Probing Optoelectronic Properties of Stable Vacancy-Ordered Double Perovskites: Insights from Many-Body Perturbation Theory

TL;DR

This study uses advanced computational methods to analyze the optoelectronic properties of stable, vacancy-ordered double perovskites, revealing their potential as lead-free materials for ultraviolet optoelectronic devices.

Contribution

It provides detailed first-principles insights into the stability, electronic structure, and optical properties of Rb₂BX₆ VODPs, highlighting their suitability for optoelectronic applications.

Findings

All materials are cubic, stable, and mostly indirect bandgap semiconductors.

G₀W₀ bandgaps range from 3.63 to 5.14 eV.

Exhibit strong ultraviolet light absorption and lower electron effective masses.

Abstract

A$_{2}$BX$_{6}$ vacancy-ordered double perovskites (VODPs) have captured substantial research interest in the scientific community as they offer environmentally friendly and stable alternatives to lead halide perovskites. In this study, we investigate Rb$_{2}$BCl$_{6}$ (B = Ti, Se, Ru, Pd) VODPs as promising optoelectronic materials employing state-of-the-art first-principles-based methodologies, specifically density functional theory combined with density functional perturbation theory (DFPT) and many-body perturbation theory [within the framework of GW and BSE]. Our calculations reveal that all these materials possess a cubic lattice structure and are both dynamically and mechanically stable. Interestingly, they all exhibit indirect bandgaps, except Rb$_{2}$RuCl$_{6}$ displays a metallic character. The G$_{0}$W$_{0}$ bandgap values for these compounds fall within the range of 3.63 to 5.14 eV. Additionally, the results of the BSE indicate that they exhibit exceptional absorption capabilities across the near-ultraviolet to mid-ultraviolet light region. Furthermore, studies on transport and excitonic properties suggest that they exhibit lower effective electron masses compared to holes, with exciton binding energies spanning between 0.16$-$0.98 eV. We additionally observed a prevalent hole-phonon coupling compared to electron-phonon coupling in these compounds. Overall, this study provides valuable insights to guide the design of vacancy-ordered double perovskites as promising lead-free candidates for future optoelectronic applications.