基于第一性原理的双钙钛矿Ba_(2)BiTaO_(6)光电性质和缺陷特性研究

Photoelectric property and defect characteristics of double perovskite Ba_(2)BiTaO_(6) based on first-principles calculations

目的通过第一性原理计算研究双钙钛矿Ba_(2)BiTaO_(6)的光电性质和缺陷特性。方法通过在钙钛矿的B位上引入具有“s孤对电子”的Bi原子生成双钙钛矿Ba_(2)BiTaO_(6),基于密度泛函理论对材料的晶体结构、光电性质和缺陷特性进行研究。结果Ba_(2)BiTaO_(6)价带顶处具有较强的sp反键耦合作用使得该材料价带顶处非常局域,具有很小的空穴有效质量。与n型透明导电氧化物ZnO和In2O3不同的是,通过调整化学势的范围,Ba_(2)BiTaO_(6)的本征缺陷表现出很好的p型特性而非n型特性。它主要的缺陷(Ba空位、Bi空位、Ba替位Bi和Bi替位Ta)均是浅受主缺陷,这表明Ba_(2)BiTaO_(6)是一种很有应用前景的p型透明导电氧化物。结论通过在钙钛矿中引入具有“s孤对电子”的元素实现强的反键耦合效应可生成一类具有p型特征的透明导电氧化物。

Purposes—To study the photoelectric properties and defect characteristics of double perovskite Ba_(2)BiTaO_(6) by first-principles calculations.Methods—A Bi atom with a lone-pair s orbital on the B site is introduced to form double perovskite Ba_(2)BiTaO_(6),then the crystal structure,photoelectric properties and defect characteristics is studied on the basis of density functional theory.Results—Ba_(2)BiTaO_(6) exhibits a dispersive upper valence band and a small-hole effective mass due to the strong sp antibonding coupling.In contrast to n-type TCOs,i.e.,ZnO and In2O3,first-principles studies on the intrinsic defects of Ba_(2)BiTaO_(6) show that it is able to exhibit a good p-type property or stay intrinsic instead of being n-type by tuning the chemical potentials and its dominated defects(VBa,VBi,BaBi,and BiTa)are shallow acceptors,indicating that Ba_(2)BiTaO_(6) is able to be a promising p-type TCO.Conclusion—It is shown that perovskites could be a class of potential p-type TCOs by introducing strong sp coupling with lone-pair-s-orbital elements.