Asymmetric anthracene-based blue host materials: synthesis and electroluminescence properties of 9-(2-naphthyl)-10-arylanthracenes

A series of bulky aryl-substituted asymmetric anthracene blue host materials, 9-(2-naphthyl)-10-(3-(1-naphthyl)phenyl)anthracene, where phenyl was varied from H (5a), Me (5b), Ph (5e), and 1-Naph (5f) at the 6-position and Me (5c) at the 2-position, was synthesized by Suzuki coupling reaction between 10-(2-naphthyl)anthracene-9-boronic acid and 1-(3-iodophenyl)naphthalene derivatives. A less bulky aryl-substituted anthracene, 9-(2-naphthyl)-10-(2,5-diphenyl)phenyl)anthracene (5d), was also synthesized for comparison. All asymmetric anthracenes showed high glass transition temperatures in the range of 84–153 °C. The photophysical and electrochemical properties in solution showed that the substituent at the 10-positions of the anthracene unit did not influence the blue emission of 420 nm and HOMO–LUMO energy level (5.5–2.5 eV). However, a gradual decrease of bathochromic shift in solid state PL was observed from the increaseg of the substituent bulkiness, exhibiting 5e (18 nm) ≤ 5f (19 nm) < 5c (25 nm) ≤ 5b (26 nm) < 5a (30 nm) < 5d (41 nm), respectably. When 5a was used as a blue host material in the multilayered device structure of ITO/DNTPD/NPD/host:dopant (9%)/PyPySPyPy/LiF/Al, enhanced OLED device performance was observed, showing a luminous current efficiency of 9.9 cd A−1, power efficiency of 6.3 lm W−1 at 20 mA cm−2, deep blue color coordinates of (0.14, 0.18), and a 932 h device lifetime at L0 = 3000 cd m−2.