[PO-A1] Poster Session 1

[P1-07] First-principles Study on Electronic Properties of Hybrid MABX₃ perovskites (MA= CH₃NH₃⁺; B= Pb, Sn, Ge; X= I, Br, Cl)

^○Narasak Pandech^1,2, Thanundon Kongnok¹, Sirichok Jungthawan¹, Sukit Limpijumnong¹, Walter R.L Lambrecht² (1.School of Physics and NANOTEC-SUT Center of Excellence on Advanced Functional Nanomaterials, Suranaree University of Technology, NakhonRatchasima 30000, Thailand, Thailand, 2.Department of Physics, Case Western Reserve University, Cleveland, Ohio 44106-7079, USA., United States of America)

Recently, hybrid MABX₃perovskites (MA= CH₃NH₃⁺; B= Pb, Sn, Ge; X= I, Br, Cl) have revolutionized emerging photovoltaic technologies with the development of highly efficient solar cells, and have attracted significant fundamental research interest. Despite the extremely fast progress in device fabrication, the materials electronic properties, which determine the photovoltaic performance, are not yet fully understood. Here, we performed calculations of these materials, using a van der Waals-corrected density functional theory (DFT) method using the Perdew-Burke-Ernzerhof (PBE) and Heyd-Scuseria-Ernzerhof (HSE) hybrid functionals. Subsequently, we use the GW-approximation to calculate the bands as quasiparticle excitations including also the spin-orbit coupling. The orientation and position of the MA-cation is found to significantly affect the electronic properties around the band edges of the Pb and Sn based compounds. Because Ge based halides already prefer a rhombohedrally distorted perovskite structure with off-centered Ge even for a simple inorganic cation (e.g. Cs), the three-fold symmetry of the MA ion is compatible with a preferred orientation of the molecules along the rhombohedral axis. The interplay between its dipole and the Ge off-centering leads to interesting ferro-electric behavior.