Design of new first and fifth generation OLED emitters by doping 12,12-dimethyl-7-phenyl-7,12-dihydrobenzo[a]acridine-3-carbonitrile (BACN): DFT study

Abstract

In this paper, DFT and TD-DFT were used to investigate the impact of potassium doping on the electronic, NLO, and photophysical properties of BACN. The results indicate that doping with one (sample M1) or two (sample M2) potassium atoms enhances the electronic and optical properties of pure BACN (sample M0), reducing the bandgap from 3.70 eV for M0 to 2.97 eV for M1 and 2.34 eV for M2. This reduction increases electronic conductivity and intramolecular charge transfer. The first order hyperpolarizability values of the doped compounds are approximately 8 times higher for M1 and 9 times higher for M2 compared to M0, suggesting that the doped compounds are excellent candidates for nonlinear optical applications compared to the undoped compound M0. Regarding photophysical properties, M1 exhibits an inverted singlet-triplet (IST) state characterized by $∆E_{\mathrm{ST}}=-0.66\mathrm{eV}$ between S₁ and T₁, with a low RISC process. The UV-Vis spectrum of M1 reveals a double excitation with maximum bands in the near UV range, while its emission spectrum shows a peak at 415.44 nm with a CIE chromatic coordinate of (0.20, 0.18), indicating that M1 is a promising candidate for fifth-generation blues OLEDs. In contrast, the absorption and emission spectra of M2 show maxima in the visible spectrum at 413.22 nm and 400.61 nm, respectively. Thus, M2 can be used as an emitter for first-generation OLEDs used as antibacterial light sources, as well as an absorber for organic solar cells (OSCs).