Fluoranthene-based triarylamines as hole-transporting and emitting materials for efficient electroluminescent devices

Abstract

Electroluminescent materials based on the fluoranthene core and containing triarylamine segments were synthesized and characterized by IR, NMR, UV-Vis, and emission spectroscopic, electrochemical, and thermal studies. The electronic absorption and emission characteristics of the new functional materials were affected by the nature of the chromophore present on the fluoranthene nucleus. Incorporation of amine functionality red shifted the absorption and emission profiles significantly, while a marginal bathochromic shift was noticed for the cyano substituent. The redox propensity of the dyes was also altered by the nature of the substituents. The electron donating amino group imparted facile oxidation while the electron-withdrawing cyano unit rendered reduction capability. The decomposition temperatures (T_d) observed for the dyes are exceptionally high (406–527 °C). Electroluminescent devices incorporating two amines, N-(4-tert-butylphenyl)-N-(naphthalen-1-yl)-7,8,9,10-tetraphenylfluoranthen-3-amine (7c) and N-phenyl-N-(7,8,9,10-tetraphenylfluoranthen-3-yl)pyren-1-amine (7d) with the configurations ITO/7c or 7d (40 nm)/TPBI or Alq₃ (40 nm)/LiF (1 nm)/Al (150 nm) were fabricated and displayed bright greenish yellow emission originating from the dyes.