From non-detectable to decent : replacement of oxygen with sulfur in naphthalene diimide boosts electron transport in organic thin-film transistors (OTFT)

Enhancing the electron mobility of organic conjugated materials without tedious modification or synthesis is highly desirable and practical. In this research, we demonstrated that the electron mobility of naphthalene diimide (NDI) in thin film transistors (TFTs) under ambient conditions can be dramatically enhanced through a simple step reaction by replacing oxygen atoms with sulfur atoms. The electron mobilities of the as-prepared compounds range from non-detectable (parent NDI), to 3.0 × 10^-4 cm² V^-1 s^-1 (NDI-1S), 3.0 × 10^-3 cm² V^-1 s^-1 (NDI-3S), 3.7 × 10^-3 cm² V^-1 s^-1 (NDI-2S-cis), and 0.01 cm² V^-1 s^-1 (NDI-2S-trans) with on/off ratios as high as 4 × 10⁵. Our primary result suggests that thionation could be a promising method to tune the band position and bandgap of organic semiconductors for high performance TFTs.