Tuning of Optoelectronic Properties in Oligo(phenyleneethynylene)-Based Cocrystals through Modulation of Charge-Transfer Interactions

Organic multicomponent cocrystals with semiconducting properties have gained wide interest due to their potential in solid-state optoelectronic applications. Herein, we report the design and synthesis of an oligo-(phenyleneethynylene) (OPE) derivative and its cocrystals with 2,3,5,6-tetrachloroterephthalonitrile (TCPN) and 1,2,4,5-tetracyanobenzene (TCNB) to explore the optical properties and charge-transfer interactions. The optical property of the charge-transfer cocrystals was dependent on the in-crystal geometry of luminophore OPE and charge-transfer interactions. The study also explored the role of molecular packing and intermolecular interactions on photoluminescence properties in the crystalline state of OPE, OPE-TCPN, and OPE-TCNB using structural data obtained from single-crystal X-ray diffraction. The theoretical investigation of the molecular assemblies demonstrated that the mixed-stacked systems allow a broader range of tunability in electronic properties compared to single-component systems. Combining different molecules (TCPN and TCNB) of complementary electronic structures of OPE, we could modulate parameters such as the band gap, charge carrier mobility, and energy levels more precisely.