Insights into Li⁺-induced morphology evolution and upconversion luminescence enhancement of KSc₂F₇:Yb/Er nanocrystals

Lanthanide doped KRE₂F₇ (RE: rare earth) nanocrystals have recently emerged as a new type of upconversion host material due to their distinct crystal structure and tailorable upconversion emissions. However, the controlled synthesis and upconversion fine-tuning through host lattice manipulation have not been well explored. Herein, via Li⁺ doping, we have systematically studied the morphology and upconversion luminescence evolution of KSc₂F₇:Yb/Er nanocrystals. An ∼21 times luminescence enhancement and a red to green ratio of ∼22 were obtained, which was caused by Li⁺ induced local crystal field variation around the doped lanthanide ions. The understanding of Li⁺-induced KSc₂F₇:Yb/Er nanocrystal manipulation has paved a new avenue for functionality improvement via high content impurity doping, which should inspire even wider exploration of nanocrystal engineering, especially luminescent nanocrystals.