Compositional Tuning of Carrier Dynamics in Cs(2)Na(1–x)Ag(x)BiCl(6) Double-Perovskite Nanocrystals

[Image: see text] We devised a hot-injection synthesis to prepare colloidal double-perovskite Cs(2)NaBiCl(6) nanocrystals (NCs). We also examined the effects of replacing Na(+) with Ag(+) cations by preparing and characterizing Cs(2)Na(1–x)Ag(x)BiCl(6) alloy NCs with x ranging from 0 to 1. Whereas Cs(2)NaBiCl(6) NCs were not emissive, Cs(2)Na(1–x)Ag(x)BiCl(6) NCs featured a broad photoluminescence band at ∼690 nm, Stokes-shifted from the respective absorption by ≥1.5 eV. The emission efficiency was maximized for low Ag(+) amounts, reaching ∼3% for the Cs(2)Na(0.95)Ag(0.05)BiCl(6) composition. Density functional theory calculations coupled with spectroscopic investigations revealed that Cs(2)Na(1–x)Ag(x)BiCl(6) NCs are characterized by a complex photophysics stemming from the interplay of (i) radiative recombination via trapped excitons localized in spatially connected AgCl(6)–BiCl(6) octahedra; (ii) surface traps, located on undercoordinated surface Bi centers, behaving as phonon-assisted nonradiative decay channels; and (iii) a thermal equilibrium between trapping and detrapping processes. These results offer insights into developing double-perovskite NCs with enhanced optoelectronic efficiency.