Highly efficient upconversion luminescence of Er heavily doped nanocrystals through 1530  nm excitation

Improving luminescence efficiency is of vital importance for applications of rare-earth-doped upconversion materials. Herein, we present highly efficient upconversion nanocrystal, which is brighter than the state-of-the-art Er³⁺/Yb³⁺ co-doped core-shell material, through Er³⁺ heavily doping and 1530 nm excitation. Moreover, upconversion characteristics and mechanisms of Er³⁺ heavily doped core nanocrystals and their core-shell counterparts are investigated carefully.