How cation nature controls the bandgap and bulk Rashba splitting of halide perovskites

Author(s)

de Araujo, Luis Octavio ; Rego, Celso R. C. ; Wenzel, W. ; Silveira, Danilo N. ; Piotrowski, Mauricio J. ; Sabino, Fernando P. ; Pramudya, Yohanes ; Guedes-Sobrinho, Diego

• Document type: Journal article
• Source: Journal of Computational Chemistry; v. N/A, p. 9-pg., 2023-02-21.

Abstract

Because of instability issues presented by metal halide perovskites based on methylammonium (MA), its replacement to Cs has emerged as an alternative to improve the materials' durability. However, the impact of this replacement on electronic properties, especially gap energy and bulk Rashba splitting remains unclear since electrostatic interactions from organic cations can play a crucial role. Through first-principles calculations, we investigated how organic/inorganic cations impact the electronic properties of MAPbI(3) and CsPbI3 perovskites. Although at high temperatures the organic cation can assume spherical-like configurations due to its rotation into the cages, our results provide a complete electronic mechanism to show, from a chemical perspective based on ab initio calculations at 0 K, how the MA dipoles suppression can reduce the MAPbI(3) gap energy by promoting a degeneracy breaking in the electronic states from the PbI3 framework, while the dipole moment reinforcement is crucial to align theory ? experiment, increasing the bulk Rashba splitting through higher Pb off-centering motifs. The lack of permanent dipole moment in Cs results in CsPbI3 polymorphs with a pronounced Pb on-centering-like feature, which causes suppression in their respective bulk Rashba effect. (AU)

• FAPESP's process: 19/21656-8 - Big Data methods to tune perovskites to target properties: alloys, defects and doping
• Grantee: Fernando Pereira Sabino
• Support Opportunities: Scholarships in Brazil - Post-Doctoral