High efficiency green phosphorescent OLEDs using double-host materials

A highly efficient green phosphorescent organic light-emitting diode (PHOLED) was achieved from two co-evaporated materials, 2,4-diphenyl-6-bis(12-phenylindolo) [2,3-a]carbazole-11-yl)-1,3,5-triazine (DICT) and 9-phenyl-3,6-bis (9-phenylfluoren-9-yl)carbazole (PBFC), in the emitting layer. By utilizing DICT: PBFC = 1:1 as double-host combination and 12 wt% tris(2-phenylpyridine) iridium (Ir(ppy)₃) as dopant, the PHOLED exhibits outstanding performance in terms of a maximum external quantum efficiency of 19.05%, a maximum current efficiency of 69.38 cd A⁻¹ and a maximum power efficiency of 77.29 lm W⁻¹, respectively. The device performance is significantly improved compared to those of the single-host material devices based on DICT (15.91%, 57.83 cd A⁻¹ and 72.45 lm W⁻¹) and PBFC (9.19%, 32.67 cd A⁻¹ and 9.64 lm W⁻¹). Furthermore, both host materials show relatively high glass transition temperatures (T_g) of 129.8 °C for DICT and 167.7 °C for PBFC, as well as excellent decomposition temperatures (T_d) of 353.5 °C for DICT and 460.3 °C for PBFC respectively. The developed double-host system could be promising combination of host materials, especially for the application of high performance OLED and other organic electronic devices.