Novel carbazole/indole/thiazole-based host materials with high thermal stability for efficient phosphorescent organic light-emitting diodes

Two host materials TIC1 (N-linked carbazole) and TIC2 ( C-3 -linked carbazole) via changing the substitution position of carbazole , indole and thiazole moieties are reported. Their structural and physical properties were fully characterized. The thermal analysis demonstrated that both TIC1 and TIC2 are thermally stable. The triplet energy levels of TIC1 and TIC2 were determined to be 2.54 and 2.58 eV, respectively. Green and blue OLEDs with TIC1 and TIC2 acting as host materials were fabricated to investigate their performances in PHOLED . Both green and blue PHOLEDs based on TIC2 show the best performance with the maximum current efficiency and maximum power efficiency of 60.0 cd/A and 48.0 lm/W (for green), 18.4 cd/A and 15.2 lm/W (for blue), respectively. The characteristic measurements of OLED devices reveal that both TIC1 and TIC2 are promising host materials for practical application. By comparing with the commercial host material of 4,4′-bis(carbazol-9-yl)biphenyl (CBP) and N , N -dicarbazoyl-3,5-benzene (mCP), the power efficiency of green and blue PHOLED was enhanced by 55.3% and 245%, respectively.