Polyarylsilyl Modification of Multi‐Resonance Thermally Activated Delayed Fluorescence Framework Enhances the Efficiency and Stability of Narrowband Green OLEDs

ABSTRACT

The development of organic light‐emitting diodes (OLEDs) that simultaneously achieve long operational stability, high efficiency, and narrowband emission remains a critical challenge for next‐generation displays. Herein, we report a peripheral modification strategy by introducing a sterically hindered disilicon‐containing unit (BTPSP) into a mono‐boron multi‐resonance thermally activated delayed fluorescence (MR‐TADF) framework via post‐functionalization. This molecular design effectively suppresses intermolecular interactions, improves molecular orientation, and strengthens thermostability without compromising the intrinsic narrowband emission. The resulting emitter BN‐I2S exhibits excellent horizontal dipole orientation, near‐unity photoluminescence quantum yield, and high thermal decomposition temperature ( T _d > 500°C). An electroluminescent (EL) device of BN‐I2S achieves a maximum external quantum efficiency of 31.8% with pure‐green emission. Notably, the EL device shows enhanced durability, with an LT ₈₀ about 12 000 h at 1000 cd m ⁻² , approximately 2.2 times longer than the reference device. This work offers a practical molecular design guideline for developing high‐performance narrowband emitters toward advanced display applications.