Boron‐Dipyrromethene Emitters with Strengthened Rigidity and Restricted Scissoring Vibration for High‐Performance OLEDs With Deep‐Red Narrowband Emission

Abstract Organic light‐emitting diodes (OLEDs) using a simple solution‐processing approach have natural advantages in cost‐effective commercialization. However, solution‐processed deep‐red OLEDs are rarely reported due to the scarcity of efficient purely organic narrowband red emitters with commendable film‐forming capabilities. Herein, a simple strategy is proposed to develop organic molecules with narrowband red emission by expanding a rigid conjugated frame to block the rotation of α position in the boron‐dipyrromethene (BODIPY) core due to restricted twisting vibration. Furtherly, by introducing a moderate donor to the meso‐position of the BODIPY core, bathochromic‐shifted emission can be achieved without sacrificing narrow full‐width at half‐maximum (FWHM) by increasing the electron density of the whole molecule and repulsive force of distal units to suppress stretching/scissoring vibration. By employing the developed BODIPY‐derived materials as terminal emitters and thermally activated delayed fluorescence material as assistant host to fabricate solution‐processed OLED devices, a maximum external quantum efficiency of 16.43% is achieved with an emission peak at 672 nm and a FWHM of 28 nm. This work, according to the knowledge, represents the best instance of solution‐processed deep‐red narrowband OLEDs based on typical fluorescent emitters.