Novel phenyl-oligothiophene derivatives containing acetylenic spacers for thin film materials: Synthesis, photophysical and morphology properties

Four novel organic semiconductor phenyl-oligothiophene derivatives containing acetylenic spacers, 5-(phenylethynyl)-2,2′:5′,2″-terthiophene, 5-(phenylethynyl)-2,2′:5′,2″:5″,2‴-quaterthiophene, 4-([2,2′:5′,2″-terthiophen]-5-ylethynyl)aniline, 4-((5′-iodo-[2,2′-bithiophen]-5-yl)ethynyl)aniline were synthesized and studied with respect to their thermal, photophysical, electrochemical and morphological properties. TGA and DSC results show all the oligomers have good thermal stability. Electrochemical measurements suggest the compounds can be used as photovoltaic materials. UV–vis spectra confirm all the molecules adopt close side-to-side packing, indicating H-aggregation. 4-([2,2′:5′,2″-Terthiophen]-5-ylethynyl)aniline exhibits excellent fluorescence properties when applied in an optoelectric field. XRD analysis indicates that the four compounds have a high degree of lamellar ordering and crystallinity. Film morphology properties reveal a clearly single-crystalline monoclinic morphology with lamellae parallel to the substrate, exhibiting that adjacent molecules have a strong intermolecular interaction. The potential liquid crystalline property is illustrated by DSC, XRD and polarization optical microscopy. These properties demonstrate that these oligomers could be promising candidates for the organic thin film materials and photovoltaic devices.

► Four novel materials PE3T, PE4T, 3TEA, I2TEA were successfully synthesized.
► The thermal, optical, electrochemical and morphological properties were studied.
► Four molecules adopted H aggregation and exhibited high film performance.
► All the oligomers were promising candidates for the organic thin film materials.