Title | Ab Initio Calculations of Band Gaps and Absolute Band Positions of Polymorphs of RbPbI3 and CsPbI3: Implications for Main-Group Halide Perovskite Photovoltaics |
Publication Type | Journal Article |
Year of Publication | 2014 |
Authors | J. Brgoch, A.J. Lehner, M.L. Chabinyc, and R. Seshadri |
Journal | JOURNAL OF PHYSICAL CHEMISTRY C |
Volume | 118 |
Pagination | 27721-27727 |
Date Published | DEC 4 |
ISSN | 1932-7447 |
Abstract | 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, APbI(3) (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. |
DOI | 10.1021/jp508880y |