Electronic and optical properties of PdSe2 from monolayer to trilayer

Based on density functional theory (DFT), the electronic and optical properties of PdSe2 from monolayer to trilayer are systematically studied. The 1.37eV indirect band gap of monolayer PdSe2 reflects its semiconductor behavior, and the band gap tends to decrease with the increase of the number of layers. The band gap of PdSe2 from monolayer to trilayer are basically consistent with the experimental values. The conduction band minimum (CBM) and valence band maximum (VBM) mostly come from the Pd-4d orbitals and Se-4p orbitals. Interestingly, two structures in the trilayer PdSe2 of ABA and ABB stackings show prominent light absorption, and their maximum light absorption values occur near the energy of 10.6eV in xx direction. The positions of absorption edge appear red shift with the increase of the number of layers in all directions. Additionally, the trilayers have high refractive index and reflectivity. From monolayer to trilayer, the static refractive index n (0) increases gradually. Therefore, they may have promising applications in optical coatings and tunable optoelectronic devices.