Two novel green-emitting cyclometalated iridium complexes of (Buppy)(2)Ir(Tfl-pic) and (Buppy)(2)Ir(Brfl-pic) were synthesized and characterized, in which Buppy is 2-(4-tert-butylphenyl) pyridine, Tfl-pic is 6-(6'-(9 ''-octyl-2 '',7 ''-bi(9,9-dioctylfluoren-2-yl)fluoren-9 ''-yl)hexyloxy) picolinic acid and Brfl is 6-(6'-(2 '',7 ''-di-bromo-9 ''-octylfluoren-9 ''-yl)hexyloxy) picolinic acid. Their thermal property, dispersibility and optophysical properties were investigated. Both iridium complexes present intense UV absorption bands and photoluminescence performance in CH2Cl2. Single-emissive-layer polymer light-emitting devices using (Buppy)(2)Ir(Tfl-pic) and (Buppy)(2)Ir(Brfl-pic) as a single dopant and a blend of poly(vinylcarbazole) and 2-(4-biphenyl)-5-(4-tert-butyl-phenyl)-1,3,4-oxadiazole as the host matrix were fabricated. The (Buppy)(2)Ir(Tfl-pic)-doped devices exhibited a maximum current efficiency of 2.44 cd A(-1). As expected, the phase separation and concentration quenching of these iridium complexes in the devices are efficiently suppressed due to appending bulky fluorene derivatives on the picolinic acid unit by a non-conjugated connection. (C) 2014 Elsevier B.V. All rights reserved.
Synthesis, opto-physics, and electroluminescence of cyclometalated iridium (III) complex with alkyltrifluorene picolinic acid
摘要:
To improve the opto-physics, electroluminescence, and dispersibility of iridium (III) complexes in polymer light-emitting devices, we synthesized and characterized two red-emitting heteroleptic cyclometalated iridium (III) complexes of (Piq)(2)Ir(Tfl-pic) and (Piq)(2)Ir(Brfl-pic), in which Piq is 1-phenylisoquinoline, Tfl-pic and Brfl-pic are alkyltrifluorene- and dibromoalkylfluorene-containing picolinic acid derivatives bridged with alkoxy chain, respectively. Compared to (Piq)(2)Ir(pic) and (Piq)(2)Ir(Brfl-pic), (Piq)(2)Ir(Tfl-pic) exhibited higher thermal stability, better dispersibility and excellent quantum efficiency. High-efficiency red emission with a maximum current efficiency of 6.28 cdA(-1) and a maximum EL peak at 608 nm was obtained in the (Piq)(2)Ir(Tfl-pic)-doped devices using a blend of poly(9,9-dioctylfluorene) and 2-(4-biphenyl)-5-(4-tert -butylphenyl)-1,3,4-oxadiazole as a host matrix. (C) 2009 Elsevier Ltd. All rights reserved.