Abstract
Heteroatomic conjugated polymers (HCPs) can have complicated molecular structures with several heteroatoms in the repeat unit, which is helpful for designing color-tunable emitters, photovoltaic donors and high mobility materials. In order to understand their relatively complex molecular superstructure characteristics in depth, heteroatomic substitution-induced diverse non-covalent interactions must be investigated. Here, we systematically studied the gelation processing and its influence on the optoelectronic properties of a series of sp(2) nitrogen (N) substituted polyfluorenes (PF8-co-DAF8) towards highly stable blue polymer light-emitting diodes (PLEDs). This heteroatomic substitution allows for diverse chain C-H center dot center dot center dot N hydrogen bonds, correlating with an excellent gelation behavior at room temperature. Films with a gelation superstructure show a weak interchain pi-pi interaction and energy transfer compared to non-gelation ones. PLEDs based on a gelation film give a stable, deep-blue emission with CIE coordinates of (0.16, 0.17) and a luminous efficiency (L. E.) of 1.30 cd A(-1), while non-gelation filmbased PLEDs display a stable, sky-blue emission (CIE: 0.20, 0.24; L. E.: 2.13 cd A(-1)). Diverse non-covalent interactions originating from the heteroatomic substitution cause a complicated molecular aggregation behavior in solution that can significantly affect the chain rearrangement in the film-casting process, thereby dominating the optoelectrical properties.