Tuning Photoelectric Properties Of All-inorganic Double Perovsike Using First-principles

In recent years,socio-economic development has become increasingly rapid and human demand for energy is increasing.To further adapt to the theme of"environmental protection and economic development",we need to find efficient and pollution-free energy.Among them,perovskite solar cell materials have attracted more and more people's concern and research due to their environmental friendliness,low production cost,environmental friendliness and high photoelectric conversion efficiency.However,there are still some problems in the application process of perovskite solar cells such as poor stability.Therefore,it is very meaningful to improve its optoelectronic performance through adjustment methods such as doping and electronic dimension control.Aiming at the three-dimensional all-inorganic lead-free double perovskites Cs₂Ag_xCu_1-xIn_yTb_1-yCl₆and Cs₂Ag Bi Br₆and their two-dimensional analogues Cs₄Ag Bi Br₈,this paper calculates their band structure,density of states,effective mass,and light adsorption spectrum based on the first principles of density functional theory.The carrier mobility,exciton binding energy and their physical mechanism are analyzed.The results are as follows:1.Base on the first principles,the effects of the different doping ratios of metal elements in the three-dimensional all-inorganic double perovskite Cs₂Ag_xCu_1-xIn_yTb_1-yCl₆on the electronic and optical properties are explored.The results show that with the ratio of Cu or Tb atoms increases,the band gap value of the perovskite decreases.Among them,the doped material Cs₂Ag_0.25Cu_0.75In_0.75Tb_0.25Cl₆expands the light detection range in the infrared region compared with pure Cs₂Ag In Cl₆,has stronger optical absorption,and has obvious red shift.In addition,the calculation results of carrier mobility show that the hole mobility of Cs₂Ag_0.25Cu_0.75In_0.75Tb_0.25Cl₆is significantly improved,thus exhibiting better hole transport performance.The above calculation results prove that the doping of different concentrations of metal atoms can effectively modulate the photoelectric properties of the double perovskite.2.Comparatively study the advantages and disadvantages of the electronic and optical properties of the three-dimensional all-inorganic lead-free double perovskite material Cs₂Ag Bi Br₆and its two-dimensional analogue Cs₄Ag Bi Br₈,and analyze the reasons for the differences in their photoelectric properties.Taking the effect of spin-orbit coupling into accout,the calculation results show that the band gap of Cs₂Ag Bi Br₆(3D)is narrower than its two-dimensional analogue Cs₄Ag Bi Br₈,which further demonstrates that the carrier mobility of Cs₂Ag Bi Br₆(3D)is higher than that of Cs₄Ag Bi Br₈(2D).In addition,Cs₄Ag Bi Br₈(2D)has poor photoresponse in the visible light region,possibly because its geometric structure restricts the transport of carriers along the c-axis.Finally,the calculation results of exciton binding energy show that Cs₄Ag Bi Br₈(2D)has stronger carrier recombination ability,which can accelerate the recombination of electron-hole pairs,and obtain stronger photoluminescence spectrum.The above calculations prove that the two-dimensional all-inorganic RP structure double perovskite Cs₄Ag Bi Br₈will be a potential candidate material for photoluminescence applications.At the same time,by adjusting the electronic dimension of the all-inorganic lead-free double perovskite material,the photoelectric performance of the device can be effectively adjusted.