Capturing optoelectronic properties of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mtext>Cs</mml:mtext><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mtext>AgSbBr</mml:mtext><mml:mrow><mml:mn>6</mml:mn><mml:mo>−</mml:mo><mml:mi>x</mml:mi></mml:mrow></mml:msub><mml:msub><mml:mtext>Cl</mml:mtext><mml:mi>x</mml:mi></mml:msub></mml:mrow></mml:math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mo>(</mml:mo><mml:mi>x</mml:mi><mml:mo>=</mml:mo><mml:mn>0</mml:mn><mml:mo>–</mml:mo><mml:mn>6</mml:mn><mml:mo>)</mml:mo></mml:mrow></mml:math> double perovskites using many-body perturbation theory
Surajit Adhikari, Priya Johari
Abstract
Lead-free inorganic ${A}_{2}M(\mathrm{I})M(\mathrm{III}){X}_{6}$ halide double perovskites (HDPs) are potentially benign materials with improved chemical stability as compared to organic lead halide perovskites. However, achieving comparable efficiency in optoelectronic devices requires careful exploration of suitable HDPs with favorable electronic, optical, and transport properties. In these efforts, we comprehensively studied ${\mathrm{Cs}}_{2}{\mathrm{AgSbBr}}_{6\text{\ensuremath{-}}x}{\mathrm{Cl}}_{x}$ $(x=0--6)$ mixed HDPs by employing state-of-the-art first-principles-based density functional theory, density functional perturbation theory, and many-body perturbation theory, namely ${G}_{0}{W}_{0}$ and the Bethe-Salpeter equation (BSE). Our findings demonstrate the thermodynamic and mechanical stability of these materials. Furthermore, the structural polymorphs for $x=2$, 3, and 4 exhibit nearly identical energies, indicating remarkably similar structural stability. The electronic band gap (indirect), calculated through HSE06 and ${G}_{0}{W}_{0}$, ranges from 1.68 to 2.49 eV. Meanwhile, the exciton binding energy, determined via standard BSE calculations, rises from 0.18 to 0.37 eV with increasing Cl concentration. The Fr\"ohlich model is also used to account for the impact of electron (hole)--phonon coupling, and electron mobility is found to increase with a decrease in Cl concentration from 5.07 to $28.07\phantom{\rule{0.28em}{0ex}}{\mathrm{cm}}^{2}\phantom{\rule{0.16em}{0ex}}{\mathrm{V}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{s}}^{\ensuremath{-}1}$, while hole mobility shows an oscillating behavior. Overall, the meritorious tunable properties of mixed HDPs underscore their potential as stable, nontoxic materials with favorable attributes for optoelectronic applications.