Derivatives of Cyanonaphthyl-Substituted Phenanthroimidazole as Blue Emitters for Nondoped Organic Light-Emitting Diodes.

Abstract

New multifunctional blue-emissive materials with superior thermal properties, viz., 4,4′-bis(1-(4-naphthyl)-1H-phenanthro[9,10-d]imidazol-2-yl)binaphthyl (NPIBN), 4,4′-bis(1-(4-cyanonaphthyl)-1H-phenanthro[9,10-d]imidazol-2-yl)biphenyl (CNPIBP), and 4,4′-bis(1-(4-cyanonaphthyl)-1H-phenanthro[9,10-d]imidazol-2-yl)binaphthyl (CNPIBN) have been synthesized. The said molecules show high photoluminescence quantum yield (Φs/f: NPIBN-0.75/0.68, CNPIBP-0.85/0.76, and CNPIBN-0.90/0.88). The fabricated nondoped/doped device with CNPIBN/4,4′-bis(carbazol-9-yl)biphenyl: CNPIBN display maximum efficiencies (ηex 4.96/5.4%; ηc 7.46/7.56 cd A–1; ηp 6.85/6.91 lm W–1) at low turn-on voltage (3.5/3.8 V). Nondoped devices based on D−π–A architecture, 4-(2-(5-(9H-carbazol-9-yl)thiophen-2-yl)-1H-phenanthro[9,10-d]imidazol-1-yl)naphthalene-1-carbonitrile exhibit maximum efficiencies (ηex 2.32%; ηc 4.00 cd A–1; ηp 3.42 lm W–1) compared to 4-(2-(5-(4-(diphenylamino)phenyl)thiophen-2-yl)-1H-phenanthro[9,10-d]imidazol-1-yl)naphthalene-1-carbonitrile (ηex 2.01%; ηc 3.89 cd A–1; ηp 3.15 lm W–1).