High-performance n-channel thin-film transistors with acene-based semiconductors

Two acene-based semiconductors were investigated with respect to their performance as n-type materials in organic field-effect transistors. The partially fluorinated ditetracenes (Ditetracen is protected by copywrite through the Patent WO/2007/000268. The patent is property of the Dritte Patentportfolio Beteiligungsgesellschaft mbH & Co. KG.) (DT) were synthesized in a high yield with different degrees of fluorination, one with four and another with two fluorine substituents (named as DT-4F and DT-2F, respectively). Both materials exhibit high thermal stability, with decomposition temperatures above 500 °C. Since both materials are supposed to have a lowered LUMO level compared to the non-fluorinated parent DT, n-type operation in thin-film transistors (TFTs) with gold source and drain contacts was expected. TFTs based on DT-2F, however, showed weak ambipolar transport only, which demonstrates insufficient fluorination to switch from hole-dominated to electron-dominated transport. On the other hand, high performance n-type TFTs have been achieved from DT-4F, with electron mobilities up to 1.0 cm2/V s. This result indicates that fluorinated DT material can act as excellent n-type semiconductor for applications in complementary circuits. This is demonstrated in a complementary inverter stage using DT-4F-based TFTs as n-type transistor and a non-fluorinated DT derivative-based TFT as p-type transistor.

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► Synthesis of two n-channel acenes via the partial fluorination of parent ditetracene (DT).
► High-performance TFTs are achieved from the fourfold-fluorinated DT with electron mobility of 1.0 cm2/V s.
► Ambipolar transport is observed from the twice fluorine-substituted DT.
► Complementary inverters with a combination of n- and p-type DTs are demonstrated with good transfer characteristics.