Highly accurate DFT investigation for triggering the ultra-strong static and dynamic nonlinear optical properties of superalkali doped aminated graphdiyne (NH2-GDY) donor-π-acceptor (D-π-A) quantum dots

Abstract

Keeping in mind the desirability of novel two-dimensional materials with an ultra-high nonlinear optical (NLO) response for the fabrication of optoelectronic devices, we have investigated nine complexes by doping superalkalis (M2X; M = Li, Na, K and X = F, Cl, Br) onto the novel aminated graphdiyne (NH2-GDY) quantum dots. The geometric, electronic and NLO responses (static and dynamic) of the M2X doped aminated graphdiyne (M2X@NH2-GDY) complexes have been systematically investigated using density functional theory (DFT) computations. All the superalkalis are preferably oriented on the triangular large porous site of NH2-GDY containing extensive delocalized π-conjugated electrons and interact via an intermolecular π-electron donor–acceptor (D-π-A) process. The lithium and potassium-containing superalkali doped complexes exhibit high structural stability due to their large interaction energies. The change in the electronic properties of the M2X doped NH2-GDY quantum dots is investigated by analyzing the NBO charge transfer, vertical ionization energies (VIEs), HOMO-LUMO energy gaps and density of states spectra. TD-DFT calculations show ultra-high transparency of these complexes in the ultraviolet region. The strong NLO characteristics of the designed complexes are demonstrated by their high static and dynamic hyperpolarizability values. Among all the nine complexes, the K2F@NH2-GDY, K2Cl@NH2-GDY and K2Br@NH2-GDY complexes possess exceptionally high βo values: 1.16 × 104, 1.06 × 104 and 1.02 × 104 au, respectively, owing to the large atomic radius and high atomic number of the potassium metal atoms. The frequency-dependent NLO responses, Electro-Optical Pockels Effects (EOPE) and Second Harmonic Generation (SHG) are analyzed to investigate the dynamic NLO response. It is revealed that the K2X@NH2-GDY complexes also exhibit exceptionally high dynamic NLO responses (107 or 108 au) at 1064 nm wavelength. Our present research not only highlights the significance of superalkali doping on aminated graphdiyne quantum dots but also indicates that the K2X@NH2-GDY complexes are potentially important for next-generation optoelectronic devices.