Uniform conjugated polymer rectangular platelets exhibiting long-range exciton diffusion

The creation of discrete organic semiconducting two-dimensional nanomaterials with high crystalline order, controlled dimensions and enhanced energy transport capability represents a major challenge. We describe the preparation of uniform rectangular platelet micelles comprising a highly ordered, crystalline semiconducting poly(di-n-hexylfluorene) core by means of seeded growth methods. The rectangular core is constructed by the π-π stacking of tilted fluorene units and the solvophobic stacking of alkyl side chains. The core structure enables long-range anisotropic exciton diffusion, particularly in the direction of interchain π-π stacking, with a diffusion coefficient of up to 2.56 ± 0.52 cm² s^-1 and diffusion lengths of >500 nm. The segmented platelet comicelles, with concentric patches comprising distinct coronas, exhibit efficient energy transfer over hundreds of nanometres from the central higher-energy core to the peripheral lower-energy polythiophene corona. Our results open emerging avenues for the design of two-dimensional organic-semiconductor-based nanostructures, which could find applications in optoelectronics, sensing and photocatalysis.