show blue and green emission at 476 nm (FWHM of 34 nm/0.19 eV) and 497 nm (FWHM of 64 nm/0.34 eV), respectively. The red-shifted emission compared with the spectra in toluene for both emitter (lPL=472 nm, FWHM =28 nm/0.16 eV for TPPO-tBu-DiKTa and lPL=481 nm, FWHM =43 nm/0.25 eV for TPA-tBu-DiKTa) is ascribed to explicit host-guest interactions. The temperature-dependent timeresolved PL decays under vacuum are shown in Figure . TPPO-tBu-DiKTa shows a fast τp of 6.5 ns and due to the suppressed non-radiative decay in the rigid matrix, the RISC process becomes detectable and a long τd of 432 µs is observed at 300 K. TPA-tBu-DiKTa shows both double-exponential prompt and delayed components, with τp of 5.2 and 13 ns, and τd of 30 and 177 µs. The intermolecular interactions between host-guest and guest-guest cannot be avoided in the film state, which is different from the properties of isolated molecules in dilute solution. Together with the progressive red-shifting of the PL spectra in films with increased TPA-tBu-DiKTa doping concentration (Figure ), the longer prompt and shorter delayed lifetime components may mainly originate from intermolecular CT states rather than the intramolecular CT state that influences the photophysics in isolated molecules. Both emitters display temperature insensitive prompt fluorescence and thermally activated delayed emission spectra from 77 to 300 K, which confirm that in mCP these two compounds are TADF emitters. The photophysical kinetics parameters for the 2 wt% doped films are summarized in Table . The rate constant for RISC (kRISC) is 1.8×10 4