Dynamical behavior of quantum cutting in alkali gadolinium fluoride phosphors

Time-resolved luminescence spectra have been measured in NaGdF4:Eu3+ in order to investigate quantum cutting in which two visible photons are emitted for one-photon absorption. In a Gd3+–Eu3+ system, two processes of energy transfer from Gd3+ to Eu3+ are dominant in the quantum cutting: a cross-relaxation (CR) process and a direct-transfer (DT) process. In temporal profiles of the luminescence spectra, it was found that one visible emission undergoing the CR process indicates a fast decay, and the other undergoing the DT process indicates a rising form. These results are explained by two energy-transfer processes contributing to the quantum cutting process.