Peripherally non-planar multiple resonance induced thermally activated delayed fluorescence materials containing silyl units

Abstract

<p>The rigid planar structure of multiple resonance thermally activated delayed fluorescence (MR-TADF) molecules based on boron/nitrogen (B/N) frameworks always causes a substantial roll-off in organic light-emitting diodes (OLEDs) due to intermolecular aggregation. Herein, four MR-TADF emitters (tCzMe3Si, tCzPh3Si, tPhCzMe3Si, and tPhCzPh3Si) were synthesized by introducing non-planar trimethyl/triphenyl silyl (Me3Si and Ph3Si) units at the <i>para</i>-carbon position of a B-substituted phenyl ring to reduce the intermolecular interaction. We further modified the peripheral electron donors of the B/N core, replacing 3,6-di-tert-butyl-9<i>H</i>-carbazole with 3,6-bis(4-(tert-butyl)phenyl)-9<i>H</i>-carbazole, resulting in a pure green emission with high photoluminescence quantum yields (up to 96%). Specifically, OLED based on tPhCzPh3Si exhibited a high external quantum efficiency of 34.6% and a pure green light peaking at 512 nm, with Commission Internationale de l��Eclairage coordinates of (0.14, 0.70).</p>