Theoretical study on optical and electronic properties of bipolar molecules with 1,8-naphthalimide and triphenylamine moieties as organic light-emitting materials.

A series of D-π-A bipolar molecules with triphenylamine (TPA) fragments as donors, 1,8-naphthalimide (NI) fragments as acceptors, and different π-conjugated bridges (CB) as π-conjugated bridges have been designed to explore their optical, electronic, and charge transport properties as charge transport and luminescent materials for organic light-emitting diodes (OLEDs). The frontier molecular orbitals (FMOs), natural population analysis (NPA), and local density of states analysis have turned out that the vertical electronic transitions of absorption and emission are characterized as intramolecular charge transfer (ICT). The calculated results show that their optical and electronic properties are affected by the π-conjugated bridges in bipolar molecules. The electron-donating (-withdrawing) π-conjugated bridges serve as donors (acceptors) for the compounds under investigation. Our results suggest that these bipolar molecules are expected to be promising candidates for holes transport and luminescent materials for OLEDs. The results presented show that varying the π-conjugated bridges of bipolar molecules is a highly promising approach to develop this series of materials for OLEDs applications.