image: The morphologies of 1D organic microrod (α phase), 2D microplate (β phase) and organic heterostructure (OHSs), the chemical structures of m-B2BCB, The molecular packing arrangement of ab plane of α phase and the packing arrangement of ac plane of β phase.
Organic heterostructures (OHSs) with high spatial and angular precision are key component of the organic optoelectronics, such as organic photovatic (OPV), organic light emitting diodes (OLED), and photo-detectors. Moreover, heterostructure can integrate multiple components into one structure to overcome the challenge of single output channel and provide feasibility for realizing more transmission modes. Besides, the OHSs inherently have advantages including simple solution preparation and synthesis, flexible molecular structure design and broad spectral tenability.
However, OHSs usually require two or more kinds of organic molecules, which brings difficulty to search the universal condition for all materials to grow together. Moreover, the phase separation during the self-assembly of OHSs remains a big challenge. As we know, polymorphism is quite a convenient approach to tune the chemical/physical properties of organic crystal based on one organic compound. Thus, Organic materials with polymorph property can be utilized to fabricate OHSs with enormous structural diversity and novel optical/electronical properties.
Very recently, through the polymorphism, Dr. Xue-Dong Wang and colleagues in Soochow University elaborately fabricated the OHSs of one organic compound of 3,3'-((1E,1'E)-anthracene-9,10-diylbis(ethane-2,1-diyl))dibenzonitril (m-B2BCB), which can simultaneously be self-assembled into one-dimensional (1D) microrods (α phase) and 2D microplates (β phase).The growth mechanism of OHSs is due to the low interplanar spacing mismatch rate of 5.8% between the (010) crystal plane of the 2D branch microplate and (001) of the 1D trunk microrod. These two organic polymorph microcrystals both have good optical waveguide performance with the Rα = 0.022 dB/μm of 1D microrod and the average Rβ = 0.036 dB/μm of 2D microplate. More significantly, the multiple output channels have been achieved in the OHSs, which exhibits the structure-dependent optical signals (green and yellow light) at the different output channel in the OHSs. This work exhibits the great value of polymorphism in OHSs, which could provide further applications on multifunctional organic integrated photonics circuits.