presents a blue-shifted emission at 468 nm and a lower FPL of 72% as a 6 wt% doped PPT film compared with DACT-II (9 wt% in CBP). The OLED with 3CzTRZ thus shows much poorer performance with an EQEmax of 10.5% [λEL: 480 nm; CIE = (0.17, 0.26)], which implies that there is not even a 100% IQE, assuming an out-coupling efficiency of 0.2~0.25 based on an isotropic orientation of the TDM. However, a structural analog of 3CzTRZ, TCzTRZ (∆EST: 0.01 eV; FPL: 99%; 10 wt% in DPEPO), developed by Lee et al., who replaced the C-N bonded tercarbazole dendron of 3CzTRZ with a C-C bonded tercarbazole dendron, does show 95% horizontal orientation of the TDM; a similar analogue, BCzTRZ, also shows a horizontal dipole orientation of its TDM as high as 89%, indicating the preferential in-plane alignment is formed both in tercarbazole and bicarbazole containing compounds. Thus, subtle changes in molecular design can have profound effects on both the propensity for horizontal orientation of the TDM and the efficiency of the device. The FPL values of the 10 wt% doped DPEPO film are 99% and 96% for TCzTRZ and BCzTRZ, respectively, both of which are significantly higher than that of 3CzTRZ (72% in DPEPO matrix). Thanks to the near unity FPL and near perfect horizontal orientation, the blue OLED shows an outstanding EQEmax of 31.8% at a lEL of 496 nm and CIE coordinates of (0.20, 0.44).