Molecular Orientation‐Directed Isomerization in Indolocarbazole‐Embedded Multiple Resonance Emitter Enables High‐Performance Pure‐Green Electroluminescence

ABSTRACT Multiple resonance thermally activated delayed fluorescence (MR‐TADF) emitters are considered ideal candidates for high‐definition displays; however, simultaneously accessing high‐efficiency, narrowband, pure‐green emission remains a significant challenge. Here, we propose an orientation‐directed isomerization strategy on the indolocarbazole (ICz) building block to construct a previously unexplored syn‐oriented para ‐N–π–N dual‐boron‐containing architecture. This design delicately balances the strong intramolecular charge transfer (ICT) arising from para ‐N–π–N topology and short‐range charge transfer (SRCT) within a rigid ICz framework, achieving the desired narrowband emission. The proof‐of‐concept emitter DBN‐ cp ICz shows pure‐green photoluminescence in toluene ( λ PL = 520 nm, full‐width at half‐maximum (FWHM) = 20 nm, and Commission Internationale de l'Éclairage (CIE) coordinates = (0.17, 0.74)). An organic light‐emitting diode using DBN‐ cp ICz delivers pure‐green electroluminescence at 522 nm, with an FWHM of 24 nm and CIE coordinates of (0.20, 0.73), exceeding the NTSC green requirement and approaching the BT.2020 standard, together with a maximum external quantum efficiency of 36.4%. The intrinsic relationship between the N–π–N electronic topology of ICz and its well‐defined excited‐state characteristics enables robust green spectral anchoring, thereby providing a solid molecular engineering principle for the development of efficient, narrowband, pure‐green MR‐TADF emitters.