DFT and TD-DFT Analysis for the Modeling of Efficient Organic Light Emitting Diode (OLED)

Three donor-bridge-acceptor molecules were modeled using pentacene, tetracene, anthracene as electron donor moieties, and 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTCDA) as electron acceptor moiety. The electron donor and acceptor moieties were connected with a σ bridge. The ground state geometry optimization was performed on the modeled structures, namely NTCDA-σ-pentacene, NTCDA-σ-tetracene, and NTCDA-σ-anthracene using density functional theory (DFT). After the optimization of ground-state geometry, all the geometries were re optimized with the ranging electric field in two opposite directions. One direction of the applied electric field is from donor moiety to acceptor moiety (D to A) and the other direction is from acceptor moiety to donor moiety (A to D). The natural population analysis was also performed to calculate the natural charges on donor, bridge, and acceptor moieties for all molecules. The effect of the electric field on the electronic and charge transfer properties of the three modeled molecules was deeply analyzed. The optical properties such as absorption wavelength, emission wavelength, excitation energy, emission energy, and electronic transitions were thoroughly analyzed using time-dependent density functional theory (TDDFT). It has been observed that charge transfer between donor and acceptor moieties is possible only when the electric field direction is from D to A. The outcome of the present investigation suggests that these three modeled donor-bridge-acceptor species are suitable for the possible application as organic light-emitting diodes.