Solution-processable semiconducting polymers could enable large-scale manufacturing of circuits used in flexible electronic devices. All-polymer solar cells, for example, rely on donor–acceptor-type semiconducting polymers, so the design and synthesis of new high-performance polymers is required.

In a communication in Advanced Materials, Dr. Yang Wang, Prof. Tsuyoshi Michinobu, and colleagues from Tokyo Institute of Technology describe a novel synthesis protocol for a series of high-molecular-weight n-type semiconducting copolymers that demonstrate high electron mobilities in unipolar n-channel organic transistors.

Prof. Michinobu: “Semiconducting polymers are receiving considerable attention in both fundamental and applied research fields, due to their potential applications in electronic devices. However, the development of high-performance n-type semiconducting polymers it still challenging.”

Dr. Wang: “In this work, using palladium copper cocatalysts and chlorobenzene as the solvent, we are able to achieve high-quality n-type semiconducting polymers, with a molecular weight up to 100 kg per mol.”

Increasing the molecular weight of the polymers was shown to enhance the electron mobilities in the thin-film-transistors (TFTs).

“In addition, by introducing sp²-nitrogen atoms into the polymer backbone and using an amine-tailed self-assembled monolayer, unipolar n-channel organic transistors with high electron mobility over 5 cm² V^–1 s^–1 are achieved.”

Modifying the Si/SiO₂ surface with a self-assembled monolayer (SAM) of amine-functionalized trimethoxysilane achieves near-perfect unipolar n-type TFTs. The TFTs based on the polymer dithiophene-thiadiazolebenzotriazole (pSNT) showed remarkably high electron mobilities, which can be attributed to the highly crystalline SAM microstructure. The researchers suggest that the high electron mobilities and superior crystallinity are a result of the addition of diazole, containing two sp²-N atoms, in the benzothiadiazole (BT)-based triple-fused ring.

To find out more about these high-performance n-type semiconducting polymers for TFTs, please visit the Advanced Materials homepage.