Asymmetric structural design of a highly oriented multi-resonance emitter enables a record 41.5% external quantum efficiency in deep-blue OLED

Narrowband emitters offer significant advantages in the fabrication of next-generation deep-blue organic light-emitting diodes (OLEDs) due to their wide color gamut, high stability, and high efficiency. It is a pressing challenge to increase the light outcoupling efficiency to further boost device performance, even though 100% internal quantum efficiency is already achievable through rational molecular design. Here, we strategically propose a novel asymmetric structure design strategy aimed at simultaneously optimizing the horizontal emitting dipole orientation and aggregation state properties of the deep-blue multi-resonance (MR) emitters. This proof-of-concept emitter A-BN is capable of displaying ultrapure deep-blue emission with a peak of ∼461 nm, a small full-width-at-half-maximum of ∼25 nm, a CIEy coordinate of ∼0.08, a high horizontal dipole ratio of ∼90 %, and a near-unity photoluminescence quantum yield of ∼98 % in the practical mass-production concentration range (1–3 wt%). The corresponding non-sensitized device achieves a maximum external quantum efficiency of 41.5% without any external light extraction techniques, representing state-of-the-art performance for deep-blue OLEDs. These findings will help drive the development of highly efficient and stable narrowband deep-blue emitters and lead to a revolution in OLED technology.