Through‐Space n‒π Interaction‐Induced Stereo‐Construction Enables Efficient Deep‐Blue HLCT OLEDs with Color Purity Close to BT.2020

Realizing deep‐blue organic light‐emitting diodes (OLEDs) with concurrent high efficiency and color purity remains a formidable challenge. Hybridized local and charge‐transfer (HLCT) emitters offer a promising solution. However, conventional donor–acceptor/donor–π–acceptor architectures typically suffer from excessive charge‐transfer character, leading to red‐shifted and broadened emission. Herein, we propose a “through‐space n‒π interaction‐induced stereo‐construction” strategy to suppress molecular vibrations and realize high‐performance deep‐blue emission with high color purity. By incorporating a pyridyl π‐bridge into a phenanthroimidazole‐based framework, three emitters (oPTPA, oP9PCZ, and oP3PCZ) were designed, in which through‐space n‒π interaction and C─H─N interaction could rigidify the molecular structure and lower the reorganization energy. Single‐crystal analysis, theoretical calculations, and photophysical studies confirm the formation of stereoscopic configurations and HLCT states with reduced vibrational relaxation. As a result, all three emitters exhibit high photoluminescence quantum yields (>70%), narrow emission bandwidths (<50 nm), and excellent thermal stability. Doped devices based on these emitters deliver external quantum efficiencies of up to 7% with suppressed efficiency roll‐off, while oP9PCZ‐and oP3PCZ‐based devices achieve deep‐blue emission with CIE y <0.04, approaching the stringent BT.2020 blue standard.