Electronic and optical properties of MAPbX₃ perovskites (X = I, Br, Cl): a unified DFT and GW theoretical analysis

Abstract

Materials engineering is a key for the enhancement of photovoltaics technology. This is particularly true for the novel class of perovskite solar cells. Accurate theoretical modelling can help establish general trends of behavior when addressing structural changes. Here, we consider the effects due to halide substitution in organohalide CHNHPbX perovskites exploring the halide series with X = Cl, Br, I. For this task, we use accurate DFT and GW methods including spin-orbit coupling. We find the expected band gap increase when moving from X = I to Cl, in line with the experimental data. Most notably, the calculated absorption coefficients for I, Br and Cl are nicely reproducing the behavior reported experimentally. A common feature of all the simulated band structures is a significant Rashba effect. This is similar for MAPbI and MAPbBr while MAPbCl shows in general a reduced Rashba interaction coefficient. Finally, a monotonic increase of the exciton reduced masses is calculated when moving from I to Br to Cl, in line with the stronger excitonic character of the lighter perovskite halides.

Rashba and Dresselhaus Couplings in Halide Perovskites: Accomplishments and Opportunities for Spintronics and Spin–Orbitronics

“…7,[24][25][26][27]29,30,58 The computational approach, whether it relies on density functional theory (DFT) with or without hybrid functionals, 29,59 GW approximation, 60 or semi-empirical modeling (e.g. k · p or tight-binding), constitutes a precious tool, combined with symmetry analysis, in the characterization of SOC-induced spin splittings.…”

Interplay between organic cations and inorganic framework and incommensurability in hybrid lead-halide perovskite CH3NH3PbBr3

“…Fundamental insight of the structural dynamics holds the key to understanding their unique electronic properties, and is the subject of intensive theoretical and experimental investigations. [5][6][7][8][9][10] Methylammonium cation (CH 3 NH + 3 , MA), the most frequently incorporated A site cation in recent photovoltaic applications, possesses a large dipole and exhibits dynamic orientational disorder at room temperature. [11,12] The orientational degrees of freedom of the anisotropic organic cation have been suggested to be responsible for the excellent electronic properties of the hybrid perovskites.…”

Accurate and efficient band gap predictions of metal halide perovskites using the DFT-1/2 method: GW accuracy with DFT expense

“…This is especially true for realistic structures in working devices, which often are compounds with mixtures of more than one organic cation, metal cation or halide anion with sophisticated surfaces and interfaces [1][2][3][4][5][6][7] . The challenges to fundamental understanding of the electronic structure of AMX 3 perovskites stem from their rich chemical and physical properties and the interplay of these properties 6,7 Several research groups [8][9][10][11][12][13][14][15][16] have successfully applied the GW method to predicting electronic structures of AMX 3 perovskites. Even et al 8 have identified the importance of a giant spin-orbit coupling (SOC) effect (about 1.0 eV) in the lead iodide perovskites, acting mainly on the conduction band (mainly consisting of Pb states).…”