Ab Initio Calculations of Band Gaps and Absolute Band Positions of Polymorphs of RbPbI3 and CsPbI3: Implications for Main-Group Halide Perovskite Photovoltaics

详细信息    查看全文

• 作者：Jakoah Brgoch ; Anna J. Lehner ; Michael Chabinyc ; Ram Seshadri
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：December 4, 2014
• 年：2014
• 卷：118
• 期：48
• 页码：27721-27727
• 全文大小：356K
• ISSN：1932-7455

文摘

Lead halide perovskites have attracted great interest because of rapid improvements in the efficiency of photovoltaics based on these materials. To predict new related functional materials, a good understanding of the correlations between crystal chemistry, electronic structure, and optoelectronic properties is required. Describing the electronic structure of these materials using density functional theory provides a choice of exchange-correlation functionals, including hybrid functionals, and inclusion of spin-orbit coupling, which is critical for the correct description of band gap and absolute band positions (ionization energy). Here, various computational schemes that employ different choices of exchange-correlation and hybrid functionals, and include or exclude spin-orbit coupling were implemented to examine these effects. Using PbI₂ as an initial structural model, it is found that standard exchange correlation functionals (PBE) in conjunction with spin-orbit coupling suffice to locate ionization energies efficiently through the use of slab calculations. Band gaps require the use of hybrid functionals carried out on single unit cells and spin-orbit coupling. Polymorphs of alkali metal lead halides, APbI₃ (A = Rb, Cs) are examined in the cubic perovskite structure and the reduced dimensional NH₄CdCl₃/Sn₂S₃ structure with quasi-two-dimensional connectivity. The somewhat elevated Born effective charges computed for these structures suggest that while the Pb²⁺ 6s lone-pairs are stereochemically inert, the presence of proximal instabilities could have implications for the functional properties of these materials.