Pure Hydrocarbon Hosts Enabling Efficient Multi‐Resonance TADF Blue‐Emitting Organic Light‐Emitting Diodes

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Abstract Pure hydrocarbon (PHC) materials are a class of highly efficient and stable host materials for organic light‐emitting diodes (OLEDs), composed solely of carbon and hydrogen atoms. Despite recent great advancements in PHC research, their applications are still mainly limited to phosphorescent OLEDs (PHOLEDs). High‐performance blue OLEDs still pose a considerable challenge. Thus, expanding PHC materials into other types of OLEDs is critical for advancing organic electronic technologies. In this study, we designed a series of original high‐triplet PHC materials based on a multi‐substitution approach of the 9,9′‐spirobifluorene (SBF) backbone and used them, for the first time, as a host in phosphorescence‐sensitized multi‐resonance thermally activated delayed fluorescence (MR‐TADF) OLEDs. Devices based on the 2,6‐bis(3,6‐di‐tert‐butyl‐9H‐carbazol‐9‐yl)boron (DtBuCzB) emitter, using FIrpic or fac‐Ir(tpz) 3 as the sensitizer, achieved high maximum external quantum efficiency (EQE max ) values ranging from 29.1 % to 33.9 %. Additionally, blue MR‐TADF OLED devices based on v ‐DABNA with a phosphorescent sensitizer (CN−Ir), demonstrated outstanding electroluminescent performance, with an EQE max of approximately 31 % due to an excellent molecular orientation induced by the PHC hosts. All devices exhibited narrow full‐width at half‐maximum spectra and minimal efficiency roll‐off. This study marks the first application of PHC materials as hosts in phosphorescence‐sensitized MR‐TADF OLEDs, highlighting their potential as promising candidates for next‐generation blue OLEDs and offering a viable pathway to achieve high‐performance devices.

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