Defect formation in Yb-doped <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>CsPbCl</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:math> from first principles with implications for quantum cutting

Abstract

Exceptionally high experimental photoluminescence quantum yields attributed to highly efficient quantum cutting have recently been observed in ytterbium-doped inorganic metal-halide perovskites such as Yb:CsPb($X=$ Cl, ${\mathrm{Br})}_{3}$. Combined with strong, tunable, broadband absorption in the visible spectrum, these materials show great promise for applications in solar down-converter technologies. Much subsequent work has been dedicated to uncovering the fundamental mechanisms behind Yb-mediated quantum cutting, and an accumulation of experimental evidence has shown that a particular speciation of Yb, believed to be a fully compensated ${(2{\mathrm{Yb}}_{\mathrm{Pb}}+{\mathrm{V}}_{\mathrm{Pb}})}^{0}$ defect complex, dominates this process. In this work, we investigate Yb defect formation in single-crystal ${\mathrm{CsPbCl}}_{3}$, and in particular the feasibility of forming ${(2{\mathrm{Yb}}_{\mathrm{Pb}}+{\mathrm{V}}_{\mathrm{Pb}})}^{0}$ defect complexes, using first-principles electronic structure calculations. A simple thermodynamic model based on defect formation energies, binding energies, and charge transition levels provides some insight into the distribution of ${\mathrm{Yb}}_{\mathrm{Pb}}$ substitutionals and Pb vacancies, underscoring the range of material compositions and synthesis conditions over which locally bound configurations of ${(2{\mathrm{Yb}}_{\mathrm{Pb}}+{\mathrm{V}}_{\mathrm{Pb}})}^{0}$ defect complexes become significant. We complement this analysis with additional calculations of structural and electronic properties and discuss the consistency of these results with the observed onset of quantum cutting.

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