Cluster-Mediated Nucleation and Growth of J- and H-Type Polymorphs of Difluoroboron Avobenzone for Organic Microribbon Lasers.

Controlled fabrication of organic polymorphisms with well-defined dimensions and tunable luminescent properties plays an important role in developing optoelectronic devices, sensors, and biolabeling agents but remains a challenge due to the weak intermolecular interactions among organic molecules. Herein, we developed a two-step solution self-assembly method for the controlled preparation of blue-emissive or green-emissive microribbons (MRs) of difluoroboron avobenzone (BF2AVB) by adjusting the cluster-mediated nucleation and subsequent one-dimensional growth processes. We found that blue-emissive MRs belong to the monoclinic phase, in which BF2AVB molecules form slipped π-stacks, resulting in J-aggregates with the solid-state photoluminescence efficiency φ = 68%. Meanwhile, green-emissive MRs are ascribed to the orthorhombic phase and exhibit cofacial π-stacks, which lead to H-aggregates with φ = 24%. Furthermore, these as-prepared MRs can both act as polymorph-dependent Fabry-Pérot resonators for lasing oscillators. The strategy described here might offer significant promise for the coherent light source of optoelectronic devices.