The First-principles On Crystal Structure And Electronic Properties Of The Hybrid Inorganic Oxides And Halides Perovskite

In recent years,over exploitation and utilization of fossil fuels have led to pollution problems one after another.The development of new-type solar cells have becoming a hot topic of universal concern in world.The inorganic oxide perovskite and organic halide perovskite materials have been widely used by researchers,due totheir easy production,low cost and high efficiency advantages.The speed of development of material is unmatched by any materials in history.However,the stability of the materials and the improvement of the material properties are still not resolved,its also a key factor limiting the large scale industrialized production.?1?We have investigated the Sr-site substitution effect on the electronic conductivity of the perovskite-type structure of(Sr_1-xCa_x)FeO₂ and(Sr_1-x-x Ba_x)FeO₂?x=0,0.25,0.5,0.75?by using first-principle calculations.Six kinds of doping form have been considered for the Ca-site and Ba-site,respectively.The different doping concentration and position lead to change in crystal structure and electronic properties.When x=0.5,?and?doping structures display Pmmm symmetry,while?and?doping structures show P4/mmm symmetry.The band structure and density of states reveal that different doping concentration and position can make the electronic conductivity change from semiconductor to semi-metallic.When x=0.25,0.75,0.5 for?and?doping,the doped system were semi-metallic properties.Whereas,when x=0.5 for?and?doping,the doped system were semiconductor properties.Further,doping can lead to an increase of the magnetic moments.It is worth noting that the Ca-doped system has higher growth in the magnetic moments compare with the Ba-doped system.This work provides a new route for the potential application in electrochemistry devices.?2?We performed first-principles calculations to investigate the structural,electronic,and optical properties of mixed halide perovskites CH₃NH₃Pb(I_1-y-y X_y)₃?X=Cl,Br;y=0,0.33,0.67?.Our results reveal the reduction of the lattice constants and dielectric constants and enhancement of band gaps with increasing doping concentration of Cl^-/Br^-at I^-site.Electronic structure calculations indicate that the valance band maximum?VBM?is mainly governed by the halide p orbitals and Pb 6s orbitals,Pb 6p orbitals contribute the conduction band minimum?CBM?and doping doesn't change the direct semiconductor material.The organic cation[CH₃NH₃]⁺not take part in the formation of the band and only one electron donates to the considered materials.The increasing trends of the band gap with Cl content from y=0?0.793 eV?to y=0.33?0.953 eV?then to y=0.67?1.126 eV?.The optical absorption in the visible spectrum range is decreased.