Decoding the Impact of Molecular Configuration on High‐Efficiency Blue Hot Exciton Emitters.

Realizing highly efficient organic light‐emitting diodes (OLEDs) based on "hot exciton" emitters is crucial for the widespread use of purely organic electroluminescence. Herein, it is demonstrated that the radiative decay rate, modulated by molecular configuration, plays a vital role in determining the optoelectronic properties of hot exciton materials. The proof‐of‐concept isomers, TPA‐1IPCN and TPA‐3IPCN, and TPA‐1IANCN and TPA‐3IANCN are intentionally designed and successfully synthesized. By employing a novel donor–acceptor–acceptor (D–A'–A) molecular architecture, implementing a molecular isomerization strategy, incorporating diverse steric hindrance moieties, and strategically manipulating the positioning of functional groups, precise modulation of the molecular configuration can be achieved to enable accurate regulation of the radiative decay rate. Consequently, various optoelectronic properties, including photoluminescent wavelength, photoluminescence quantum yield, fluorescence lifetime, packing mode in aggregated state, and molecular horizontal dipole ratios in films, undergo significant modifications. As a result, non‐doped blue OLED based on TPA‐1IPCN exhibits outstanding maximum external quantum efficiency (EQE) of 10.3% with minimal efficiency roll‐off—one of the highest reported values for blue OLEDs based on hot exciton materials. [ABSTRACT FROM AUTHOR]