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.