Various iridium complexes consisting of phenylpyrazole (ppz) ligands and isoquinolinecarboxylic acids (iq) as ancillary ligands were designed by energy band-gap calculations via ab initio calculations and synthesized to give rise to various emission wavelengths as expected. Fine color tuning was achieved through varying the position of the methyl substituent on the phenylpyrazole moiety with HOMO electron densities. Additional color tuning was made possible by altering the LUMO through the use of different ancillary ligands such as 1-isoquinolinecarboxylic acid (1iq) and 3-isoquinolinecarboxylic acid (3iq).

We developed a new host material TCTEB with a conformationally homogeneous, sterically bulky structure due to nonbonded interactions between adjacent methylene groups. The host presented good thermal stability (T g = 122 1C and T d = 321 1C) and high triplet energy (3.0 eV). The maximum quantum efficiency, current efficiency and power efficiency of the OLED device using the TCTEB host were 8.5%, 13.7 cd A À1 , and 11.3 lm W À1 , respectively, when doped with 8 wt% FIrpic.