On the other hand, a clear delayed decay was observed for both 1B-CzCrs and 2B-CzCrs in a 3,3'di(9H-carbazol-9-yl)-1,1'-biphenyl (mCBP) host at 5 wt% doping concentration (Fig. ). It is worth noting that 1B-DTACrs exhibited no TADF behavior, while 1B-CzCrs showed delayed emission in host matricesThe S1 and T1 levels of the 5 wt% doped film in mCBP are the same as those in solid toluene, but the 77 K spectra in mCBP are slightly broader, with FWHM of 28 nm for each (Table ).