Origin of the exclusive ternary electroluminescent behavior of BN-doped nanographenes in efficient single-component white light-emitting electrochemical cells

Elisa Fresta, Jacopo Dosso, Juan Cabanillas-González, Davide Bonifazi, Rubén D. Costa
Adv. Funct. Mater., 2020, 30, 1906830.
DOI: 10.1002/adfm.201906830


White light-emitting electrochemical cells (WLECs) still represent a significant milestone, since only a few examples with moderate performances have been reported. Particularly, multi-emissive 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 multi-layered approaches. Herein, we rationalized the origin of the exclusive white ternary electroluminescent behavior of BN-doped nanographenes with a B3N3 doping pattern (hexa-perihexabenzoborazinocoronene), leading to one of the most efficient (~3 cd/A) and stable over days single-component and single-layered WLECs. Up 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 multi-emissive mechanism is operative for both photo- and electro-luminescence 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 towards designing a new family of multi-emissive white emitters based on BN-doped nanographenes that realizes one of the best performing single-component white-emitting devices compared to the prior-art.

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