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

Organic conjugated molecules with a rigid rod-like π-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 π–π 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 ≈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.