Eu-Doped CsSrCl3 Large Nanocrystal Clusters with Self-Reduction Effect and Near-Unity Quantum Yield

Europium halide perovskites have emerged as promising candidates for environmental-friendly blue-emitting materials. However, their development is hindered by low photoluminescence quantum yields (PLQY, e.g. ∼2%–5% for intrinsic CsEuCl 3 ) and poor stability against air. Here, a one-step procedure is introduced for synthesizing Eu 2+ -doped CsSrCl 3 large nanocrystal clusters (CsSrCl 3 :Eu LNCs) with the effect of self-reduction, eliminating the use of conventional reductant oleylamine (OAm) and ensuring phase purity. CsSrCl 3 :Eu LNCs show photoluminescence emission centered at 430 nm with a full width at half maximum (FWHM) of 25 nm and a PLQY of ∼40%, which can be further enhanced to ∼97% after passivating the surface defects by adding trioctylphosphine (TOP), the highest among all reported lead-free blue-emitting perovskite nanocrystals. The stability of CsSrCl 3 :Eu can also be improved significantly by epitaxially growing a ZnS shell on the surface. This work will shed more light on lanthanide and alkaline-earth metal (AEM)-based perovskites for nontoxic light-emitting materials.