Synthesis and structural analysis of dimethylaminophenyl-end-capped diketopyrrolopyrrole for highly stable electronic devices with polymeric gate dielectric

Abstract

Herein, we report the synthesis and structural analysis of 3,6-bis(5-(4-(dimethylamino)phenyl)thiophen-2-yl)-2,5-dihexadecylpyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione [DPP(PhNMe₂)₂], a stable diketopyrrolopyrrole derivative end-capped with a strongly electron-donating dimethylaminophenyl moiety. Optical and electrochemical characterization determined the band gap, HOMO, and LUMO energies of the above compound as 1.63, −4.65, and −3.02 eV, respectively. The prepared DPP(PhNMe₂)₂ was fabricated into thin films to construct field-effect transistors and resistance load-type inverters, the responses of which to static/dynamic electrical stimuli were analyzed in detail. Specifically, field-effect transistors demonstrated stable output/transfer characteristics during 100 sweeping cycles and showed excellent performance stability (over 300 days) under ambient conditions, with the corresponding dynamic switching characteristics being well maintained during 500 on–off cycles. The above inverters also showed good performance under ambient conditions. To clarify the origin of this performance enhancement, the above thin films were subjected to structural analysis by atomic force microscopy, density function theory calculations, and two-dimensional grazing incidence X-ray diffraction, which revealed that DPP(PhNMe₂)₂ molecules were stacked over the surface of the gate dielectric via their NMe₂ groups. Based on the obtained results, the improved device performance was ascribed to the end-on orientation and close packing of DPP(PhNMe₂)₂ molecules along the π–π stacking direction.