Twisted Phenanthro[9,10‐d]imidazole Derivatives as Non‐doped Emitters for Efficient Electroluminescent Devices with Ultra‐Deep Blue Emission and High Exciton Utilization Efficiency

Herein, two deep‐blue emissive molecules (SAF‐PI and SAF‐DPI) are designed and synthesized using spiro[acridine‐9,9’‐fluorene] as a donor (D) substituted with 2‐(3‐methylphenyl)‐1‐phenyl‐phenanthro[9,10‐d]imidazole as an acceptor (A), forming twisted D−A and A−D−A structures, respectively. The photophysical studies and density functional theory (DFT) calculations reveal that both molecules exhibit hybridized local excited and charge transfer (HLCT) characteristics with deep blue emission color. They are effectively applied as non‐doped emitters in OLEDs. Particularly, SAF‐PI‐based device achieves the high‐definition television (HDTV) standard blue color emission peaked at 428 nm with CIE coordinate of (0.156, 0.053), a narrow full width at half maximum of 55 nm, a maximum external quantum efficiency (EQEmax) of 4.57% and an exciton utilization efficiency of 65%. New hybridized local and charge‐transfer (HLCT) molecules bearing spiro‐acridine (SAF) as a donor and 2‐(3‐methylphenyl)‐1‐phenyl‐phenanthro[9,10‐d]imidazole (PI) as an acceptor exhibit deep blue emission and are successfully employed as the non‐doped emitter in OLEDs. The devices show efficient and stable deep‐blue emission satisfying HDTV standard with an EQEmax of 4.57%, a narrow FWHM of 55 nm and CIE coordinates of (0.156, 0.053).