Molecularly Engineered Dual-Emission Pathways with Monomer-Excimer Interplay for Single-Component Blue and White...

The design of an organic molecule that inherently exhibits multiple emissive channels provides an elegant strategy for structurally simple yet spectrally broad white organic light-emitting diodes (OLEDs). Herein, we report the rational design and synthesis of a donor-π-acceptor luminophore (DBP-PXZ), comprising a phenoxazine donor moiety and a tetrahydrodibenzo-phenanthridine acceptor fragment linked through a twisted phenylene bridge. The photoluminescence (PL) spectrum of the solid sample of the compound exhibits dual emission bands, resulting in single-component white emission with CIE coordinates of (0.31, 0.38). PL spectral analysis of the solid solutions in polar host matrices and in a PMMA matrix demonstrates that controlled modulation of intermolecular proximity selectively activates or suppresses a low-energy emissive channel. Close chromophore packing activates intermolecular charge transfer (CT)-type excimer emission, while spatial isolation suppresses this pathway and yields purely blue emission from the monomeric CT state. Computational calculations support the stabilization of an intermolecular CT excited state of dimeric models relative to the monomeric ones. Leveraging this dual-emissive nature, host-free OLEDs based on a thin layer of DBP-PXZ as emissive layer exhibit a broadband electroluminescence spectrum spanning the range of ca. 385-800 nm. The device with an emissive layer of diluted DBP-PXZ with a wide-bandgap host effectively suppresses excimer formation and enables a pure blue EL spectrum. This work highlights DBP-PXZ as a single-component emitter enabling tunable blue-to-white emission via monomeric and excimer CT states, offering a compositionally simplified and heavy-metal-free emitter approach inspired by a sustainability-driven OLED design.