Effect of organic spacers on electronic, optical and transport properties of two-dimensional layered lead-halide perovskites

Two-dimensional layered perovskite materials promise a route towards stable, highly efficient solar cells. We perform a computational analysis of the electronic, optical and transport properties for some possible materials. [Display omitted] Using density functional theory in combination with Green’s function formalism we study the electronic, transport and optical properties of two-dimensional layered butylammonium (BA)-lead-halide ([CH3(CH2)3NH3]2PbX4 ((BA)2PbX4)) and phenylethylammonium (PEA)-lead-halide ([C6H5(CH2)2NH3]2PbX4 (PEA)2PbX4 (X = I and Br) perovskite materials, which have been used in recent experiments aiming to improve the properties of perovskite solar cells. We find that, regardless of the halide composition, PEA spacers lead to larger electronic transmission both along and across the lead-halide layers. In addition, the PEA molecules are found to contribute to the density of states near the band edges, which may also affect the charge carrier dynamics in the system. However, the systems containing PEA cations show smaller absorption in the visible range of the spectrum. These results show the importance of organic spacer cations in determining the optoelectronic and transport properties of 2D layered lead-halide perovskites and help establish some general rules about how different spacer molecules affect the properties of the material.