A General Synthetic Strategy to a Library of Luminescent All-Organic Core–Shell Microstructures

Achieving good control over all-organic core–shell configurations represents an enormous challenge due to the difficulties in pairing appropriate constituent materials and tuning their growth kinetics. Here, we first prepare a series of structure- and color-tunable organic binary charge-transfer (CT) microtubes, and then use a seed-mediated strategy to encapsulate a pre-existing CT crystal with another one into dual-emitting core–shell heterostructures. Specific intermolecular interactions and similar molecular packing motifs among diverse CT crystals enable tunable two-photon excited fluorescence (TPEF), comparable lattice distances and small structural mismatch, which can be used to direct the rational construction of such a configuration with integrated TPEF properties. By tracking the real-time growth processes, we infer that the core–shell configuration made of all-organic CT crystals was determined depending on surface-interface energy balance and desired lattice matching. Upon incorporation of a dopant into a shell, its emission color can thus be tailored, giving more color-tunable core–shell configurations. The present two-step epitaxial strategy provides a simple yet effective approach to access a library of core–shell heterostructures, which opens a door to construct functional organic heterostructures for optoelectronic devices.