Supplement Number 1

See the supplementary material for the experimental section, crystal structures, schematic diagram of the synthesis process, XPS curves, EDS mapping images, STEM images, valence band spectra, absorption spectra, analysis of light effective area, power-dependent UC spectra, UC emission spectra at different Er doping concentrations, TPV curves, structural parameters of different systems, XRD patterns, and tables for comparing device performance and UC luminescence lifetime.