In comparison to the three aforementioned triazine-based TADF emitters, each possessing only one carbazole donor, emitters with more than one carbazole have also been investigated. Lee et al. reported a stable deep blue emitter DCzTRZ (lPL: 459 nm; FPL: 43% in toluene) in which the two carbazole donor group are disposed mutally meta to each other and to the triazine acceptor. The DEST of DCzTRZ is 0.25 eV, which is similar to that of m-CzTRZ (0.22 eV in 10 wt% mCP). The blue OLED has an EQEmax of 17.8% at CIE coordinates of (0.15, 0.15), which is slight less efficient than that of m-CzTRZ (19.2%). It is surprising to observe a much bluer emission spectrum in comparison with the device based on m-CzTRZ, although the solution PL spectrum in toluene is eactly the same. The blud-shift of the EL may be caused by the different device configurations, choice of host and doping concentration between the two devices.