There is no obvious change to the steady-state PL spectra of Cz-C-TRZ in air and vacuum, centered at 448 nm (Figure ), whose PL lifetime is 5.1 ns measured at 298 K in air (Figure ). At 298 K, time-gated PL measurements detected two well-separated phosphorescence bands centered at 460 nm and 575 nm, with associated lifetimes of 7.1 ms and 197 ms, respectively (Figure ). However, at 80 K, only one green phosphorescence band at 515 nm was observed, similar to that recorded in 2-MeTHF glass at 77 K (Figure ). Compared to the phosphorescence spectra of Cz-Ph and TRZ (Figures and), we conclude that blue RTP and green LTP originate from Cz-Ph and TRZ, as T 1 and T 2 , respectively, similar to the theoretical prediction (Figure ). Given that the TRZ moiety is prone to forming p-p stacked assemblies, we postulated that orange RTP likely originates from aggregates.