Hierarchical Nanowire Architectures Self-Assembled from Ultra-Deep-Blue Fluorene-Based Conjugated Molecules toward Organic Light-Emitting Diodes with CIEy=0.06

Organic conjugated molecules with a rigid rod-like pi-backbone structure automatically and easily self-assemble into an anisotropic nanostructure. However, supersecondary structures obtained from the hierarchical secondary self-assembly of nanostructures have rarely been reported for non-amphiphilic conjugated molecules. Here, a nanowire architecture as a supersecondary structure from an ultra-deep-blue fluorene-based conjugated molecule (FCz-C8-Am) to improve the emission efficiency and stability is reported. In significant contrast to the four reference molecules, the FCz-C8-Am molecules grow into soft nanowires and further self-assemble into a series of nanowire architectures in the gelation process. This is associated with the synergistic effect of the hydrogen bonds among the amide units, pendant pi-pi stacking interactions between pendant Cz units, and appropriate soft steric interaction among side-chains, which are the three design requirements for preparing these nanowire architectures. Interestingly, this supersecondary architecture of FCz-C8-Am has a stable ultra-deep-blue emission, with an efficiency of approximate to 77% and a Commission Internationale de L'Eclairage (CIE) value of (0.16, 0.06) in the solid state. These findings provide a profound understanding of the relationship between the inherent molecular structure, supramolecular interaction, and supersecondary nano-architecture, offering useful information for the development of new functional optoelectronic materials.

Automated summary

Organic conjugated molecules can self-assemble into nanostructures, but supersecondary structures are rarely reported for non-amphiphilic molecules. This study reports a nanowire architecture as a supersecondary structure to improve emission efficiency and stability.