Upconversion phosphors emit a high-energy photon after absorbing two or more lower-energy ones. Energy transfer among the active ions plays a key role in its efficiency.
We present a new model based on a rate equation system coupled with structural and spectroscopic information such as the host lattice, the sites and concentrations of active ions, and their energy levels and lifetimes.
For the first time, a model can predict the decay curves as a function of concentration and excitation power. This detailed information can be used to synthesize materials with higher upconversion efficiency.

This work was carried out by Pedro Villanueva in the group of PD Dr. Karl Krämer.

References:

• P. Villanueva-Delgado, K. W. Krämer, R. Valiente;
  "Simulating Energy Transfer and Upconversion in β-NaYF₄: Yb³⁺, Tm³⁺"
  J. Phys. Chem. C, 2015, 119(41), 23648-23657; doi:10.1021/acs.jpcc.5b06770.