Yb- and Mn-Doped Lead-Free Double Perovskite CsAgBiX (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 Yb ions into lead-free double perovskite CsAgBiX (X = Cl, Br) NCs via a hot injection method. The doping of Yb 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 Mn ions in CsAgBiCl NCs and observed emergence of dopant emission. Our work illustrates an effective and facile route toward modifying and optimizing optical properties of double perovskite CsAgBiX (X = Cl, Br) NCs with an indirect bandgap nature, which can broaden a range of their potential applications in optoelectronic devices.