Air-Stable n-channel Diketopyrrolopyrrole Diketopyrrolopyrrole Oligomers for High Performance Ambipolar Organic Transistors

n-channel organic semiconductors are prone to oxidation upon exposed to ambient conditions. Herein, we report design and synthesis of dilcetopyrrolopyrrole (DPP)-based oligomers for ambipolar organic thin-film transistors (OFETs) with excellent air and bias stability at ambient conditions. The cyclic voltammetry measurements reveal exceptional electrochemical stability during the redox cycle of oligomers. Structural properties including aggregation, crystallinity, and morphology in thin film were investigated by UV-Visible spectroscopy, atomic force microscopy (AFM), thin-film X-ray-diffraction (XRD), and grazing incidence small-angle X-ray scattering (GISAXS) measurements. AFM reveals morphological changes induced by different processing conditions whereas GISAXS,measurements show an increase in the population offaceon oriented crystallites in films subjected to a combination of solvent and thermal treatments. These measurements also highlight the, significance of clialcogen atom from sulfur to selenium on the photophysical, optical, electronic, and solid-state properties Of DPP-DPP oligomers. Charge carrier mobilities of the oligomers were investigated by fabricating top-gate bottom-contact (TG-BC) thinfilm transistors by annealing the thin films under various conditions. Combined solvent and thermal annealing of DPP-DPP oligorner thin films results in consistent electron mobilities as high as similar to 0.2 cm(2) V-1 s(-1) with an on/off ratio exceeding 10(4). Fieldeffect behavior was retained for up to similar to 4 weeks, which illustrates remarkable air and bias stability. This work paves, the way toward, the development of n-channel DPP-DPP-based oligomers exhibiting retention of field-effect behavior with superior stability at ambient conditions.