The optimized ground-state geometries of tBuPh-BN and DPA-tBuPh-BN were calculated using Density Functional Theory (DFT) at the PBE0/6-31G(d,p) level (Figure ). The highest occupied molecular orbital (HOMO) and lowest The excited-state energies and difference densities were calculated using Spin-Component Scaling second-order algebraic diagrammatic construction (SCS-(ADC)2/cc-pVDZ). As shown in Figure The ultraviolet-visible (UV-vis) absorption and photoluminescence (PL) properties of the two emitters were first investigated in toluene at room temperature (Figure ). The absorption spectra of tBuPh-BN and DPA-tBuPh-BN show low-energy bands at 463 and 455 nm, respectively, which are attributed to the SRCT S0-S1 transitions and are close to that of DtBuCzB (labs of 467 nm). The higher molar absorptivity (ɛ) of this SRCT band in tBuPh-BN (52×10 3 M -1 cm -1 ) than that in DPA-tBuPh-BN (42×10 1 cm -1 ) is correlated to the higher calculated oscillator strength of the S0-S1 transitions (0.28 for tBuPh-BN and 0.25 for DPA-tBuPh-BN). tBuPh-BN is a narrowband emitter, with its photoluminescence peaking at lPL of 490 nm and having a FWHM, of 25 nm (0.13 eV). The emission properties are comparable to those of DtBuCzB (lPL of 481 nm, FWHM of 22 nm in toluene), which illustrates that the nature of the S1 state is the same in these compounds. By contrast for DPA-tBuPh-BN, the DPA donor positioned para to the boron atom reduces its electron-withdrawing character and weakens the SRCT transition localized on the CzBN core, resulting in a blue-shifted and slightly broader emission band at 477 nm (FWHM of 28 nm/0.15 eV). The photophysics of DPA-tBuPh-BN is reminiscent of that of tDPA-DtCzB (lPL of 470 nm and FWHM of 21 nm in toluene). The larger Stokes shifts of tBuPh-BN (27 nm)