Yb- and Mn-Doped Lead-Free Double Perovskite Cs₂AgBiX₆ (X = Cl^-, Br^-) Nanocrystals

Lead-free double perovskite nanocrystals (NCs) have emerged as a new category of materials that hold the potential for overcoming the instability and toxicity issues of lead-based counterparts. Doping chemistry represents a unique avenue toward tuning and optimizing the intrinsic optical and electronic properties of semiconductor materials. In this study, we report the first example of doping Yb³⁺ ions into lead-free double perovskite Cs₂AgBiX₆ (X = Cl^-, Br^-) NCs via a hot injection method. The doping of Yb³⁺ endows the double perovskite NCs with a newly emerged near-infrared emission band (sensitized from the NC hosts) in addition to their intrinsic trap-related visible photoluminescence. By controlling the Yb-doping concentration, the dual emission profiles and photon relaxation dynamics of the double perovskite NCs can be systematically tuned. Furthermore, we have successfully inserted divalent Mn²⁺ ions in Cs₂AgBiCl₆ NCs and observed emergence of dopant emission. Our work illustrates an effective and facile route toward modifying and optimizing optical properties of double perovskite Cs₂AgBiX₆ (X = Cl^-, Br^-) NCs with an indirect bandgap nature, which can broaden a range of their potential applications in optoelectronic devices.