickness of PQTBTz-TT-C8 films.
• Film thickness directly impacted series resistance and overall device performance.
• Crystallinity and electronic coupling between polymer chains remained largely unaffected by spin-coating conditions.
• Charge transport models (polaron hopping, Gaussian DOS) showed prefactors independent of spin-coating parameters.

Conclusions:

• The spin-coating rate is a critical parameter for tuning the thickness of PQTBTz-TT-C8 films in OFETs.
• Device performance is primarily governed by film thickness due to its effect on series resistance.
• The edge-on stacking of polymer chains contributes to the thickness-dependent performance variations.