Origin of the Exclusive Ternary Electroluminescent Behavior of BN-Doped Nanographenes in Efficient Single-Component White Light-Emitting Electrochemical Cells

White-light-emitting electrochemical cells (WLECs) still represent a significant milestone, since only a few examples with moderate performances have been reported. Particularly, multiemissive white emitters are highly desired, as a paradigm to circumvent phase separation and voltage-dependent emission color issues that are encountered following host:guest and multilayered approaches. Herein, the origin of the exclusive white ternary electroluminescent behavior of BN-doped nanographenes with a B₃N₃ doping pattern (hexa-perihexabenzoborazinocoronene) is rationalized, leading to one of the most efficient (≈3 cd A⁻¹) and stable-over-days single-component and single-layered WLECs. To date, BN-doped nanographenes have featured blue thermally activated delayed fluorescence (TADF). This doping pattern provides, however, white electroluminescence spanning the whole visible range (x/y CIE coordinates of 0.29–31/0.31–38 and average color rendering index (CRI) of 87) through a ternary emission involving fluorescence and thermally activated dual phosphorescence. This temperature-dependent multiemissive mechanism is operative for both photo- and electroluminescence processes and holds over the device lifespan, regardless of the device architecture, active layer composition, and operating conditions. As such, this work represents a new stepping-stone toward designing a new family of multiemissive white emitters based on BN-doped nanographenes that realizes one of the best-performing single-component white-emitting devices compared to the prior-art.