Speciation of Lanthanide Metal Ion Dopants in Microcrystalline All-Inorganic Halide Perovskite CsPbCl3

Lanthanides are versatile modulators of optoelectronic properties owing to their narrow optical emission spectra across the visible and near-infrared range. Their use in metal halide perovskites (MHPs) has recently gained prominence, although their fate in these materials has not yet been established at the atomic level. We use cesium-133 solid-state NMR to establish the speciation of all nonradioactive lanthanide ions (La³⁺, Ce³⁺, Pr³⁺, Nd³⁺, Sm³⁺, Sm²⁺, Eu³⁺, Eu²⁺, Gd³⁺, Tb³⁺, Dy³⁺, Ho³⁺, Er³⁺, Tm³⁺, Yb³⁺, Lu³⁺) in microcrystalline CsPbCl₃. Our results show that all lanthanides incorporate into the perovskite structure of CsPbCl₃ regardless of their oxidation state (+2, +3).