Optical properties of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>Cs</mml:mi><mml:msub><mml:mi>Cu</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi>X</mml:mi><mml:mn>3</mml:mn></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:mi>Cl</mml:mi><mml:mo>,</mml:mo><mml:mo> </mml:mo><mml:mi>Br</mml:mi><mml:mo>,</mml:mo><mml:mo> </mml:mo><mml:mi>and</mml:mi><mml:mo> </mml:mo><mml:mi mathvariant="normal">I</mml:mi><mml:mo>)</mml:mo></mml:mrow></mml:math>: A comparative study between hybrid time-dependent density-functional theory and the Bethe-Salpeter equation
Jiuyu Sun, Carsten A. Ullrich
Abstract
CsCu${}_{2}$X${}_{3}$ (X= Cl, Br, I) are quasi-one-dimensional, all-inorganic perovskites which are promising for optoelectronic applications. In this work, optical absorption spectra of CsCu${}_{2}$X${}_{3}$, with particular emphasis on excitonic features, are calculated via the Bethe-Salpeter equation (BSE) and time-dependent density-functional theory (TDDFT), in combination with the $G\phantom{\rule{0}{0ex}}W$ method. It is found that hybrid TDDFT, with a material-dependent admixture of nonlocal exchange determined by the dielectric constant, produces optical spectra in excellent agreement with the BSE. This suggests that hybrid functionals are very well suited for calculating the optical properties of perovskites and other materials, at a fractional cost of standard $G\phantom{\rule{0}{0ex}}W$+BSE.