First-principles Study On Photoelectric Properties Of All-inorganic A₂BNiX₆ Type Double Perovskite Molecules

A₂BB'X₆double perovskite become a hot spot and attract wide attention due to their stable structure,non-toxic,excellent properties,and low cost in solar cells field.In order to screen excellent double perovskite molecules,we designed ten A₂BNi X₆molecules with density functional theory in this work.We studied the structure stability,electronic and optical properties of these molecules and analyzed their effects of elements at different positions on energy bands and optical properties.These studies paved a new way for the double perovskite light-absorbing solar cells materials.The main content of this paper is as follows:(1)A₂BNi X₆molecules(where A=K,Rb,Cs,Ag;B=Li,Na,K,Rb,Ag,Au;X=F,Cl,Br,I)are established from elements that can be present at various positions.Then by calculating their tolerance factor t and octahedron factor?,it is judged that33 molecules may exist.(2)The energy bands of these 10 kinds of A₂BNi X₆molecules were calculated respectively.By observing the energy band diagrams,it was found that most of the A₂BNi X₆type double perovskites have a direct band gap,which is very beneficial to the absorption of visible light.In particular,the four kinds of double perovskites of A₂BNi F₆whose X position is F atom are 1.52-1.69e V,which is very suitable as a light absorbing material.(3)Calculate the optical properties of these 10 kinds of A₂BNi X₆molecules,including absorption coefficient,refractive index,reflectance,and extinction coefficient.Optical properties research shows that A₂BNi F₆double perovskite is a transparent material and has a wide range of application prospects in transparent light-emitting materials.