Design of novel graphdiyne-based materials with large second-order nonlinear optical properties

In this study, we designed a series of new alkali metal-adsorbed graphdiyne (GDY) structures (denoted as AM₃@GDY (AM = Li, Na, K)) with an intramolecular electron donor–acceptor framework using density functional theory calculations. It is found that the three alkali metals are energetically preferred to be adsorbed on the three hollows of the largely delocalized π-conjugated GDY surface, while the adsorption of alkali metals largely affects the electronic properties of the complexes, and reduces the vertical ionization potentials. More interestingly, the doping of alkali metal atoms dramatically enhances the static first hyperpolarizabilities (β_tot) of AM₃@GDY, of which the K₃@GDY cluster possesses a remarkably giant β_tot value of ∼1.61 × 10⁵ a.u., which is enough for it to exhibit strong nonlinear optical (NLO) behavior. These findings may provide new insights into the design of novel graphdiyne-based NLO materials and promote further potential applications in optoelectronic nanodevices.