Phenothiazine and anthracene derivatives as emitters for vacuum-deposited and solution-processed optoelectronic devices

Abstract

Organic twisted compounds exhibit unique electronic structures and intermolecular interactions, which contribute significantly to the development of solid-state fluorescent materials that have potential applications in optoelectronic devices. The incorporation of two twisted moieties at the vinylic carbon atom leads to steric hinderance, resulting in non-planarity in the molecular system, consequently manifesting enhanced solid-state emission. Herein, we report on six phenothiazine and anthracene derivatives, i.e. (PTZ)₃, An(PTZ)₂, An(TPE)₂, (PTZ)₄, (PTZ)₅, and PTZ-Ph-(PTZ)₂, synthesized using the Corey Fuchs reaction followed by a Pd-Catalyzed Suzuki cross-coupling reaction. These derivatives exhibit excellent solid-state emission owing to their non-planar nature. When dispersed in a rigid matrix, all the derivatives demonstrate photoluminescence quantum yields of up to 60%. In addition, the compounds show high thermal stability. (PTZ)₄ is implemented as a doping-free fluorescent emitter, as well as a host and guest material, in vacuum-deposited organic light-emitting diodes (OLEDs). The devices show a low turn-on voltage of 3.7 V, CIE coordinates of (0.18, 0.34), and low efficiency roll-offs. Various concentrations of (PTZ)₃ and (PTZ)₄, a thermally activated delayed fluorescence sensitizer, and a host material are used for the fabrication of solution-processed hybrid OLEDs. These devices display low turn-on voltages (3.2 V to 3.4 V) and electroluminescence with colours ranging from greenish blue to yellowish-green.