Electronic structure and photo absorption property of pseudo-cubic perovskites CH$_3$NH$_3$PbX$_3$ (X=I, Br) including van der Waals interaction

TL;DR

This study uses density functional theory with van der Waals interactions to analyze the electronic and optical properties of pseudo-cubic CH₃NH₃PbX₃ (X=I, Br), confirming their direct bandgaps and matching experimental absorption spectra.

Contribution

It provides a detailed computational analysis including vdW interactions of the electronic structure and optical properties of pseudo-cubic perovskites, aligning well with experimental data.

Findings

Confirmed direct bandgaps of 1.49 eV (I) and 1.92 eV (Br).

Calculated photo absorption onset matches experimental colors.

Demonstrated importance of vdW correction for accurate results.

Abstract

Using density functional theory with the inclusion of van der Waals (vdW) interaction, we have investigated electronic energy bands, density of states, effective masses of charge carriers, and photo absorption coefficients of pseudo-cubic CH$_3$NH$_3$PbX$_3$ (X=I, Br). Our results confirm the direct bandgap of 1.49 (1.92) eV for X=I (Br) in the pseudo-cubic $Pm$ phase with lattice constant of 6.324 (5.966) \AA, being agreed well with experiment and indicating the necessity of vdW correction. The calculated photo absorption coefficients for X=I (Br) have the onset at red (orange) color and the first peak around violet (ultraviolet) color in overall agreement with the experiment.