Extended Data Fig. 6: Emission lines of the upconversion NPs.
From: Directive giant upconversion by supercritical bound states in the continuum
![Extended Data Fig. 6](https://cdn.statically.io/img/media.springernature.com/full/springer-static/esm/art%3A10.1038%2Fs41586-023-06967-9/MediaObjects/41586_2023_6967_Fig10_ESM.jpg)
Energy-level scheme of core–shell NPs (a) and core–shell–shell NPs (b) and their corresponding experimental upconversion photoluminescence (UCPL) spectra (c).