Surface-Doped Organic Charge Transfer Cocrystal Heterostructures and Their Variable Dual-Color Light Emission and Propagation

A novel strategy for constructing the organic core–shell structures/heterostructures (OCSHs) was developed by the surface doping of a charge transfer (CT) Py-TFP cocrystal (Py = pyrene; TFP = tetrafluoroterephthalonitrile) with the donor (D) or acceptor (A) replacement reaction. The lattice-selective doping of Pe (Pe = perylene) or TCNB (TCNB = 1,2,4,5-tetracyanobenzene) molecules on the Py-TFP surface resulted from both the molecular size match/mismatch and the distribution of the intermolecular hydrogen bonds. Spectroscopic analyses disclosed that the components of two types of lattice-oriented external shells, (Py-TFP)1–x(Pe-TFP)x and (Py-TFP)1–y(Py-TCNB)y, have the doping ratios of 0 < x ⩽ 2.00% and 0 < y ⩽ 4.03%, respectively. Their di-block core–shell heterostructures display the spatially segregated yellow-blue dual-color emission and the position-dependent optical waveguide with active and passive waveguide modes. Meanwhile, the Pe doped Py-TFP core–shell cocrystal presents (1,0,0) and (0,1,1) lattice-dependent emission and lightwave transmission. This study provides an effective fabrication strategy for the OCSH construction, and this core–shell cocrystallized heterojunction can be available for photonic and optoelectronic functional applications.