Post-Synthetic Doping and Ligand Engineering of Cs₂AgInCl₆ Double Perovskite Nanocrystals

Abstract

Lead-free double perovskite (DP) nanocrystals (NCs) have emerged as a promising class of perovskite nanomaterials with potential applications in various optical and optoelectronic domains. Meanwhile, doping impurity ions into perovskite structures represents a unique and effective means to tailor and optimize the properties of perovskite materials. Herein, we introduce a postsynthetic doping approach to the fabrication of Mn2+-doped Cs2AgInCl6 DP NCs with enhanced optical characteristics. We demonstrate that, in the postsynthetic reaction, the initial surface-doped Mn2+ ions undergo a gradual inward migration process within the NCs, resulting in homogeneous Mn2+ doping with a maximum photoluminescence (PL) quantum yield (QY) of 5.2%. This PL QY value can be further improved to 8.2% through codoping with Na+ ions and careful engineering of the NC surface state. In-depth studies involving conventional one-dimensional proton and two-dimensional NMR spectroscopic techniques unveil the pivotal role played by the surface ligands and their states. Based on our findings, we propose a comprehensive postsynthetic doping mechanism. Our study not only presents an accessible doping technique for lead-free perovskite NCs but also offers valuable insights into the dopant dynamics and ligand engineering for perovskite-type nanomaterials in a broader context.

Lanthanide Doping into All-Inorganic Heterometallic Halide Layered Double Perovskite Nanocrystals for Multimodal Visible and Near-Infrared Emission

“…All-inorganic lead halide perovskite (APbX 3 , A: Cs + , Rb + ; X: Cl – , Br – , I – ) nanocrystals (NCs) have garnered an unprecedented amount of attention in recent years due to their superior optoelectronic properties, holding immense potential for various applications. − Nevertheless, the toxicity of lead element inclusion and their potential impacts on environmental pollution have hindered their widespread adoption for technology commercialization . To address this concern, researchers have developed an extensive library of lead-free perovskite derivatives through composition substitution and tuning and crystal dimensionality engineering. − For instance, substituting the Pb 2+ component by either monovalent or trivalent cations of one type (e.g., M­(I): Cu + , Ag + , or M­(III): Bi 3+ , Sb 3+ , In 3+ ) results in low-dimensional perovskite derivatives, such as AM­(I) 2 X 3 , A 2 M­(I)­X 3 , A 3 M­(I) 2 X 5 , A 3 M­(III)­X 6 , or A 3 M­(III) 2 X 9 . − Additionally, replacing every two Pb 2+ cations with a pair of monovalent and trivalent cations leads to the formation of A 2 M­(I)­M­(III)­X 6 (M­(I): Na + , Ag + , K + , In + ; M­(III): Bi 3+ , Sb 3+ , In 3+ , Au 3+ , lanthanide ions, Ln 3+ ) double perovskites while retaining their three-dimensional (3D) crystal structures. − Combining both the lead-substitution and dimensionality engineering strategies, a new class of all-inorganic heterometallic halide layered double perovskites (LDPs) with a chemical formula of A 4 M­(II)­M­(III) 2 X 12 (M­(II): Cu 2+ , Cd 2+ , Mn 2+ , Sn 2+ , and Zn 2+ ; M­(III): Bi 3+ , Sb 3+ , In 3+ ) has been recently discovered. ,− The LDP structure exhibits a 2D layered crystalline structure with a unique sandwiched heterometallic halide octahedra arrangement (i.e., M­(III)­X 6 -M­(II)­X 6 -M­(III)­X 6 , Figures A and S1). The simultaneous incorporation of divalent and trivalent cations, and thereby the expansion of the compositional space of LDPs, provides ample opportunities for discovering new LDP materials with customizable control over their properties. − …”