First-principles Study On The Effect Of Doping On The Optoelectric Properties And Elastic Properties Of CsPbI₃ And SrTiO₃

CsPbI₃ is a representative light-absorbing material in perovskite solar cells.The low photoelectric conversion efficiency and instability as well as the defects of the material itself lead to the bottleneck of its development.SrTiO₃ is a new type of photocatalytic material with excellent photocatalytic performance.It can decompose water and organic pollutants by photocatalysis,but its wide band gap leads to low efficiency of using sunlight.Ion doping is an effective method to improve the photoelectric ability and elastic properties.It is blind to explore with experimental methods.Therefore,the first principle method is used for theoretical research.The first,the first-principles method was used to study the doping of CsPbI₃ with Double metals Cu+Zn and Zr+Nb.The electronic and optical properties of the co-doped system were analyzed,And compare the photoelectric performance of CsPbI₃ after co-doping of two cation metal.The results of calculations show that the doping of Cu+Zn eliminates the occupied state of single atom doping and reduces the band gap of CsPbI₃.The Cu+Zn co-doped system belongs to indirect band gap semiconductor.The multi-body effect of Zr+Nb co-doping due to interaction between charges,and high-concentration impurity carriers shift the Fermi level into the conduction band to widen the energy gap.The optical property calculation results show that:The absorption intensity of the Cu+Zn co-doped system in the visible light region is stronger than that of the Zr+Nb co-doped system.The Zr+Nb co-doped system exhibits metal properties and increases the conductivity of the intrinsic CsPbI₃.The maximum peak increase in the real part of Cu+Zn co-doped CsPbI₃ dielectric constant,and the peaks are red-shifted,which may become a new high dielectric material.The second,the photoelectric properties and elastic properties of Br atoms doped with CsPbI₃ under different pressures?0 GPa⁶0 GPa?were studied.The calculation results show that Cs₈Pb₈I₂₂Br₂ is a direct band gap semiconductor,The band gap value is 1.469 eV.With the increase of pressure,the band gap gradually decreases and disappears,and the electrical conductivity is enhanced.The total state density of the material decreases significantly with the increase of pressure.With the doping of Br atoms and the increase of pressure,the overlap degree between the material electron clouds increases,and the charge transfer between atoms increases,indicating the optimal conductivity at 60 GPa.Optical properties and elastic properties indicate that as the pressure increases,the range of light absorption increases.The modulus of elasticity at high pressure,including bulk modulus B,Young's modulus E,and shear modulus G,Indicates that the material has stable mechanical properties,at 30 GPa,the material ductility and compressibility are both in a good state.The third,the photoelectric properties of the perovskite material SrMO₃ were studied by a first-principles method,in which the M atoms were Ti,Zr,Nb,Tc,Ir.The results show that SrTcO₃ and SrIrO₃ show the characteristics of p type semiconductor,and SrNbO₃ show the characteristics of n type semiconductor,all belong to metal conductors and belong to perovskite with excellent conductivity.SrIrO₃ metal has the strongest conductivity.The imaginary part,absorption spectrum,reflectance and energy loss peak of SrIrO₃ are red-shifted,indicating that and SrIrO₃ can acquire more solar energy and taller plasma resonance frequency.The fourth,the first-principles method was used to study the photoelectric and mechanical properties of atomic metal+non-metal?Tc+N?,different kinds of metals?Tc+Ir?and the same metal Al atom doped with SrTiO₃.The results of calculation show that Tc+N co-doping system and Tc+Ir co-doping system are all metal conductors,and the conductivity is stronger than that of SrTiO₃.Al-doped SrTiO₃ is an indirect semiconductor,and the energy gap is reduced relative to intrinsic SrTiO₃.The differential density and Mulliken charge show that the covalent bond strength of the system increases with the impurity atoms,and the system is more stable,which is consistent with the electronic structure analysis.The optical performance calculation results show that the imaginary part of the dielectric function of the Tc+N and Tc+Ir co-doping system is red-shifted and exhibits absorption in all visible light ranges,indicating that the light absorption range is enlarged and the light absorption curve is significantly red-shifted Which can be an optical device.The elastic modulus of B,G,E and so on increased after impurity atoms were doped,and the ductility of Tc+Ir co-doping system was the best.