Engineering Intrinsic Flexibility in Polycrystalline Molecular Semiconductor Films by Grain Boundary Plasticization

Area of Science:

• Materials Science
• Organic Electronics
• Polymer Science

Background:

• Developing flexible organic semiconductors is crucial for next-generation electronic devices.
• Perylene diimides (PDIFs) are promising n-type organic semiconductors but often lack mechanical flexibility.
• Achieving flexible films without compromising charge transport properties remains a challenge.

Purpose of the Study:

• To develop mechanically flexible films of core-cyanated perylenediimide (PDIF-CN2) molecular semiconductor.
• To investigate a novel grain boundary plasticization strategy using a specially designed polymeric binder (PB).
• To evaluate the mechanical stability and charge transport properties of the resulting blend films.

Main Methods:

• Synthesized a novel polymeric binder (PB) with a naphthalenediimide-dithiophene π-conjugated backbone end-functionalized with PDI units.
• Developed a grain boundary plasticization strategy by blending PDIF-CN2 with the novel PB.
• Characterized the morphology and mechanical flexibility of the blend films, including bending tests.
• Fabricated thin-film transistors (TFTs) using the PB/PDIF-CN2 blend films and measured their electron mobilities.

Main Results:

• Achieved mechanically flexible films of PDIF-CN2 via grain boundary plasticization.
• The blend films exhibited a homogeneous morphology, similar to pure PDIF-CN2 films, and maintained this structure upon bending to radii as small as 2 mm.
• Thin-film transistors fabricated with PB/PDIF-CN2 blends demonstrated substantial electron mobilities even after repeated bending.
• The novel PB effectively connected PDIF-CN2 crystallites at grain boundaries, preventing phase separation.

Conclusions:

• The grain boundary plasticization strategy successfully produced flexible PDIF-CN2 films with excellent mechanical and charge transport properties.
• This approach offers a new pathway for creating textured, flexible semiconducting π-electron films.
• The developed polymeric binder is effective in enhancing the mechanical robustness of molecular semiconductor films.