Phosphorescent organic light-emitting diodes fabricated using iridium complexes with carbazole-based benzothiazole ligands

•Carbazole-based benzothiazole compounds were synthesized as main ligands for phosphorescent Ir(III) complex.•Two Ir(III) complexes were synthesized as red dopants.•The Ir(III) complexes showed their PL and EL in deep red region of the spectrum.•Red and white phosphorescent OLEDs were fabricated using the Ir(III) complexes.

We designed and synthesized two novel red-emitting iridium complexes, (2-Btc)2Ir(pic) and (2-BtcPh)2Ir(pic), that contain 2-(9-ethylcarbazol-2-yl)-benzothiazole (Btc) and 2-(9-phenylcarbazol-2-yl)-benzothiazole (BtcPh) as the main ligands, respectively, and picolinic acid (pic) as an ancillary ligand. Red emissions at 637 and 624 nm were observed from (2-Btc)2Ir(pic) and (2-BtcPh)2Ir(pic), respectively, in dichloromethane solution. Red phosphorescent organic light-emitting diodes (OLEDs) with ITO/PEDOT:PSS (40 nm)/TAPC (30 nm)/TPBi:TCTA:red dopants (x%) (25 nm)/TSPO1 (35 nm)/LiF (1 nm)/Al structure were fabricated. Red phosphorescent OLEDs using (2-BtcPh)2Ir(pic) as a dopant at a 5% doping ratio exhibited a maximum external quantum efficiency of 10.5%, maximum power efficiency of 11.0 lm/W, and maximum luminance of 1145 cd/m2 with CIE coordinates of (0.65, 0.34). Moreover, a white phosphorescent OLED with an ITO/PEDOT:PSS (40 nm)/TAPC (20 nm)/mCP:FIrpic (3%) (20 nm)/TPBi:FPQIrpic (10%):(2-BtcPh)2Ir(pic) (1%) (5 nm)/TPBi (25 nm)/LiF (1 nm)/Al structure exhibited a maximum external quantum efficiency of 11.7%, maximum power efficiency of 28.8 lm/W, maximum luminous efficiency as high as 29.0 cd/A, and maximum luminance of 16,020 cd/m2 with CIE coordinates of (0.44, 0.49).

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