Structure, Stability, and Electronic Properties of the 2D van der Waals Selenophosphate LiGaP2Se6

We report the two-dimensional (2D) bimetallic selenophosphate, LiGaP₂Se₆, prepared through direct combination reactions and P₂Se₅ flux methods. The material is a member of the broad class of van der Waals 2D materials of the type M₂P₂Q₆ (M = metals). The structure was determined using single-crystal X-ray diffraction and refined in the chiral space group P3̅1c, with lattice parameters a = b = 6.2993(9) Å, c = 13.308(3) Å, α = β = 90°, γ = 120°. Differential thermal analysis indicated a congruent melting point at ∼458 °C. Optoelectronic properties were assessed using ultraviolet-visible (UV-vis) spectroscopy, showing a band gap of 2.01 eV, and photoemission yield spectroscopy in air (PYSA), which determined a work function of 5.44 eV. Notably, stability studies on LiGaP₂Se₆ revealed remarkable resilience despite its Li content, showing no structural changes after 2 weeks in ambient air or after soaking in a water/ethanol bath.