RESUMEN
We report the synthesis and characterization of two solution-processable pyromellitic diimide (PyDI)-acetylene-based conjugated homopolymers. Adjacent PyDI cores were connected with triple bond linkages by reacting 3,6-dibromo-N,N'-dialkyl pyromellitic diimides with bis(tributylstannyl)acetylene under Stille coupling conditions. Cyclic voltammetry revealed that these polymers have sufficient electron affinity to accept electrons. Absorption spectra revealed that one polymer, with a simple octyl chain, has greater intermolecular interaction or conjugation after forming a thin film, and that film exhibited electron transport in top-gate bottom-contact mode organic field-effect transistor (OFET) devices. X-ray diffraction (XRD) and atomic force microscopy (AFM) results show that the octyl polymer is amorphous on the bulk scale. The polymer exhibited electron mobility of about 2 × 10-4 cm2 V-1 s-1 with on/off ratio of 103 and is the simplest n-channel polymer yet reported. A 4-trifluoromethylphenethyl side chain did not result in measurable electron mobility. The octyl polymer exhibited negative Seebeck coefficient on the order of -40 µV/K in thermoelectric devices, further substantiating its n-channel activity. The demonstration of electron transport from such a simple polymer has opened a new path for obtaining n-channel semiconducting activity from polymer films.
RESUMEN
Sodium ß-alumina (SBA)-based gate dielectric films have been developed for all solution-processed, transparent and low voltage field-effect transistors (FETs). Its high dielectric constant has been ascribed to sodium (Na+) ions in the crystal structure; however, there are no published experimental results concerning the contribution of Na+ ions to the dielectric behavior, and the degree of crystallinity of the thin films. In addition, as an ionic conductor, ß-alumina could give rise to some issues such as leakage current caused by Na diffusion, threshold voltage shift due to interface charge accumulation and longer response time due to slower polarization of the Na+ ions. This paper will address these issues using zinc tin oxide (ZTO) FETs, and propose possible measures to further improve SBA-based gate materials for electronic devices.
RESUMEN
A highly soluble pyromellitic diimide-based polymer was obtained through imidization polymerization. The novel architecture features diimide subunits linked alternately at 3-6 and N,N' positions. The polymer is highly transparent in the near ultraviolet-visible regions. Smooth and uniform thin-films were obtained through spin-coating even after blending the polymer with PCBM in 1:9 polymer:PCBM weight ratio. While the polymer itself has modest electron mobility in typical bottom-gate top-contact OFETs, an electron mobility of 3 × 10(-3) cm(2)V(-1)s(-1) was achieved for the blend, which increased to 10(-2) cm(2)V(-1)s(-1) on exposure to propylamine. Thus, polyimides are demonstrated as promising binder materials for solution-processible n-channel semiconductor blends, of which very few examples are known.