Boosting the Photoluminescence Quantum Yield and Stability of Lead-Free CsEuCl Nanocrystals via Ni Doping.

Colloidal CsPbX (X = Br, Cl, or I) perovskite nanocrystals (PNCs) have emerged as low-cost, high-performance light-emitting materials, whereas the toxicity of lead limits their applications. Europium halide perovskites offer promising alternatives to lead-based perovskites due to their narrow spectral width and high monochromaticity. Nonetheless, the photoluminescence quantum yields (PLQYs) of CsEuCl PNCs have been very low (∼2%). Herein, Ni-doped CsEuCl PNCs have been first reported, exhibiting bright blue emission centered at 430.6 ± 0.6 nm with a full width at half-maximum of 23.5 ± 0.3 nm and a PLQY of 19.7 ± 0.4%. To the best of our knowledge, this is the highest PLQY value reported for CsEuCl PNCs so far, an order of magnitude higher than in previous work. DFT calculations demonstrate that Ni enhances PLQY by concurrently increasing the oscillator strength and removing Eu which hinders the photorecombination process. B-site doping offers a promising approach to enhance the performance of lanthanide-based lead-free PNCs.