An Er<sup>3+</sup>-Doped Cs<sub>2</sub>NaScCl<sub>6</sub> Lead-Free Double Perovskite with Efficient Broadband Visible to Near-Infrared Emission and Multimodal Upconversion Luminescence
Chunli Zhao, Yuan Gao, Tiantian Song, Jing Wang, Jianbei Qiu
Abstract
Lanthanide ions are widely used as dopants for halide perovskites for their broad energy level coverage from the visible to near-infrared (NIR) range. In this work, Cs 2 NaScCl 6:Er 3+ was synthesized by an improved solid-state reaction method, which showed effective NIR emission under ultraviolet excitation. Through calculations based on density functional theory and Bader charge analysis, it is shown that [ErCl 6 ] 3– octahedra show a strong localization effect in the Cs 2 NaScCl 6:Er 3+ lattice, which is conducive to the charge transfer process of Cl–Er 3+, and charge transfer sensitization is responsible for the efficient visible to NIR luminescence of Er 3+, where the NIR emission around λ em = 1540 nm originated from the Er 3+: 4 I 13/2 → 4 I 15/2 transition with an ultrahigh photoluminescence quantum yield that reached ∼28.3%. Notably, Cs 2 NaScCl 6:Er 3+ also exhibited bright upconversion luminescence of green light (at 540 nm) under excitation by a variety of NIR laser diodes (808, 980, and 1550 nm) via self-sensitization processes.