The First-Principles On Crystal Structure And Electronic Properties Of The Hybrid Organic-Inorganic Lead And Inorganic Stannum Halides Perovskite

In recent years,the optical absorption efficiency of perovskite series materials has experienced unprecedented rapid promotion with the development of new solar cells.Among them,organic-inorganic halide perovskite and full inorganic halide perovskite have attracted much attention due to their advantages: easy synthesis and low cost.However,how to break through the lack of stability and further improve the performance of the material has become a new topic for researchers.In this paper,DFT theoretical calculation and simulation were used to investigate the effects of doped homopolar elements at sites A,B and AB on cell parameters,conductivity,optical properties and stability of perovskites.Here are the main work:?1?We explor the structural,electronic,optical properties and stability of tetragonal phase mixed halide perovskites CH₃NH₃Pb(I_1-yX_y)₃?X = Cl,Br;y = 0,0.25,0.5,0.75?,using first-principles calculations.The calculation of electronic structure reveals that the valance band maximum is governed by the halide p-orbitals and Pb 6s-orbitals while the conduction band minimum formed by the mixed contribution from the p orbitals of Pb atom and s orbitals of I atom.For the stability and optical properties of CH₃NH₃Pb(I_1-yX_y)₃,the absorption coefficients show a blueshift of the absorption onsets but their stabilities show gradually increase with the increasing of X contents.Three different doping occupation phases of MAPb?I0.5X0.5?3 demostrate that the impact of doping positions in linear optical property can not be neglected but there is no change in stability.On the basis of all calculated results,we conclude that the best accouplement between absorption coefficiencyand stability can be achieved at y = 0.25 in CH₃NH₃Pb(I_1-yBr_y)₃ perovskites.?2?We performed a first-principles investigation based on density functional theory?DFT?to explore the inherent mechanism: structural,electronic,stability and optical properties of both cubic???and orthorhombic???phases CsPb_1-xSn_xIBr₂?x = 0,0.25,0.5 and 0.75?perovskite series.According to our calculations,the energy-conversion properties tended to controlled by the new hybrid states of Sn²⁺ and Pb²⁺ with the doping of Sn atoms.The calculations of formation energies,defect formation energies,electron localization function and charge density distribution demonstrated that all the doped CsPb_1-xSn_xIBr₂ perovskite series became stabler.Notablely,?-Cs Pb0_.25Sn_0.75IBr₂ and ?-Cs Pb_0.75Sn_0.25IBr₂ show the strongest absorption within the visible-light range,maximum amount of photons absorbent and suitable band gaps.Our study provides theoretical insight into the rationale design of highly efficient and stable inorganic halide perovskites photovoltaic devices and sheds a new light on designing and synthesizing the next generation of photovoltaic materials.