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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