The ultraviolet-visible (UV-vis) absorption and photoluminescence (PL) spectra of DiKTa3 in toluene at room temperature are shown in Figure . The lowest-energy absorption band is at 450 nm and has a molar absorptivity of 1.6 × 10 4 M -1 cm -1 , values that resemble those of Hel-DiDiKTa (453 nm, 1.4 × 10 4 M -1 cm -1 ) and can be assigned to the S0-S1 transition. The redshifted band and lower molar absorptivity compared to that in DiKTa (433 nm, 2.1 × 10 4 M -1 cm -1 ) align with the trends of the calculated oscillator strength and energy of the S0-S1 transition (2.72 eV and 0.0016 for DiKTa3 and 3.46 eV and 0.20 for DiKTa). DiKTa3 emits at lPL of 491 nm, shows narrowband emission, with a FWHM of 52 nm/0.26 eV, and has a small Stokes shift of 38 nm/0.21 eV in toluene. Its emission is red-shifted compared to DiKTa (453 nm) and Hel-DiDiKTa (473 nm). The shoulder emission band peaking at 515 nm and the higher-intensity absorption band at 429 nm (2.4 × 10 4 M -1 cm -1 ) may come from the transitions between different vibrational energy levels as the PL spectra remain unchanged as a function of changing excitation wavelengths between 405-455 nm (Figure ). In addition, the energy of the emission band is insensitive to solvent polarity, which indicates that its SRCT state has significant locally-excited character (Figure ). The FPL of DiKTa3 in degassed toluene is measured to be 0.4%, the magnitude of which is mainly due to the significant non- radiative decay. This low FPL value is perhaps not surprising as that of Hel-DiDiKTa is also ≈ 1% and such low FPL is not uncommon in triple-helicene compounds. which is slightly larger than the calculation result (0.14 eV) and similar to that of single DiKTa (0.20 eV). The time-resolved PL decay in degassed toluene is shown in Figure . The prompt emission of DiKTa3 decays with lifetime τPL of 6.7 ns. No delayed emission was observed in solution because of the low FPL, large DEST, and significant non-radiative decay. The photophysical properties of DiKTa3 in doped polymethyl methacrylate (PMMA) films were then investigated. The FPL remains very low at 0.6% in 1 wt% doped film. DiKTa3 emits at lPL of 492 nm with FWHM of 54 nm/0.26 eV at 300 K (Figure ). The S1, T1 energies and DEST value in film, determined from the SS PL and Ph spectra at 77 K, are 2.64, 2.41 eV and 0.23 eV (Figure ), which are close to those measured in toluene. The prompt emission decays with a τPL of 4.0 ns (Figure ). There is a weak observed delayed emission, with a lifetime, τd, of 487 ns (Figure ). This delayed emission increases in intensity with increasing temperature, thus we can assign this to TADF. Recognizing that DiKTa3 is chiral, we next investigated its chiroptical properties. The enantiomers of the racemic sample of DiKTa3 were firstly separated by chiral HPLC to afford ee. of 100% and 99.6% for the first and the second enantiomers, respectively (Figure ). The simulated ECD spectra of (P,P,P)-DiKTa3 in toluene based on PBE0/6-31G(d,p) and M062X/6-31G(d,p) calculations were employed be able to assign the absolute configuration by comparison with the measured ECD spectra (Figure ). Both simulated ECD spectra of 39.4, 39.5, 39.4° for each functional, respectively (Figure ). They give similar predicted magnetic transition dipole moment values |m|, small q of 33 and 3° and high cosq of 0.84 and 1, respectively. The computed electric transition dipole moment values |μ| are higher using M062X/6-31G(d,p), which leads to a lower calculated gabs value of 2.1 × 10 -2 compared to that of PBE0 (5.6 × 10 -1 ). However, both predicted values are vastly overestimated compared to the experimental result in toluene. This is likely due to the differences between the near-identical optimized torsion angles and those observed in the single crystal structure (38.4, 35.7 and 42.8°, Figure ). Therefore, the chiroptical properties of (P,P,P)-DiKTa3 were also calculated using the crystal structure geometry at the M062X/6-31G(d,p) level for comparison (Figure ). The calculated |m| is close to the calculations based on the optimized geometries. However, the differences between the three torsion angles breaks the symmetry of the molecule, resulting in an increased |μ| and smaller cosq of 0.38. The corresponding gabs value is calculated to be 8.1 × 10 -4 , which is much closer to the value measured in toluene for the compound (6.8 × 10 -4 ).