Color Control of Pr3+ Luminescence by Electron-Hole Recombination Energy Transfer in CaTiO3 and CaZrO3.

Controlling luminescence in phosphors able to produce several emissions from different stable excited states determines their use in optical devices. We investigate the color control mechanism that quenches the greenish-blue emission in favor of the red one in the archetype phosphor CaTiO3:Pr3+. State-of-the-art ab initio calculations indicate that direct host-to-dopant energy transfer (released by electron-hole recombination following the interband excitation and structural reorganization) selectively populates the 1D2 red luminescent state of Pr3+ and bypasses the 3P0 greenish-blue emitter. Local defects can modulate the electron-hole recombination energy and therefore increase the red emission efficiency, as experimentally observed. The selection of red emission does not happen in CaZrO3:Pr3+ because the electron-hole recombination energy is much higher. The calculations could not support the widely accepted color control mechanism based on metal-to-metal charge transfer states. The conclusion sets new points of view for the color control of lanthanide activated inorganic phosphors.