Molecular tweak boosts performance of organic semiconductors for flexible electronic devices

Adding a simple, sulfur-containing chemic radical to a semiconducting molecule tin dramatically boost the molecule's show successful a transistor, RIKEN chemists person found. This suggests that the properties of carbon-based semiconductors could beryllium tuned by incorporating these groups.

Most electronic devices are presently based connected silicon. However, integrated semiconductor molecules connection a mode to marque cheaper, flexible devices specified arsenic show screens, wearable sensors and disposable radio-frequency recognition tags. But astir integrated semiconductors cannot yet lucifer the show of their silicon rivals.

Two benchmark integrated semiconductors are pentacene and its derivative TIPS-pentacene. They incorporate electrons that smear retired crossed the molecules, forming the alleged p-conjugated system, which immunodeficiency the transport of electrical charge.

In pentacene crystals, the molecules are arranged successful a herringbone pattern, a communal operation for integrated semiconductors. When these herringbone patterns signifier a sandwich-like structure, the complaint transport is precise poor. In contrast, TIPS-pentacene molecules person a much antithetic pattern—stacking similar bricks successful a wall. This shapes the molecules' p-conjugation successful a mode that improves complaint transport and reduces the interaction of imperfections successful the crystal. However, it has been hard to guarantee that caller integrated semiconductors follow the brickwork structure.

Now, Kazuo Takimiya of the RIKEN Center for Emergent Matter Science and his colleagues person recovered that adding methylthio groups (CH₃S–) to integrated semiconductors tin assistance molecules to signifier this beneficial pattern.

The researchers tested their attack connected a molecule called pyrene, modifying each molecule with either 2 oregon 4 methylthio groups. Pyrene itself has a sandwich herringbone structure, but the compound carrying 4 methylthio groups, called MT-pyrene, had a brickwork structure.

The squad past grew 50–150 nanometer-thick plates of crystalline MT-pyrene and utilized them to nutrient 26 field-effect transistors. The devices each performed well, exhibiting 1 of the highest recorded complaint mobilities for immoderate integrated semiconductor with the brickwork structure.

The researchers recovered that erstwhile each molecule had 4 methylthio groups, they disrupted definite interactions betwixt neighboring molecules. This prevented them from forming a sandwich herringbone structure, and ensured that they could lone stack face-to-face, similar bricks. This optimized the interactions betwixt p-electrons and yet enhanced complaint transport.

The squad is assured that this strategy tin beryllium extended to different integrated molecules. "We deliberation that methylthiolation is simply a promising attack that tin beryllium applied to galore different integrated semiconductors," says Takimiya. The squad plans to measure however different elemental chemic groups impact the crystal structures of materials. They besides anticipation to make simpler methods to nutrient larger amounts of specified crystals.

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