Simulation Calculation On The Structure And Photoelectric Properties Of Organic-inorganic Layered Perovskite

The tunability of layered perovskite structure and potential gap combined with the instability of perovskite materials in water environment are research hot topics.In this paper,the effects of carbon chain length of?C₄H₉NH₃?₂SnI₄ layered perovskite is investigated and organic elements partially doped Cs⁺on the structure is also taken into consideration.Besides,the band gap of perovskite structure and the microcosmic mechanism of single and multiple water adsorpted on perovskite cluster molecules have been studied.First,the perovskite model of?C₄H₉NH₃?₂SnI₄ is constructed.With the variation of organic elements,the structure,energy gap,electron density and density of states of?C₄H₉NH₃?₂SnI₄ are calculated based on the first principles.The result show that that the?C₄H₉NH₃?₂SnI₄ after carbon chain changes are direct gap semiconductors.The increase of carbon chain leads to the enlargement of the deflection of SnI₆ octahedron.With the shrink of the deflection between octahedrons,the energy gap of perovskite is smaller and the photoelectric efficiency is higher.The change of perovskite organic elements has no direct influence on the energy gap of perovskite.The length of carbon chain can affect the hydrogen bond between the amino head of organic elements and the I^-in inorganic elements.Then the deflection between the octahedrons of SnI₆ and the band gap are affected.The deflection between octahedrons can be expressed by Sn-I-Sn bond.As Sn-I-Sn bond becomes larger,the deflection of SnI₆ octahedron in a-b plane and the band gap of perovskite become smaller.Then,we replace a part of organic elements of?C₄H₉NH₃?₂SnI₄ perovskite with Cs⁺.The structure is optimized and the energy band is calculated.It can be concluded that?C₄H₉NH₃?₂SnI₄ perovskite doped with Cs⁺are still direct gap semiconductors.When the proportion of doped Cs⁺increases,the deflection of SnI6 octahedron in a-b plane and the energy gap of perovskite decreases.Doping Cs⁺on perovskite can affect the number of hydrogen bonds,which also affect the structure of SnI6 octahedron and the deflection between octahedrons.The band gap are affected and the position of Cs⁺in the structure also affects the symmetry of perovskite structure.In all doped structures,?C₄H₉NH₃?CsSnI₄ with equal ratio doping has better symmetry and smaller energy gap.At the same time,the perovskite cluster model of?CH₃NH₃?₄SnI₆ is constructed.Based on the quantum chemistry theory,the structure optimization and energy calculation is conducted.The independent gradient model analysis and atomic theory analysis of multiple adsorption configurations of single and multiple water molecules on?CH₃NH₃?₄SnI₆ perovskite clusters are studied.The result show that perovskite cluster can adsorb stably single or multiple water molecules.When the number of the interaction between perovskite cluster and water molecule increases,the stablility of the adsorption configuration will enhance.The interactions type between perovskite clusters and water molecules also affect the stability of structure.The interaction between two water molecules is slightly stronger than that between one amino head and one water molecule.The interaction between two amino heads and the same water molecule is the weakest.As perovskite clusters adsorb more than one water molecule,it is easier to form a ring structure composed of amino head and water molecule.The interaction between water molecule and perovskite cluster belongs to hydrogen bond.