第一性原理计算研究氟化钙钛矿热稳定性

Study on thermostability of fluorinated perovskite through first principle calculations

为深入研究氟化作用对卤铅钙钛矿基发光材料热稳定性的影响,文中通过第一性原理计算,分别对F^(-)表面掺杂和体相均匀掺杂的钙钛矿型CsPbBR_(3-δ)F_(δ)材料的晶体结构、能带结构、热稳定性进行研究与探讨.由第一性原理计算结果可知,F^(-)取代Br^(-)可以有效调节和控制发光材料CsPbBr_(3-δ)F_(δ)的晶格常数、电子结构、配体阴离子与Pb^(2+)之间的电子转移过程和材料的热稳定性.随着F^(-)取代Br^(-)数量的增加,材料的晶格常数逐渐减小,禁带宽度逐渐变大.通过对比态密度强度可以发现,F^(-)取代分布在CsPbBR_(3-δ)F_(δ)晶格表面的Br^(-)可显著增多电子占据能级的数量,这可极大增强配体离子与发光中心的电子转移过程,进而提升卤铅钙钛矿基发光材料的发光性能;另一方面,源于F^(-)和BR^(-)的p轨道混合构成该材料的价带顶,也会对材料的电子转移过程进行有效地调控.研究表明,氟化钙钛矿材料是应用于发光材料的较好的选择.

In order to investigate the influence of fluoridation on halogen lead perovskite based luminescent materials,the lattice parameters,electronic band structure and thermal stability of CsPbBr_(3-δ)F_(δ) with F^(-) substituting for Br^(-) in the surface and the bulk of the crystal structure have been studied and discussed by first principles calculations.The results of first principle calculations show that the lattice constants,electronic band structure,electron transfer process between the ligand anions and Pb^(2+) and thermal stability of CsPbBr_(3-δ)F_(δ) could be effectively regulated and controlled through the substitution of Br^(-) by F^(-.)With the increase of the doping amount of F^(-) substituting for Br^(-),the lattice constants get decreased meanwhile the band gap values get increased.Through the comparison between the intensity of the density of states,it can be found that the F^(-)substituting for Br^(-)which were distributed on the lattice surface of CsPbBr_(3-δ)F_(δ) could significantly increase amount of state which could be occupied by the electron.This could greatly enhance the electron transfer process between ligand ions and luminescence centers,and thus improve the luminescence properties of halogen lead perovskite-based luminescence materials.In addition,the mixture of the p orbits of F^(-) and Br^(-) which constituting the top of the valence band would also significantly modulate the electron transfer process.In conclusion,fluoride halogen lead perovskite materials could be excellent candidates for luminescent materials.