Revealing the impact of organic spacers and cavity cations on quasi-2D perovskites via computational simulations

Abstract

Two-dimensional hybrid lead iodide perovskites based on methylammonium (MA) cation and butylammonium (BA) organic spacer—such as {hbox {BA}_{2}hbox {MA}_{n-1}hbox {Pb}_{n}hbox {I}_{3n+1}}—are one of the most explored 2D hybrid perovskites in recent years. Correlating the atomistic profile of these systems with their optoelectronic properties is a challenge for theoretical approaches. Here, we employed first-principles calculations via density functional theory to show how the cation partially canceled dipole moments through the {{hbox {NH}_{3}}^{+}} terminal impact the structural/electronic properties of the {hbox {Pb}_{n}hbox {I}_{3n+1}} sublattices. Even though it is known that at high temperatures, the organic cation assumes a spherical-like configuration due to the rotation of the cations inside the cage, our results discuss the correct relative orientation according to the dipole moments for ab initio simulations at 0 K, correlating well structural and electronic properties with experiments. Based on the combination of relativistic quasiparticle correction and spin-orbit coupling, we found that the MA horizontal-like configuration concerning the inorganic sublattice surface leads to the best relationship between calculated and experimental gap energy throughout n = 1, 2, 3, 4, and 5 number of layers. Conversely, the dipole moments cancellation (as in BA-MA aligned-like configuration) promotes the closing of the gap energies through an electron depletion mechanism. We found that the anisotropy rightarrow isotropy optical absorption conversion (as a bulk convergence) is achieved only for the MA horizontal-like configuration, which suggests that this configuration contribution is the majority in a scenario under temperature effects.