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

Abstract

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 10 mobilities of as-prepared compounds range from non-detectable (parent NDI), to 3.0×10 -4 cm 2 V -1 s -1 (NDI-1S), 3.0×10 -3 cm 2 V -1 s -1 (NDI-3S), 3.7×10 -3 cm 2 V -1 s -1 (NDI-2S-cis), and 0.01 cm 2 V -1 s -1 (NDI-2S-trans) with on/off ratio as high as 4×10 5 . 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. 15 Experimental section Synthesis of NDI-1S, NDI-2S-trans and NDI-2S-cisA solution of lawesson's reagent (485 mg, 1.2 mmol, 2.0 eq. to 75

Thionation Enhances the Performance of Polymeric Dopant‐Free Hole‐Transporting Materials for Perovskite Solar Cells

“…Thionation is a straightforward oxygen–sulfur atomic substitution that remarkably tunes the material's optical and electronic properties without the need to synthesize a new compound from scratch but via a simple and single‐step reaction . Seferos and coworkers demonstrated that perylene diimide small molecules display enhanced charge transport characteristics upon thionation, because of the change in their morphological and photophysical properties .…”

Switching charge-transfer characteristics from p-type to n-type through molecular “doping” (co-crystallization)

“…a suitable energy level and effective charge transport) for air-stable high performance devices. 8 In addition, introducing too many electron-withdrawing elements ( e.g. N atoms, –F, –CN and so on) into the backbone of known systems might dramatically change the electron density of the π-conjugated frameworks, which makes the targeted compounds extremely unstable.…”

Drastic Improvement of Air Stability in an n-Type Doped Naphthalene-Diimide Polymer by Thionation

“…Generally, it is assumed that ambient stability of n-type conductivity can be achieved using materials with a LUMO energy level more negative than −3.9 eV. [42][43][44][45][46] The lowering of the LUMO energy of the semiconductor can be obtained by diverse modifications of the electron withdrawing cores such as in naphthalene diimide (NDI) based co-polymers, one of the most studied class of n-type materials [47][48][49][50][51][52][53][54][55] With the core positions being partially blocked in PNDIT2 by the comonomer, the strategy of lowering the LUMO by replacing the imide group by a mono-thioimide group, known as thionation, appears highly suitable for the development of stable n-doped small molecule NDIs [56][57][58][59] and NDI-based polymers. 60,61 Here we make use of thionated PNDIT2, referred to as 2S-trans-PNDIT2 ( Figure 1b) in which two carbonyl oxygens are substituted by sulphur with full trans-regioselectivity.…”