B,N‐Embedded Hetero[9]Helicene‐Induced Chiral Assemblies for Amplified Circularly Polarized Electroluminescence

Abstract

ABSTRACT Circularly polarized organic light‐emitting diodes (CP‐OLEDs) based on B,N‐embedded heterohelicenes are promising due to their narrowband emission and high electroluminescence efficiency, yet their development has been hindered by intrinsically weak circularly polarized electroluminescence (CPEL) with dissymmetry factor ( g EL ) typically only 10 −3 , which falls far short of the theoretical limit (±2). Herein, we overcome this limitation via a co‐assembly strategy employing B,N‐embedded hetero[9]helicene ( BN9H ) as a dual‐role component. Possessing both a chiral scaffold and multi‐resonance thermally activated delayed fluorescence (MR‐TADF), BN9H is co‐assembled with luminescent nematic liquid crystal ( PFQ ). In this assembly, BN9H acts not only as a chiral inducer, driving the achiral PFQ host into a long‐range ordered chiral nematic superstructure, but also as an efficient energy acceptor. The co‐assemblies exhibit narrowband emission (FWHM [full width at half maximum] = 34 nm) and a dramatically amplified | g lum | of 0.18 which nearly two orders of magnitude higher than BN9H itself. Corresponding CP‐OLEDs based on those chiral assemblies achieve excellent integrated performance: narrowband green electroluminescence (FWHM = 33 nm), EQE max of 4.6%, and high | g EL | of up to 0.11. This work breaks the long‐standing | g EL | bottleneck for chiral MR‐TADF molecules and establishes a new paradigm for developing high‐performance CPEL devices with balanced efficiency, color purity, and strong chiroptical activity.