Tuning the electronic and optical properties of diphenylsulphone based thermally activated delayed fluorescent materials via structural modification: A theoretical study

A series of designed diphenylsulphone based thermally activated delayed fluorescent materials have been investigated using quantum chemical approach. We focused on the variation in electronic and optical properties as different substituents being introduced to the parent molecule. The calculated results show that the broad range emission wavelengths (352-731 nm) can be tuned via either H/R substitution on the donor/acceptor moieties or “CH”/N substitution on the donor moieties. The emission wavelengths are significantly bathochromic-shifted (15-252 nm) by introduction of electron-accepting groups (CN) on the acceptor fragment or electron-donating groups (CH3) on the donor fragments. While, “CH”/N substitution on the donor fragment results in hypochromatic shifts (10-127 nm). On basis of the hole-electron distributions analysis, the locally excited triplet states are close to or higher than the triplet intramolecular charge transfer state for most of the investigated molecules. Furthermore, the calculated singlet-triplet energy gap values of the designed four red emission molecules (0.007-0.014 eV), two green ones (0.010-0.013 eV) and a blue one (0.058 eV) are relatively small, indicating that these investigated derivatives are excellent thermally activated delayed fluorescent candidates. Our theoretical studies provide hints for the design of efficient broad emission thermally activated delayed fluorescent materials in the future.